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Beavers are remarkable animals that engineer the landscape by building dams and transforming linear streams into a series of ponds. The impact of this engineering on lowland ecosystems is widely recognized in temperate regions, but beavers are now moving from the forest into arctic tundra regions, where their extent and impacts are unknown. In the Arctic, perennially frozen ground – permafrost – stores vast amounts of carbon, and the stability of permafrost is jeopardized when the landscape is inundated due to beaver engineering and changes in hydrology. Furthermore, stream life in the Arctic is limited by low temperatures, but deeper water associated with pond building increases water temperature in winter. This in turn alters stream ecology and may create refugia for new species moving into the Arctic, including fish. Beaver expansion into new areas has been observed with concern by people living in affected regions, particularly potential impacts to fish, water quality, and boat access. This research will co-produce knowledge with local people to understand concerns and observed impacts of beaver colonization. Scientific fieldwork at beaver ponds will illuminate changes in hydrology and permafrost. This understanding will be combined with satellite images of beaver ponds across the entire Arctic to determine the extent of beaver engineering and recent changes. This research is vital to our understanding of the current and future arctic ecosystem; it will be shared widely through education and media, including a Netflix series featuring beavers moving into tundra.

The Arctic Beaver Observation Network (A-BON) will observe beaver engineering across circumarctic treeline and tundra environments during the last half-century by mapping and tracking beaver ponds using satellite imagery. Investigators will work closely with residents of three Alaskan communities (Shungnak, Kotzebue, and Noatak) to document long-term, experiential observations of beaver habitat and activity, particularly changes wrought to the landscape and to fish. These observations will provide local to regional insights clarifying the timing of beaver arrival and the impacts to socio-ecological systems. Scientific fieldwork will characterize how beavers alter physical attributes of the aquatic and terrestrial tundra environment, from initial perturbation to ongoing landscape evolution. A-BON will coordinate circumarctic efforts surrounding this issue, encouraging dialogue and data sharing among local communities, scientists, and land managers. A-BON adds to the NSF Arctic Observing Network portfolio a project with a strong remote sensing component complemented by a strong local need, perspective and collaboration. A-BON will provide a baseline circumarctic understanding of a new disturbance regime. This co-production of knowledge will inform a multitude of related studies on the ramifications of beaver colonization, from energy cycling to fish, riparian vegetation, subsistence land-use practices and human health.

We propose to integrate spaceborne InSAR observations with extensive fieldwork data collected near Toolik Lake on the North Slope of Alaska to establish a relationship between remotely sensed deformation signals and hydraulic properties of arctic tundra soils. Our study area is in the continuous permafrost of the upper Kuparuk River Basin near Toolik Lake on the North Slope of Alaska. This region preserves the juxtaposition of two major soil types: older, acidic soils which also covers most of Siberia to far north-western Canada, and younger, non-acidic soils which also covers most of the North American and European Arctic. Compared to the younger, non-acidic soils, the older, acidic soils preserve shallower thaw layers and deeper organic soil accumulations. The two soil types are representations of continuous permafrost in the Northern Hemisphere. Thus our study site is an ideal model area to study how representative different soil types will control hydrological dynamics as the climate warms and permafrost thaws. 

The Arctic is warming faster than other parts of the world, and it has the potential to amplify global warming. The amplification comes from thawing permafrost (frozen soils) that release greenhouse gases, especially carbon dioxide and methane, that lead to additional warming, more thaw, and more greenhouse gases released. However, how fast the permafrost will thaw, how much greenhouse gas will be released, and how important gradual thaw is versus abrupt thaw caused by melting ground ice or floods, is unknown. This Arctic Observatory Network research will document changes in permafrost thaw, greenhouse gas releases, and energy balance in terrestrial and freshwater systems in the Alaskan and Russian Arctic. Arctic ecosystems have seen an acceleration of permafrost thaw and greenhouse gas release to the atmosphere that may not be easily reversed. Further observations are required to determine the rates of change and potential impacts on climate, in order to best inform society on what to expect and how to prepare. In addition to advancing understanding of environmental change, broader impacts of the research include contributions to teaching, learning, and outreach by including findings in school classrooms, support of undergraduate summer research, and outreach to indigenous communities and K-12 schools in Alaska. Two communities in the Alaskan and Russian Arctic will learn to map methane bubbling hotspots that create dangerous ice, which will result in co-production of knowledge and improved safety for winter travelers. Other benefits to society include improved understanding of how permafrost thaw threatens roads and buildings, and how a thawing arctic influences climate change at lower latitudes. This research will extend time-series data on carbon, water, and energy balance in four different tundra ecosystems in northern Alaska (year-round eddy covariance measured since 2007), and at two sites in Cherskii, Russia. The records already collected show evidence of recent change and tipping points, highlighting the value of supporting long-term measurements. In addition, carbon dioxide and methane fluxes measured by eddy covariance and ebullition will be monitored in a new thermokarst lake in Siberia, and ebullition will be measured on existing and new Alaskan and Siberian lakes mapped using remote sensing. Long-term monitoring of hydrology and stream chemistry of Imnavait Creek and depth of thaw in its catchment will be maintained and expanded. To help interpret these core data, we will continue camera records of plant phenology and dates of snowmelt and snow return, harvests to assess plant biomass and NPP, and analysis of soil properties and stocks of C and N. Permafrost boreholes will be instrumented near our eddy covariance towers at Imnavait Creek and near the new lake in Cherskii. All data will continue to be made publicly available and archived with the Arctic Data Center, NSF-LTER Data Portal, and Ameriflux. Data already collected by this project have been used extensively by other researchers, and are incorporated into observing networks such as Ameriflux, the Phenocam Network, and other efforts including NASA projects and satellite campaigns. Research will also be disseminated though scientific publications and presentations.

This work will coordinate data collection using standard equipment and protocols at the Alaskan borehole sites and at a selected and comparable number of sites in Russia. The Alaskan and Eurasian borehole temperature data sets will provide the baseline to reconstruct past surface temperatures, to assess the future rates of change in near-surface permafrost temperatures and permafrost boundaries, and to provide spatial data for validation of climate scenario models and temperature reanalysis approaches. This proposal provides the US contribution to the ongoing activities of Global Terrestrial Network for Permafrost that obtains temperatures in a large number of globally distributed boreholes in order to provide a ?snapshot? of permafrost temperatures in both time and space. The project continues to provide opportunities for field experience and educational participation at levels ranging from elementary school (e.g., K-12) through postdoctoral internships both in Alaska and in Russia. Our technical manual on methods for permafrost temperature measurements and reporting data provides others with the procedures to conduct independent observations. Data obtained from our TSP project becomes freely available soon after quality assurance is completed. This project was renewed in 2019 for $2.9m under award #1832238.

Rock glaciers consist of rocky debris, either cemented by interstitial ice or covering a core of massive ice, and flow slowly under their own weight. Despite very slow velocities, rock glaciers have been documented to have accelerated in recent years by as much as an order of magnitude or more compared to their historical rates. While some recent evidence suggests that warming temperatures and changing precipitation patterns may play an important role, the specific controls on rock glacier velocity remains poorly understood. Additionally, while rock glaciers span from mountainous regions at the equator to high arctic latitudes, the degree of variability of rock glacier morphology, internal structure, and velocity across the world is unknown. Arctic rock glaciers in particular are under-studied, especially given the pace of climate change in the Arctic compared to other regions of the world. This study adds to a larger, comparative dissertation project by working to better constrain these unknowns by closely examining an arctic rock glacier in the Brooks Range with multiple methods. First, uncrewed aerial systems (UAS) equipped with camera equipment allow for high accuracy point clouds and digital elevation models which allow for precise geomorphological analysis and, when taken over multiple years, yields extremely accurate velocity measurements across the surface of each rock glacier. These data products also reveal otherwise hidden morphological features such as surface cracks, which have important implications for kinematics and ice content. Second, we employ a multi-physics approach to understanding internal structure, leveraging both ground-penetrating radar and frequency domain electromagnetics, which serve as complementary datasets to interpret stratigraphy and ice content. The combination of geomorphological analysis, geophysical investigation, and examination of kinematics creates a holistic picture of a rock glacier in the Alaskan arctic. Pilot research conducted by the PI and advisor (Kynan Hughson) has yielded 1-2cm/pixel digital elevation models for two rock glaciers in Southcentral Alaska and one mid-latitude rock glacier in southern Colorado. While rapid warming in the Arctic has well-known effects on permafrost, potentially including rock glaciers as permafrost bodies, other unique environmental changes such as increased precipitation as both rain and snow resulting from evaporation from an increasingly ice-free Arctic Ocean may also have impacts that have never been investigated. As such, an additional field site in the northern Brooks Range greatly enhances the comparative aspect of this study while also acting as a standalone project.

Lakes play a pivotal role in global carbon (C) cycling and are critical zones for C transformations as lake sediments store large amounts of organic carbon (OC), acting as long-term geologic sinks. Understanding processes controlling lake C cycling is of importance in the Arctic due to changes driven by rapidly rising temperatures. It remains uncertain whether Arctic lakes will continue acting as C sinks or sources in the face of global climate change. The amount of C stored in lakebed sediments is controlled by 1) how much C reaches the lakebed and 2) how that C is altered both biologically and chemically at the lakebed. Terrestrial runoff from permafrost, groundwater, and phytoplankton productivity control the amount of OC delivered to the lakebed. Lakebed C can be lost from sediments through microbial respiration, of which, aerobic respiration is thought to be the most efficient mode of OC remineralization however, oxygen-rich conditions may foster OC stabilization with metal oxides, like iron (Fe) and manganese (Mn), protecting labile OC. Large deposits of fresh OC to sediments can drive anoxic conditions in which Fe and Mn reduction are favorable pathways for OC remineralization, potentially transforming these systems into C sources through the production and release of greenhouse gases. To investigate the vulnerability and fate of OC-metal complexes, we took sediment cores and porewater samples in Toolik Lake, an Arctic lake in Northern Alaska. Preliminary results from porewater samples suggests that portions of Toolik Lake are dominated by high concentrations of dissolved Fe while others are dominated by Mn. Differences in sediment metal concentrations could alter how much C is sequestered in the lakebed suggesting that portions of the lake may function as better C sinks than others. DIC-δ13C isotope profiles of porewaters suggest that Toolik Lake also differs in microbial respiration activity, suggesting that some parts of the lake are hotspots for organic matter degradation. Future work will identify spatial differences in the abundance and nature of OC-metal complexes in sediments while also characterizing OC sources delivered to the lakebed and their impact on C, Fe, and Mn cycling to assess the complexity of both C delivery and sedimentary sequestration which is crucial for informing the global C budget.

The Arctic is warming about four times faster than elsewhere on Earth, resulting in thaw of permafrost—permanently frozen soil underlying many Arctic landscapes. Permafrost occurs under approximately one fourth of the northern hemisphere's land surface and contains as much carbon (stored as undecomposed organic material) as the entire atmosphere. When permafrost thaws, microorganisms (such as fungi and bacteria) decompose and convert this organic material to carbon dioxide and methane, two of the most important greenhouse gases in our atmosphere. This mechanism is referred to as positive climate feedback because the warming of permafrost generates higher concentrations of carbon dioxide and methane in the atmosphere which increases atmospheric temperatures even further. This permafrost–climate feedback is one of the least well-understood global climate feedbacks, partially due to our lack of understanding of permafrost microbial communities. There is limited data about how permafrost thaw affects the microbial community—or microbiome—including the ecological processes underpinning the composition of the microbial community after permafrost thaws. New evidence shows that microbial communities are not only shaped by the environment in which they live, but that random chance—or coincidence—also determines which microbes are present at any given time. The degree of coincidence influences our ability to predict microbiomes and their functions. The proposed work will deepen the understanding of the ecological processes that are shaping the post-thaw composition and activity of soil microorganisms. At the same time this project will train the next generation of polar researchers (at the postdoctoral, graduate, and undergraduate levels) and build a network of permafrost microbiologists able to address questions about the role of microorganisms in the permafrost–climate feedback.

The proposed work will improve understanding of the poorly known dynamics of post-thaw microbiomes in permafrost landscapes, which are rapidly changing due to the amplification of Arctic climate warming. The goal of the work is to address this knowledge gap through a series of heavily integrated research, education, and broader impacts activities. Specifically, this project will (1) synthesize publicly available and as-yet-unpublished DNA sequence data on post-thaw microbiomes from permafrost across the globe; (2) use ecological modeling to assess the contribution of stochasticity to the post-thaw microbiome composition over space, time, and disturbance intensity using a field sampling approach; (3) test mechanisms of assembly in post-thaw microbiomes in highly controlled laboratory incubations performed across many ecological axes; (4) equip the next generation of Arctic scholars and/or natural resource managers with the skills necessary to excel in scientific research, networking and collaboration, and science communication by training a postdoctoral researcher, a PhD student, and undergraduate and graduate students; (5) develop a professional network of permafrost microbial ecologists to elucidate the complex unknowns of permafrost and post-thaw microbiomes; and (6) support efforts to continue work in making polar and biogeosciences more diverse and inclusive. Together, these activities will contribute to enhanced understanding of the permafrost–climate feedback, which will guide planning and policy.

As members of the NISAR Science Team, we provide guidance and expertise in these important components central to NISAR objectives. We work with the NISAR Project Scientist and Science Team to provide scientific guidance in measurement requirements, product definition, algorithm development, calibration, validation, and early engagement activities with the broader science and applications user communities as defined in the NISAR Utilization Plan. We support addressing NISAR assessment of wetlands inundation state and dynamics as a primary consideration, we address continued maturation of the wetlands Algorithm Theoretical Basis Document (ATBD) and execution of calibration-validation (cal/val) efforts focusing on wetlands cal/val needs up to NISAR launch and continuing through commissioning and through six months post-launch. We execute cal/val workflows to prototype evaluation procedures addressing NISAR science objectives, and going forward, we will execute these protocols post-launch to evaluate NISAR datasets.

Our overall goal is to monitor and study the insect biodiversity in Arctic habitats, with an emphasis on gaining insights into functional and physiological biodiversity in aquatic insects. Although arthropod diversity is lower in the Arctic than in other biomes, the ~2000 species of insects that live there must accommodate extraordinarily frigid environmental challenges. However, the physiological adaptations that allow for resilience in harsh wintry conditions are poorly understood on the genetic level. Before we can make predictions about insect response to altered climate regimes, we need to quantify existing diversity, their distributions, and evolutionary history. Here, we propose to study charismatic Arctic dwelling insects; dragonfly Somatochlora sahlbergi and stonefly, Nemoura arctica at the phylogenetic, population, genomic, and physiological level. One of our eventual goals to establish a long-term project for monitoring and studying diversity of aquatic insects in arctic habitats; we have begun monitoring odonates in the Arctic and would expand on our pilot data while adding Plecoptera as a second aquatic focal taxon.

The EvoME Institute strives to understand how adaptive evolution shapes mechanistic responses to climate change at multiple levels of biological organization from genes to ecosystems, and determines the resilience of meta-ecosystem functions.

Spring-fed streams with perennial flow and stable temperatures (e.g. annual fluctuations ~3-4˚C) are widespread in arctic Alaska, where all other stream types freeze solid during winter. These ecosystems are hot-spots of productivity and provide critical winter habitat for key species (e.g. Dolly Varden char Salvelinus malma). Arctic spring-fed ecosystems, with their relatively warm thermal regimes embedded in an intensely seasonal arctic landscape, also provide a unique research context, particularly with regard to their uncoupling of annual light and temperature regimes and its subsequent effect on seasonal ecosystem processes. Our research at Ivishak Spring (69.024˚, -147.721˚) has shown that, unlike most other ecosystems, where light-driven seasonal cycles of gross primary production (GPP) and organic carbon (C) demand are closely coupled (e.g. high during summer, low during winter), arctic spring-streams have cycles of GPP and C demand that are seasonally uncoupled (i.e. warm winter temperatures drive high rates of C demand by consumers when GPP is light-limited). Consequently, springs impose significant bioenergetic costs while providing essential winter refuge (i.e. a freeze-or-famine scenario). Since mean winter temperatures among arctic spring-streams range from ~1˚C to 13˚C, the range in severity of winter bioenergetic costs should be wide, with metabolic penalties in the warmest streams conceivably so severe that some taxa are unable to overwinter successfully. The objective of our proposed study is to assess the interactive effects of light and temperature on ecosystem processes (GPP, ecosystem respiration, nutrient uptake, secondary production, food-web attributes) and organismal growth rates, metabolism and tissue stoichiometry in these uniquely polar habitats. Our approach will be based on 10 spring-streams forming a thermal gradient (~1 to ~13˚C) used to test predictions at the individual, population, and ecosystem levels of organization. Recognizing the typically coupled (and so confounded) effects of light and temperature on ecosystem function is important because difficulties isolating these drivers impede understanding of their independent effects on ecosystem processes. GPP is usually maximized during high light availability, which is also when metabolic demands of ectotherms are greatest due to high temperatures, and minimized during dark, cold periods when metabolic demands are lowest. Due to such profoundly coupled relationships, the relative roles of light vs. temperature in driving resource supply and use are obscured. Attempts to decouple these cycles, and complementary ecosystem responses, however, are difficult due to a scarcity of ecosystems providing effective controls. To our knowledge, the only natural ecosystems providing such controls are arctic spring-streams, where the combination of stable, relatively warm temperatures and extreme annual fluctuations in day-length provide opportunities to advance understanding of the independent effects of light and temperature. Such uncoupling of light and temperature cycles renders arctic spring-stream ecosystems compelling models for research on drivers of ecosystem processes. We plan to leverage these uniquely polar ecosystems to support research that will advance both polar and global ecology by contributing to understanding of how light-temperature coupling affects ecosystems across latitudes.

Staff from Georgia Tech's low frequency radio lab will travel to TFS to repair receiver equipment that was installed 2 years ago. The receiver will need extensive repairs, software updates, and other upkeep. Currently, our antenna is located within the boundary of the field station. We will be applying for a permit to move the antenna further away from the site in an attempt to reduce the electromagnetic noise.

Deployment of HF beacon receiver in support of AFOSR and NSF research projects.

Liquid water in the Arctic flows at or near the surface above frozen ground known as permafrost. As permafrost thaws, water flows along new paths, mobilizing previously frozen carbon. If permafrost soils thaw and dry, carbon is released three times more readily than if permafrost soils thaw and remain saturated, implying that water patterns partially control carbon release. Yet, the patterns or drivers of permafrost saturation and how they vary with climate remain poorly understood. This research will use field measurements, remote sensing, and modeling to investigate the dynamics, drivers, and sensitivity of hillslope saturation patterns on the North Slope of Alaska. Results will help to create an ‘H2cOld: Water in the Arctic’ traveling outreach activity for rural K-12 students and communities throughout the southern Appalachians and Idaho. The project will also train four undergraduate students and a graduate student for science careers.

This project is the final two years of a previous Department of Energy - Argonne National Laboratory project (under PI Julie Jastrow). The goal of the project is to constrain the variability in soil carbon stocks across multiple scales in ice wedge polygons from the coastal plain to the Arctic Foothills by sampling soils to 2m depth across micro features in ice wedge polygons.

Liquid water in the Arctic flows at or near the surface above frozen ground known as permafrost. As permafrost thaws, water flows along new paths, mobilizing previously frozen carbon. If permafrost soils thaw and dry, carbon is released three times more readily than if permafrost soils thaw and remain saturated, implying that water patterns partially control carbon release. Yet, the patterns or drivers of permafrost saturation and how they vary with climate remain poorly understood. This research will use field measurements, remote sensing, and modeling to investigate the dynamics, drivers, and sensitivity of hillslope saturation patterns on the North Slope of Alaska. Results will help to create an ‘H2cOld: Water in the Arctic’ traveling outreach activity for rural K-12 students and communities throughout the southern Appalachians and Idaho. The project will also train four undergraduate students and a graduate student for science careers.

This project continues to use AON-ITEX plots to quantify the effects of long- and short-term warming on plant phenology, floral rewards, and pollination. This project also documents spatio-temporal patterns in the plant-pollinator networks of Toolik and Imnavait.

Thawing of the permafrost landscape is leading to thaw-driven erosion. With episodic failure, erosional features rapidly deliver sediments, metals, nutrients, and pathogens into downstream water pathways, impacting downstream ecosystems. This proposal will investigate the mechanical development of retrogressive thaw slumps (RTSs) and thermoerosional gullies (gullies) by investigating land stability and the associated erosive power at Toolik Field Station. At Toolik, there has been extensive work on RTS and gully classification, electrical resistivity tomography along RTSs and gullies, and carbon and nutrient transport at RTSs and gullies. However, a clear understanding of their occurrence, growth rates, and evolution requires a granular scale understanding of failure. I hypothesize that RTSs are a result of instability within the interleaved horizontal layers, whereas gullies are a result of instability along the interleaved vertical layers of the subsurface. To test this hypothesis, I propose to take core samples and drone images to map the ice and grain-size distribution in the subsurface. I will use these insights to set up a granular scale computational model that will inform land stability at these sites. Depending on the location of the carbon and nutrient rich layer, I can further simulate the extent of carbon and nutrient transport. I also plan to use Optically Stimulated Luminescence to date the age of last activity and identify geomorphic features associated with stability. The preliminary work specifically at Toolik, the proposed new surveys through the Tundra Award, and my granular scale simulations enable me to understand the mechanics of landscape evolution and provide a process based understanding of carbon and nutrient transport.

Ecosystem recovery from disturbance (i.e. succession) has fascinated ecologists for more than a century, and has gained recent attention due to the increased frequency and severity of disturbances across the globe. Predicting how climate change will impact ecosystem succession remains limited due to the long timescales in which ecosystem biogeochemistry recovers after disturbance, and methodological limitations associated with studying succession. Model predictions of biogeochemcial cycles during succession remain uncertain, especially when made during environmental conditions in which they were not parameterized for. On the North Slope of Alaska, recovery from a recent unprecedented fire (i.e. the 2007 Anaktuvuk River fire scar) is occurring with one of the fastest warming rates on earth. We have monitored carbon and energy fluxes with eddy covariance towers since the inception of vegetation recovery (2008), and conducted a soil and biomass harvest in 2011 across a burn severity gradient (i.e. a Severely-, Moderately-, and Un-burned site). Historical data indicate that the two burn sites will undergo important successional transitions over the next 10 years, that if captured, will improve biogeochemical models of succession. LTREB funding will be used to create a multi-decadal record of C, N, P fluxes and stocks to parameterize, validate, and test a commonly used biogeochemical model for arctic tundra (i.e. the Multiple Element Limitation [MEL] model).

Overview: The Arctic is rapidly warming. Some responses to this warming involve acceleration of processes com- mon to other ecosystems around the world (e.g., shifts in plant species), whereas others are unique to the Arctic but with global consequences for society (e.g., carbon loss from permafrost thaw). The objectives of the Arctic Long-Term Ecological Research (ARC-LTER) project for 2023-2029 are to determine how and how fast trends in climate change and especially climate variability are changing arctic ecosystem structure and function. To understand these changes we will extend our use of the concepts of biogeo- chemical and community “openness” and “connectivity,” developed during our previous award, to under- stand the responses of arctic terrestrial and freshwater ecosystems. These objectives will be met through continued long-term monitoring of changes in undisturbed and disturbed ecosystems along the terrestrial to aquatic continuum in the vicinity of Toolik Lake, Alaska. In addition, we will measure the recovery of these ecosystems from natural or imposed disturbances, maintain existing long-term experiments, and ini- tiate new experimental manipulations and observational studies to achieve the objectives. Based on the data generated, carbon and nutrient budgets and measures of species composition and abundance will be compiled for major components of the arctic landscape. Through a combination of data analysis and modeling we will assess how climate change and climate variability will affect biogeochemistry and com- munity dynamics of ecosystems, and determine how ecosystem responses will propagate across the land- scape.

Intellectual Merit: Building on our ongoing focus of how ecosystem openness and connectivity affect the response of bioge- ochemical cycles and communities to climate change and disturbance, the proposed research is centered on the hypothesis that climate variability is a stronger driver of change in the Arctic than are the mean, long-term trends in climate. The research will answer three interconnected questions: (1) How does cli- mate variability affect the openness and connectivity of arctic ecosystems? (2) How does climate varia- bility affect key consumers and their influence on ecosystems? (3) How does climate variability affect carbon dynamics along the terrestrial-aquatic continuum? Natural climate and environmental variability will be analyzed or manipulated to examine how key consumers like fish and small mammals move on the landscape and influence system productivity, organism abundance, and species composition, and how key processes such as organic matter production and consumption along the terrestrial-aquatic continuum function to control carbon dynamics and balance of tundra ecosystems. The research will use synthesis of ongoing, long-term observations and experiments, and new activities combining observations, experi- ments, and modeling. These activities will answer the research questions about how trends in mean cli- mate, climate variability, and disturbances all interact to control arctic ecosystem structure and function, now and in the future.

Broader impacts: ARC-LTER research has broad impacts on science with over 68,000 citations of the 730 journal publica- tions by our researchers and collaborators since 1975. The 145 publications since 2017 have been cited 2,660+ times. This impact will grow with new publications from ongoing long-term and proposed re- search. Associated researchers, postdocs, and students benefit from access to long-term data and the abil- ity to conduct complementary studies in our monitoring and experimental sites. This approach will main- tain a pipeline of support for the many excellent assistant and associate researchers now affiliated with the project. Education and outreach to non-scientists will be expanded, and a new ARC-DEI plan guides our efforts to broaden diversity and participation in all our activities. These activities include: (i) engagement of K-12 teachers in summer research programs via our Schoolyard program, Earth Camp, NSF RET, and NSF PolarTREC efforts, (ii) support, mentoring, and inclusion of undergraduates (including two REUs) and graduate students associated with ARC, (iii) briefings to Alaska State, North Slope Borough, and US government agencies overseeing environmental and natural resource programs, (iv) collaboration with the NSF SEARCH program co-producing knowledge with Indigenous experts for use in decision making, (v) engaging learners in analysis of ARC data by producing education modules, and (vi) graduate student par- ticipation in workshops, LTER all-scientist meetings, and in an open, annual ARC-LTER meeting.

Mercury – especially in the form of methylmercury – is a potent neurotoxin with negative health impacts on both humans and wildlife. Mercury contamination is of particular concern in the Arctic due to long-range transport and deposition to this region, which leads to high storage of mercury in peatlands. Wildfires in the Arctic have the potential to release this stored mercury and to increase the rate of transformation from inorganic forms to the bioavailable form of methylmercury. Yet data gaps remain regarding the legacy impact of Arctic wildfires on Mercury patterns in terrestrial and aquatic ecosystems. In this proposed research, I ask: (1) How does wildfire legacy in the Arctic impact soil mercury storage and transport of mercury into nearby rivers? (2) How does wildfire legacy in the Arctic impact mercury methylation in soils and sediments? I will use the fire chronosequence at the Anaktuvuk River fire scar to address these research questions. I plan to sample both soil cores and surface waters. I hypothesize: (1) Soils that experienced more intense fires will have lower total mercury soil concentrations than those that experienced less intense fires or no fires since more mercury was released (e.g., evaded, eroded) during these fires and nearby ecosystems may have received some of this mercury deposition. (2) Total mercury concentrations in river reaches near more intense fire sites will be higher than those that experienced less intense fires or no fires due to enhanced organic matter losses and transport of organic matter-bound mercury. (3) Mercury methylation will be greater in soils that experienced moderate fire intensity due to enhanced soil pH and retention of some organic matter.

Snow Measurement campaign in support of NASA's Snow Experiment (SnowEx)

We will study one of the most vulnerable elements of the rapidly changing Arctic -- ice-rich permafrost (IRP). IRP is at the center of a web of interacting ecosystem components that we call the IRP system (IRPS). Our key questions are: How are climate change and infrastructure affecting IRPS? What roles do ecosystems play in the development and degradation of IRP? and How can people and their infrastructure adapt to changing IRP systems? We are particularly interested in how differences in vegetation, water, and time influence the accumulation and degradation of ground ice in IRP landscapes, and how the loss of ground ice can radically change these landscapes, their components, and the infrastructure built on them. Our ultimate goal is to understand IRPS at local, regional and circumpolar scales.

The Alaska Division of Geological & Geophysical Surveys has a long-standing program aimed at understanding the geologic evolution of northern Alaska. This region is strategically important for its natural resource endowment, but also as a laboratory for understanding Earth history. Our research effort includes a variety of topical studies such as: fold-thrust belt evolution, foreland basin dynamics, sequence stratigraphy, high precision chronostratigraphy, and paleoclimate.

Arctic tundra ecosystems are experiencing structural and functional changes due to climate warming and associated changes in winter precipitation. Greater snow cover in the Arctic provides soil thermal insulation and induces vegetation changes that may affect the vulnerability of stored C. Higher mineralization of centurial C in forms of CO2 or CH4 emissions may feedback on the climate system. Specifically, vegetation shifts favoring ecosystem productivity and associated alterations in thermal and hydrological regimes with warming may trigger CO2 and CH4 emissions. Therefore, the CO2 and CH4 forms of C emission are relevant to climate models, but the biophysical mechanistic understanding of these warming-C cycling feedbacks is currently lacking for Arctic tundra. We measured O2, CO2 and CH4 soil concentration and flux over a growing season in a snow fence (to mimic predicted increases in snow cover) located in moist acidic tundra at Toolik Lake, AK. To account for soil physical changes that may affect gas diffusivity we also measured the 222Rn flux. We found that this site may switch from a CH4 neutral state to a source of CH4 with warming. In contrast, CO2 efflux did not appear to be sensitive to increases in soil temperature, likely because reduced gas diffusion coefficients under enhanced winter precipitation. Reduced diffusion of O2 into the soil may have prompted the large production of CH4, although, ecosystem CH4 emission were limited by diffusion. The d13C-CH4 also suggests a progressive increase in the prevalence of methanogenesis by the CO2 reduction pathway relative to acetate fermentation with increased winter soil thermal insulation. Methanotrophy appeared to be limited by redox changes at shallow depths within the experimental treatment sites. Our findings indicate that biophysical factors affecting gas diffusion drive CO2 and CH4 dynamics in arctic moist acidic tundra.

The main hypothesis of the PER2Water research project is that permafrost is a secondary source of persistent organic pollutants (POPs) which are released into water during seasonal and permanent permafrost thaw. As permafrost degradation is forecasted in the Northern Hemisphere in the 21st century, research questions emerge on the characteristics and impacts of such a phenomenon. Within the proposed project, we plan to test whether organic pollutants are stored in permafrost, and whether they are released into fresh waters during thaw. Furthermore, seasonal characteristics of pollutant release and their temporal coincidence with permafrost thaw will be investigated. Finally, the long-term impacts of the POPs release from permafrost will be explored, in the context of climate warming, permafrost degradation, and a connection between the large-scale peatland fires and pollution release from permafrost. Considering that permafrost zones occupy about 25% of the exposed land area, permafrost is a likely sink for POPs. POPs are a group of chemicals resistant to degradation, so they accumulate in the environment over long periods of time, posing a long-term risk to ecosystems and human health; they also exhibit bioaccumulative and toxic properties. A wider definition of POPs includes polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), and many other both intentionally and unintentionally produced chemicals (such as dioxins or furans). The ecosystems and indigenous people of the Arctic are particularly at risk because of the preferential accumulation of these chemicals in cold regions and due to bio-magnification. Published data shows that the permafrost may have been heavily contaminated by some organic pollutants, e.g. historical PAHs, and the pollutants trapped in the ice-rich permafrost layer may be released as a result of future climate warming. Furthermore, pollution related to human activity today and in historical times may be transported across international boundaries far from their sources, even to regions where they have never been used or produced. Especially PAHs are of interest, as due to the increasing frequency of forest and peatland fires in the Arctic and sub-Arctic. The study will be carried out at Toolik Field Station, and it will include both a hydrological and a hydrochemical component. We plan to sample several water bodies (rivers and lakes) and sediment, as connected to the active layer of permafrost (including the thaw of yedoma in the study). Water samples will be taken regularly during three weeks at the turn of August and September. Sediment samples will be collected in a vertical profile (from lake bottom) and in a spatially distributed design from riverbeds. Water samples will be preserved at Toolik Field Station and analyzed in laboratories in Poland (Kazimierz Wielki University, Gdańsk University of Technology, Adam Mickiewicz University in Poznań) to determine the concentrations of polycyclic aromatic hydrocarbons, polychlorinated biphenyls, metals and metalloids, and – in collaboration with Vienna Technical University, to conduct non-targeted analysis for organic compounds in the sample. In the proposed project, we will implement interdisciplinary experience of the project leader (in geography, hydrology, and hydrochemistry) and co-investigators (in analytical and environmental chemistry, geography, hydrology, geomorphology, and hydrodynamics), including the interpretation of data in the context of changing discharge in the sampled rivers and meteorological background. The novel information obtained through the planned project will fill an important research gap in the discussion on whether organic pollutants released from thawing permafrost is a local or a global phenomenon, and whether it includes legacy permafrost such as yedoma.

The Arctic is warming at a rate faster than elsewhere on Earth, resulting in changes to Arctic ecosystems that may affect global climate. Permafrost is ground that remains frozen for at least two consecutive years. It occurs under approximately one fourth of the northern hemisphere's land surface and contain as much carbon as the entire atmosphere. Permafrost thaw leads to changes in the dominant vegetation and makes the carbon stored in the permafrost soil vulnerable to decomposition, but existing measurements and models disagree about the implications of these changes for the global carbon cycle. This research project investigates how processes mediated by microbes, minerals, and their interactions with vegetation affect the vulnerability of carbon in permafrost soils. The researchers are carrying out laboratory and growth chamber studies to investigate microbial communities and the transformations of carbon with permafrost thaw. They are incorporating the results of those studies into Earth system models to understand feedbacks to the climate system. This research is addressing critical knowledge gaps about how carbon stored in frozen permafrost will affect the Earth’s carbon cycle, which is information urgently needed to inform climate change adaptation and mitigation strategies. This project is addressing the question: how will feedbacks between plants and soils (specifically minerals and microbes) affect arctic soil carbon balance in response to global change? Using state-of-the-science tools, such as microbial sequencing and stable isotope tracing, the researchers are carrying out (1) laboratory incubations to determine how soil microbial communities and mineralogy affect the fate of plant exudates and the vulnerability of native soil organic matter in thawed permafrost, and (2) plant–soil growth chamber mesocosms to trace belowground plant deposits into permafrost soils under ambient and elevated CO2. These findings are being used to develop and evaluate a microbial-enabled model that can handle the complexity of plant–microbe–mineral feedbacks. This soil model is being integrated into the Community Land Model (CLM) to predict the impact of permafrost thaw on the arctic carbon budget. This research enables better long-term projections of permafrost-climate feedbacks. The project is training the next generation of interdisciplinary Arctic scholars well-versed in scales ranging from microbial genes to global elemental cycles through PhD assistantships, postdoctoral research, and undergraduate laboratory education. In addition, the project provides training for up to 50 early career researchers on the theory and practice of land modeling, with a special focus on Arctic systems.

Permafrost covers 20-25% of the land surface in the Northern Hemisphere. Recent air temperature increase in the Arctic and Subarctic is significantly higher than the global average. Climate simulations predict continuing warming and increased wildfires occurrence. This rapid change is already leading to permafrost degradation, inducing ground subsidence and thermokarst, affecting land usability and stability of infrastructure. An increase in active layer thickness alters soil hydrology and groundwater drainage patterns. Besides, large amounts of carbon and other inorganic elements, previously trapped in permafrost, are released towards aquatic systems. Microorganisms convert newly available highly biodegradable organic carbon into greenhouse gases, amplifying global warming. As permafrost is known to contain vast amounts of frozen carbon, twice its current content in the atmosphere, its thawing poses a major risk because of the positive feedback on climate. Ultimately, climate change, through permafrost and habitat disturbance, affects local communities built on permafrost and threatens the traditional indigenous lifestyle. A better understanding of the impacts of permafrost thaw on soils, surface/groundwater fluxes (critical zone) and carbon cycle, as well as their controlling factors, will contribute to the understanding of permafrost-climate feedback. Contributing to fill this knowledge gap, the overarching goal of the PRISMARCTYC project is to understand the different hydrogeomorphological and biogeochemical processes modifying permafrost soils, surface and groundwater runoff, driven by permafrost degradation in small watersheds. This goal will be achieved by comparing different sites in Siberia and Alaska with different permafrost settings (e.g., ice-rich Yedoma permafrost or carbon-rich permafrost peatland; continuous or discontinuous permafrost), climate-sensitivity, vegetation, permafrost degradation types along a latitudinal and longitudinal gradient. The key study sites in Siberia and Alaska have been chosen based on the expertise of the team members to cover a broad range of permafrost settings and degradation types, to allow cross-comparison. Central Yakutian lowlands (Eastern Siberia) and Chersky (North-Eastern Yakutia, Eastern Siberia) will be the two main study areas where intensive fieldwork will be conducted. Olekma (Southern Yakutia, Eastern Siberia) and Batagay (Northern Yakutia, Eastern Siberia) will be the secondary study sites, where field research will be less detailed. Igarka (Western Siberia) and Alaska (transect from Denali Range to North Slope Toolik station) are selected as comparative sites as they were already studied by members of the project.

This project aims to use innovative, high-throughput technologies to develop a novel framework that links daytime photosynthesis and starch/amino acid mobilisation to variations in night-time leaf respiration. Variations in leaf respiration can have large impacts on ecosystem functioning and the Earth’s climate. Although advances have been made in respiration modelling, current models are unable to predict dynamic, day-to-day variations in respiratory rates. Expected outcomes include equations that predict daily variations in night-time leaf respiration for environments across Australia and overseas. Benefits to planners include the ability to more accurately model vegetation-atmosphere carbon exchange and future changes in climate. This is a collaborative project with the ARC LTER project and will share resources (including users days). Sampling will be on LTER plots and will be covered by the LTER permits.

This ongoing project, which is funded annually, will be renewed in January 2025: Our hydro-meteorological monitoring program continues at the Sagavanirktok and Dietrich rivers, both of which drain from the Central Brooks Range. Meteorological variables important to hydrology, such as air temperature and precipitation, are observed throughout the watersheds. Snowpack and aufeis conditions are surveyed at the end of winter. We measure water levels in the Dietrich River, as well as at several locations in the Sagavanirktok River, both upstream and downstream of the Ivishak River confluence. During both spring breakup and summer, we conduct manual measurements of river discharge.

Historical patterns and processes of species generation, maintenance, and coexistence are heavily influenced by climatic changes and glacial cycles. Hybridization and polyploidy are two of the most common processes involved in the generation and maintenance of plant species, causing both breakdown between species boundaries and promotion of reproductive isolation leading to speciation. The shrub willows (Salix L., Salicaceae) of the North American Arctic and alpine tundra are an ideal system to study species diversity in response to habitat expansions and contractions due to their habitat specificity, high levels of hybridization and polyploidy, and propensity to coexist in close sympatry. Using North American tundra willows as a focal system, I will test the factors that allow for species to exist in sympatry, with a focus on patterns of hybridization and polyploidy. Because of the taxonomic complexity of Salix and difficulties defining species boundaries, I am using population genomic and historical demographic analyses to delimit species boundaries and identify patterns and processes of speciation in taxa with Arctic-alpine disjunct populations. This project will contribute to our understanding of historical biodiversity generation and maintenance in response to climatic changes and provide a historical context for predicting species distributions in the future.

Continuation of Year 3

Thawing ice-rich permafrost is transforming Arctic tundra landscapes from being relatively flat and evenly moist into a mosaic of dry mounds and narrow ponds. As thaw progresses, a well-drained landscape with a maze of tiny surface drainages may form. This dense network of small channels represents the capillaries of the Arctic hydrologic system and serves as the originators of the water that feeds large rivers. An expanding capillary hydrologic system may change habitat for wildlife due to an overall drying of the tundra landscape, increased river runoff, and through more nutrients exported from terrestrial to aquatic environments. Further, an expanding capillary hydrological network that is identifiable from sub-meter resolution satellite imagery can serve as an indicator of ice-rich permafrost thaw and, therefore, warn of hazard to infrastructure. The development and expansion of a surface drainage system may also decrease the likelihood of moss to thrive, which results in loss of a vegetation cover that effectively cools the ground and preserves the upper permafrost from thawing. The project will produce a pan-Arctic map of the capillary hydrological system and in selected areas, advance understanding of how the capillary system has changed over time. The geospatial products will be made publicly accessible on the Permafrost Discovery Gateway to enable discovery and knowledge-generation by scientists, stakeholders, and the public. Field observations have shown that runoff from many Arctic rivers has increased in recent decades. Simultaneously, several studies have documented ice wedge degradation across the Arctic, and a handful of local field and remote sensing studies in Northern Alaska have shown that the capillary hydrologic system is expanding due to partial melting of ice wedges. This project aims to map the extent of the capillary hydrologic system across the pan-Arctic tundra and assess the role of the capillary system in generating water flow and lateral carbon flux to large rivers. Graph analysis techniques applied to the pan-Arctic ice-wedge polygon map, as well as deep learning/AI algorithms trained to detect a capillary system from very high spatial resolution satellite imagery, will allow the network of ice wedges and the capillary hydrologic system to be mapped across the Arctic tundra. Field measurements in northern and northwestern Alaska will include geochemical water sampling, coring of permafrost to assess ice-wedge status (degradation or stabilization), and ground-truthing for the remote sensing hydrologic network analyses. This new information will inform a numerical hydrology model to quantify how important the capillaries are in contributing freshwater and carbon flows to the Arctic Ocean. Earlier hydrological model experiments have shown that the formation of connected troughs-networks can double the runoff from the landscape even if the rain and snowfall amounts remain unchanged. The pan-Arctic map of hydrological capillaries will support a first study on how important sub-meter wide channels are to large Arctic river runoff.

Overview: Plant phenology, or the timing of leaf-out, flowering, and senescence, is one of the traits most affected by climate change. In the Arctic as well as other biomes, changes in plant phenology can alter ecosystem structure and function at multiple levels, ranging from timing and amounts of primary productivity to interactions with herbivores and pollinators. Studies of controls on plant phenology in the Arctic have focused on the role of temperature changes and the timing of snow removal, but there has been little attention paid to how these factors interact with the genetic background of the target organisms or their responses in photoperiod and light quality. If populations migrate in response to climate change, they will be exposed to simultaneous changes in temperature and light regime. Previous work identified a significant difference between northern and southern populations of the sedge, Eriophorum vaginatum, in the timing of senescence, with southern plants always senescing later and growing season length between populations largely retained. This suggests that length of growing season among ecotypes is associated with their respective home sites. Consequently, senescence is likely to be under genetic constraint. The differences are consistent with results from population genomic studies that show genetic structure along a latitudinal gradient and a major gene flow barrier at tree line. Furthermore, growth chamber experiments show a significant effect of changes in photoperiod on timing of senescence. This project will investigate the role of local adaptation as it affects the phenology of E. vaginatum and two of its potential competitors, the shrubs Betula nana and Salix pulchra. The overarching hypothesis is that temperature, light, and genetics in different combinations drive the phenology shift in the Arctic, and this shift varies across species and between populations that represent local or regional ecotypes.

Intellectual Merit: This project will uniquely explore the complex interplay between temperature, photoperiod, light quality, light quantity, and genetics in regulating phenology of southern and northern populations of three dominant Arctic plant species. Field experiments will involve novel manipulations and multifactorial treatments including temperature, light, and transplanting. Growth chamber experiments will maintain an arctic temperature regime while altering day length or light quality to determine the response of populations from different latitudes to changes in light regime. Red, far-red, and blue light will be monitored at five sites ranging from 65.4ºN to 70.3 ºN to examine how light quality varies diurnally, seasonally, and latitudinally. At the same sites, phenocams will monitor seven transplanted populations of E. vaginatum to determine how local light and temperature conditions interact with genetic background to affect timing of phenological events. Differential response of locally adapted populations will be explored through studies of allelic variation and expression of phytochrome family genes and related transcription factors that respond to changes in day length and light quality. To understand the role of phenology and growing season length in determining primary productivity, photosynthesis will be monitored at the leaf and ecosystem scales.

Broader Impacts: This project will have broader impacts on arctic science and education from K-12 to undergraduate, graduate students, and post-doc scientists. By combining insights from population biology, genetics, and ecosystem science, it will lead to a much deeper understanding of the role of focal species in the tussock tundra ecosystem than would be possible with a more discipline-centric approach. The project will build on a strong tradition of involving undergraduates and women in arctic field research, by recruiting assistants from a small university with majority first-generation students and a leading Minority Serving Institution. The project will be incorporated into undergraduate teaching and training at the Marine Biological Laboratory. It will also involve high school students from Wilkes-Barre in growth chamber studies. The project will support a postdoc to be based at Wilkes University, who will have the opportunity to participate in undergraduate teaching and to carry out research with undergraduates and high school students.

Routine visit to USGS gage on the Hulahula River to take discharge measurements and maintain gage

snow studies Arctic Refuge

The ALANA project, part of the Humanities in Arctic Research platform of the University of Bern, aims to understand human-environment interactions in the Arctic across prehistory, leveraging archaeological data, satellite imagery, and interdisciplinary methodologies. Collaborating with the Alaska Museum of the North, ��ķ��Ƶ and the Bureau of land Management Alaska, the project will conduct a remote sensing and on-ground survey in the Toolik and Galbraith Lake region in the North Slope Borough (Alaska, USA). Arctic archaeology has largely focused on coastal areas and the interaction between marine ecosystems and past human populations. Comparatively little is known about inland subsistence systems and their resilience and adaptability with regard to past climatic fluctuations. We have gained access to an area that is especially important for studying early anthropogenic activity in the Alaskan Arctic. We aim at documenting the archaeological landscape by means of remote sensing and pedestrian survey and correlating it with the existing climate data record using radiocarbon dating as well as potentially archaeobotanical- and faunal analysis. In addition, we aim to incorporate indigenous insights from the local Nunamiut community at Anaktuvuk Pass. This will allow us to bring archaeological data in conversation with the paleoclimatic record and indigenous knowledge and see shifts in seasonal settlement patterns across several millennia.

One of the shrub species rapidly expanding as a result of climate change is Siberian alder. Through nitrogen (N) fixation, Siberian alder has the potential to significantly influence N availability, decomposition, as well as plant and soil microbial community structure and function in arctic ecosystems. However, the direct effects of alder on arctic ecosystem processes remain poorly understood. We plan to investigate the effects of Siberian alder proximity and density on plant and soil microbial community composition, foliar chemistry, decomposition, soil nutrient availability, and extracellular enzyme activity. We propose collecting preliminary data, with a group no larger than 3 researchers, during the summer of 2022. Our proposed work will improve our understanding of the direct effects of alder as well as address the within patch heterogeneity of those effects.

The overarching goal of the project is to understand tundra ecosystem change across landscape types and enable realistic forecasts of change across the Arctic. The power of the International Tundra Experiment (ITEX)- Arctic Observatory Network (AON) is founded on a capacity to synthesize and compare results across sites that use standardized sampling protocols. Specifically, this project will (1) maintain the data-streams at ITEX-AON sites in Alaska near Toolik Lake, Imnavait Creek, Utqiagvik (Barrow), and Atqasuk; (2) lead two new ITEX network syntheses focused on soil carbon and phenocam imagery; (3) increase scientific literacy; and, (4) expand citizen science opportunities across communities in northern Alaska. The project will sustain an array of large and publicly available data-streams documenting ecosystem change occurring across the Arctic and will team up with citizen scientists to expand the monitoring footprint of the network and the societal relevance of this work to communities across the North Slope of Alaska. The ITEX network was chartered in 1990 to document and understand the ecological impacts of a warming Arctic. The US-led ITEX projects expanded their monitoring efforts across a larger spatial area with the use of automated sampling to form an Arctic Observatory Network (AON) in 2009. The ITEX-AON currently includes traditional ITEX measurements (phenology, cover, carbon flux and nutrient cycling), as well as phenocams, automated mobile sensor platforms (MISP) and mid-scale aerial imagery of 1 km2 ARCSS (Arctic System Science) grids established in the 1990s. In this phase of the project, collection of core data sets will be sustained and new data sets will be added with the aim of identifying and understanding patterns of change and feedbacks. Specifically, ITEX-AON will expand its collection of vegetation functional traits to better understand ecosystem response and predict future change. ITEX-AON will also further expand automated measurements to link plot level change (sampled by hand or with hand-held equipment) with landscape level observations (sampled by phenocams or drones) and high resolution regional imagery (sampled by aircraft or satellite). The new phase of ITEX-AON will include two synthesis efforts: (1) an examination of soil carbon dynamics across the ITEX network, and (2) a multi-scale phenological analysis using phenocam and high resolution satellite imagery to determine fine-scale spatiotemporal patterns of seasonal greening trends across the Arctic. Mentoring of postdocs, and training of graduate and undergraduate students are some of the primary broader impacts of this project. The project will continue to provide a test bed for engineering and software development that will be shared freely among the ITEX network and broader science community and will expand outreach activities aimed at improving science literacy.

The climate sensitivity of tundra shrub growth is germane to future ecosystem function in the rapidly warming tundra biome. To better understand the climate sensitivity of xylogenesis and radial growth of upright tundra shrubs in this environment, we propose to study the quantitative wood anatomy (QWA) of three species of Arctic shrubs growing around the Toolik Lake Research Area (Salix alaxensis, Salix lanata, and Betula nana). This work will quantify a time series of wood morphology on the cellular level to detail how sensitive the rate and morphology of shrub growth is to inter- and intra-annual climate fluctuations over the past 30 years. Specifically, we want to know if the window of growth sensitivity tends to expand during relatively long growing seasons and determine how tundra shrubs respond to summer dry periods. Our results will contribute to tundra vegetation models that seek to forecast how warming temperatures will impact shrub expansion and carbon sequestration in the future. This project is intended to obtain preliminary data to be used for a larger proposal in the future.

The current proposal seeks to: 1) quantify BVOC emissions across the NSA as a function of vegetation and meteorological (temperature and light) conditions, 2) develop a predictive understanding of emission response and integrate this into an emissions model, and 3) connect these emissions and emissions responses to the production of SOA. The merits of this work will be realized by contributions to academic discussion and understanding of: 1) biogenic emissions across the vegetation zones of the Alaskan Arctic under different temperature and radiation regimes; 2) contribution of terrestrial and marine biogenic sources to organic aerosol at Toolik and Utqiaġvik; and 3) improved understanding of the potential impacts of changing climate and vegetation, i.e. expansion of different shrubs (Salix, Betula, Alder), on current and future biogenic emissions and subsequent production of SOA. Detailed characterization of Alaskan Arctic-specific BVOCs are relevant in terms of understanding ecosystem processes. Further, this NSA project enables continued investigation of long term trends in Arctic organic aerosol sources and composition.

The permafrost (perennially frozen ground) regions occupy nearly a quarter of the Earth's terrestrial surface. Permafrost is experiencing large changes stemming from the unprecedented degree of environmental change being observed in the Arctic. Changes in the permafrost system have profound effects on the ecology, hydrology, geomorphology, and human occupation of cold environments. The Circumpolar Active Layer Monitoring (CALM) program represents the only coordinated program providing collection, standardization, open access, and dissemination of active-layer data world-wide. This award will support the continuation of the active-layer observations conducted by the CALM program at the network of 168 sites distributed over circumpolar Arctic region. CALM program is an integral part of the Global Terrestrial Network for Permafrost.

When water flows through ecosystems it picks up dissolved organic carbon (DOC) from plants and soils. As a result, water can control whether an ecosystem releases carbon (a carbon source) or stores carbon (a carbon sink). Consequently, the movement of water plays a key role in global carbon cycling, but DOC is also an important control on water quality across the globe. Understanding how water affects the production and movement of DOC can improve society's ability to provide water for industrial, agricultural, and domestic uses. How and when DOC moves through different types of rivers and ecosystems, especially during floods, is a major knowledge gap in carbon cycling and water quality research. This project will conduct analyses of river DOC dynamics from geographically diverse areas. The project will examine movement of DOC into and out of watersheds and evaluate if DOC dynamics can be estimated from local to continental regions using river flow and watershed properties. This DOC research is combined with an innovative education plan that will improve the translation of hydrological sciences to public audiences via undergraduate curriculum development and student-led scientific outreach. These advances will focus on training students to be effective science communicators and outreach practitioners.

Main content is determining the effects of extreme drought, wildfire, and abrupt thaw on C decomposition & CH4 flux and related microorganisms (e.g. methanogen and methane oxidizer), and interactions and legacies (biogeochemical and microbiological) of those three extreme events occurred in the Arctic regions. Especially, my major interest is microbial information such as changes in soil metagenome, microbial carbon use efficiency (CUE), and microbial C cycle illustrated by stable isotope probing, etc. In collaboration with Prof. Eugenie Euskirchen.

Behavioral datasets will be obtained from multi-species groups of birds, foraging for food in a variety of environments. Data will be analyzed using new deep learning methods to precisely track animal’s movements, and behavior will be compared across species, habitats, and weather conditions, and analyzed from a cognitive/neuroscience/statistics perspective. This research addresses the question of how animals make complex cognitive decisions within groups, in a diversity of real-world ecosystems.

The Northern Lights or aurorae result when energetic particles interact with the atmosphere, producing colorful light emissions in the night sky. The Arctic region near the North Pole is a prime location for viewing aurorae. This project is a follow-on to an NSF funded program that deployed and calibrated a radio interferometer array in Toolik Lake, Alaska. This instrumentation will be used to view the aurorae at radio wavelengths and make new discoveries about how they are created. Graduate and undergraduate students will be trained and the scientific datasets will be shared with the public. A significant manifestation of geophysical electromagnetic energy and particle flows is the terrestrial aurora which involves many acceleration processes affecting electrons and ions. These processes occur in both the magnetosphere and the ionosphere above high latitude observatories such as Toolik Lake. Radio emissions from the accelerated auroral electron beams, with their complicated temporal and spatial variations, provide an means of studying the physics of auroral particle acceleration. One particular type of radio emission, Auroral Medium Frequency Burst (MFB), is especially promising in this regard because it is associated with the onset of the auroral substorm, a pattern of auroral activity in which aurora expands to cover a large region of the sky. MFB is, however, relatively poorly understood: even its source altitude is unknown. Experiments using the radio interferometer at Toolik Lake, by answering outstanding questions about MFB and other auroral radio emissions, comprise significant advances in the study of particle acceleration in the space environement and the origin of important large-scale processes such as auroral storms and substorms.

This is an NSF funded project to measure methane, carbon dioxide, and nitrous oxide over various ecotypes in the Arctic, especially in the transition from summer to winter. We will be taking measurements from a Van equipped with our instruments by driving along the Dalton Highway between Toolik Lake and Prudhoe Bay. 

Permafrost contains large amounts of soil organic carbon (SOC) and nitrogen (N), situated underneath the seasonally-thawing active layer. Climate-warming and thawing-induced N release at the thaw-front is therefore only accessible to deep-rooting plant species and may stimulate their CO2-uptake. At the same time, deep roots may act as microbial vectors for downwards transfer of active-layer microbes into newly thawed permafrost, where such exogenic communities might stimulate SOC-degradation. Interactions between plants, microbes and thawing soil thus play a critical but poorly understood role in the permafrost-climate feedback. We aim to understand over what time scale and to what extent the presence of deep- rooting plant species causes re-distribution of permafrost N to the shallower ecosystem and of the microbial community to the deeper, thawing soil layers, and how this affects C-uptake and respiration. Specifically, this project will create as legacy a unique, long-term ecosystem manipulation experiment to unravel interactive effects of permafrost thaw and deep-rooting plant species on C and N dynamics.

Warming air temperatures are thawing frozen ground (permafrost) in the Arctic at a rapid rate. As frozen ground thaws it undergoes temperature fluctuations above and below freezing, known as freeze-thaw cycles. Freeze-thaw can impact the availability of important nutrients such as nitrogen and phosphorus, the activity of microorganisms, soil moisture and associated changes in oxygenation, and the release of greenhouse gases from thawing ground. The implications of freeze-thaw in thawing permafrost are amplified in the Arctic, which stores just under half of all soil carbon across the globe. This research will determine how exposure of previously frozen ground to freeze-thaw alters soil function and nutrient availability. This project supports one postdoctoral scholar and will fund freeze-thaw research and the development of an educational R/RStudio module for an Arctic dataset. Freeze-thaw is a disruptive, temperature driven process with direct impacts to both abiotic and biotic soil properties and their coupled interactions. Rising air temperatures expose previously unavailable compounds to plant uptake, microbial activity, and mineral sorption and precipitation while also altering biogeochemical processes within thawed soil. Freeze-thaw has been recorded to influence the migration of soil solutes (such as P, N, and Fe) through cryosuction in non-permafrost soils. In permafrost-affected soils, freeze-thaw triggered solute migration may coincide with nutrient pulses to the soil environment following microbial cell lysis and death or soil aggregate instability and breakage. In alpine and grassland systems, cryosuction during freeze-thaw can increase anoxic soil conditions with varying levels of Fe reduction and result in subsequent impacts to soil aromatics and dissolved organic carbon concentrations. The number of freeze-thaw cycles, freezing rate, and spatial distribution of freeze-thaw may vary, altering the degree of transport during cryosuction as well as informing microbial adaptation and resiliency. The proposed work will combine field data with freeze-thaw experiments to investigate temporal and spatial variations in freeze-thaw and the direct impacts to critical processes of soil biogeochemistry across a hillslope gradient in Alaskan tundra permafrost at the Toolik Field Station. The investigator will test the hypothesis that permafrost soil chemistry will be altered during the first freeze-thaw cycle, resulting in continuous changes in redox and nutrient availability throughout subsequent freeze-thaw. The study aims to restructure our understanding of permafrost thaw to include responses of the soil nutrient regime, redox chemistry, and microbial communities to freezing rate, repeated freeze-thaw, and spatial variation of freeze-thaw cycling.

We are attempting to associate ecoregions with local snow strength along the Dalton Highway

The project performs high-resolution (10-100 m) probabilistic mapping of soil freeze thaw (FT) dynamics and clarify environmental linkages driving local scale trends in permafrost active layer thickness (ALT) over the ABoVE domain. The proposed FT and ALT processing will capture finer scale features and processes represented from detailed field studies, but lacking in coarser satellite and landscape model assessments. We will resolve the complex ALT heterogeneity and clarify its relations with local environmental gradients in soil, terrain, vegetation, and disturbance. We will accomplish these objectives using a physics-based modeling and machine learning framework integrating multi-source and multi-sensor remote sensing, in situ biophysical measurements, and other ABoVE geospatial data.

the aim of the project is to get an overview of Arctic freshwaters (i.e. rivers and lakes) contamination with moder anthropogenic pollutant – micro- and mesoplastics. The aim is a task with global significance, small rivers connect to other rivers and eventually reach the sea serving as a vector, transporting pollution. Most of micro- and mesoplastic found in the sea has origin from terrestrial land. Within the project we will shed light on micro- and mesoplastic pollution in Arctic lakes and its accumulation processes (installing sediment traps during physical access in Sudurnes station, Iceland) and we will create an Artic rivers micro- and mesoplastic longitudinal (high to low and sub-Arctic) pollution gradient what can serve as a baseline data for future monitoring.

The project will mainly aim to understand the relations between GHG emissions (methane, Co2) active layer thickness and vegetation. To achieve this goal will be monitored 8 sites with different vegetation communities (4 types and 2 replicate for each) with different active layer conditions during a part of the winter season and along all the growing season. The relations between snow thickness, snow characteristics (density, temperature, thermal conductivity and moisture), active layer thermal and hygrometric regime and vegetation will be considered in order to understand their impact on the GHG emissions. In particular for analysing the role of the vegetation will be analysed also the phenology and the NEE of the different vegetation communities and for each target species its main traits (Leaf Area Index, leaf width, lenght, weight, Specific Leaf Area). Moreover the main characteristics of the soil (chemical and ohysical characteristics) and his microbiota will be analysed in different period of the year. In addition to the punctual observation in the 8 selected sites, vegetation mapping of a larger area and UaV imagery to define the apparent thermal inertia and other indices useful to define the thawing layer depth and the different vegetation and their phenology will be carried out to upscale the fluxes results of the selected sites. Finally to calibrate the apparent thermal inertia map and the vegetation map obtained through the remote sensing elettrical tomography investigation and field vegetation survey were realized.

The rapid pace of climate change in the Arctic is dramatically impacting permafrost-dominated watersheds. Understanding these systems' hydrological and biogeochemical responses to warming is critical for informing Arctic communities and ecosystems and constraining global carbon and water fluxes. This study aims to characterize the impact of seasonality and climate change on groundwater discharge and transport in rivers underlain by permafrost in the North Slope of Alaska. This study will utilize deuterium/hydrogen (dD) and oxygen-18/oxygen-16 (d18O) stable isotopic ratios of water and the dissolved uranium isotopic composition (234U/238U) to characterize hydrology and water-rock interaction time of streamwaters underlain by permafrost. This project will examine variations caused by seasonal permafrost thaw/freeze dynamics, as well as elucidate the source of groundwater discharge and assess major cation and trace metal release from permafrost thaw or the overlaying active layer. Fieldwork, conducted in close proximity to the Toolik Field Station, will involve collecting water samples in watershed drainages and monitoring active layer thickness throughout freeze and thaw seasons. This study employs a multi-faceted approach, including sediment flux measurements, isotopic analysis, and thaw depth monitoring. Results aim to demonstrate the utility of a coupled uranium and water isotope approach to characterizing climate-induced shifts in active layer deepening and permafrost-derived material transport in Arctic rivers.

soil carbon flux from tussock and moss

Overview: The Arctic is one of the most rapidly warming regions on Earth. Responses to this warming involve acceleration of processes common to other ecosystems around the world (e.g., shifts in plant community composition) and changes to processes unique to the Arctic (e.g., carbon loss from permafrost thaw). The objectives of the Arctic Long-Term Ecological Research (LTER) Project for 2017-2023 are to use the concepts of biogeochemical and community “openness” and “connectivity” to understand the re- sponses of arctic terrestrial and freshwater ecosystems to climate change and disturbance. These objec- tives will be met through continued long-term monitoring of changes in undisturbed terrestrial, stream, and lake ecosystems in the vicinity of Toolik Lake, Alaska, observations of the recovery of these ecosys- tems from natural and imposed disturbances, maintenance of existing long-term experiments, and initia- tion of new experimental manipulations. Based on these data, carbon and nutrient budgets and indices of species composition will be compiled for each component of the arctic landscape to compare the biogeo- chemistry and community dynamics of each ecosystem in relation to their responses to climate change and disturbance and to the propagation of those responses across the landscape.

Intellectual Merit: The research is organized around the concepts of ecosystem “openness” and land- scape “connectivity”: “Biogeochemical openness” is the degree to which ecosystems depend on external sources of nutrients and organic carbon versus nutrients recycled internally and organic carbon fixed lo- cally by photosynthesis. “Community openness” is the degree to which the movement of organisms in and out of the ecosystem determines community and trophic structure. Finally, “landscape connectivity” describes the nature and strength of interactions among ecosystem components and the resultant propaga- tion of ecological signals across the landscape. Components of the arctic landscape differ widely in bio- geochemical and community openness. The proposed research will compare key ecosystems of the Arc- tic to determine how their degree of openness governs their responses to climate change and acute dis- turbance such as fire and surface slumping associated with permafrost thaw. The proposed research will also determine how the responses to climate change and disturbance are mediated by landscape connec- tivity and the movement of nutrients, carbon, and organisms across arctic landscapes, and how that movement is facilitated or impeded by the degree of openness of the ecosystems.

Broader impacts: Historically, research by Arctic-LTER scientists has had broad impacts on the scien- tific community with over 35,000 citations of the 579 journal publications by Arctic LTER researchers and their collaborators since 1975 (currently ~ 10 citations per day). The 147 publications since 2010 have been cited ~2,500 times (currently ~ 2.5 citations per day). This impact will continue through publi- cations based on ongoing long-term and proposed research. The Arctic LTER actively fosters work by other researchers and their students and postdocs through access to data and encouragement to make measurements and conduct complementary studies in Arctic LTER long-term experiments. This openness is reflected in the number of top-quality assistant and associate researchers now affiliated with the Arctic LTER. The Arctic LTER will also continue to have broader impacts through education and outreach. These activities include: (i) a new schoolyard program that will engage K-12 students at Barrow, AK and K-12 teachers from both Barrow and the Environmental Literacy Program at Colorado State University, (ii) the Polar Hands-on Laboratory for journalists through the Logan Science Journalism Program at the Marine Biological Laboratory, (iii) courses in Arctic Ecology with Arctic LTER investigators serving as faculty, (iv) talks and short courses given by LTER researchers to Alaskan Native communities at Anak- tuvuk Pass, Kaktovik, and Barrow, (v) briefings to the US Bureau of Land Management, Arctic National Wildlife Refuge, Alaska Division of Natural Resources, Alaska Fish and Game, and North Slope Borough officials, (vi) serving on national and international advisory boards and panels, (vii) support of two stu- dents per year in the NSF REU program, plus providing opportunities for students on other projects to work on Arctic LTER sites and experiments, and (viii) graduate student participation in an open, annual meeting.

The MRI Collaborative’s Development of Monitors for Alaskan and Canadian Auroral Weather in Space (MACAWS) is a sensor web network that provides both real-time and historical Global Navigation Satellite System (GNSS) TEC and scintillation data products. This data is needed for geospace science and space weather monitoring in the currently unsampled or under-sampled auroral regions in North America (Alaska) and northwestern Canada. These regions are significant as they are the locations of origin for the majority of space weather events that affect the United States. Alaska is rapidly expanding in both commercial and DOD operations, and GNSS infrastructure is needed to aid in monitoring space weather events.

The Arctic (north of 65N) and boreal regions (between 45N and 65N) have undergone dramatic temperature and ecological changes over the past century and the rate of this change has accelerated in recent decades. Satellite observations of leaf area index (LAI) and normalized difference vegetation index (NDVI) suggest that northern high latitudes shows a significant trend of greening in the past three decades as a result of vegetation growth. A major unknown is how these changes will impact biosphere-atmosphere exchange and subsequently feedback on Arctic climate and air quality. Formaldehyde (HCHO) serves as an important indicator of biogenic volatile organic compound (VOC) emissions on regional and global scales. HCHO column abundance can now be observed from space by several satellite-based sensors including OMI on Aura (2004-), GOME-2 on MetOp-A (2006-) and MetOpB (2012-), OMPS on SUOMI-NPP (2011-) and JPSS-1 (2017-), and TROPOMI on Sentinel-5P (2017-). But there are large uncertainties and inconsistencies among these satellite sensors, due to instrument sensitivities, retrieval algorithms, timing of observation with respect to the diurnal cycle, and other factors. In this work, we use two ground-based instruments (Pandora and MAXDOAS for total column and vertical profiling, respectively), to provide validation of HCHO columns for these satellite sensors at northern high latitudes, with a major focus on boreal forest region. In collaboration with scientists from Harvard-Smithsonian Center for Astrophysics, we will establish a long-term record of HCHO column densities in Arctic and boreal region over the past twenty years. This will improve our understanding of biosphere-atmosphere exchange at high latitudes in past and future decades. Our main scientific questions include: 1. Do ground-based measurements of HCHO agree with satellite-based observations? If not, how can we use ground-based measurements of HCHO column densities to improve satellite-based retrievals? 2. Can we use ground-based and satellite-based measurements, together with chemical transport models, to estimate regional emissions of biogenic VOC in boreal and Arctic regions? 3. Is there a long-term trend of HCHO column density in boreal region as a result of Arctic greeningand warming? What is the impact of Arctic greening on air quality and atmospheric composition inArctic? By improving our understanding on biosphere-atmosphere exchange at northern high latitudes and their impact on climate and air quality, this work aims to make significant contributions to three key science questions in the Earth science program of Science Mission Directorate (SMD). They are: (1) How is the global Earth system changing? (2) What causes these changes in the Earth system? (3) How will the Earth system change in the future? This work aligns well with NASA Pandora project and related satellite remote sensing research at NASA Goddard Space Flight Center. The Pandora project and associated networks are priorities of the NASA Tropospheric Composition Program within the Earth Science Division (ESD) of the Science Mission Directorate (SMD). With NASA Pandora instrument, we will join NASA’s emerging Pandora Global Network (PGN) and expand PGN’s ability to integrate air quality data across a larger, more global scale for future satellite validation. This works aligns well with Alaska NASA EPSCoR’s research priority: "Monitoring of environmental change, mapping and remote sensing, and hazard prediction and mitigation." Given the lack of long-term observations in Arctic, we also hope to develop a long-term ground-based remote sensing site at UAF and surrounding areas in Alaska. Our ultimate goal is to make UAF a primary high-latitude gas and aerosol satellite validation site for NASA, ESA, and other space agencies.

The researchers' goal is to understand the influence of both environmental dynamics and increasing anthropogenic activity on the behavior and phenology of migratory caribou (Rangifer tarandus), waterfowl, and songbird communities in Arctic-boreal Alaska and northwestern Canada.

The goal of this project is to develop a new diagnostic for space accelerator experiments by using an ultra-sensitive camera on the ground to capture the light produced when the beam from a space accelerator hits the atmosphere. We have previously developed measurement techniques by observing the natural aurora from Poker Flat Research Range. Next, we will take advantage of the upcoming Beam PIE rocket launch in February/March 2022 to measure the light from a space accelerator for the first time. By showing that we can assess how an accelerator performs from the ground, we will develop a valuable diagnostic tool for future missions. Toolik Field Station is an ideal location for ground measurements of the Beam PIE rocket flight due to its location near the apogee of the rocket trajectory.

Pan-Arctic mosquito survey: investigating mosquito diversity and microbiomes in the Arctic

Intellectual merit: For approximately nine months of each year, the waters of arctic lakes are under ice. Although wind no longer acts directly on the water surface setting it in motion, the waters of arctic lakes are not still. Respiration occurs in the water column and within the sediments with rates temperature dependent. Classical studies have demonstrated circulation is induced by sediments heating the overlying water and by decomposition processes which create localized increases in salt content which further modify density. Gravity currents flow to deeper depths and an overall convective circulation results. The lower water column may become anoxic and green house gases accumulate. A large fraction of snow melt waters exits lakes without mixing. Spring heating induces vertical convective mixing.
Over the last several years we have collected a unique time series of under ice temperature and conductivity data from arctic lakes of different sizes. These data show departures and extensions of the classical picture described above which warrant further investigation both by analysis of the existing data and by studies which link the hydrodynamics under the ice, during melting, and just after ice off to biogeochemistry. Based on these observations, we hypothesize that lake morphometry and geological setting cause between lake differences in the magnitude of cryoconcentration, respiration and sediment temperatures and thus differences in resistance to the convective mixing induced by spring time heating with consequences for persistence of anoxia and evasion of green house gases. Internal waves contribute to mixing of snowmelt water with its high concentrations of CO2, labile organic matter, and nutrients so important for a lake’s productivity in spring and summer.
We propose time series studies to 1) quantify physical controls on under ice thermal structure and circulation, mixing of snow melt waters, mixing during spring and fall, 2) to quantify respiration rates in arctic lakes of differing morphology and on different geological substrates, and 3) to illustrate the linkages and feedbacks between these physical and biogeochemical processes. Measurements will include temperature and conductivity, meteorology, sediment temperatures, ice thickness, snow cover, and respiration with newly developed oxygen and pCO2 sensors. Winter limnological studies are rare, and rarer still in the Arctic with its harsh environment. The proposed research, with its goals of better understanding physical limnology under the ice and controls on winter respiration and spring time gas evasion will fill a major gap in limnological understanding of high latitude lakes.

Broader Impacts: The hydrodynamics of lakes influence biological and biogeochemical processes in a multitude of ways, yet the field of physical limnology is under-represented in the United States and the techniques and knowledge are not broadly disseminated. The proposed work will contribute to development of personnel with training in physical limnology and biogeochemistry as well as dissemination of conceptual knowledge, techniques, and computer software. Workshops will be conducted for graduate student training and overall results will extend the knowledge of sensors, sensor networks, climatic controls on lake physics, and winter respiration in arctic lakes.

Due to recent climate warming Arctic ecosystems experience more pronounced changes than others in various parts of the globe in recent decades. Observational studies document expansion of the some flora and fauna species. Especially visible is expansion of shrub communities (e.g. birch, willow, and alder), that are increasing in cover and height. Thanks to the presence of peat forming species and accumulation of the peat layers, peatlands in the Arctic are important archives of palaeoenvironmental data, that took place over last thousends years. Reconstruction of the past environmental changes is possible thanks to application of the multi-proxy detailed long-term palaeoecological studies of permafrost peatlands. They allow to improve our understanding of relationships between plant populations and climate, pollution, fire, and hydrology, with implications for elucidating the response of high-latitude vegetation to climate warming that were documented during Late Holocene. In our paleoecological studies we focus on the late Holocene (the last ca. 5000 years) because this period contains several phases of marked climate change. During the time covered in this study, warm periods such as the Roman Period and Medieval Climate Anomaly and recent warming were separated by cold intervals (2.8 kyr event, Migration Period and the Little Ice Age). Our study area is located in Arctic zone in northern Alaska, from the northern foothills of the Brooks Range, toward Prudhoe Bay. In this project we plan work to conduct the first comprehensive multiproxy late Holocene palaeoecological studies (plant macrofossils, pollen, non-pollen palinomorps, testate amoebae, charcoal, and geochemics) supported by detailed radiocarbon and lead dating on 14 peat monoliths, taken at 10 sites, represent various peatland habitats (e.g. bog, poor fen, rich fen) in one region in order to examine the temporal and spatial vegetation structure in this poorly researched area. We want to reconstruct the local vegetation changes since peatland initiation or permafrost layer and explore the relationship among the different species. In addition we want to evaluate the relative importance of regional climate, impact of potential long-distant air pollution, dust and fire and local autogenic succession in the development of the peatlands and plants ococuring there along a small-scale continental gradient. We postulate that some of plant communities respond to this factors. However, some of plant population developed in peatlands ecossytems can be resistant to climate changes and plant succession remain unchanged over thousand years. Our temporal perspective, multiproxy long-term approach, and high resolution, contiguous sampling approach allows the identification of the time of the appearance, expansion, and retraction of local plant taxa. Due to detailed paleobotanical studies we will be able to create a model of the plan succession in this region to species level. Understanding how these organisms may respond to conditions projected by climate models is important for understanding the future of petland ecosystems in the Arctic zone. By analysis peat monoliths from Alaska and gathering valuable paleodata about plant succession in this region, we will have the opportunity for intercontinental comparison of artic vegetation development and determine similarities and differences in the vegetation responses to climatic changes in N America, Europe, and Asia.

The climate sensitivity of tundra shrub growth is germane to future ecosystem function in the rapidly warming tundra biome. To better understand the climate sensitivity of xylogenesis and radial growth of upright tundra shrubs in this environment, we propose to study the quantitative wood anatomy (QWA) of three species of Arctic shrubs growing around the Toolik Lake Research Area (Salix alaxensis, Salix lanata, and Betula nana). This work will quantify a time series of wood morphology on the cellular level to detail how sensitive the rate and morphology of shrub growth is to inter- and intra-annual climate fluctuations over the past 30 years. Specifically, we want to know if the window of growth sensitivity tends to expand during relatively long growing seasons and determine how tundra shrubs respond to summer dry periods. Our results will contribute to tundra vegetation models that seek to forecast how warming temperatures will impact shrub expansion and carbon sequestration in the future. This project is intended to obtain preliminary data to be used for a larger proposal in the future.

The proposed research develops capacity for the remote estimation of aboveground and belowground plant functional traits and streamlines their inclusion in process models to quantify and predict regional C balance. Specifically, we will characterize directly observable plant functional traits from remotely sensed data; predict non-observable (e.g., belowground) traits by leveraging trait-environment relationships and trait covariation; and integrate this information into a newly developed modeling framework to quantify and predict terrestrial C stocks, fluxes, and their uncertainties in the Alaskan tundra. We will test four hypotheses: (1) Plant functional traits are predominantly shaped by climate, with local soil moisture moderating trait response to climate, but optimal trait values for a given environment depend on community type because plant functional types (PFTs) have different sensitivities to altered resources associated with climate warming. (2) Trait dispersion depends on environmental stress; where environmental conditions are more favorable for growth, there is greater variation in traits and overall greater trait diversity; (3) Given trait tradeoffs and trait-environment interactions, root traits are predictable from leaf and size traits, climate and soil factors; and (4) Variation in traits affect Arctic C balance. Leaf traits as they relate to photosynthetic parameters will have the strongest effects on C uptake. Root traits will exhibit fewer direct effects on C uptake but will be important in supporting nutrient uptake that then influences C uptake. To test these hypotheses, we will study the variation in plant traits across the major tundra vegetation communities present along local soil gradients nested within a macroclimate gradient in northern Alaska, quantifying trait-environment relationships and trait covariation at the community- and PFT-levels. Using machine-learning approaches, we will integrate ground-based measurements with information derived from multi-scale remote sensing platforms from drone, hypertemporal, LiDAR, and hyperspectral imagery to produce maps of leaf, size and root traits, greatly expanding the trait information available for modelers. We will use Bayesian data-model fusion methods to improve the parameterization and formulation of the Terrestrial Ecosystem Model, which is widely used in Arctic carbon studies, and perform simulation experiments to evaluate how differences in plant functional traits affect C dynamics. To synergize the trait-based modeling community, we will create a workshop to share findings and strategies for improving the representation of trait variation in ecosystem and Earth System Models (ESMs).

Across the Arctic and sub-arctic, permafrost degradation has been reshaping and modifying northern ecosystems through substantial changes in soil water content, soil nutrient availability, oxidation-reduction environment, and vegetation succession. While natural variations in air temperature throughout the year are expected in any given ecosystem, unprecedented warming as a result of climate change is adding rapid spatial and temporal change to the already highly heterogeneous system. Our main research objectives are to (1) identify the soil properties that are impacted to the greatest extent by an altered thermal regime, (2) quantify the level of variance between soil types and within heterogeneous watersheds, and (3) assess how that variability can be best transformed into predictability for improved terrain characteristic estimations.

Our overarching goal is to understand, quantify and model the current and future impact of herbivores on the carbon and nutrient dynamics in tundra ecosystems. We focus on the most abundant and therefore important herbivores, small rodents (voles and lemmings), in the Alaskan arctic tundra. 

This project will measure winds at ~250 km altitude in Earth’s auroral thermosphere. Although such winds have been observed for decades using various methods, they remain poorly understood, especially at spatial scales spanning ~100 km or less. Limited wind data is now widely recognized as one of the major obstacles impeding further progress in accurate modeling of weather phenomena at these heights. To “zoom in” on small-scale flow structures, seven Fabry-Perot spectrometers now in Alaska will be configured to monitor thermospheric temperatures and wind vectors at hundreds of separate sampling locations across our study area. The array will produce two dimensional maps of temperatures and 3-component vector winds, with a spatial resolution of around 80 km, a temporal cadence of a few minutes, and with absolute measurement accuracies of around 5 m/s in wind and 10 Kelvins in temperature. Continuous observing runs lasting up to ~16 hours will be possible near mid-winter. No previous thermospheric wind and temperature observations have ever achieved this level of detail and fidelity. Nevertheless, the observations that do currently exist lead us to the following overarching hypothesis motivating this proposal: “Eddies and waves at horizontal length scales of ~100 km or less are important contributors to the dynamics of Earths auroral thermosphere and, although individual motions are not important at these scales, their cumulative impact is – both for the basic physics of the thermosphere and for operational prediction of its weather.” The proposed observing campaigns will be used to test this hypothesis, by determining whether such small scale motions actually do play a meaningful role in thermospheric dynamics.

Response of populations of tundra plants to climate change

The U.S. Climate Reference Network (USCRN) is a systematic and sustained network of climate monitoring stations with sites across the conterminous U.S. (114 stations), Alaska (19 stations installed, with up to 29 by 2022), and Hawaii (2 stations). These stations use high-quality instruments to measure temperature, precipitation, wind speed, soil conditions, and more. Information is available on what is measured and the USCRN station instruments. The vision of the USCRN program is to provide a continuous series of climate observations for monitoring trends in the nation's climate and supporting climate-impact research.

This project encompasses Ruby's PhD dissertation research explorations. The main goals are to collect preliminary phenological data, test experimental methods, and scout locations for potential future experimental manipulations in Summer 2022. Specifically, (1) how do early and late season environmental fluctuations influence growing season dynamics? (2) does fall warming and increased shrub abundance allow for the expansion/invasion of plant pathogens and parasites? (3) pilot potential "growing season length" manipulation techniques. Methods aim to leverage existing Arctic LTER experimental infrastructure (greenhouses & shadehouses) and historic observational plots.