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Sample records for arctic ecosystem final

  1. Carbon and nitrogen isotope studies in an arctic ecosystem. Final report

    SciTech Connect

    Schell, D.M.

    1994-06-01

    The dynamics of carbon fixation and storage in tundra soils has received considerable attention with respect to global carbon cycling. Recent findings by investigators using chamber measurements of fixation/respiration rates in arctic tundra have led to the conclusion that tundra is no longer storing carbon but is instead a source of carbon dioxide to the atmosphere. The author has sought to test these conclusions and to determine methods by which the long-term accumulation or loss of carbon in tundra can be determined. Little is known, however, of the processes that control storage and the current rates of carbon fixation and peat formation in arctic Alaska. This project focused on several aspects of carbon dynamics and the roles of decomposition and herbivory at the DOE research site at Imnavait Creek, Alaska. Through the use of natural abundance stable and radioisotope techniques, several conclusions emerged. Peat carbon continues to accumulate in wetter areas of foothill valleys and on the coastal plain of arctic Alaska. Radiocarbon profiles of bomb {sup 14}C were used to date layers of vegetation and litter to obtain decomposition rates and to extrapolate these values to intersection with the permafrost horizon where further decomposition is assumed to cease. Carbon storage in riparian moss at Imnavait Creek was estimated at 3 g C/m{sup 2}-yr. Profiles of {sup 137}Cs closely matched those of {sup 14}C and may provide a more expeditious means of assessing recent carbon accumulation rates in tundra. Carbon and nitrogen stable isotope ratios in tundra vegetation vary markedly over hydrologic gradients in apparent response to changing growth rates and sources of nitrogenous nutrients. Within a taxon, {delta}{sup 15}N values varied by several {per_thousand} over a tens of meters distance.

  2. Changing Arctic ecosystems: ecology of loons in a changing Arctic

    USGS Publications Warehouse

    Uher-Koch, Brian; Schmutz, Joel; Whalen, Mary; Pearce, John M.

    2014-01-01

    The U.S. Geological Survey (USGS) Changing Arctic Ecosystems (CAE) initiative informs key resource management decisions for Arctic Alaska by providing scientific information on current and future ecosystem response to a changing climate. From 2010 to 2014, a key study area for the USGS CAE initiative has been the Arctic Coastal Plain of northern Alaska. This region has experienced rapid warming during the past 30 years, leading to the thawing of permafrost and changes to lake and river systems. These changes, and projections of continued change, have raised questions about effects on wildlife populations that rely on northern lake ecosystems, such as loons. Loons rely on freshwater lakes for nesting habitat and the fish and invertebrates inhabiting the lakes for food. Loons live within the National Petroleum Reserve-Alaska (NPR-A) on Alaska’s northern coast, where oil and gas development is expected to increase. Research by the USGS examines how breeding loons use the Arctic lake ecosystem and the capacity of loons to adapt to future landscape change.

  3. [Energy flow in arctic aquatic ecosystems

    SciTech Connect

    Schell, D.M.

    1985-12-31

    This study is aimed at determining the major pathways of energy flow in freshwater ecosystems of the Alaskan arctic coastal plain. Selected sites for study of the processes supplying energy to streams and lakes to verify the generality of past findings will be surveyed for collection of organisms including the Colville River drainage and the lake region around Teshekpuk Lake. Specific objectives are to collect food web apex organisms (fish and birds) from a variety of sites in the coastal plain to verify descriptive models of ecosystem structure and food web pathways and to compare the utilization rates by insect larvae of fresh litter and in situ primary production relative to more refractory peaty materials through seasonal sampling for isotopic analysis.

  4. [Energy flow in arctic aquatic ecosystems

    SciTech Connect

    Schell, D.M.

    1985-01-01

    This study is aimed at determining the major pathways of energy flow in freshwater ecosystems of the Alaskan arctic coastal plain. Selected sites for study of the processes supplying energy to streams and lakes to verify the generality of past findings will be surveyed for collection of organisms including the Colville River drainage and the lake region around Teshekpuk Lake. Specific objectives are to collect food web apex organisms (fish and birds) from a variety of sites in the coastal plain to verify descriptive models of ecosystem structure and food web pathways and to compare the utilization rates by insect larvae of fresh litter and in situ primary production relative to more refractory peaty materials through seasonal sampling for isotopic analysis.

  5. Changing Arctic ecosystems--research to understand and project changes in marine and terrestrial ecosystems of the Arctic

    USGS Publications Warehouse

    Geiselman, Joy; DeGange, Anthony R.; Oakley, Karen; Derksen, Dirk; Whalen, Mary

    2012-01-01

    Ecosystems and their wildlife communities are not static; they change and evolve over time due to numerous intrinsic and extrinsic factors. A period of rapid change is occurring in the Arctic for which our current understanding of potential ecosystem and wildlife responses is limited. Changes to the physical environment include warming temperatures, diminishing sea ice, increasing coastal erosion, deteriorating permafrost, and changing water regimes. These changes influence biological communities and the ways in which human communities interact with them. Through the new initiative Changing Arctic Ecosystems (CAE) the U.S. Geological Survey (USGS) strives to (1) understand the potential suite of wildlife population responses to these physical changes to inform key resource management decisions such as those related to the Endangered Species Act, and (2) provide unique insights into how Arctic ecosystems are responding under new stressors. Our studies examine how and why changes in the ice-dominated ecosystems of the Arctic are affecting wildlife and will provide a better foundation for understanding the degree and manner in which wildlife species respond and adapt to rapid environmental change. Changes to Arctic ecosystems will be felt broadly because the Arctic is a production zone for hundreds of species that migrate south for the winter. The CAE initiative includes three major research themes that span Arctic ice-dominated ecosystems and that are structured to identify and understand the linkages between physical processes, ecosystems, and wildlife populations. The USGS is applying knowledge-based modeling structures such as Bayesian Networks to integrate the work.

  6. The Northern Bering Sea: An Arctic Ecosystem in Change

    NASA Astrophysics Data System (ADS)

    Grebmeier, J. M.; Cooper, L. W.

    2004-12-01

    Arctic systems can be rich and diverse habitats for marine life in spite of the extreme cold environment. Benthic faunal populations and associated biogeochemical cycling processes are influenced by sea-ice extent, seawater hydrography (nutrients, salinity, temperature, currents), and water column production. Benthic organisms on the Arctic shelves and margins are long-term integrators of overlying water column processes. Because these organisms have adapted to living at cold extremes, it is reasonable to expect that these communities will be among the most susceptible to climate warming. Recent observations show that Arctic sea ice in the North American Arctic is melting and retreating northward earlier in the season and the timing of these events can have dramatic impacts on the biological system. Changes in overlying primary production, pelagic-benthic coupling, and benthic production and community structure can have cascading effects to higher trophic levels, particularly benthic feeders such as walruses, gray whales, and diving seaducks. Recent indicators of contemporary Arctic change in the northern Bering Sea include seawater warming and reduction in ice extent that coincide with our time-series studies of benthic clam population declines in the shallow northern Bering shelf in the 1990's. In addition, declines in benthic amphipod populations have also likely influenced the movement of feeding gray whales to areas north of Bering Strait during this same time period. Finally a potential consequence of seawater warming and reduced ice extent in the northern Bering Sea could be the northward movement of bottom feeding fish currently in the southern Bering Sea that prey on benthic fauna. This would increase the feeding pressure on the benthic prey base and enhance competition for this food source for benthic-feeding marine mammals and seabirds. This presentation will outline recent biological changes observed in the northern Bering Sea ecosystem as documented in

  7. Climate change on arctic environment, ecosystem services and society (CLICHE)

    NASA Astrophysics Data System (ADS)

    Weckström, J.; Korhola, A.; Väliranta, M.; Seppä, H.; Luoto, M.; Tuittila, E.-S.; Leppäranta, M.; Kahilainen, K.; Saarinen, J.; Heikkinen, H.

    2012-04-01

    The predicted climate warming has raised many questions and concerns about its impacts on the environment and society. As a respond to the need of holistic studies comprising both of these areas, The Academy of Finland launched The Finnish Research Programme on Climate Change (FICCA 2011-2014) in spring 2010 with the main aim to focus on the interaction between the environment and society. Ultimately 11 national consortium projects were funded (total budget 12 million EUR). Here we shortly present the main objectives of the largest consortium project "Climate change on arctic environment, ecosystem services and society" (CLICHE). The CLICHE consortium comprises eight interrelated work packages (treeline, diversity, peatlands, snow, lakes, fish, tourism, and traditional livelihoods), each led by a prominent research group and a team leader. The research consortium has three main overall objectives: 1) Investigate, map and model the past, present and future climate change-induced changes in central ecosystems of the European Arctic with unprecedented precision 2) Deepen our understanding of the basic principles of ecosystem and social resilience and dynamics; identify key taxa, structures or processes that clearly indicate impending or realised global change through their loss, occurrence or behaviour, using analogues from the past (e.g. Holocene Thermal Maximum, Medieval Warm Period), experiments, observations and models 3) Develop adaptation and mitigation strategies to minimize the adverse effects of climate change on local communities, traditional livelihoods, fisheries, and tourism industry, and promote sustainable development of local community structures and enhance the quality of life of local human populations. As the project has started only recently no final results are available yet. However, the fieldwork as well as the co-operation between the research teams has thus far been very successful. Thus, the expectations for the final outcome of the project

  8. Observation Platforms and Data Streams of the Arctic Next Generation Ecosystem Experiment (NGEE-Arctic)

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.; Wullschleger, S. D.; Graham, D. E.; Hubbard, S. S.; Norby, R. J.; Rogers, A.; Torn, M. S.; Wilson, C. J.

    2013-12-01

    The goal of the Arctic Next Generation Ecosystem Experiment (NGEE-Arctic) is to deliver a process-rich ecosystem model, extending from bedrock to the top of the vegetative canopy, in which the evolution of Arctic ecosystems in a changing climate can be modeled at the scale of a high resolution Earth System Model grid cell. Increasing our confidence in climate projections for high-latitude regions of the world requires a coordinated set of observation platforms that target improved process understanding and model representation of important ecosystem-climate feedbacks. The Next-Generation Ecosystem Experiments (NGEE Arctic) seeks to address this challenge by quantifying the physical, chemical, and biological behavior of terrestrial ecosystems in Alaska. Initial research has focused upon the highly dynamic landscapes of the North Slope (Barrow, Alaska) where thaw lakes, drained thaw lake basins, and ice-rich polygonal ground offer distinct land units for investigation and modeling. This vision includes mechanistic studies in the field and in the laboratory; modeling of critical and interrelated water, nitrogen, carbon, and energy dynamics; and characterization of important interactions from molecular to landscape scales that drive feedbacks to the climate system. To complete these investigations, an integrated program of field monitoring has been initiated. These include observations of meteorological, hydrological, ecological and geophysical processes. These data streams are intended to supplement and extend existing polar data sets to advance our understanding of the Arctic environment and its response to a rapidly changing climate.

  9. Mercury bioaccumulation and biomagnification in a small Arctic polynya ecosystem.

    PubMed

    Clayden, Meredith G; Arsenault, Lilianne M; Kidd, Karen A; O'Driscoll, Nelson J; Mallory, Mark L

    2015-03-15

    Recurring polynyas are important areas of biological productivity and feeding grounds for seabirds and mammals in the Arctic marine environment. In this study, we examined food web structure (using carbon and nitrogen isotopes, δ(13)C and δ(15)N) and mercury (Hg) bioaccumulation and biomagnification in a small recurring polynya ecosystem near Nasaruvaalik Island (Nunavut, Canada). Methyl Hg (MeHg) concentrations increased by more than 50-fold from copepods (Calanus hyperboreus) to Arctic terns (Sterna paradisaea), the abundant predators at this site. The biomagnification of MeHg through members of the food web - using the slope of log MeHg versus δ(15)N - was 0.157 from copepods (C. hyperboreus) to fish. This slope was higher (0.267) when seabird chicks were included in the analyses. Collectively, our results indicate that MeHg biomagnification is occurring in this small polynya and that its trophic transfer is at the lower end of the range of estimates from other Arctic marine ecosystems. In addition, we measured Hg concentrations in some poorly studied members of Arctic marine food webs [e.g. Arctic alligatorfish (Ulcina olrikii) and jellyfish, Medusozoa], and found that MeHg concentrations in jellyfish were lower than expected given their trophic position. Overall, these findings provide fundamental information about food web structure and mercury contamination in a small Arctic polynya, which will inform future research in such ecosystems and provide a baseline against which to assess changes over time resulting from environmental disturbance. PMID:25149682

  10. Modeling evapotranspiration in Arctic coastal plain ecosystems using a modified BIOME-BGC model

    NASA Astrophysics Data System (ADS)

    Engstrom, Ryan; Hope, Allen; Kwon, Hyojung; Harazono, Yoshinobu; Mano, Masayoshi; Oechel, Walter

    2006-06-01

    Modeling evapotranspiration (ET) in Arctic coastal plain ecosystems is challenging owing to the unique conditions present in this environment, including permafrost, nonvascular vegetation, and a large standing dead vegetation component. In this study the ecosystem process model, BIOME-BGC, was adapted to represent these unique conditions in Arctic ecosystems by including a new water storage and evaporation routine that accounts for nonvascular vegetation and the effects of permafrost, adding ground heat flux as an input, and representing ground shading by dead vegetation. The new Arctic version and the original BIOME-BGC models are compared to observed ET from two eddy flux towers in Barrow, Alaska over four summer seasons (1999-2002). The two towers are located less than 1 km apart, yet represent contrasting moisture conditions. One is located in a drained thaw lake, marsh area, while the other is located in a drier, upland area characterized by mesic tundra. Results indicate that the original BIOME-BGC model substantially underestimated ET, while the Arctic version slightly overestimated ET at both sites. The new Arctic model version worked particularly well at the wet tower because the model was able to capture energy limitations better than water limitations. Errors in the simulation of snowmelt date led to errors in the ET estimates at both sites. Finally, the substantial differences in soil moisture led to substantially different ET rates between the sites that were difficult to simulate and indicates that soil moisture heterogeneity is a strong controller on ET in these ecosystems.

  11. A new way to study the changing Arctic ecosystem

    SciTech Connect

    Hubbard, Susan

    2011-01-01

    Berkeley Lab scientists Susan Hubbard and Margaret Torn discuss the proposed Next Generation Ecosystem Experiment, which is designed to answer one of the most urgent questions facing researchers today: How will a changing climate impact the Arctic, and how will this in turn impact the planet's climate? More info: http://newscenter.lbl.gov/feature-stories/2011/09/14/alaska-climate-change/

  12. A new way to study the changing Arctic ecosystem

    ScienceCinema

    Hubbard, Susan

    2013-05-29

    Berkeley Lab scientists Susan Hubbard and Margaret Torn discuss the proposed Next Generation Ecosystem Experiment, which is designed to answer one of the most urgent questions facing researchers today: How will a changing climate impact the Arctic, and how will this in turn impact the planet's climate? More info: http://newscenter.lbl.gov/feature-stories/2011/09/14/alaska-climate-change/

  13. Communicating Climate and Ecosystem Change in the Arctic

    NASA Astrophysics Data System (ADS)

    Soreide, N. N.; Overland, J. E.; Calder, J. A.; Rodionov, S.

    2005-12-01

    There is an explosion of interest in Northern Hemisphere climate, highlighting the importance of recent changes in the Arctic on mid-latitude climate and its impact on marine and terrestrial ecosystems. Traditional sea ice and tundra dominated arctic ecosystems are being reorganizing into warmer sub-arctic ecosystem types. Over the previous two years we have developed a comprehensive, near real-time arctic change detection protocol to track physical and biological changes for presentation on the web: http://www.arctic.noaa.gov/detect. The effort provides a continuous update to the Arctic Climate Impact Assessment (ACIA) Report, released in November 2004. Principles for the protocol include an accessible narrative style, scientifically credible and objective indicators, notes multiple uses for the information, acknowledges uncertainties, and balances having too many indicators-which leads to information overload-and too few-which does not capture the complexity of the system. Screening criteria include concreteness, public awareness, being understandable, availability of historical time series, and sensitivity. The site provides sufficient information for an individual to make their own assessment regarding the balance of the evidence for tracking change. The product provides an overview, recent news, links to many arctic websites, and highlights climate, global impacts, land and marine ecosystems, and human consequences. Since its inception a year ago, it has averaged about 9000 hits an day on the web, and is a major information source as determined by Google search. The future direction focuses on understanding the causes for change. In spring 2005 we also presented a near real-time ecological and climatic surveillance website for the Bering Sea: www.beringclimate.noaa.gov. The site provides up-to-date information which ties northward shifts of fish, invertebrate and marine mammal populations to physical changes in the Arctic. This site is more technical than the

  14. Crossing the final ecological threshold in high Arctic ponds.

    PubMed

    Smol, John P; Douglas, Marianne S V

    2007-07-24

    A characteristic feature of most Arctic regions is the many shallow ponds that dot the landscape. These surface waters are often hotspots of biodiversity and production for microorganisms, plants, and animals in this otherwise extreme terrestrial environment. However, shallow ponds are also especially susceptible to the effects of climatic changes because of their relatively low water volumes and high surface area to depth ratios. Here, we describe our findings that some high Arctic ponds, which paleolimnological data indicate have been permanent water bodies for millennia, are now completely drying during the polar summer. By comparing recent pond water specific conductance values to similar measurements made in the 1980s, we link the disappearance of the ponds to increased evaporation/precipitation ratios, probably associated with climatic warming. The final ecological threshold for these aquatic ecosystems has now been crossed: complete desiccation. PMID:17606917

  15. Crossing the final ecological threshold in high Arctic ponds

    PubMed Central

    Smol, John P.; Douglas, Marianne S. V.

    2007-01-01

    A characteristic feature of most Arctic regions is the many shallow ponds that dot the landscape. These surface waters are often hotspots of biodiversity and production for microorganisms, plants, and animals in this otherwise extreme terrestrial environment. However, shallow ponds are also especially susceptible to the effects of climatic changes because of their relatively low water volumes and high surface area to depth ratios. Here, we describe our findings that some high Arctic ponds, which paleolimnological data indicate have been permanent water bodies for millennia, are now completely drying during the polar summer. By comparing recent pond water specific conductance values to similar measurements made in the 1980s, we link the disappearance of the ponds to increased evaporation/precipitation ratios, probably associated with climatic warming. The final ecological threshold for these aquatic ecosystems has now been crossed: complete desiccation. PMID:17606917

  16. Energy flow in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1988-12-31

    Natural isotope abundances to trace major pathways of energy flow to consumers in Imnavait Creek and the tundra ecosystem of the R4D watershed with comparative work in the coastal tundra. Our overall goals are to a determine if carbon is accumulating in upland and coastal tundra; determine the role of eroded peat carbon in the aquatic ecosystem; and to determine the distribution of carbon and nitrogen isotopes in the tundra-pond ecosystem to establish the feasibility of using natural differences as tracers. Past work on fishes, birds, and the prey species of insects and aquatic crustaceans has shown that peat carbon is very important in the energy supply supporting the food webs over the course of the year. Obligate freshwater fishes from the coastal lakes and Colville River have been shown to contain up to 60 percent peat carbon at the end of the winter season. In contrast, migratory shorebirds and passerines contained much smaller radiocarbon abundances in summer, indicating a major shift to recent in situ primary production in pond and stream ecosystems in summer months. For the past two years, we have narrowed our focus to the processes supplying carbon to the beaded stream system at MS-117 and have concentrated on determining the transfer and accumulation rates of carbon in the watershed.

  17. Using digital photos and models to analyze episodic winter snowmelt events in low-Arctic ecosystems

    NASA Astrophysics Data System (ADS)

    Pedersen, S. H.; Tamstorf, M. P.; Westergaard-Nielsen, A.; Liston, G. E.; Schmidt, N. M.

    2013-12-01

    Terrestrial snow cover is a key parameter controlling both abiotic and biotic ecosystem processes in the Arctic. Yet knowledge and observations of snow cover in Greenland are limited. However, one exception is Kobbefjord (64°07'N, 51°21'W) in West Greenland. Since 2007, Nuuk Ecological Research Operations (NERO), led by Greenland Ecosystem Monitoring, have run an ecosystem baseline monitoring program responsible for collecting extensive snow observation datasets using manual, automated, and remotely-sensed methods. The available snow datasets provide a unique opportunity to describe and analyze the spatial and temporal distribution of snow-cover features and interactions in a low-Arctic setting where snow-dependent ecosystem components and processes are also observed. The aim of this study is to understand the temporal and spatial snow evolution in a low-Arctic ecosystem where a range of validation data is available, with a particular emphasis on infrequent winter snowmelt events. Extreme winter melt events associated with air temperatures rising abruptly to above 0.0 °C and with wind speeds greater than 20 m/s have been observed. We identified these melt events and quantified their effect on the snowpack and water balance to address possible consequences for a range of biological parameters. Finally, we compared the inter-annual air temperature variation during the last five years (2007-2013) with a 119-year climate record to place these recent variations within a long-term climate perspective. We implemented a spatially distributed snow-evolution modeling system (SnowModel) to provide temporal and spatial descriptions of snow within the study area from 2007 through 2013. SnowModel was driven by climate data collected by NERO. The available snow observations enabled validation of the modeled snow depth through 1) independent manual and automated snow depth measurements, and 2) a spatial validation of the modeled snow cover depletion through snow classification

  18. Improved Climate Prediction through a System Level Understanding of Arctic Terrestrial Ecosystems: Next Generation Ecosystem Experiments (NGEE-Arctic)*

    NASA Astrophysics Data System (ADS)

    Hubbard, S. S.; Graham, D. E.; Hinzman, L. D.; Liang, L.; Liljedahl, A.; Norby, R. J.; Rogers, A.; Rowland, J. C.; Thornton, P. E.; Torn, M. S.; Riley, W. J.; Wilson, C. J.; Wullschleger, S. D.

    2013-12-01

    Characterized by vast amounts of carbon stored in permafrost and a rapidly evolving landscape, the Arctic has emerged as an important focal point for the study of climate change. Although recognized as an ecosystem highly vulnerable to climate change, mechanisms that govern feedbacks between the terrestrial and climate system are not well understood. Increasing our confidence in climate projections for high-latitude regions of the world requires coordinated investigations that target improved process understanding and model representation of important ecosystem-climate feedbacks. The Next-Generation Ecosystem Experiments (NGEE-Arctic) seeks to address this challenge by quantifying the physical, chemical, and biological behavior of terrestrial ecosystems in Alaska. The NGEE-Arctic project is a large, multi-disciplinary activity sponsored by the Department of Energy, Office of Science. Recent NGEE-Arctic research has focused on the highly dynamic landscapes of the North Slope Arctic tundra where thaw lakes, drained thaw lake basins, and ice-rich polygonal ground offer distinct land units for investigation and modeling. The project is working on the Barrow Environmental Observatory to study interactions that drive critical climate feedbacks within these environments through greenhouse gas fluxes and changes in surface energy balance associated with permafrost degradation and the many other processes that arise as a result of these landscape dynamics. Ongoing are mechanistic studies in the field and in the laboratory; modeling of critical and interrelated water, nitrogen, carbon, and energy dynamics; and characterization of important interactions from molecular to landscape scales that drive feedbacks to the climate system. A suite of climate-, intermediate- and fine-scale models are being used to guide observations and interpret data, while characterization information and process studies serve to initialize state variables in models, provide new algorithms and

  19. Alaska's Arctic Landscapes: Land cover, Monitoring and Assessing Arctic Ecosystems and their Change Agents

    NASA Astrophysics Data System (ADS)

    Guyer, P. S.

    2013-12-01

    The challenge for agencies who manage the 89,000 square miles constituting Alaska's arctic ecoregion is in understanding what, where and to what extent important ecosystems exist. How do each of these ecosystems function? What are the key components of these ecosystems? How are they affected by the changing climate, fire, permafrost changes and development? Answers to these management questions come not from one specific project or program but from a series of data gathering efforts. Landcover mapping of Alaska's arctic using satellite imagery began in the mid 1990's. Over the past three years the land cover has been updated using additional ground truth data and the most up to date image processing software. In 2012, the updated map was used for the first time to select sites for an inventory and monitoring pilot project. The project established a baseline of information for long-term monitoring of regional ecological components. That same year the Bureau of Land Management began a Rapid Ecoregional Assessment across the North Slope of Alaska. This effort will utilize the known environments established by the land cover map and will model the effects of climate change, fire, permafrost change and development. The assessment and modeling effort will show how the effect of these change agents would shape long term conservation, restoration and development efforts. These interactions together will advance the understanding of the arctic ecoregion its values, processes and functions and how the agents of change will shape the future.

  20. Satellite Monitoring of Disturbances in Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Prieto-Blanco, A.; Disney, M.; Lewis, P.

    2008-12-01

    We explored the capability of satellite remote sensing to detect temporal changes in northern Fennoscandian regions through the application of a temporal model of surface bidirectional reflectance. Remote sensing offers the potential to monitor changes over large areas and at hard to access locations. Specifically in remote Arctic locations, where ground surveys and aircraft observations are constrained by weather conditions and logistics, remote sensing provides a unique capability for repetitive and frequent sampling. A major disturbance in mountain birch forests typical of northern Sweden and Finland is caused by outbreaks of defoliating insects such as the autumn moth (Epirrita autumnata) and the winter moth (Operophtera brumata). These outbreaks occur more or less cyclically every 9-10 years and attack mainly birch (Betula spp.) leaving a mosaic of open woodland within the forest. It is expected that global warming will affect the incidence and the intensity of this outbreaks. The ecological and economical consequences can be severe hence the importance of close monitoring of shifts in the distribution of events. Defoliated areas of up to 6000 to 7000 ha of birch forest have been reported. Severely affected areas could potentially be detected by satellite providing valuable data to understand the behavior, estimate the damage and predict the development of forest pests. Quantification of the impact of such outbreaks will also permit far more accurate estimation of the terrestrial carbon budget of such regions. Here we applied a generic algorithm to detect sudden changes on land surface cover to daily 500m MODIS surface reflectance data over the Fennoscandian area. Moderate Resolution Imaging Spectraradiometer (MODIS) sensors on board the polar orbiting satellites Terra and Aqua provide an overpass at least once a day over the area of interest. Unfortunately, frequent cloud cover limits the acquisition of satellite imagery and persistent cloud cover may

  1. Changing seasonality of Arctic hydrology disrupts key biotic linkages in Arctic aquatic ecosystems.

    NASA Astrophysics Data System (ADS)

    Deegan, L.; MacKenzie, C.; Peterson, B. J.; Fishscape Project

    2011-12-01

    Arctic grayling (Thymallus arcticus) is an important circumpolar species that provide a model system for understanding the impacts of changing seasonality on arctic ecosystem function. Grayling serve as food for other biota, including lake trout, birds and humans, and act as top-down controls in stream ecosystems. In Arctic tundra streams, grayling spend their summers in streams but are obligated to move back into deep overwintering lakes in the fall. Climatic change that affects the seasonality of river hydrology could have a significant impact on grayling populations: grayling may leave overwintering lakes sooner in the spring and return later in the fall due to a longer open water season, but the migration could be disrupted by drought due to increased variability in discharge. In turn, a shorter overwintering season may impact lake trout dynamics in the lakes, which may rely on the seasonal inputs of stream nutrients in the form of migrating grayling into these oligotrophic lakes. To assess how shifting seasonality of Arctic river hydrology may disrupt key trophic linkages within and between lake and stream components of watersheds on the North Slope of the Brooks Mountain Range, Alaska, we have undertaken new work on grayling and lake trout population and food web dynamics. We use Passive Integrated Transponder (PIT) tags coupled with stream-width antenna units to monitor grayling movement across Arctic tundra watersheds during the summer, and into overwintering habitat in the fall. Results indicate that day length may prime grayling migration readiness, but that flooding events are likely the cue grayling use to initiate migration in to overwintering lakes. Many fish used high discharge events in the stream as an opportunity to move into lakes. Stream and lake derived stable isotopes also indicate that lake trout rely on these seasonally transported inputs of stream nutrients for growth. Thus, changes in the seasonality of river hydrology may have broader

  2. Arctic epishelf lakes as sentinel ecosystems: Past, present and future

    NASA Astrophysics Data System (ADS)

    Veillette, Julie; Mueller, Derek R.; Antoniades, Dermot; Vincent, Warwick F.

    2008-12-01

    Ice shelves are a prominent but diminishing feature of the northern coastline of Ellesmere Island in the Canadian High Arctic (latitude 82-83°N). By blocking embayments and fiords, this thick coastal ice can create epishelf lakes, which are characterized by a perennially ice-capped water column of freshwater overlying seawater. The goal of this study was to synthesize new, archived, and published data on Arctic epishelf lakes in the context of climate change. Long-term changes along this coastline were evaluated using historical reports, cartographic analysis, RADARSAT imagery, and field measurements. These data, including salinity-temperature profiling records from Disraeli Fiord spanning 54 years, show the rapid decline and near disappearance of this lake type in the Arctic. Salinity-temperature profiling of Milne Fiord, currently blocked by the Milne Ice Shelf, confirmed that it contained an epishelf lake composed of a 16-m thick freshwater layer overlying seawater. A profiling survey along the coast showed that there was a continuum of ice-dammed lakes from shallow systems dammed by multiyear landfast sea ice to deep epishelf lakes behind ice shelves. The climate warming recently observed in this region likely contributed to the decline of epishelf lakes over the last century, and the air temperature trend predicted for the Arctic over the next several decades implies the imminent loss of this ecosystem type. Our results underscore the distinctive properties of coastal ice-dammed lakes and their value as sentinel ecosystems for the monitoring of regional and global climate change.

  3. Mercury in Arctic Marine Ecosystems: Sources, Pathways, and Exposure

    PubMed Central

    Kirk, Jane L.; Lehnherr, Igor; Andersson, Maria; Braune, Birgit M.; Chan, Laurie; Dastoor, Ashu P.; Durnford, Dorothy; Gleason, Amber L.; Loseto, Lisa L.; Steffen, Alexandra; St. Louis, Vincent L.

    2014-01-01

    Mercury in the Arctic is an important environmental and human health issue. The reliance of Northern Peoples on traditional foods, such as marine mammals, for subsistence means that they are particularly at risk from mercury exposure. The cycling of mercury in Arctic marine systems is reviewed here, with emphasis placed on the key sources, pathways and processes which regulate mercury levels in marine food webs and ultimately the exposure of human populations to this contaminant. While many knowledge gaps exist limiting our ability to make strong conclusions, it appears that the long range transport of mercury from Asian emissions is an important source of atmospheric Hg to the Arctic and that mercury methylation resulting in monomethylmercury production (an organic form of mercury which is both toxic and bioaccumulated) in Arctic marine waters is the principal source of mercury incorporated into food webs. Mercury concentrations in biological organisms have increased since the onset of the industrial age and are controlled by a combination of abiotic factors (e.g., monomethylmercury supply), food web dynamics and structure, and animal behavior (e.g., habitat selection and feeding behavior). Finally, although some Northern Peoples have high mercury concentrations of mercury in their blood and hair, harvesting and consuming traditional foods has many nutritional, social, cultural and physical health benefits which must be considered in risk management and communication. PMID:23102902

  4. Pleistocene graminoid-dominated ecosystems in the Arctic

    NASA Astrophysics Data System (ADS)

    Blinnikov, Mikhail S.; Gaglioti, Benjamin V.; Walker, Donald A.; Wooller, Matthew J.; Zazula, Grant D.

    2011-10-01

    We review evidence obtained from analyses of multiple proxies (floristics, mammal remains, paleoinsects, pollen, macrofossils, plant cuticles, phytoliths, stable isotopes, and modeling) that elucidate the composition and character of the graminoid-dominated ecosystems of the Pleistocene Arctic. The past thirty years have seen a renewed interest in this now-extinct biome, sometimes referred to as "tundra-steppe" (steppe-tundra in North American sources). While many questions remain, converging evidence from many new terrestrial records and proxies coupled with better understanding of paleoclimate dynamics point to the predominance of xeric and cold adapted grassland as the key former vegetation type in the Arctic confirming earlier conjectures completed in the 1960s-1980s. A variety of still existing species of grasses and forbs played key roles in the species assemblages of the time, but their mixtures were not analogous to the tundras of today. Local mosaics based on topography, proximity to the ice sheets and coasts, soil heterogeneity, animal disturbance, and fire regimes were undoubtedly present. However, inadequate coverage of terrestrial proxies exist to resolve this spatial heterogeneity. These past ecosystems were maintained by a combination of dry and cold climate and grazing pressure/disturbance by large (e.g., mammoth and horse) and small (e.g., ground squirrels) mammals. Some recent studies from Eastern Beringia (Alaska) suggest that more progress will be possible when analyses of many proxies are combined at local scales.

  5. Changing Arctic ecosystems: resilience of caribou to climatic shifts in the Arctic

    USGS Publications Warehouse

    Gustine, David; Adams, Layne; Whalen, Mary; Pearce, John

    2014-01-01

    The U.S. Geological Survey (USGS) Changing Arctic Ecosystems (CAE) initiative strives to inform key resource management decisions for Arctic Alaska by providing scientific information and forecasts for current and future ecosystem response to a warming climate. Over the past 5 years, a focal area for the USGS CAE initiative has been the North Slope of Alaska. This region has experienced a warming trend over the past 60 years, yet the rate of change has been varied across the North Slope, leading scientists to question the future response and resilience of wildlife populations, such as caribou (Rangifer tarandus), that rely on tundra habitats for forage. Future changes in temperature and precipitation to coastal wet sedge and upland low shrub tundra are expected, with unknown consequences for caribou that rely on these plant communities for food. Understanding how future environmental change may affect caribou migration, nutrition, and reproduction is a focal question being addressed by the USGS CAE research. Results will inform management agencies in Alaska and people that rely on caribou for food.

  6. Hydrological and geochemical response and recovery in disturbed Arctic ecosystems

    SciTech Connect

    Not Available

    1992-01-01

    This progress report is a funding, extension request to continue the database work for the Hydrological and Geochemical Response and Recovery in Disturbed Arctic Ecosystems Program. Throughout the period from 1985 to 1992 the Department of Energy supported research on the hydrology and geochemistry of the headwater basin of Imnavait Creek has focused on the quantification of the input from atmospheric sources of biologically significant and other related chemical variables; the transport of these variables in surface and subsurface flow and their efflux from the basin; and the development of geochemical budgets. The acquisition of multi-year data sets (the longest and most detailed sets in the Arctic) have made it possible to define seasonal ranges and amplitudes; determine spatial and temporal relationships within the different flow compartments; to begin to model the pathways and rates of movement through and across different landscape units. The length of record has also made it possible to examine the quantity and influence of local and extra-regional additions.

  7. Linking ecosystem characteristics to final ecosystem services for public policy

    PubMed Central

    Wong, Christina P; Jiang, Bo; Kinzig, Ann P; Lee, Kai N; Ouyang, Zhiyun

    2015-01-01

    Governments worldwide are recognising ecosystem services as an approach to address sustainability challenges. Decision-makers need credible and legitimate measurements of ecosystem services to evaluate decisions for trade-offs to make wise choices. Managers lack these measurements because of a data gap linking ecosystem characteristics to final ecosystem services. The dominant method to address the data gap is benefit transfer using ecological data from one location to estimate ecosystem services at other locations with similar land cover. However, benefit transfer is only valid once the data gap is adequately resolved. Disciplinary frames separating ecology from economics and policy have resulted in confusion on concepts and methods preventing progress on the data gap. In this study, we present a 10-step approach to unify concepts, methods and data from the disparate disciplines to offer guidance on overcoming the data gap. We suggest: (1) estimate ecosystem characteristics using biophysical models, (2) identify final ecosystem services using endpoints and (3) connect them using ecological production functions to quantify biophysical trade-offs. The guidance is strategic for public policy because analysts need to be: (1) realistic when setting priorities, (2) attentive to timelines to acquire relevant data, given resources and (3) responsive to the needs of decision-makers. PMID:25394857

  8. Linking ecosystem characteristics to final ecosystem services for public policy.

    PubMed

    Wong, Christina P; Jiang, Bo; Kinzig, Ann P; Lee, Kai N; Ouyang, Zhiyun

    2015-01-01

    Governments worldwide are recognising ecosystem services as an approach to address sustainability challenges. Decision-makers need credible and legitimate measurements of ecosystem services to evaluate decisions for trade-offs to make wise choices. Managers lack these measurements because of a data gap linking ecosystem characteristics to final ecosystem services. The dominant method to address the data gap is benefit transfer using ecological data from one location to estimate ecosystem services at other locations with similar land cover. However, benefit transfer is only valid once the data gap is adequately resolved. Disciplinary frames separating ecology from economics and policy have resulted in confusion on concepts and methods preventing progress on the data gap. In this study, we present a 10-step approach to unify concepts, methods and data from the disparate disciplines to offer guidance on overcoming the data gap. We suggest: (1) estimate ecosystem characteristics using biophysical models, (2) identify final ecosystem services using endpoints and (3) connect them using ecological production functions to quantify biophysical trade-offs. The guidance is strategic for public policy because analysts need to be: (1) realistic when setting priorities, (2) attentive to timelines to acquire relevant data, given resources and (3) responsive to the needs of decision-makers. PMID:25394857

  9. Responses of arctic and alpine ecosystems to altered seasonality under climate change

    NASA Astrophysics Data System (ADS)

    Ernakovich, J. G.; Hopping, K. A.; Berdanier, A.; Simpson, R. T.; Kachergis, E. J.; Steltzer, H.; Wallenstein, M. D.

    2012-12-01

    Arctic and alpine ecosystems are largely structured by strong seasonal patterns in abiotic drivers, including solar radiation and air and soil temperature. Because air temperature and precipitation patterns are changing rapidly, the length of the growing season is increasing due to shifts in snowfall, earlier snowmelt in spring, and delayed snowfall in autumn. Although arctic and alpine environments are both characterized by short growing seasons, they differ in fundamental ways that will affect their responses to changing seasonality. We compare meteorological data from sixteen arctic and alpine sites and biological data from two arctic and two alpine sites. We propose that although alpine and arctic ecosystems appear similar under historical climate conditions, especially during the growing season, winter conditions and climate change will result in divergent responses. Biotic responses to changing seasonality will affect belowground and aboveground community composition, trophic dynamics, and the functioning of these ecosystems, including net carbon balance.

  10. Monitoring ecosystem dynamics in an Arctic tundra ecosystem using hyperspectral reflectance and a robotic tram system

    NASA Astrophysics Data System (ADS)

    Goswami, Santonu

    Global change, which includes climate change and the impacts of human disturbance, is altering the provision and sustainability of ecosystem goods and services. These changes have the capacity to initiate cascading affects and complex feedbacks through physical, biological and human subsystems and interactions between them. Understanding the future state of the earth system requires improved knowledge of ecosystem dynamics and long term observations of how these are being impacted by global change. Improving remote sensing methods is essential for such advancement because satellite remote sensing is the only means by which landscape to continental-scale change can be observed. The Arctic appears to be impacted by climate change more than any other region on Earth. Arctic terrestrial ecosystems comprise only 6% of the land surface area on Earth yet contain an estimated 25% of global soil organic carbon, most of which is stored in permafrost. If projected increases in plant productivity do not offset forecast losses of soil carbon to the atmosphere as greenhouse gases, regional to global greenhouse warming could be enhanced. Soil moisture is an important control of land-atmosphere carbon exchange in arctic terrestrial ecosystems. However, few studies to date have examined using remote sensing, or developed remote sensing methods for observing the complex interplay between soil moisture and plant phenology and productivity in arctic landscapes. This study was motivated by this knowledge gap and addressed the following questions as a contribution to a large scale, multi investigator flooding and draining experiment funded by the National Science Foundation near Barrow, Alaska (71°17'01" N, 156°35'48" W): (1) How can optical remote sensing be used to monitor the surface hydrology of arctic landscapes? (2) What are the spatio-temporal dynamics of land-surface phenology (NDVI) in the study area and do hydrological treatment has any effect on inter-annual patterns? (3

  11. Estimating Pan Arctic Net Ecosystem Exchange using Functional Relationships with Air temperature, Leaf Area Index and Photosynthetic Active Radiation

    NASA Astrophysics Data System (ADS)

    Mbufong, H.; Kusbach, A.; Lund, M.; Persson, A.; Christensen, T. R.; Tamstorf, M. P.; Connolly, J.

    2015-12-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) is often attributed to the high spatial heterogeneity of Arctic tundra. Current models of carbon exchange thus handle the Arctic as either a single or few ecosystems, responding to environmental change in the same manner. In this study, we developed and tested a simple NEE model using the Misterlich light response curve (LRC) function with photosynthetic photon flux density (PPFD) as the main driving variable. Model calibration was carried out with eddy covariance carbon dioxide data from 12 Arctic tundra sites. The model input parameters (fcsat, Rd and α) were estimated as a function of air temperature and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship. They describe the saturation flux, dark respiration and initial light use efficiency, respectively. While remotely sensed LAI is readily available as a MODIS Terra product (MCD15A3), air temperature was estimated from a direct relationship with MODIS land surface temperature (MOD11A2, LST). Therefore, no specific knowledge of the vegetation type is required. Preliminary results show the model captures the spatial heterogeneity of the Arctic tundra but so far, overestimates NEE on all 17 test sites which include heaths, bogs, fens, and tussock tundra vegetation. The final updated results and error assessment will be presented at the conference in December.

  12. Exploratory hydrocarbon drilling impacts to Arctic lake ecosystems.

    PubMed

    Thienpont, Joshua R; Kokelj, Steven V; Korosi, Jennifer B; Cheng, Elisa S; Desjardins, Cyndy; Kimpe, Linda E; Blais, Jules M; Pisaric, Michael F J; Smol, John P

    2013-01-01

    potential for these industrial wastes to impact sensitive Arctic ecosystems. PMID:24223170

  13. Biogeochemistry and nitrogen cycling in an Arctic, volcanic ecosystem

    NASA Astrophysics Data System (ADS)

    Fogel, M. L.; Benning, L.; Conrad, P. G.; Eigenbrode, J.; Starke, V.

    2007-12-01

    As part of a study on Mars Analogue environments, the biogeochemistry of Sverrefjellet Volcano, Bocfjorden, Svalbard, was conducted and compared to surrounding glacial, thermal spring, and sedimentary environments. An understanding of how nitrogen might be distributed in a landscape that had extinct or very cold adapted, slow- growing extant organisms should be useful for detecting unknown life forms. From high elevations (900 m) to the base of the volcano (sea level), soil and rock ammonium concentrations were uniformly low, typically less than 1- 3 micrograms per gm of rock or soil. In weathered volcanic soils, reduced nitrogen concentrations were higher, and oxidized nitrogen concentrations lower. The opposite was found in a weathered Devonian sedimentary soil. Plants and lichens growing on volcanic soils have an unusually wide range in N isotopic compositions from -5 to +12‰, a range rarely measured in temperate ecosystems. Nitrogen contents and isotopic compositions of volcanic soils and rocks were strongly influenced by the presence or absence of terrestrial herbivores or marine avifauna with higher concentrations of N and elevated N isotopic compositions occurring as patches in areas immediately influenced by reindeer, Arctic fox ( Alopex lagopus), and marine birds. Because of the extreme conditions in this area, ephemeral deposition of herbivore feces results in a direct and immediate N pulses into the ecosystem. The lateral extent and distribution of marine- derived nitrogen was measured on a landscape scale surrounding an active fox den. Nitrogen was tracked from the bones of marine birds to soil to vegetation. Because of extreme cold, slow biological rates and nitrogen cycling, a mosaic of N patterns develops on the landscape scale.

  14. Exploratory Hydrocarbon Drilling Impacts to Arctic Lake Ecosystems

    PubMed Central

    Thienpont, Joshua R.; Kokelj, Steven V.; Korosi, Jennifer B.; Cheng, Elisa S.; Desjardins, Cyndy; Kimpe, Linda E.; Blais, Jules M.; Pisaric, Michael FJ.; Smol, John P.

    2013-01-01

    potential for these industrial wastes to impact sensitive Arctic ecosystems. PMID:24223170

  15. Changing Arctic ecosystems--the role of ecosystem changes across the Boreal-Arctic transition zone on the distribution and abundance of wildlife populations

    USGS Publications Warehouse

    McNew, Lance; Handel, Colleen; Pearce, John; DeGange, Anthony R.; Holland-Bartels, Leslie; Whalen, Mary

    2013-01-01

    Arctic and boreal ecosystems provide important breeding habitat for more than half of North America’s migratory birds as well as many resident species. Northern landscapes are projected to experience more pronounced climate-related changes in habitat than most other regions. These changes include increases in shrub growth, conversion of tundra to forest, alteration of wetlands, shifts in species’ composition, and changes in the frequency and scale of fires and insect outbreaks. Changing habitat conditions, in turn, may have significant effects on the distribution and abundance of wildlife in these critical northern ecosystems. The U.S. Geological Survey (USGS) is conducting studies in the Boreal–Arctic transition zone of Alaska, an environment of accelerated change in this sensitive margin between Arctic tundra and boreal forest.

  16. Soil Biota and Litter Decay in High Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    González, G.; Rivera, F.; Makarova, O.; Gould, W. A.

    2006-12-01

    Frost heave action contributes to the formation of non-sorted circles in the High Arctic. Non-sorted circles tend to heave more than the surrounding tundra due to deeper thaw and the formation of ice lenses. Thus, the geomorphology, soils and vegetation on the centers of the patterned-ground feature (non-sorted circles) as compared to the surrounding soils (inter-circles) can be different. We established a decomposition experiment to look at in situ decay rates of the most dominant graminoid species on non-sorted circles and adjacent inter-circle soils along a climatic gradient in the Canadian High Arctic as a component of a larger study looking at the biocomplexity of small-featured patterned ground ecosystems. Additionally, we investigated variation in soil chemical properties and biota, including soil microarthropods and microbial composition and biomass, as they relate to climate, topographic position, and litter decay rates. Our three sites locations, from coldest to warmest, are Isachsen, Ellef Ringnes Island (ER), NU (bioclimatic subzone A); Mould Bay (MB), Prince Patrick Island, NT (bioclimatic subzone B), and Green Cabin (GC), Aulavik National Park, Thomsen River, Banks Island, NT (bioclimatic subzone C). Our sample design included the selection of 15 non-sorted circles and adjacent inter-circle areas within the zonal vegetation at each site (a total of 90 sites), and a second set of 3 non-sorted circles and adjacent inter-circle areas in dry, mesic and wet tundra at each of the sites. Soil invertebrates were sampled at each site using both pitfall traps, soil microbial biomass was determined using substrate induced respiration and bacterial populations were determined using the most probable number method. Decomposition rates were measured using litterbags and as the percent of mass remaining of Carex misandra, Luzula nivalis and Alopecuris alpinus in GC, MB and ER, respectively. Our findings indicate these graminoid species decayed significantly over

  17. Influence of the Tussock Growth Form on Arctic Ecosystem Carbon Stocks

    NASA Astrophysics Data System (ADS)

    Curasi, S.; Rocha, A. V.; Sonnentag, O.; Wullschleger, S. D.; Myers-Smith, I. H.; Fetcher, N.; Mack, M. C.; Natali, S.; Loranty, M. M.; Parker, T.

    2015-12-01

    The influence of plant growth forms on ecosystem carbon (C) cycling has been under appreciated. In arctic tundra, environmental factors and plant traits of the sedge Eriophorum vaginatum cause the formation of mounds that are dense amalgamations of belowground C called tussocks. Tussocks have important implications for arctic ecosystem biogeochemistry and C stocks, but the environmental and biological factors controlling their size and distribution across the landscape are poorly understood. In order to better understand how landscape variation in tussock size and density impact ecosystem C stocks, we formed the Carbon in Arctic Tussock Tundra (CATT) network and recruited an international team to sample locations across the arctic. The CATT network provided a latitudinal and longitudinal gradient along which to improve our understanding of tussocks' influence on ecosystem structure and function. CATT data revealed important insights into tussock formation across the arctic. Tussock density generally declined with latitude, and tussock size exhibited substantial variation across sites. The relationship between height and diameter was similar across CATT sites indicating that both biological and environmental factors control tussock formation. At some sites, C in tussocks comprised a substantial percentage of ecosystem C stocks that may be vulnerable to climate change. It is concluded that the loss of this growth form would offset C gains from projected plant functional shifts from graminoid to shrub tundra. This work highlights the role of plant growth forms on the magnitude and retention of ecosystem C stocks.

  18. How is climate warming altering the carbon cycle of a tundra ecosystem in the Siberian Arctic?

    NASA Astrophysics Data System (ADS)

    Belelli Marchesini, Luca; (Ko) van Huissteden, Jacobus; van der Molen, Michiel; Parmentier, Frans-Jan W.; Maximov, Trofim; Budishchev, Artem; Gallagher, Angela; (Han) Dolman, Albertus J.

    2015-04-01

    Climate has been warming over the the Arctic region with the strongest anomalies taking place in autumn and winter for the period 2000-2010, particularly in northern Eurasia. The quantification of the impact on climate warming on the degradation of permafrost and the associated potential release to the atmosphere of carbon stocked in the soil under the form of greenhouse gases, thus further increasing the radiative forcing of the atmosphere, is currently a matter of scientific debate. The positive trend in primary productivity in the last decades inferred by vegetation indexes (NDVI) and confirmed by observations on the enhanced growth of shrub vegetation represents indeed a contrasting process that, if prevalent could offset GHG emissions or even strengthen the carbon sink over the Arctic tundra. At the site of Kytalyk, in north-eastern Siberia, net fluxes of CO2 at ecosystem scale (NEE) have been monitored by eddy covariance technique since 2003. While presenting the results of the seasonal (snow free period) and inter-annual variability of NEE, conceived as the interplay between meteorological drivers and ecosystem responses, we test the role of climate as the main source of NEE variability in the last decade using a data oriented statistical approach. The impact of the timing and duration of the snow free period on the seasonal carbon budget is also considered. Finally, by including the results of continuous micrometeorological observations of methane fluxes taken during summer 2012, corroborated with seasonal CH4 budgets from two previous shorter campaigns (2008, 2009), as well as an experimentally determined estimate of dissolved organic carbon (DOC) flux, we provide an assessment of the carbon budget and its stability over time. The examined tundra ecosystem was found to sequester CO2 during the snow free season with relatively small inter-annual variability (-97.9±12.1gC m-2) during the last decade and without any evident trend despite the carbon uptake

  19. Critical review of mercury fates and contamination in the Arctic tundra ecosystem.

    PubMed

    Poissant, Laurier; Zhang, Hong H; Canário, João; Constant, Philippe

    2008-08-01

    Mercury (Hg) contamination in tundra region has raised substantial concerns, especially since the first report of atmospheric mercury depletion events (AMDEs) in the Polar Regions. During the past decade, steady progress has been made in the research of Hg cycling in the Polar Regions. This has generated a unique opportunity to survey the whole Arctic in respect to Hg issue and to find out new discoveries. However, there are still considerable knowledge gaps and debates on the fate of Hg in the Arctic and Antarctica, especially regarding the importance and significance of AMDEs vs. net Hg loadings and other processes that burden Hg in the Arctic. Some studies argued that climate warming since the last century has exerted profound effects on the limnology of High Arctic lakes, including substantial increases in autochthonous primary productivity which increased in sedimentary Hg, whereas some others pointed out the importance of the formation and postdeposition crystallographic history of the snow and ice crystals in determining the fate and concentration of mercury in the cryosphere in addition to AMDEs. Is mercury re-emitted back to the atmosphere after AMDEs? Is Hg methylation effective in the Arctic tundra? Where the sources of MeHg are? What is its fate? Is this stimulated by human made? This paper presents a critical review about the fate of Hg in the Arctic tundra, such as pathways and process of Hg delivery into the Arctic ecosystem; Hg concentrations in freshwater and marine ecosystems; Hg concentrations in terrestrial biota; trophic transfer of Hg and bioaccumulation of Hg through food chain. This critical review of mercury fates and contamination in the Arctic tundra ecosystem is assessing the impacts and potential risks of Hg contamination on the health of Arctic people and the global northern environment by highlighting and "perspectiving" the various mercury processes and concentrations found in the Arctic tundra. PMID:18707754

  20. Ecosystem Metabolism and Air-Water Fluxes of Greenhouse Gases in High Arctic Wetland Ponds

    NASA Astrophysics Data System (ADS)

    Lehnherr, I.; Venkiteswaran, J.; St. Louis, V. L.; Emmerton, C.; Schiff, S. L.

    2012-12-01

    Freshwater lakes and wetlands can be very productive systems on the Arctic landscape compared to terrestrial tundra ecosystems and provide valuable resources to many organisms, including waterfowl, fish and humans. Rates of ecosystem productivity dictate how much energy flows through food webs, impacting the abundance of higher-level organisms (e.g., fish), as well as the net carbon balance, which determines whether a particular ecosystem is a source or sink of carbon. Climate change is predicted to result in warmer temperatures, increased precipitation and permafrost melting in the Arctic and is already altering northern ecosystems at unprecedented rates; however, it is not known how freshwater systems are responding to these changes. To predict how freshwater systems will respond to complex environmental changes, it is necessary to understand the key processes, such as primary production and ecosystem respiration, that are driving these systems. We sampled wetland ponds (n=8) and lakes (n=2) on northern Ellesmere Island (81° N, Nunavut, Canada) during the open water season for a suite of biogeochemical parameters, including concentrations of dissolved gases (O2, CO2, CH4, N2O) as well as stable-isotope ratios of dissolved inorganic carbon (δ13C-DIC), dissolved oxygen (δ18O-DO), and water (δ18O-H2O). We will present rates of primary production and ecosystem respiration, modeled from the concentration and stable isotope ratios of DIC and DO, as well as air-water gas exchange of greenhouse gases in these high Arctic ponds and lakes. Preliminary results demonstrate that ecosystem metabolism in these ponds was high enough to result in significant deviations in the isotope ratios of DIC and DO from atmospheric equilibrium conditions. In other words ecosystem rates of primary production and respiration were faster than gas exchange even in these small, shallow, well-mixed ponds. Furthermore, primary production was elevated enough at all sites except Lake Hazen, a

  1. Changing Arctic ecosystems: sea ice decline, permafrost thaw, and benefits for geese

    USGS Publications Warehouse

    Flint, Paul; Whalen, Mary; Pearce, John M.

    2014-01-01

    Through the Changing Arctic Ecosystems (CAE) initiative, the U.S. Geological Survey (USGS) strives to inform resource management decisions for Arctic Alaska by providing scientific information on current and future ecosystem response to a warming climate. A key area for the USGS CAE initiative has been the Arctic Coastal Plain of northern Alaska. This region has experienced a warming trend over the past 30 years, leading to reductions in sea ice and thawing of permafrost. Loss of sea ice has increased ocean wave action, leading to erosion and salt water inundation of coastal habitats. Saltwater tolerant plants are now thriving in these areas and this appears to be a positive outcome for geese in the Arctic. This finding is contrary to the deleterious effects that declining sea ice is having on habitats of ice-dependent animals, such as polar bear and walrus.

  2. Simulating net ecosystem productivity and the sensitivity of a sub-arctic boreal forest ecosystem

    NASA Astrophysics Data System (ADS)

    Ueyama, M.; Harazono, Y.; Kim, Y.; Tanaka, N.

    2005-12-01

    BIOME-BGC was used to examine how air temperature and precipitation affect NEP in a sub-arctic black spruce forest. The model was tuned using data from the eddy correlation measurement site in UAF black spruce forest during 2003 and 2004. The climate dataset of Fairbanks airport between 1949 and 2004 was used for the model spin-up. The model almost reproduced the observed NEE, in which climate in 2003 was normal and that in 2004 was drought in summer. The model, however, failed to simulate the late winter NEE, during which obvious daytime uptake were observed under extreme low temperature. Annual simulation of GPP and ecosystem respiration was 2.2 and 1.8 kg CO2 m-2 yr-1 in 2003 and 2.4 and 1.9 kg CO2 m-2 yr-1 in 2004. While warm growing season temperature enhanced the photosynthesis and respiration in 2004, significant drought in August 2004 were restricted both the photosynthesis and heterotrophic respiration. Simulated annual NEE was 0.2 kg CO2 m-2 yr-1 in 2003 and 0.3 kg CO2 m-2 yr-1 in 2004. The simulation explored the impact of seasonal warmer (+5oC), wetter (120% of precipitation) and drier (80% of precipitation) spells on net ecosystem productivity, comparing the long term Fairbanks weather between 1980 and 2000. Wetter condition in either season did not significantly affect annual NEP. While drought summer decreased annual NEP by 30% mainly due to reduction in GPP by 9%, low snowfall winter also reduced the annual NEP by 19%, in which low snow water brought drought stress in following summer and then suppressed both GPP to 93% and ecosystem respiration to 96%. Warmer summer and autumn decreased annual NEP to 37% and 65%. In this case, GPP did not increase and maintenance and heterotrophic respiration were enhanced to 120% and 126%, respectively, in warmer summer and 103% and 107%, respectively, in warmer autumn. The simulation unambiguously showed productivity of the sub-arctic boreal forest was significantly sensitive to warmer temperature in summer and

  3. Rough-legged buzzards, Arctic foxes and red foxes in a tundra ecosystem without rodents.

    PubMed

    Pokrovsky, Ivan; Ehrich, Dorothée; Ims, Rolf A; Kondratyev, Alexander V; Kruckenberg, Helmut; Kulikova, Olga; Mihnevich, Julia; Pokrovskaya, Liya; Shienok, Alexander

    2015-01-01

    Small rodents with multi-annual population cycles strongly influence the dynamics of food webs, and in particular predator-prey interactions, across most of the tundra biome. Rodents are however absent from some arctic islands, and studies on performance of arctic predators under such circumstances may be very instructive since rodent cycles have been predicted to collapse in a warming Arctic. Here we document for the first time how three normally rodent-dependent predator species-rough-legged buzzard, arctic fox and red fox - perform in a low-arctic ecosystem with no rodents. During six years (in 2006-2008 and 2011-2013) we studied diet and breeding performance of these predators in the rodent-free Kolguev Island in Arctic Russia. The rough-legged buzzards, previously known to be a small rodent specialist, have only during the last two decades become established on Kolguev Island. The buzzards successfully breed on the island at stable low density, but with high productivity based on goslings and willow ptarmigan as their main prey - altogether representing a novel ecological situation for this species. Breeding density of arctic fox varied from year to year, but with stable productivity based on mainly geese as prey. The density dynamic of the arctic fox appeared to be correlated with the date of spring arrival of the geese. Red foxes breed regularly on the island but in very low numbers that appear to have been unchanged over a long period - a situation that resemble what has been recently documented from Arctic America. Our study suggests that the three predators found breeding on Kolguev Island possess capacities for shifting to changing circumstances in low-arctic ecosystem as long as other small - medium sized terrestrial herbivores are present in good numbers. PMID:25692786

  4. Rough-Legged Buzzards, Arctic Foxes and Red Foxes in a Tundra Ecosystem without Rodents

    PubMed Central

    Pokrovsky, Ivan; Ehrich, Dorothée; Ims, Rolf A.; Kondratyev, Alexander V.; Kruckenberg, Helmut; Kulikova, Olga; Mihnevich, Julia; Pokrovskaya, Liya; Shienok, Alexander

    2015-01-01

    Small rodents with multi-annual population cycles strongly influence the dynamics of food webs, and in particular predator-prey interactions, across most of the tundra biome. Rodents are however absent from some arctic islands, and studies on performance of arctic predators under such circumstances may be very instructive since rodent cycles have been predicted to collapse in a warming Arctic. Here we document for the first time how three normally rodent-dependent predator species—rough-legged buzzard, arctic fox and red fox – perform in a low-arctic ecosystem with no rodents. During six years (in 2006-2008 and 2011-2013) we studied diet and breeding performance of these predators in the rodent-free Kolguev Island in Arctic Russia. The rough-legged buzzards, previously known to be a small rodent specialist, have only during the last two decades become established on Kolguev Island. The buzzards successfully breed on the island at stable low density, but with high productivity based on goslings and willow ptarmigan as their main prey – altogether representing a novel ecological situation for this species. Breeding density of arctic fox varied from year to year, but with stable productivity based on mainly geese as prey. The density dynamic of the arctic fox appeared to be correlated with the date of spring arrival of the geese. Red foxes breed regularly on the island but in very low numbers that appear to have been unchanged over a long period – a situation that resemble what has been recently documented from Arctic America. Our study suggests that the three predators found breeding on Kolguev Island possess capacities for shifting to changing circumstances in low-arctic ecosystem as long as other small - medium sized terrestrial herbivores are present in good numbers. PMID:25692786

  5. Active layer dynamics and arctic hydrology and meteorology. Final report

    SciTech Connect

    Not Available

    1993-10-01

    Man`s impact on the environment is increasing with time. To be able to evaluate anthropogenic impacts on an ecosystems, it is necessary first to understand all facets of how the ecosystems works: what the main processes (physical, biological, chemical) are, at what rates they proceed, and how they can be manipulated. Arctic ecosystems are dominated by physical processes of energy exchange. This project has concentrated on a strong program of hydrologic and meteorologic data collection, to better understand dominant physical processes. Field research focused on determining the natural annual and diurnal variability of meteorologic and hydrologic variables, especially those which may indicate trends in climatic change. Comprehensive compute models are being developed to simulate physical processes occurring under the present conditions and to simulate processes under the influence of climatic change.

  6. Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens.

    PubMed

    Gharajehdaghipour, Tazarve; Roth, James D; Fafard, Paul M; Markham, John H

    2016-01-01

    Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ(15)N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra. PMID:27045973

  7. Pan-Arctic modelling of net ecosystem exchange of CO2.

    PubMed

    Shaver, G R; Rastetter, E B; Salmon, V; Street, L E; van de Weg, M J; Rocha, A; van Wijk, M T; Williams, M

    2013-08-19

    Net ecosystem exchange (NEE) of C varies greatly among Arctic ecosystems. Here, we show that approximately 75 per cent of this variation can be accounted for in a single regression model that predicts NEE as a function of leaf area index (LAI), air temperature and photosynthetically active radiation (PAR). The model was developed in concert with a survey of the light response of NEE in Arctic and subarctic tundras in Alaska, Greenland, Svalbard and Sweden. Model parametrizations based on data collected in one part of the Arctic can be used to predict NEE in other parts of the Arctic with accuracy similar to that of predictions based on data collected in the same site where NEE is predicted. The principal requirement for the dataset is that it should contain a sufficiently wide range of measurements of NEE at both high and low values of LAI, air temperature and PAR, to properly constrain the estimates of model parameters. Canopy N content can also be substituted for leaf area in predicting NEE, with equal or greater accuracy, but substitution of soil temperature for air temperature does not improve predictions. Overall, the results suggest a remarkable convergence in regulation of NEE in diverse ecosystem types throughout the Arctic. PMID:23836790

  8. Pan-Arctic modelling of net ecosystem exchange of CO2

    PubMed Central

    Shaver, G. R.; Rastetter, E. B.; Salmon, V.; Street, L. E.; van de Weg, M. J.; Rocha, A.; van Wijk, M. T.; Williams, M.

    2013-01-01

    Net ecosystem exchange (NEE) of C varies greatly among Arctic ecosystems. Here, we show that approximately 75 per cent of this variation can be accounted for in a single regression model that predicts NEE as a function of leaf area index (LAI), air temperature and photosynthetically active radiation (PAR). The model was developed in concert with a survey of the light response of NEE in Arctic and subarctic tundras in Alaska, Greenland, Svalbard and Sweden. Model parametrizations based on data collected in one part of the Arctic can be used to predict NEE in other parts of the Arctic with accuracy similar to that of predictions based on data collected in the same site where NEE is predicted. The principal requirement for the dataset is that it should contain a sufficiently wide range of measurements of NEE at both high and low values of LAI, air temperature and PAR, to properly constrain the estimates of model parameters. Canopy N content can also be substituted for leaf area in predicting NEE, with equal or greater accuracy, but substitution of soil temperature for air temperature does not improve predictions. Overall, the results suggest a remarkable convergence in regulation of NEE in diverse ecosystem types throughout the Arctic. PMID:23836790

  9. Arctic foxes as ecosystem engineers: increased soil nutrients lead to increased plant productivity on fox dens

    PubMed Central

    Gharajehdaghipour, Tazarve; Roth, James D.; Fafard, Paul M.; Markham, John H.

    2016-01-01

    Top predators can provide fundamental ecosystem services such as nutrient cycling, and their impact can be even greater in environments with low nutrients and productivity, such as Arctic tundra. We estimated the effects of Arctic fox (Vulpes lagopus) denning on soil nutrient dynamics and vegetation production near Churchill, Manitoba in June and August 2014. Soils from fox dens contained higher nutrient levels in June (71% more inorganic nitrogen, 1195% more extractable phosphorous) and in August (242% more inorganic nitrogen, 191% more extractable phosphorous) than adjacent control sites. Inorganic nitrogen levels decreased from June to August on both dens and controls, whereas extractable phosphorous increased. Pup production the previous year, which should enhance nutrient deposition (from urine, feces, and decomposing prey), did not affect soil nutrient concentrations, suggesting the impact of Arctic foxes persists >1 year. Dens supported 2.8 times greater vegetation biomass in August, but δ15N values in sea lyme grass (Leymus mollis) were unaffected by denning. By concentrating nutrients on dens Arctic foxes enhance nutrient cycling as an ecosystem service and thus engineer Arctic ecosystems on local scales. The enhanced productivity in patches on the landscape could subsequently affect plant diversity and the dispersion of herbivores on the tundra. PMID:27045973

  10. Economic Valuation of Ecosystem Goods and Services in a Melting Arctic

    NASA Astrophysics Data System (ADS)

    O'Garra, T.

    2014-12-01

    The Arctic region is composed of unique ecosystems that provide a range of goods and services to local and global populations. However, Arctic sea-ice is melting at an unprecedented rate, threatening many of these ecosystems and the services they provide. Yet as the ice melts and certain goods and services are lost, other resources such as oil and minerals will become accessible. The question is: how do the losses compare with the opportunities? And how are the losses and potential gains likely to be distributed? To address these questions, this study provides a preliminary assessment of the quantity, distribution and economic value of the ecosystem services (ES) provided by Arctic ecosystems, both now and in the future given a scenario of sure climate change. Using biophysical and economic data from existing studies (and some primary data), preliminary estimates indicate that the Arctic currently provides 357m/yr (in 2014 US) in subsistence hunting value to local communities, of which reindeer/caribou comprise 83%. Reindeer herding provides 110m/yr to Arctic communities. Interestingly, 'non-use (existence/cultural) values' associated with Arctic species are very high at 11bn/yr to members of Arctic states. The Arctic also provides ES that accrue to the global community: oil resources (North Slope; 5bn profits in 2013), commercial fisheries ( 515mn/yr) and most importantly, climate regulation services. Recent models (Whiteman; Euskirchen) estimate that the loss of climate regulation services provided by Arctic ice will cost 200 - 500bn/yr, a value which dwarfs all others. Assuming no change in atmospheric temperature compared to 2014, the net present value of the Arctic by 2050 (1.4% discount rate) comes to over $9 trillion. However, given Wang and Overland (2009) predictions of ice-free summers by 2037, we expect many of these benefits will be lost. For example, it is fairly well-established that endemic species, such as polar bears, will decline with sea-ice melt

  11. Regional-Scale Vegetation Dynamics in Patterned-Ground Ecosystems of Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Kelley, A. M.; Walker, D. A.; Jia, G. J.; Raynolds, M. K.

    2006-12-01

    Regional-scale patterns of vegetation have been analyzed along a number of climate gradients throughout the world; these spatial dynamics provide important insights into the controlling factors of vegetation and the potential plant responses to environmental change. Only a few studies to date have collectively examined the vegetation biomass and production of arctic tundra ecosystems and their relationships to broadly ranging climate variables. No prior study has taken a systematic and consistent approach to examining vegetation biomass patterns along the full temperature gradient of the arctic biome. An additional complicating factor for studying vegetation of arctic tundra is the high spatial variability associated with small patterned-ground features (e.g. non-sorted circles and small non-sorted polygons), resulting from intense freeze-thaw processes. In this study, we sampled and analyzed the aboveground plant biomass components of patterned-ground ecosystems in the Arctic of northern Alaska and Canada along an 1800-km north-south gradient that spans approximately 11 degrees C of mean July temperatures. At each of ten locations along the regional temperature gradient, we ran several 50-m transects and harvested the aboveground biomass of three 20 x 50 cm plots for each transect. Vegetation biomass was dried, sorted by plant functional groups and tissue types, weighed, and analyzed as functions of the summer warmth index (SWI sum of mean monthly temperatures > 0). The absolute biomass (g/m2) of shrubs and graminoids increased exponentially with SWI, whereas forb and lichen biomass showed no change along the gradient. Moss biomass increased linearly with SWI, but with greater variabiliy than the other types. Relative aboveground biomass (% of total) of shrubs and graminoids increased with SWI, whereas percent lichen biomass decreased, and forbs again exhibited no significant change. Percentage of moss biomass was a parabolic function of SWI, with high relative

  12. Landscape Characterization of Arctic Ecosystems Using Data Mining Algorithms and Large Geospatial Datasets

    NASA Astrophysics Data System (ADS)

    Langford, Z. L.; Kumar, J.; Hoffman, F. M.

    2015-12-01

    Observations indicate that over the past several decades, landscape processes in the Arctic have been changing or intensifying. A dynamic Arctic landscape has the potential to alter ecosystems across a broad range of scales. Accurate characterization is useful to understand the properties and organization of the landscape, optimal sampling network design, measurement and process upscaling and to establish a landscape-based framework for multi-scale modeling of ecosystem processes. This study seeks to delineate the landscape at Seward Peninsula of Alaska into ecoregions using large volumes (terabytes) of high spatial resolution satellite remote-sensing data. Defining high-resolution ecoregion boundaries is difficult because many ecosystem processes in Arctic ecosystems occur at small local to regional scales, which are often resolved in by coarse resolution satellites (e.g., MODIS). We seek to use data-fusion techniques and data analytics algorithms applied to Phased Array type L-band Synthetic Aperture Radar (PALSAR), Interferometric Synthetic Aperture Radar (IFSAR), Satellite for Observation of Earth (SPOT), WorldView-2, WorldView-3, and QuickBird-2 to develop high-resolution (˜5m) ecoregion maps for multiple time periods. Traditional analysis methods and algorithms are insufficient for analyzing and synthesizing such large geospatial data sets, and those algorithms rarely scale out onto large distributed- memory parallel computer systems. We seek to develop computationally efficient algorithms and techniques using high-performance computing for characterization of Arctic landscapes. We will apply a variety of data analytics algorithms, such as cluster analysis, complex object-based image analysis (COBIA), and neural networks. We also propose to use representativeness analysis within the Seward Peninsula domain to determine optimal sampling locations for fine-scale measurements. This methodology should provide an initial framework for analyzing dynamic landscape

  13. Endoparasites in the feces of arctic foxes in a terrestrial ecosystem in Canada

    PubMed Central

    Elmore, Stacey A.; Lalonde, Laura F.; Samelius, Gustaf; Alisauskas, Ray T.; Gajadhar, Alvin A.; Jenkins, Emily J.

    2013-01-01

    The parasites of arctic foxes in the central Canadian Arctic have not been well described. Canada’s central Arctic is undergoing dramatic environmental change, which is predicted to cause shifts in parasite and wildlife species distributions, and trophic interactions, requiring that baselines be established to monitor future alterations. This study used conventional, immunological, and molecular fecal analysis techniques to survey the current gastrointestinal endoparasite fauna currently present in arctic foxes in central Nunavut, Canada. Ninety-five arctic fox fecal samples were collected from the terrestrial Karrak Lake ecosystem within the Queen Maud Gulf Migratory Bird Sanctuary. Samples were examined by fecal flotation to detect helminths and protozoa, immunofluorescent assay (IFA) to detect Cryptosporidium and Giardia, and quantitative PCR with melt-curve analysis (qPCR-MCA) to detect coccidia. Positive qPCR-MCA products were sequenced and analyzed phylogenetically. Arctic foxes from Karrak Lake were routinely shedding eggs from Toxascaris leonina (63%). Taeniid (15%), Capillarid (1%), and hookworm eggs (2%), Sarcocystis sp. sporocysts 3%), and Eimeria sp. (6%), and Cystoisospora sp. (5%) oocysts were present at a lower prevalence on fecal flotation. Cryptosporidium sp. (9%) and Giardia sp. (16%) were detected by IFA. PCR analysis detected Sarcocystis (15%), Cystoisospora (5%), Eimeria sp., and either Neospora sp. or Hammondia sp. (1%). Through molecular techniques and phylogenetic analysis, we identified two distinct lineages of Sarcocystis sp. present in arctic foxes, which probably derived from cervid and avian intermediate hosts. Additionally, we detected previously undescribed genotypes of Cystoisospora. Our survey of gastrointestinal endoparasites in arctic foxes from the central Canadian Arctic provides a unique record against which future comparisons can be made. PMID:24533320

  14. Crossing the Threshold - Reviewed Evidence for Regime Shifts in Arctic Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Mård Karlsson, J.; Destouni, G.; Peterson, G.; Gordon, L.

    2009-12-01

    The Arctic is rapidly changing, and the Arctic terrestrial ecosystems may respond to changing conditions in different ways. We review the evidence of regime shifts (ecosystem change from one set of mutually reinforcing feedbacks to another) in Arctic terrestrial ecosystems in relation to the hydrological cycle, as part of a larger interdisciplinary research project on Pan-Arctic ice-water-biogeochemical system responses and social-ecological resilience effects in a warming climate, which has in turn been part of the International Polar Year project Arctic-HYDRA. Such regime shifts may have implications for the Earth system as a whole, through changes in water flows and energy balance that yield feedbacks to hydrology and the local and global climate. Because the presence or absence of permafrost is a main control on local hydrological processes in the Arctic, we use the ecological response to permafrost warming to define three types of regime shifts: 1) Conversion of aquatic to terrestrial ecosystems due to draining of lakes and wetlands caused by permafrost degradation and thermokarst processes, which may have a large impact on local people and animals that depend on these ecosystems for food, domestic needs, and habitat, and on climate as the water conditions influence the direction of CO2 exchange. 2) Conversion of terrestrial to aquatic ecosystems as forests are being replaced by wet sedge meadows, bogs, and thermokarst ponds that favor aquatic birds and mammals, as thawing permafrost atop continuous permafrost undermines and destroys the root zone, leading to collapse and death of the trees. 3) Shifts in terrestrial ecosystems due to transition from tundra to shrubland and/or forest, caused by warming of air and soil, resulting in increased surface energy exchanges and albedo, which may in turn feed back to enhanced warming at the local-regional scale. We compare the impact, scale and key processes for each of these regime shifts, and assess the degree to

  15. Delayed responses of an Arctic ecosystem to an extreme summer: impacts on net ecosystem exchange and vegetation functioning

    NASA Astrophysics Data System (ADS)

    Zona, D.; Lipson, D. A.; Richards, J. H.; Phoenix, G. K.; Liljedahl, A. K.; Ueyama, M.; Sturtevant, C. S.; Oechel, W. C.

    2014-10-01

    The importance and consequences of extreme events on the global carbon budget are inadequately understood. This includes the differential impact of extreme events on various ecosystem components, lag effects, recovery times, and compensatory processes. In the summer of 2007 in Barrow, Arctic Alaska, there were unusually high air temperatures (the fifth warmest summer over a 65-year period) and record low precipitation (the lowest over a 65-year period). These abnormal conditions were associated with substantial desiccation of the Sphagnum layer and a reduced net Sphagnum CO2 sink but did not affect net ecosystem exchange (NEE) from this wet-sedge arctic tundra ecosystem. Microbial biomass, NH4+ availability, gross primary production (GPP), and ecosystem respiration (Reco) were generally greater during this extreme summer. The cumulative ecosystem CO2 sink in 2007 was similar to the previous summers, suggesting that vascular plants were able to compensate for Sphagnum CO2 uptake, despite the impact on other functions and structure such as desiccation of the Sphagnum layer. Surprisingly, the lowest ecosystem CO2 sink over a five summer record (2005-2009) was observed during the 2008 summer (~70% lower), directly following the unusually warm and dry summer, rather than during the extreme summer. This sink reduction cannot solely be attributed to the potential damage to mosses, which typically contribute ~40% of the entire ecosystem CO2 sink. Importantly, the return to a substantial cumulative CO2 sink occurred two summers after the extreme event, which suggests a substantial resilience of this tundra ecosystem to at least an isolated extreme event. Overall, these results show a complex response of the CO2 sink and its sub-components to atypically warm and dry conditions. The impact of multiple extreme events requires further investigation.

  16. Oceanic periglacial in the evolution of the Arctic marine ecosystem

    SciTech Connect

    Matishov, G.G.

    1996-12-31

    A study of the Arctic marine and land environment and biota is connected with the analysis of the global climatic changes and the general history of Arctic and subarctic ecological systems. Ancient glaciation not only influenced the geomorphology of landscapes, physical and chemical properties of the ocean and its seas, but also caused the global change of the morphoclimatic zonality in the ocean as a whole. Submarine and subaqual hydrological, geomorphological and biological processes on the shelves of polar and temperate latitudes had intensified especially during the melting of continental glaciers. The study of the periglacial problem consists, as a whole, in the research of the geological and biological phenomena which take place in the pelagial and the benthal outside the ice sheets and are connected with them by causal, spatial and temporal relations.

  17. Climate Change Experiments in Arctic Ecosystems: Scientific Strategy and Design Criteria

    NASA Astrophysics Data System (ADS)

    Wullschleger, S. D.; Hinzman, L. D.; McGuire, A. D.; Oberbauer, S. F.; Oechel, W. C.; Norby, R. J.; Thornton, P. E.; Schuur, E. A.; Shugart, H. H.; Walsh, J. E.; Wilson, C. J.

    2010-12-01

    Arctic and subarctic ecosystems are sensitive to changes in climate. These are among the largest and coldest of all ecosystems and are perceived by many as especially vulnerable to environmental change. Warming, in particular, is expected to be greatest in northern latitudes with potentially significant consequences for tundra, taiga, and peat lands. Observational evidence suggests that warming is already affecting physical and ecological processes in high-latitude ecosystems. Models predict that permafrost degradation and the northward expansion of shrubs into tundra represent important feedbacks on climate. Manipulative experiments can help understand the vulnerability of ecosystems to climate warming. Previous attempts to manipulate the environment of ecosystems in arctic and subarctic regions have focused on warming plant and soils, but treatments have been limited to small scales and modest increases in temperature. Manipulating the environment at larger scales and exposing ecosystems to higher temperatures for longer periods of time will be required to fully describe the physical, chemical, and biological mechanisms that govern land-atmosphere interactions. A variety of logistical and engineering challenges must be overcome and new approaches developed before we can address the questions being asked of the scientific community especially as we continue to move toward large-scale and long-term experiments. In light of the many uncertainties that surround the response of high-latitude ecosystems to global climate change, it is important that the scientific community consider how manipulative experiments can address and resolve ecosystem impacts and feedbacks to climate. A workshop sponsored by the Department of Energy, Office of Science was recently held at the University of Alaska, Fairbanks. The goal of the workshop was to highlight conclusions from observational and modeling studies about the response of arctic and subarctic ecosystems to a changing climate

  18. Canopy Spectral Imaging (NDVI) As A Proxy For Shrub Biomass And Ecosystem Carbon Fluxes Across Arctic Tundra Habitats

    NASA Astrophysics Data System (ADS)

    Flower, C. E.; Welker, J. M.; Gonzalez-Meler, M. A.

    2015-12-01

    There is widespread consensus that climate change is contributing to rapid vegetation shifts in the ecologically sensitive Arctic tundra. These tussock grass dominated systems are shifting to tussock/woody shrub communities leading to likely alterations in carbon (C) sequestration and ecosystem productivity, which in turn can manifest in "greening" and changes in normalized difference vegetation index values (NDVI). While the expansion of woody vegetation is well established, our understanding of the ecosystem dynamics associated with this new habitat remain largely unknown. To untangle how the Arctic tundra may be impacted by these vegetation shifts we paired vegetation measurements (i.e. shrub biomass, leaf area, and shrub canopy area) and ecosystem C fluxes (e.g. net ecosystem exchange, NEE, and ecosystem respiration) with ground-level measurements of NDVI. Measurements were conducted at the Toolik Field Station in dry heath and moist acidic tundra habitats which are two primary habitat types on the North Slope of Alaska. We found strong positive relationships between shrub leaf area and biomass as well as shrub canopy area and biomass, relationships that were corroborated with NDVI measurements. This lends support for the use of NDVI as a proxy measurement of leaf area and shrub biomass. Additionally, NDVI was negatively correlated with ecosystem respiration across habitats, with respiratory fluxes consistently higher in the moist acidic relative to the dry heath tundra. Finally, we observed a significant positive nonlinear relationship between NEE and NDVI (R2~0.8; P<0.01). Shrub removal revealed that NEE was strongly controlled by woody shrubs. The positive relationship between NDVI and NEE highlights the potential shifts in the C balance of the Arctic tundra associated with woody encroachment. This increased plant productivity may offset greenhouse gas losses from permafrost degradation contributing some resilience to this system otherwise considered a

  19. Boreal fire influence on Arctic tropospheric ozone, ecosystems and climate forcing

    NASA Astrophysics Data System (ADS)

    Arnold, S.; Monks, S. A.; Emmons, L. K.; Sitch, S.; Rap, A.; Law, K.; Tilmes, S.; Lamarque, J.

    2013-12-01

    Temperature observations show that the Arctic has warmed rapidly in the past few decades compared to the northern hemisphere as a whole. Model calculations suggest that changes in short-lived pollutants such as ozone and aerosol may have contributed significantly to this warming. Arctic tropospheric budgets of short-lived pollutants are impacted by both local anthropogenic emissions and by long-range transport of gases and aerosols from Europe, Asia and N. America, but also by local Boreal wildfires in summer. Our understanding of how fires impact Arctic budgets of climate-relevant atmospheric constituents is limited, and is reliant on sparse observations and models of tropospheric chemistry. A better understanding of Boreal fire influence on Arctic ozone is essential for improving the reliability of our projections of future Arctic and Northern Hemisphere climate change, especially in light of proposed climate-fire feedbacks which may enhance the intensity and extent of high latitude wildfire under a warming climate. Using the NCAR Community Earth System Model (CESM) and a scheme for tagging and tracking NOx emitted by high latitude wildfires and its resultant tropospheric ozone production, we investigate the impacts of fire-sourced ozone on summertime high latitude radiative forcing and on ecosystems. The large fraction of NOy present as PAN in the Arctic suggests there may be a strong sensitivity of NOy and ozone enhancement to the efficiency of vertical transport from source regions, which determines the stability of PAN as air is advected poleward. We use these simulations and aircraft observations to characterise the vertical distributions of sensitivities of Arctic NOy and ozone to remote anthropogenic and local widlfire sources, and use an offline radiative transfer model to quantify impacts on local ozone radiative forcing. We compare these vertical sensitivities with those of a primary-emitted CO-like source tracer, to investigate the role of PAN

  20. Symptoms of change in multi-scale observations of arctic ecosystem carbon cycling

    NASA Astrophysics Data System (ADS)

    Stoy, P. C.; Williams, M. D.; Hartley, I. P.; Street, L.; Hill, T. C.; Prieto-Blanco, A.; Wayolle, A.; Disney, M.; Evans, J.; Fletcher, B.; Poyatos, R.; Wookey, P.; Merbold, L.; Wade, T. J.; Moncrieff, J.

    2009-12-01

    Arctic ecosystems are responding rapidly to observed climate change. Quantifying the magnitude of these changes, and their implications for the climate system, requires observations of their current structure and function, as well as extrapolation and modelling (i.e. ‘upscaling’) across time and space. Here, we describe the major results of the International Polar Year (IPY) ABACUS project, a multi-scale investigation across arctic Fennoscandia that couples plant and soil process studies, isotope analyses, flux and micrometeorological measurements, process modelling, and aircraft and satellite observations to improve predictions of the response of the arctic terrestrial biosphere to global change. We begin with a synthesis of eddy covariance observations from the global FLUXNET database. We demonstrate that a simple model parameterized using pan-arctic chamber measurements explains over 80% of the variance of half-hourly CO2 fluxes during the growing season across most arctic and montane tundra ecosystems given accurate measurements of leaf area index (LAI), which agrees with the recently proposed ‘functional convergence’ paradigm for tundra vegetation. The ability of MODIS to deliver accurate LAI estimates is briefly discussed and an adjusted algorithm is presented and validated using direct observations. We argue for an Information Theory-based framework for upscaling in Earth science by conceptualizing multi-scale research as a transfer of information across scales. We then demonstrate how error in upscaled arctic C flux estimates can be reduced to less than 4% from their high-resolution counterpart by formally preserving the information content of high spatial and spectral resolution aircraft and satellite imagery. Jaynes’ classic Maximum Entropy (MaxEnt) principle is employed to incorporate logical, biological and physical constraints to reduce error in downscaled flux estimates. Errors are further reduced by assimilating flux, biological and remote

  1. Long-Term Release of Carbon Dioxide from Arctic Tundra Ecosystems in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Euskirchen, E. S.; Bret-Harte, M. S.; Edgar, C.; Shaver, G. R.

    2014-12-01

    Recent data syntheses and modeling studies of arctic tundra carbon dioxide (CO2) balance have suggested that the tundra is a CO2 sink, a source or neutral. Much of this uncertainty arises from a lack of data pertaining to winter CO2 flux, as well as how these ecosystems have responded to recent warming trends. Due to a harsh, remote environment, long-term, continuous measurements of arctic tundra CO2 fluxes over the full annual cycle have been non-existent. In September 2007, we began eddy covariance measurements of net ecosystem exchange (NEE, where a negative value denotes a sink) of CO2 in northern Alaska at two ecosystems, heath and wet sedge tundra. These measurements continue to the present, and represent the longest continuous record of arctic tundra NEE currently available. From January 2008 - December 2013, the ecosystems were annual sources of CO2, with the wet sedge tundra acting as a greater source (mean ± standard deviation of 50 ± 30 g C m-2 y-1) than the heath tundra (16 ± 6 g C m-2 y-1). During these same years, the ecosystems were sinks of CO2 in the summer (June - August), with less variability between the ecosystems, -77 ± 15 g C m-2 in the wet sedge tundra, and -70 ± 12 g C m-2 in the heath. Environmental controls over NEE differed between ecosystems and seasons, with the wet sedge tundra acting particularly responsive in terms of CO2 release during periods with warm air temperatures from fall to early winter. During cold winter periods, CO2 release from the snowpack in both ecosystems was related to increases in wind speed and drops in atmospheric pressure. Overall, the measured differences in the annual versus summer NEE illustrate how the sink strength of the tundra can be overestimated if data are only collected during the growing season. Furthermore, eddy covariance measurements of methane (CH4) in the wet sedge tundra during late spring to early fall from 2012 to present show that this ecosystem releases 0.34 ± 11 mg CH4 m-2 d-1

  2. Ecosystem-Vegetation Dynamics in sub-arctic Stordalen Mire, Sweden

    NASA Astrophysics Data System (ADS)

    Mugnani, M. P.; Varner, R. K.; Steele, K.; Frey, S. D.; Crill, P. M.

    2012-12-01

    Increased global temperatures have contributed to the thaw of permafrost and a subsequent atmospheric release of stored methane (CH4) from sub-arctic ecosystems. Palsas, small frost uplifted mounds that support specialized dry-tolerant vegetation species, degrade when permafrost thaws, allowing other species such a Sphagnum and Eriophorum to encroach on the microhabitats and outcompete other species, altering the carbon feedback into the thin arctic soil. Other climate change-related events including increased precipitation, seasonal temperature abnormalities and changes in humidity and nutrient availability may alter vegetation dynamics in terms of diversity and abundance in sub-arctic regions. During July 2012, measurements of vegetation composition and species abundance estimates were made in Stordalen Mire (68° 21' N, 19° 03' E), Abisko Sweden, two hundred kilometers north of the Arctic Circle. The mire is an area of discontinuous permafrost populated by micro-ecosystems that vary in vegetation species and abundance depending on growth conditions. All ecosystems provide beneficial services to support a range of life forms including rodents, birds, insects and reindeer. Five representative ecosystems of the mire were chosen to conduct studies on vegetation diversity and percent cover-based abundance: palsa, Eriophorum-dominated fen, Sphagnum-dominated peatland, lakeshore edge and lakeside heath. In each ecosystem vegetation species were recorded in six transects with quadrats along with a corresponding percent cover estimation and scale number based on the Braun-Blanquet percent cover method. To determine nutrient dynamics between ecosystems, soil peat samples were also taken at random from all ecosystem transects. These were analyzed for carbon and inorganic nitrogen as well as ammonium and nitrate. In the vegetation data analysis, the Shannon-Wiener Diversity Index showed that the lakeside heath ecosystem was the most diverse and even in species distribution

  3. Overarching perspectives of contemporary and future ecosystems in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Wassmann, Paul

    2015-12-01

    The Arctic region has a number of specific characteristics that provide the region an exceptional global position. It comprises 5% of the earth surface, 1% of world ocean volume, 3% of world ocean area, 25% of world continental shelf, 35% of world coastline, 11% of global river runoff and 20 of worlds 100 longest rivers. The Arctic region encompasses only 0.05% of the global population, but 22% undiscovered petroleum, 15% of global petroleum production, many metals and non-metals resources and support major global fisheries (60 and 80°N). In times of increasing resource demand and limitation the world focuses increasingly onto the Arctic Ocean (AO) and adjacent regions. This development is emphasised by the recent awareness of rapid climate change in the AO, the most significant on the globe, and has resulted in increased attention to the oceanography of the high north. The loss of Arctic sea ice has emerged as a leading signal of global warming. It is taking place at a rate 2-3 times faster than global rates and sea-ice cover has decreased more than 10% per decade, while sea-ice volume may have been reduced by minimum 40% over the last 30 years (Meier et al., 2014). The reduction of ice cover and thickness makes the region available for commercial interest. The region drives also critical effects on the biophysical, political and economic system of the Northern Hemisphere (e.g., Grambling, 2015). These striking changes in physical forcing have left marine ecological footprints of climate change in the Arctic ecosystem (Wassmann et al., 2011). However, predicting the future of the pan-Arctic ecosystem remains a challenge not only because of the ever-accelerating nature of both physical and biological alterations, but also because of lack of marine ecological knowledge, that is staggering for the majority of regions (except the Barents, Chukchi and Beaufort seas).

  4. Ecosystem model intercomparison of under-ice and total primary production in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Jin, Meibing; Popova, Ekaterina E.; Zhang, Jinlun; Ji, Rubao; Pendleton, Daniel; Varpe, Øystein; Yool, Andrew; Lee, Younjoo J.

    2016-01-01

    Previous observational studies have found increasing primary production (PP) in response to declining sea ice cover in the Arctic Ocean. In this study, under-ice PP was assessed based on three coupled ice-ocean-ecosystem models participating in the Forum for Arctic Modeling and Observational Synthesis (FAMOS) project. All models showed good agreement with under-ice measurements of surface chlorophyll-a concentration and vertically integrated PP rates during the main under-ice production period, from mid-May to September. Further, modeled 30-year (1980-2009) mean values and spatial patterns of sea ice concentration compared well with remote sensing data. Under-ice PP was higher in the Arctic shelf seas than in the Arctic Basin, but ratios of under-ice PP over total PP were spatially correlated with annual mean sea ice concentration, with higher ratios in higher ice concentration regions. Decreases in sea ice from 1980 to 2009 were correlated significantly with increases in total PP and decreases in the under-ice PP/total PP ratio for most of the Arctic, but nonsignificantly related to under-ice PP, especially in marginal ice zones. Total PP within the Arctic Circle increased at an annual rate of between 3.2 and 8.0 Tg C/yr from 1980 to 2009. This increase in total PP was due mainly to a PP increase in open water, including increases in both open water area and PP rate per unit area, and therefore much stronger than the changes in under-ice PP. All models suggested that, on a pan-Arctic scale, the fraction of under-ice PP declined with declining sea ice cover over the last three decades.

  5. Diverging Plant and Ecosystem Strategies in Response to Climate Change in the High Arctic

    NASA Astrophysics Data System (ADS)

    Maseyk, K. S.; Welker, J. M.; Czimczik, C. I.; Lupascu, M.; Lett, C.; Seibt, U. H.

    2014-12-01

    Increasing summer precipitation means Arctic growing seasons are becoming wetter as well as warmer, but the effect of these coupled changes on tundra ecosystem functioning remains largely unknown. We have determined how warmer and wetter summers affect coupled carbon-water cycling in a High Arctic polar semi-desert ecosystem in NW Greenland. Measurements of ecosystem CO2 and water fluxes throughout the growing season and leaf ecophysiological traits (gas exchange, morphology, leaf chemistry) were made at a long-term climate change experiment. After 9 years of exposure to warmer (+ 4°C) and / or wetter (+ 50% precipitation) treatments, we found diverging plant strategies between the responses to warming with or without an increase in summer precipitation. Warming alone resulted in an increase in leaf nitrogen, mesophyll conductance and leaf-mass per area and higher rates of leaf-level photosynthesis, but with warming and wetting combined leaf traits remain largely unchanged. However, total leaf area increased with warming plus wetting but was unchanged with warming alone. The combined effect of these leaf trait and canopy adjustments is a decrease in ecosystem water-use efficiency (the ratio of net productivity to evapotranspiration) with warming only, but a substantial increase with combined warming and wetting. We conclude that increasing summer precipitation will alter tundra ecohydrological responses to warming; that leaf-level changes in ecophysiological traits have an upward cascading consequence for ecosystem and land surface-climate interactions; and the current relative resistance of High Arctic ecosystems to warming may mask biochemical and carbon cycling changes already underway.

  6. Arctic ecosystem functional zones: identification and quantification using an above and below ground monitoring strategy

    NASA Astrophysics Data System (ADS)

    Hubbard, Susan S.; Ajo-Franklin, Jonathan B.; Dafflon, Baptiste; Dou, Shan; Kneafsey, Tim J.; Peterson, John E.; Tas, Neslihan; Torn, Margaret S.; Phuong Tran, Anh; Ulrich, Craig; Wainwright, Haruko; Wu, Yuxin; Wullschleger, Stan

    2015-04-01

    Although accurate prediction of ecosystem feedbacks to climate requires characterization of the properties that influence terrestrial carbon cycling, performing such characterization is challenging due to the disparity of scales involved. This is particularly true in vulnerable Arctic ecosystems, where microbial activities leading to the production of greenhouse gasses are a function of small-scale hydrological, geochemical, and thermal conditions influenced by geomorphology and seasonal dynamics. As part of the DOE Next-Generation Ecosystem Experiment (NGEE-Arctic), we are advancing two approaches to improve the characterization of complex Arctic ecosystems, with an initial application to an ice-wedge polygon dominated tundra site near Barrow, AK, USA. The first advance focuses on developing a new strategy to jointly monitor above- and below- ground properties critical for carbon cycling in the tundra. The strategy includes co-characterization of properties within the three critical ecosystem compartments: land surface (vegetation, water inundation, snow thickness, and geomorphology); active layer (peat thickness, soil moisture, soil texture, hydraulic conductivity, soil temperature, and geochemistry); and permafrost (mineral soil and ice content, nature, and distribution). Using a nested sampling strategy, a wide range of measurements have been collected at the study site over the past three years, including: above-ground imagery (LiDAR, visible, near infrared, NDVI) from various platforms, surface geophysical datasets (electrical, electromagnetic, ground penetrating radar, seismic), and point measurements (such as CO2 and methane fluxes, soil properties, microbial community composition). A subset of the coincident datasets is autonomously collected daily. Laboratory experiments and new inversion approaches are used to improve interpretation of the field geophysical datasets in terms of ecosystem properties. The new strategy has significantly advanced our ability

  7. Modeling Active Layer and Permafrost Dynamics of Ice Wedge Polygon Dominated Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Kumar, J.; Bisht, G.; Liljedahl, A.; Mills, R. T.; Karra, S.; Painter, S. L.; Thornton, P. E.

    2013-12-01

    Permafrost soils contains vast stock of frozen organic carbon. As warming climate accelerates the thaw of the permafrost, increasing amount of organic matter is exposed to respiration leading to release of carbon to the atmosphere in the form of CO2 and CH4 . Permafrost thermal dynamics play a key role influencing hydrologic and biogeochemical processes in these ecosystems. Large areas of Arctic landscape are covered by the patterned ground features created by repeated freezing and thawing of soil underlain by aerially continuous permafrost. These microtopographic features in the landscape controls the local surface-subsurface hydrology and thermal regimes through differential transport of heat and water. Study of these interacting thermal-hydrologic-biogeochemical in permafrost soils are further complicated by the complex topography and heterogeneity of subsurface. We have developed and applied a coupled multiscale-multiphase-multicomponent surface-subsurface flow and reactive transport model PFLOTRAN for modeling of thermal-hydrologic-biogeochemical processes in permafrost soils. We study the permafrost thermal dynamics, role of microtopography in local scale hydrology at the Department of Energy's Next Generation Ecosystem Experiment (NGEE) - Arctic field sites near Barrow, Alaska. High resolution LiDAR data is used to represent the microtopography at sub-meter resolution in PFLOTRAN. Long term simulations have been conducted at the field sites informed by the observations from field and laboratory campaigns to study and understand the hydrologic and biogeochemical processes in these Arctic ecosystems.

  8. Changing snow cover in tundra ecosystems tips the Arctic carbon balance

    NASA Astrophysics Data System (ADS)

    Zona, D.; Hufkens, K.; Gioli, B.; Kalhori, A. A. M.; Oechel, W. C.

    2014-12-01

    The Arctic environment has witnessed important changes due to global warming, resulting in increased surface air temperatures and rain events which both exacerbate snow cover deterioration (Semmens et al, 2013; Rennert et al, 2009; White et al, 2007; Min et al, 2008; Sharp et al, 2013; Schaeffer et al, 2013). Snow cover duration is declining by almost 20% per decade, a far higher rate than model estimates (Derksen and Brown, 2012). Concomitant with increasing temperatures and decreasing snow cover duration, the length of the arctic growing season is reported to have increased by 1.1 - 4.9 days per decade since 1951 (Menzel et al, 2006), and, plant productivity and CO2 uptake from arctic vegetation are strongly influenced by changes in growing season length (Myneni et al., 1997; Schaefer et al., 2005; Euskirchen et al., 2006). Based on more than a decade of eddy flux measurements in Arctic tundra ecosystems across the North slope of Alaska, and remotely sensed snow cover data, we show that earlier snow melt in the spring increase C uptake while an extended snow free period in autumn is associated with a higher C loss. Here we present the impacts of changes in snow cover dynamics between spring and autumn in arctic tundra ecosystems on the carbon dynamics and net C balance of the Alaskan Arctic. ReferencesDerksen, C., Brown R. (2012) Geophys. Res. Lett., doi:10.1029/2012GL053387 Euskirchen, E.S., et al. (2006) Glob. Change Biol., 12, 731-750. Menzel, A., et al. 2006. Glob. Change Biol., 12, 1969-1976. Min SK, Zhang X, Zweirs F (2008) Science 320: 518-520. Rennert K J, Roe G, Putkonen J and Bitz C M (2009) J. Clim. 22 2302-15. Schaefer, K., Denning A.S., Leonard O. (2005) Global Biogeochem. Cycles, 19, GB3017. Schaeffer, S. M., Sharp, E., Schimel, J. P. & Welker, J. M. (2013). Soil- plant N processes in a High Arctic ecosystem, NW Greenland are altered by long-term experimental warming and higher rainfall. Glob. Change Biol., 11, 3529-39. doi: 10.1111/gcb.12318

  9. Measurement-based upscaling of Pan Arctic Net Ecosystem Exchange: the PANEEx project

    NASA Astrophysics Data System (ADS)

    Njuabe Mbufong, Herbert; Kusbach, Antonin; Lund, Magnus; Persson, Andreas; Christensen, Torben R.; Tamstorf, Mikkel P.; Connolly, John

    2016-04-01

    The high variability in Arctic tundra net ecosystem exchange (NEE) of carbon (C) can be attributed to the high spatial heterogeneity of Arctic tundra due to the complex topography. Current models of C exchange handle the Arctic as either a single or few ecosystems, responding to environmental change in the same manner. In this study, we developed and tested a simple pan Arctic NEE (PANEEx) model using the Misterlich light response curve (LRC) function with photosynthetic photon flux density (PPFD) as the main driving variable. Model calibration was carried out with eddy covariance carbon dioxide (CO2) data from 12 Arctic tundra sites. The model input parameters (Fcsat, Rd and α) were estimated as a function of air temperature (AirT) and leaf area index (LAI) and represent specific characteristics of the NEE-PPFD relationship, including the saturation flux, dark respiration and initial light use efficiency, respectively. LAI and air temperature were respectively estimated from empirical relationships with remotely sensed normalized difference vegetation index (NDVI) and land surface temperature (LST). These are available as MODIS Terra product MOD13Q1 and MOD11A1 respectively. Therefore, no specific knowledge of the vegetation type is required. The PANEEx model captures the spatial heterogeneity of the Arctic tundra and was effective in simulating 77% of the measured fluxes (r2 = 0.72, p < 0.001) at the 12 sites used in the calibration of the model. Further, the model effectively estimates NEE in three disparate Alaskan ecosystems (heath, tussock and fen) with an estimation ranging between 10 - 36% of the measured fluxes. We suggest that the poor agreement between the measured and modeled NEE may result from the disparity between ground-based measured LAI (used in model calibration) and remotely sensed LAI (estimated from NDVI and used in NEE estimation). Moreover, our results suggests that using simple linear regressions may be inadequate as parameters estimated

  10. Transitions in Arctic ecosystems: Ecological implications of a changing hydrological regime

    NASA Astrophysics Data System (ADS)

    Wrona, Frederick J.; Johansson, Margareta; Culp, Joseph M.; Jenkins, Alan; Mârd, Johanna; Myers-Smith, Isla H.; Prowse, Terry D.; Vincent, Warwick F.; Wookey, Philip A.

    2016-03-01

    Numerous international scientific assessments and related articles have, during the last decade, described the observed and potential impacts of climate change as well as other related environmental stressors on Arctic ecosystems. There is increasing recognition that observed and projected changes in freshwater sources, fluxes, and storage will have profound implications for the physical, biogeochemical, biological, and ecological processes and properties of Arctic terrestrial and freshwater ecosystems. However, a significant level of uncertainty remains in relation to forecasting the impacts of an intensified hydrological regime and related cryospheric change on ecosystem structure and function. As the terrestrial and freshwater ecology component of the Arctic Freshwater Synthesis, we review these uncertainties and recommend enhanced coordinated circumpolar research and monitoring efforts to improve quantification and prediction of how an altered hydrological regime influences local, regional, and circumpolar-level responses in terrestrial and freshwater systems. Specifically, we evaluate (i) changes in ecosystem productivity; (ii) alterations in ecosystem-level biogeochemical cycling and chemical transport; (iii) altered landscapes, successional trajectories, and creation of new habitats; (iv) altered seasonality and phenological mismatches; and (v) gains or losses of species and associated trophic interactions. We emphasize the need for developing a process-based understanding of interecosystem interactions, along with improved predictive models. We recommend enhanced use of the catchment scale as an integrated unit of study, thereby more explicitly considering the physical, chemical, and ecological processes and fluxes across a full freshwater continuum in a geographic region and spatial range of hydroecological units (e.g., stream-pond-lake-river-near shore marine environments).

  11. An eddy covariance derived annual carbon budget for an arctic terrestrial ecosystem (Disko, Greenland)

    NASA Astrophysics Data System (ADS)

    McConnell, Alistair; Lund, Magnus; Friborg, Thomas

    2016-04-01

    Ecosystems with underlying permafrost cover nearly 25% of the ice-free land area in the northern hemisphere and store almost half of the global soil carbon. Future climate changes are predicted to have the most pronounced effect in northern latitudes. These Arctic ecosystems are therefore subject to dramatic changes following thawing of permafrost, glacial retreat, and coastal erosion. The most dramatic effect of permafrost thawing is the accelerated decomposition and potential mobilization of organic matter stored in the permafrost. This will impact global climate through the mobilization of carbon and nitrogen accompanied by release of greenhouses gases, including carbon dioxide. This study presents the initial findings and first full annual carbon (CO2) budget, derived from eddy covariance measurements, for an Arctic landscape in West Greenland. The study site, a terrestrial Arctic maritime climate, is located at Østerlien, near Qeqertarsuaq, on the southern coast of Disko Island in central West Greenland (69° 15' N, 53° 34' W) within the transition zone from continuous to discontinuous permafrost. The mean annual air temperature is -5 C and the annual precipitation as rain is 150-200 mm. Arctic ecosystem feedback mechanisms and processes interact on micro, local and regional scales. This is further complicated by several potential feedback mechanisms likely to occur in permafrost-affected ecosystems, involving the interactions of microorganisms, vegetation and soil. The eddy covariance method allows us to interrogate the processes and drivers of land-atmosphere carbon exchange at extremely high temporary frequency (10 Hz), providing landscape-scale measurements of CO2, H2O and heat fluxes for the site, which are processed to derive daily, monthly and now, annual carbon fluxes. We discuss the scientific methodology, challenges, and analysis, as well as the practical and logistic challenges of working in the Arctic, and present an annual carbon budget

  12. Seasonal dynamics of bacterial biomass and production in a coastal arctic ecosystem: Franklin Bay, western Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Garneau, Marie-Ã. Ve; Roy, SéBastien; Lovejoy, Connie; Gratton, Yves; Vincent, Warwick F.

    2008-07-01

    The Canadian Arctic Shelf Exchange Study (CASES) included the overwintering deployment of a research platform in Franklin Bay (70°N, 126°W) and provided a unique seasonal record of bacterial dynamics in a coastal region of the Arctic Ocean. Our objectives were (1) to relate seasonal bacterial abundance (BA) and production (BP) to physico-chemical characteristics and (2) to quantify the annual bacterial carbon flux. BA was estimated by epifluorescence microscopy and BP was estimated from 3H-leucine and 3H-thymidine assays. Mean BA values for the water column ranged from 1.0 (December) to 6.8 × 105 cells mL-1 (July). Integral BP varied from 1 (February) to 80 mg C m-2 d-1 (July). During winter-spring, BP was uncorrelated with chlorophyll a (Chl a), but these variables were significantly correlated during summer-autumn (rs = 0.68, p < 0.001, N = 38), suggesting that BP was subject to bottom-up control by carbon supply. Integrated BP data showed three distinct periods: fall-winter, late winter-late spring, and summer. A baseline level of BB and BP was maintained throughout late winter-late spring despite the persistent cold and darkness, with irregular fluctuations that may be related to hydrodynamic events. During this period, BP rates were correlated with colored dissolved organic matter (CDOM) but not Chl a (rs BP.CDOM∣Chl a = 0.20, p < 0.05, N = 176). Annual BP was estimated as 6 g C m-2 a-1, implying a total BP of 4.8 × 1010 g C a-1 for the Franklin Bay region. These results show that bacterial processes continue throughout all seasons and make a large contribution to the total biological carbon flux in this coastal arctic ecosystem.

  13. In the dark: A review of ecosystem processes during the Arctic polar night

    NASA Astrophysics Data System (ADS)

    Berge, Jørgen; Renaud, Paul E.; Darnis, Gerald; Cottier, Finlo; Last, Kim; Gabrielsen, Tove M.; Johnsen, Geir; Seuthe, Lena; Weslawski, Jan Marcin; Leu, Eva; Moline, Mark; Nahrgang, Jasmine; Søreide, Janne E.; Varpe, Øystein; Lønne, Ole Jørgen; Daase, Malin; Falk-Petersen, Stig

    2015-12-01

    Several recent lines of evidence indicate that the polar night is key to understanding Arctic marine ecosystems. First, the polar night is not a period void of biological activity even though primary production is close to zero, but is rather characterized by a number of processes and interactions yet to be fully understood, including unanticipated high levels of feeding and reproduction in a wide range of taxa and habitats. Second, as more knowledge emerges, it is evident that a coupled physical and biological perspective of the ecosystem will redefine seasonality beyond the "calendar perspective". Third, it appears that many organisms may exhibit endogenous rhythms that trigger fitness-maximizing activities in the absence of light-based cues. Indeed a common adaptation appears to be the ability to utilize the dark season for reproduction. This and other processes are most likely adaptations to current environmental conditions and community and trophic structures of the ecosystem, and may have implications for how Arctic ecosystems can change under continued climatic warming.

  14. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  15. Carbon and nitrogen isotope studies in an arctic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    This proposal requests funding for the completion of our current ecological studies at the MS-117 research site at Toolik Lake, Alaska. We have been using a mix of stable and radioisotope techniques to assess the fluxes of carbon and nitrogen within the ecosystem and the implications for long-term carbon storage or loss from the tundra. Several tentative conclusions have emerged from our study including: Tundra in the foothills is no longer accumulating carbon. Surficial radiocarbon abundances show little or no accumulation since 1000--2500 yrs BP. Coastal plain tundra is still accumulating carbon, but the rate of accumulation has dropped in the last few thousand years. Carbon export from watersheds in the Kuparuk and Imnavait Creek drainages are in excess of that expected from estimated primary productivity; and Nitrogen isotope abundances vary between species of plants and along hydrologic gradients.

  16. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-01-01

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO[sub 2] increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  17. Carbon and nitrogen isotope studies in an arctic aquatic ecosystem

    SciTech Connect

    Schell, D.M.

    1989-12-31

    The Phase II studies of the R4D Program on stream and watershed ecology reflect the accomplishments and accumulation of baseline information obtained during the past studies. Although our rough estimates indicate that nitrogen inputs to the watershed ba lance losses, the carbon fluxes suggest that they are not in equilibrium and that there is a net loss of carbon from the tundra ecosystem through respiration and transport out of the watershed via the stream system. Radiocarbon profiles of soil sections coupled with mass transport calculations revealed that peat accumulation has essentially ceased in the R4D watershed and appears to be in ablative loss. Thus the carbon flux measurements provide validation tests for the PLANTGRO and GAS-HYDRO models of the PHASE II studies. These findings are also important in the context of global CO{sub 2} increases from positive feedback mechanisms in peatlands associated with climatic warming in the subarctic regions.

  18. Photodemethylation of Methylmercury in Eastern Canadian Arctic Thaw Pond and Lake Ecosystems.

    PubMed

    Girard, Catherine; Leclerc, Maxime; Amyot, Marc

    2016-04-01

    Permafrost thaw ponds of the warming Eastern Canadian Arctic are major landscape constituents and often display high levels of methylmercury (MeHg). We examined photodegradation potentials in high-dissolved organic matter (DOC) thaw ponds on Bylot Island (BYL) and a low-DOC oligotrophic lake on Cornwallis Island (Char Lake). In BYL, the ambient MeHg photodemethylation (PD) rate over 48 h of solar exposure was 6.1 × 10(-3) m(2) E(-1), and the rate in MeHg amended samples was 9.3 × 10(-3) m(2) E(-1). In contrast, in low-DOC Char Lake, PD was only observed in the first 12 h, which suggests that PD may not be an important loss process in polar desert lakes. Thioglycolic acid addition slowed PD, while glutathione and chlorides did not impact northern PD rates. During an ecosystem-wide experiment conducted in a covered BYL pond, there was neither net MeHg increase in the dark nor loss attributable to PD following re-exposure to sunlight. We propose that high-DOC Arctic thaw ponds are more prone to MeHg PD than nearby oligotrophic lakes, likely through photoproduction of reactive species rather than via thiol complexation. However, at the ecosystem level, these ponds, which are widespread through the Arctic, remain likely sources of MeHg for neighboring systems. PMID:26938195

  19. ESRP approach to using final ecosystem services

    EPA Science Inventory

    The U.S. Environmental Protection Agency has developed the ecosystem Services Research Program (ESRP) as one of its major research efforts. The goal of this program is to create “A comprehensive theory and practice for quantifying ecosystem services so that their value and their...

  20. Arctic ecosystem structure and functioning shaped by climate and herbivore body size

    NASA Astrophysics Data System (ADS)

    Legagneux, P.; Gauthier, G.; Lecomte, N.; Schmidt, N. M.; Reid, D.; Cadieux, M.-C.; Berteaux, D.; Bêty, J.; Krebs, C. J.; Ims, R. A.; Yoccoz, N. G.; Morrison, R. I. G.; Leroux, S. J.; Loreau, M.; Gravel, D.

    2014-05-01

    Significant progress has been made in our understanding of species-level responses to climate change, but upscaling to entire ecosystems remains a challenge. This task is particularly urgent in the Arctic, where global warming is most pronounced. Here we report the results of an international collaboration on the direct and indirect effects of climate on the functioning of Arctic terrestrial ecosystems. Our data from seven terrestrial food webs spread along a wide range of latitudes (~1,500 km) and climates (Δ mean July temperature = 8.5 °C) across the circumpolar world show the effects of climate on tundra primary production, food-web structure and species interaction strength. The intensity of predation on lower trophic levels increased significantly with temperature, at approximately 4.5% per °C. Temperature also affected trophic interactions through an indirect effect on food-web structure (that is, diversity and number of interactions). Herbivore body size was a major determinant of predator-prey interactions, as interaction strength was positively related to the predator-prey size ratio, with large herbivores mostly escaping predation. There is potential for climate warming to cause a switch from bottom-up to top-down regulation of herbivores. These results are critical to resolving the debate on the regulation of tundra and other terrestrial ecosystems exposed to global change.

  1. Nitrogen accumulation and partitioning in a High Arctic tundra ecosystem from extreme atmospheric N deposition events.

    PubMed

    Choudhary, Sonal; Blaud, Aimeric; Osborn, A Mark; Press, Malcolm C; Phoenix, Gareth K

    2016-06-01

    Arctic ecosystems are threatened by pollution from recently detected extreme atmospheric nitrogen (N) deposition events in which up to 90% of the annual N deposition can occur in just a few days. We undertook the first assessment of the fate of N from extreme deposition in High Arctic tundra and are presenting the results from the whole ecosystem (15)N labelling experiment. In 2010, we simulated N depositions at rates of 0, 0.04, 0.4 and 1.2 g Nm(-2)yr(-1), applied as (15)NH4(15)NO3 in Svalbard (79(°)N), during the summer. Separate applications of (15)NO3(-) and (15)NH4(+) were also made to determine the importance of N form in their retention. More than 95% of the total (15)N applied was recovered after one growing season (~90% after two), demonstrating a considerable capacity of Arctic tundra to retain N from these deposition events. Important sinks for the deposited N, regardless of its application rate or form, were non-vascular plants>vascular plants>organic soil>litter>mineral soil, suggesting that non-vascular plants could be the primary component of this ecosystem to undergo measurable changes due to N enrichment from extreme deposition events. Substantial retention of N by soil microbial biomass (70% and 39% of (15)N in organic and mineral horizon, respectively) during the initial partitioning demonstrated their capacity to act as effective buffers for N leaching. Between the two N forms, vascular plants (Salix polaris) in particular showed difference in their N recovery, incorporating four times greater (15)NO3(-) than (15)NH4(+), suggesting deposition rich in nitrate will impact them more. Overall, these findings show that despite the deposition rates being extreme in statistical terms, biologically they do not exceed the capacity of tundra to sequester pollutant N during the growing season. Therefore, current and future extreme events may represent a major source of eutrophication. PMID:26956177

  2. Effects of disturbance on ecosystem dynamics of tundra and riparian vegetation: A project in the R4D program. Final report

    SciTech Connect

    Reynolds, J.F.

    1995-12-31

    Models were proposed as research tools to test the basic understanding of the structure and function of arctic ecosystems, as a means for providing initial management assessments of potential response to energy-related development, and as a vehicle for extrapolation of research results to other arctic sites and landscapes. This final summary report reviews progress made on models at a variety of scales from nutrient uptake by individual roots to nutrient availability within arctic landscapes, and examines potentials and critical limitations of these models for providing insight on patch and landscape level function in tundra regions.

  3. Hydrology modifies ecosystem responses to warming through interactions between soil, leaf and canopy processes in a high Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Maseyk, K. S.; Welker, J. M.; Lett, C.; Czimczik, C. I.; Lupascu, M.; Seibt, U. H.

    2013-12-01

    Arctic ecosystems are experiencing temperature increases more strongly than the global average, and increases in precipitation are also expected amongst the climate impacts on this region in the future. These changes are expected to strongly influence both plant physiology and soil biogeochemistry, and therefore ecosystem carbon balance, hydrology and nutrient cycling. We have investigated the effects of a long-term (10 years) increase in temperature (T2), soil water (W) and the combination of both (T2W) on leaf-level structure and function and ecosystem CO2 and water fluxes in a tundra ecosystem at a field manipulation experiment in NW Greenland. Leaf-level gas exchange, chlorophyll fluorescence, carbon (C), nitrogen (N) and morphology were measured on Salix arctica plants in treatment and control plots in June-July 2011, and continuous measurements of net ecosystem fluxes of carbon and water were made using automatic chambers coupled to a trace gas analyzer. Contrasting responses to the treatments were observed between leaf-level and net ecosystem fluxes. Plants in the elevated temperature treatment had the highest leaf-level photosynthetic capacity in terms of net CO2 assimilation rates and photosystem II efficiencies, and lowest rates of non-photochemical energy dissipation during photosynthesis. The plants in the plots with both elevated temperatures and additional water had the lowest photosystem II efficiencies and the highest rates of non-photochemical energy dissipation. However, net photosynthetic rates remained similar to control plants with additional water, due in part to higher stomatal conductance (W) and lower dark respiration rates (T2W). In contrast, net ecosystem CO2 and water fluxes were highest in the T2W plots, due largely to a 35% increase in leaf area. Total growing season C accumulation was 3-5 times greater, water fluxes were 1.5-2 times higher, and water use efficiency was about 3 times higher in the combined treatment than the control

  4. Spatial and temporal trends of contaminants in Canadian Arctic freshwater and terrestrial ecosystems: a review.

    PubMed

    Braune, B; Muir, D; DeMarch, B; Gamberg, M; Poole, K; Currie, R; Dodd, M; Duschenko, W; Eamer, J; Elkin, B; Evans, M; Grundy, S; Hebert, C; Johnstone, R; Kidd, K; Koenig, B; Lockhart, L; Marshall, H; Reimer, K; Sanderson, J; Shutt, L

    1999-06-01

    The state of knowledge of contaminants in Canadian Arctic biota of the freshwater and terrestrial ecosystems has advanced enormously since the publication of the first major reviews by Lockhart et al. and Thomas et al. in The Science of the Total Environment in 1992. The most significant gains are new knowledge of spatial trends of organochlorines and heavy metal contaminants in terrestrial animals, such as caribou and mink, and in waterfowl, where no information was previously available. Spatial trends in freshwater fish have been broadened, especially in the Yukon, where contaminant measurements of, for example, organochlorines were previously non-existent. A review of contaminants data for fish from the Northwest Territories, Yukon and northern Quebec showed mercury as the one contaminant which consistently exceeds guideline limits for subsistence consumption or commercial sale. Lake trout and northern pike in the Canadian Shield lakes of the Northwest Territories and northern Quebec generally had the most elevated levels. Levels of other heavy metals were generally not elevated in fish. Toxaphene was the major organochlorine contaminant in all fish analyzed. The concentrations of organochlorine contaminants in fish appear to be a function not only of trophic level but of other aspects of the lake ecosystem. Among Arctic terrestrial mammals, PCBs and cadmium were the most prominent contaminants in the species analyzed. Relatively high levels (10-60 micrograms g-1) of cadmium were observed in kidney and liver of caribou from the Yukon, the Northwest Territories and northern Quebec, with concentrations in western herds being higher than in those from the east. For the organochlorine contaminants, a west to east increase in zigma PCBs, HCB and zigma HCH was found in caribou, probably as a result of the predominant west to east/north-east atmospheric circulation pattern which delivers these contaminants from industrialized regions of central and eastern North

  5. Effects of Conversion from Boreal Forest to Arctic Steppe on Soil Communities and Ecosystem Carbon Pools

    NASA Astrophysics Data System (ADS)

    Han, P. D.; Natali, S.; Schade, J. D.; Zimov, N.; Zimov, S. A.

    2014-12-01

    The end of the Pleistocene marked the extinction of a great variety of arctic megafauna, which, in part, led to the conversion of arctic grasslands to modern Siberian larch forest. This shift may have increased the vulnerability of permafrost to thawing because of changes driven by the vegetation shift; the higher albedo of grassland and low insulation of snow trampled by animals may have decreased soil temperatures and reduced ground thaw in the grassland ecosystem, resulting in protection of organic carbon in thawed soil and permafrost. To test these hypothesized impacts of arctic megafauna, we examined an experimental reintroduction of large mammals in northeast Siberia, initiated in 1988. Pleistocene Park now contains 23 horses, three musk ox, one bison, and several moose in addition to the native fauna. The park is 16 square km with a smaller enclosure (< 1 km) where animals spend most of their time and our study was focused. We measured carbon-pools in forested sites (where scat surveys showed low animal use), and grassy sites (which showed higher use), within the park boundaries. We also measured thaw depth and documented the soil invertebrate communities in each ecosystem. There was a substantial difference in number of invertebrates per kg of organic soil between the forest (600 ± 250) and grassland (300 ± 250), though these differences were not statistically significant they suggest faster nutrient turnover in the forest or a greater proportion of decomposition by invertebrates than other decomposers. While thaw depth was deeper in the grassland (60 ± 4 cm) than in the forest (40 ± 6 cm), we did not detect differences in organic layer depth or percent organic matter between grassland and forest. However, soil in the grassland had higher bulk density, and higher carbon stocks in the organic and mineral soil layers. Although deeper thaw depth in the grassland suggests that more carbon is available to microbial decomposers, ongoing temperature monitoring

  6. Conceptual data modeling of wildlife response indicators to ecosystem change in the Arctic

    USGS Publications Warehouse

    Walworth, Dennis; Pearce, John M.

    2015-01-01

    Large research studies are often challenged to effectively expose and document the types of information being collected and the reasons for data collection across what are often a diverse cadre of investigators of differing disciplines. We applied concepts from the field of information or data modeling to the U.S. Geological Survey (USGS) Changing Arctic Ecosystems (CAE) initiative to prototype an application of information modeling. The USGS CAE initiative is collecting information from marine and terrestrial environments in Alaska to identify and understand the links between rapid physical changes in the Arctic and response of wildlife populations to these ecosystem changes. An associated need is to understand how data collection strategies are informing the overall science initiative and facilitating communication of those strategies to a wide audience. We explored the use of conceptual data modeling to provide a method by which to document, describe, and visually communicate both enterprise and study level data; provide a simple means to analyze commonalities and differences in data acquisition strategies between studies; and provide a tool for discussing those strategies among researchers and managers.

  7. The relation between productivity and species diversity in temperate-Arctic marine ecosystems.

    PubMed

    Witman, Jon D; Cusson, Mathieu; Archambault, Philippe; Pershing, Andrew J; Mieszkowska, Nova

    2008-11-01

    Energy variables, such as evapotranspiration, temperature, and productivity explain significant variation in the diversity of many groups of terrestrial plants and animals at local to global scales. Although the ocean represents the largest continuous habitat on earth with a vast spectrum of primary productivity and species richness, little is known about how productivity influences species diversity in marine systems. To search for general relationships between productivity and species richness in the ocean, we analyzed data from three different benthic marine ecosystems (epifaunal communities on subtidal rock walls, on navigation buoys in the Gulf of St. Lawrence, and Canadian Arctic macrobenthos) across local to continental spatial scales (<20 to >1000 km) using a standardized proxy for productivity, satellite-derived chlorophyll a. Theoretically, the form of the function between productivity and species richness is either monotonically increasing or decreasing, or curvilinear (hump- or U-shaped). We found three negative linear and three hump-shaped relationships between chlorophyll a and species richness out of 10 independent comparisons. Scale dependence was suggested by more prevalent diversity-productivity relationships at smaller (local, landscape) than larger (regional, continental) spatial scales. Differences in the form of the functions were more closely allied with community type than with scale, as negative linear functions were restricted to sessile epifauna while hump-shaped functions occurred in Arctic macrobenthos (mixed epifauna, infauna). In two of the data sets, (St. Lawrence epifauna and Arctic macrobenthos) significant effects of chlorophyll a co-varied with the effects of salinity, suggesting that environmental stress as well as productivity influences diversity in these marine systems. The co-varying effect of salinity may commonly arise in broad-scale studies of productivity and diversity in marine ecosystems when attempting to sample the

  8. Spatial and temporal trends and effects of contaminants in the Canadian Arctic marine ecosystem: a review.

    PubMed

    Muir, D; Braune, B; DeMarch, B; Norstrom, R; Wagemann, R; Lockhart, L; Hargrave, B; Bright, D; Addison, R; Payne, J; Reimer, K

    1999-06-01

    Recent studies have added substantially to our knowledge of spatial and temporal trends of persistent organic pollutants and heavy metals in the Canadian Arctic marine ecosystem. This paper reviews the current state of knowledge of contaminants in marine biota in the Canadian Arctic and where possible, discusses biological effects. The geographic coverage of information on contaminants such as persistent organochlorines (OCs) (PCBs, DDT- and chlordane-related compounds, hexachlorocyclohexanes, toxaphene) and heavy metals (mercury, selenium, cadmium, lead) in tissues of marine mammal and sea birds is relatively complete. All major beluga, ringed seal and polar bear stocks along with several major sea bird colonies have been sampled and analysed for OC and heavy metal contaminants. Studies on contaminants in walrus are limited to Foxe Basin and northern Québec stocks, while migratory harp seals have only been studied recently at one location. Contaminant measurements in bearded seal, harbour seal, bowhead whale and killer whale tissues from the Canadian Arctic are very limited or non-existent. Many of the temporal trend data for contaminants in Canadian Arctic biota are confounded by changes in analytical methodology, as well as by variability due to age/size, or to dietary and population shifts. Despite this, studies of OCs in ringed seal blubber at Holman Island and in sea birds at Prince Leopold Island in Lancaster Sound show declining concentrations of PCBs and DDT-related compounds from the 1970s to 1980s then a levelling off during the 1980s and early 1990s. For other OCs, such as chlordane, HCH and toxaphene, limited data for the 1980s to early 1990s suggests few significant declines in concentrations in marine mammals or sea birds. Temporal trend studies of heavy metals in ringed seals and beluga found higher mean concentrations of mercury in more recent (1993/1994) samples than in earlier collections (1981-1984 in eastern Arctic, 1972-1973 in western Arctic

  9. Next Generation Ecosystem Experiment: Quantification and prediction of coupled processes in the terrestrial Arctic system

    NASA Astrophysics Data System (ADS)

    Hubbard, S. S.; Hinzman, L. D.; Graham, D. E.; Liang, L.; Norby, R.; Riley, W. J.; Rogers, A.; Rowland, J. C.; Thornton, P. E.; Torn, M. S.; Wilson, C. J.; Wullschleger, S. D.; NGEE Scientific Team

    2011-12-01

    Predicting the evolution of Arctic ecosystems to a changing climate is complicated by the many interactions and feedbacks that occur within and between components of the system. A new DOE Biological and Environmental Research project, called the Next-Generation Ecosystem Experiments (NGEE) is being initiated to address "how does permafrost degradation in a warming Arctic, and the associated changes in landscape evolution, hydrology, soil biogeochemical processes, and plant community succession, affect feedbacks to the climate system?". A multi-disciplinary team will use observations, experiments, and simulations carried out from the pore to the landscape scales to address these questions. We will combine field research (performed around thermokarst features in Alaska on the North Slope and Seward Peninsula), laboratory research using a variety of approaches and techniques, and remote sensing observations to improve modeling capabilities for high-latitude systems. Our research is organized into four interrelated 'Challenges' to quantify: (1) environmental controls on permafrost degradation and its influence on hydrological state, stocks, fluxes and pathways; (2) mechanisms that drive structural and functional responses of the tundra plant community to changing resource availability; (3) controls, mechanisms and rates driving biodegradation of soil organic matter; and (4) the impact of permafrost degradation on ecosystem albedo, energy partitioning and total climate forcing. Coordinated data acquisition will be performed using a variety of commonly-used terrestrial ecosystem characterization approaches as well as novel molecular microbiological, geophysical, isotopic and synchrotron techniques. These datasets will be used in parallel with models to identify the key controls on coupled geomechanical, hydrological, soil biogeochemical, vegetation and land-surface processes, as well as the manifestation of these coupled processes over a broad range of space and time

  10. Controls over nutrient flow through plants and microbes in Arctic tundra. Final report

    SciTech Connect

    Schimel, J.

    1994-02-01

    Ecosystem productivity in the Arctic is strongly controlled by N availability to plants. Thus, disturbances to the Arctic system are likely to have their greatest impacts by altering the supply of nutrients to plants. Thus, to understand the dynamics of Arctic tundra, a complete understanding of the controls on N cycling in tundra soils is necessary. This project focused on understanding nutrient dynamics in arctic tussock tundra, specifically evaluating the role of microbial uptake and competition for nutrients as a control on plant N-uptake. The project consisted of several major components: Short- and long-term partitioning of NH{sub 4}{sup +} in tussock tundra (1990--1991); Measurement of NH{sub 4}{sup +} uptake rates by Eriophorum vaginatum and by soil microbes; Determination of microbial NH{sub 4}{sup +} and NO{sub 3}{minus} uptake kinetics; and Determination of the partitioning of NH{sub 4}{sup +} and amino acids between E. vaginatum and soil microbes.

  11. Advanced Ecosystem Mapping Techniques for Large Arctic Study Domains Using Calibrated High-Resolution Imagery

    NASA Astrophysics Data System (ADS)

    Macander, M. J.; Frost, G. V., Jr.

    2015-12-01

    Regional-scale mapping of vegetation and other ecosystem properties has traditionally relied on medium-resolution remote sensing such as Landsat (30 m) and MODIS (250 m). Yet, the burgeoning availability of high-resolution (<=2 m) imagery and ongoing advances in computing power and analysis tools raises the prospect of performing ecosystem mapping at fine spatial scales over large study domains. Here we demonstrate cutting-edge mapping approaches over a ~35,000 km² study area on Alaska's North Slope using calibrated and atmospherically-corrected mosaics of high-resolution WorldView-2 and GeoEye-1 imagery: (1) an a priori spectral approach incorporating the Satellite Imagery Automatic Mapper (SIAM) algorithms; (2) image segmentation techniques; and (3) texture metrics. The SIAM spectral approach classifies radiometrically-calibrated imagery to general vegetation density categories and non-vegetated classes. The SIAM classes were developed globally and their applicability in arctic tundra environments has not been previously evaluated. Image segmentation, or object-based image analysis, automatically partitions high-resolution imagery into homogeneous image regions that can then be analyzed based on spectral, textural, and contextual information. We applied eCognition software to delineate waterbodies and vegetation classes, in combination with other techniques. Texture metrics were evaluated to determine the feasibility of using high-resolution imagery to algorithmically characterize periglacial surface forms (e.g., ice-wedge polygons), which are an important physical characteristic of permafrost-dominated regions but which cannot be distinguished by medium-resolution remote sensing. These advanced mapping techniques provide products which can provide essential information supporting a broad range of ecosystem science and land-use planning applications in northern Alaska and elsewhere in the circumpolar Arctic.

  12. The resilience and functional role of moss in boreal and arctic ecosystems

    SciTech Connect

    Turetsky, Merritt; Bond-Lamberty, Benjamin; Euskirchen, Eugenie S.; Talbot, Julie; Frolking, Steve; McGuire, A. David; Tuittila, Eeva-Stiina

    2012-08-24

    Mosses in boreal and arctic ecosystems are ubiquitous components of plant communities, represent an important component of plant diversity, and strongly influence the cycling of water, nutrients, energy and carbon. Here we use a literature review and synthesis as well as model simulations to explore the role of moss in ecological stability and resilience. Our literature review of moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories in boreal and arctic regions. Our modeling simulations suggest that loss of moss within northern plant communities will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. While two models (HPM and STM-TEM) showed a significant effect of moss removal, results from the Biome-BGC and DVM-TEM models suggest that northern, moss-rich ecosystems would need to experience extreme perturbation before mosses were eliminated. We highlight a number of issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, phenotypical plasticity in traits, and whether the effects of moss on ecosystem processes scale with local abundance. We also suggest that as more models explore issues related to ecological resilience, issues related to both parameter and conceptual uncertainty should be addressed: are the models more limited by uncertainty in the parameterization of the processes included or by what is not represented in the model at all? It seems clear from our review that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species.

  13. Review: Potential catastrophic reduction of sea ice in the western Arctic Ocean: Its impact on biogeochemical cycles and marine ecosystems

    NASA Astrophysics Data System (ADS)

    Harada, Naomi

    2016-01-01

    The reduction of sea ice in the Arctic Ocean, which has progressed more rapidly than previously predicted, has the potential to cause multiple environmental stresses, including warming, acidification, and strengthened stratification of the ocean. Observational studies have been undertaken to detect the impacts on biogeochemical cycles and marine ecosystems of these environmental stresses in the Arctic Ocean. Satellite analyses show that the reduction of sea ice has been especially great in the western Arctic Ocean. Observations and model simulations have both helped to clarify the impact of sea-ice reductions on the dynamics of ecosystem processes and biogeochemical cycles. In this review, I focus on the western Arctic Ocean, which has experienced the most rapid retreat of sea ice in the Arctic Ocean and, very importantly, has a higher rate of primary production than any other area of the Arctic Ocean owing to the supply of nutrient-rich Pacific water. I report the impact of the current reduction of sea ice on marine biogeochemical cycles in the western Arctic Ocean, including lower-trophic-level organisms, and identify the key mechanism of changes in the biogeochemical cycles, based on published observations and model simulations. The retreat of sea ice has enhanced primary production and has increased the frequency of appearance of mesoscale anticyclonic eddies. These eddies enhance the light environment and replenish nutrients, and they also represent a mechanism that can increase the rate of the biological pump in the Arctic Ocean. Various unresolved issues that require further investigation, such as biological responses to environmental stressors such as ocean acidification, are also discussed.

  14. Improved Climate Prediction through a System Level Understanding of Arctic Terrestrial Ecosystems

    NASA Astrophysics Data System (ADS)

    Wullschleger, S. D.; Graham, D. E.; Hinzman, L. D.; Hubbard, S. S.; Liang, L.; Liljedahl, A. K.; Norby, R. J.; Rogers, A.; Rowland, J. C.; Thornton, P. E.; Torn, M. S.; Riley, W. J.; Wilson, C. J.

    2012-12-01

    Characterized by vast amounts of carbon stored in permafrost and a rapidly evolving landscape, the Arctic has emerged as an important focal point for the study of climate change. These are sensitive systems, yet the mechanisms responsible for those sensitivities are not well understood and many remain uncertain in terms of their representation in Earth System models. Increasing our confidence in climate projections for high-latitude regions of the world will require a coordinated set of investigations that target improved process understanding and model representation of important ecosystem-climate feedbacks. The Next-Generation Ecosystem Experiments (NGEE Arctic) seeks to address this challenge by quantifying the physical, chemical, and biological behavior of terrestrial ecosystems in Alaska. Initial research focuses on the highly dynamic landscapes of the North Slope where thaw lakes, drained thaw lake basins, and ice-rich polygonal ground offer distinct land units for investigation and modeling. Activities in the early stage of the project are focused on the Barrow Environmental Observatory (BEO), where a multi-disciplinary team of scientists will study interactions that drive critical climate feedbacks within these environments through greenhouse gas fluxes and changes in surface energy balance associated with permafrost degradation, and the many processes that arise as a result of these landscape dynamics. Our scaling approach builds on the hypothesis that the transfer of information across spatial scales can be organized around these discrete geomorphological units for which processes are represented explicitly at finer scales, with information passed to coarser scales through sub-grid parameterization of Earth System models. By extending an already well-established framework for fractional sub-grid area representations to allow dynamic sub-grid areas and hydrological and geophysical connections among sub-grid units, we expect to be able to characterize

  15. Effects on the structure of Arctic ecosystems in the short- and long-term perspectives.

    PubMed

    Callaghan, Terry V; Björn, Lars Olof; Chernov, Yuri; Chapin, Terry; Christensen, Torben R; Huntley, Brian; Ims, Rolf A; Johansson, Margareta; Jolly, Dyanna; Jonasson, Sven; Matveyeva, Nadya; Panikov, Nicolai; Oechel, Walter; Shaver, Gus; Henttonen, Heikki

    2004-11-01

    Species individualistic responses to warming and increased UV-B radiation are moderated by the responses of neighbors within communities, and trophic interactions within ecosystems. All of these responses lead to changes in ecosystem structure. Experimental manipulation of environmental factors expected to change at high latitudes showed that summer warming of tundra vegetation has generally led to smaller changes than fertilizer addition. Some of the factors manipulated have strong effects on the structure of Arctic ecosystems but the effects vary regionally, with the greatest response of plant and invertebrate communities being observed at the coldest locations. Arctic invertebrate communities are very likely to respond rapidly to warming whereas microbial biomass and nutrient stocks are more stable. Experimentally enhanced UV-B radiation altered the community composition of gram-negative bacteria and fungi, but not that of plants. Increased plant productivity due to warmer summers may dominate food-web dynamics. Trophic interactions of tundra and sub-Arctic forest plant-based food webs are centered on a few dominant animal species which often have cyclic population fluctuations that lead to extremely high peak abundances in some years. Population cycles of small rodents and insect defoliators such as the autumn moth affect the structure and diversity of tundra and forest-tundra vegetation and the viability of a number of specialist predators and parasites. Ice crusting in warmer winters is likely to reduce the accessibility of plant food to lemmings, while deep snow may protect them from snow-surface predators. In Fennoscandia, there is evidence already for a pronounced shift in small rodent community structure and dynamics that have resulted in a decline of predators that specialize in feeding on small rodents. Climate is also likely to alter the role of insect pests in the birch forest system: warmer winters may increase survival of eggs and expand the range

  16. Ecosystem dynamics of the Pacific-influenced Northern Bering and Chukchi Seas in the Amerasian Arctic

    NASA Astrophysics Data System (ADS)

    Grebmeier, Jacqueline M.; Cooper, Lee W.; Feder, Howard M.; Sirenko, Boris I.

    2006-10-01

    The shallow continental shelves and slope of the Amerasian Arctic are strongly influenced by nutrient-rich Pacific waters advected over the shelves from the northern Bering Sea into the Arctic Ocean. These high-latitude shelf systems are highly productive both as the ice melts and during the open-water period. The duration and extent of seasonal sea ice, seawater temperature and water mass structure are critical controls on water column production, organic carbon cycling and pelagic-benthic coupling. Short food chains and shallow depths are characteristic of high productivity areas in this region, so changes in lower trophic levels can impact higher trophic organisms rapidly, including pelagic- and benthic-feeding marine mammals and seabirds. Subsistence harvesting of many of these animals is locally important for human consumption. The vulnerability of the ecosystem to environmental change is thought to be high, particularly as sea ice extent declines and seawater warms. In this review, we focus on ecosystem dynamics in the northern Bering and Chukchi Seas, with a more limited discussion of the adjoining Pacific-influenced eastern section of the East Siberian Sea and the western section of the Beaufort Sea. Both primary and secondary production are enhanced in specific regions that we discuss here, with the northern Bering and Chukchi Seas sustaining some of the highest water column production and benthic faunal soft-bottom biomass in the world ocean. In addition, these organic carbon-rich Pacific waters are periodically advected into low productivity regions of the nearshore northern Bering, Chukchi and Beaufort Seas off Alaska and sometimes into the East Siberian Sea, all of which have lower productivity on an annual basis. Thus, these near shore areas are intimately tied to nutrients and advected particulate organic carbon from the Pacific influenced Bering Shelf-Anadyr water. Given the short food chains and dependence of many apex predators on sea ice, recent

  17. Mammalian herbivores confer resilience of Arctic shrub-dominated ecosystems to changing climate.

    PubMed

    Kaarlejärvi, Elina; Hoset, Katrine S; Olofsson, Johan

    2015-09-01

    Climate change is resulting in a rapid expansion of shrubs in the Arctic. This expansion has been shown to be reinforced by positive feedbacks, and it could thus set the ecosystem on a trajectory toward an alternate, more productive regime. Herbivores, on the other hand, are known to counteract the effects of simultaneous climate warming on shrub biomass. However, little is known about the impact of herbivores on resilience of these ecosystems, that is, the capacity of a system to absorb disturbance and still remain in the same regime, retaining the same function, structure, and feedbacks. Here, we investigated how herbivores affect resilience of shrub-dominated systems to warming by studying the change of shrub biomass after a cessation of long-term experimental warming in a forest-tundra ecotone. As predicted, warming increased the biomass of shrubs, and in the absence of herbivores, shrub biomass in tundra continued to increase 4 years after cessation of the artificial warming, indicating that positive effects of warming on plant growth may persist even over a subsequent colder period. Herbivores contributed to the resilience of these systems by returning them back to the original low-biomass regime in both forest and tundra habitats. These results support the prediction that higher shrub biomass triggers positive feedbacks on soil processes and microclimate, which enable maintaining the rapid shrub growth even in colder climates. Furthermore, the results show that in our system, herbivores facilitate the resilience of shrub-dominated ecosystems to climate warming. PMID:25967156

  18. Net Ecosystem Exchange of CO2 with Rapidly Changing High Arctic Landscapes

    NASA Astrophysics Data System (ADS)

    Emmerton, C. A.

    2015-12-01

    High Arctic landscapes are expansive and changing rapidly. However our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest-latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near zero sink of atmospheric CO2 (NEE: -0.3±13.5 g C m-2). A nearby meadow wetland accumulated over two magnitudes more carbon (NEE: -79.3±20.0 g C m-2) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southern latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely-detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote-sensing, however high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases substantially, climate-related changes of dry high Arctic landscapes may be restricted by poor soil moisture retention, and therefore have some inertia against

  19. Hydrological and geochemical response and recovery in disturbed Arctic ecosystems. Progress report

    SciTech Connect

    Not Available

    1992-07-01

    This progress report is a funding, extension request to continue the database work for the Hydrological and Geochemical Response and Recovery in Disturbed Arctic Ecosystems Program. Throughout the period from 1985 to 1992 the Department of Energy supported research on the hydrology and geochemistry of the headwater basin of Imnavait Creek has focused on the quantification of the input from atmospheric sources of biologically significant and other related chemical variables; the transport of these variables in surface and subsurface flow and their efflux from the basin; and the development of geochemical budgets. The acquisition of multi-year data sets (the longest and most detailed sets in the Arctic) have made it possible to define seasonal ranges and amplitudes; determine spatial and temporal relationships within the different flow compartments; to begin to model the pathways and rates of movement through and across different landscape units. The length of record has also made it possible to examine the quantity and influence of local and extra-regional additions.

  20. Influences of seasonality, geomorphology, and hydrology on primary production and respiration in Arctic stream ecosystems

    NASA Astrophysics Data System (ADS)

    Herstand, M. R.; Bowden, W. B.; Gooseff, M. N.; Whittinghill, K. A.; Wlostowski, A. N.; Wollheim, W. M.

    2011-12-01

    Stream ecosystem processes in the Arctic are poorly understood in the spring and fall 'shoulder' seasons. We hypothesize that seasonal changes in solar radiation, hydrologic conditions, and landscape inputs are all reflected in the seasonal patterns of Gross Primary Productivity (GPP) and Community Respiration (CR). We continuously monitored the GPP and CR of three streams with different geomorphic characteristics (alluvial lake inlet, alluvial lake outlet, and beaded peat) near Toolik Lake Field Station, Alaska from breakup to freeze-up during 2011. We used open-system whole stream metabolism (WSM) methods, with dissolved oxygen estimates every five minutes. Dissolved and particulate nutrient chemistry, benthic chlorophyll, and nutrient uptake rates from solute injections were also measured across the seasons, and had correlations with GPP and CR. The fall freeze-up season was especially productive, as the well-developed benthic community responded to either lower flows (preventing sloughing) and/or increasing dissolved nutrient loads during landscape plant senescence. Storm events and high flow conditions (observed throughout seasons) decreased the GPP:CR ratio. Average monthly air temperatures have increased on the North Slope, especially during the shoulder seasons, increasing the duration of the ice-free stream season. Increasing the fall shoulder season may increase the annual stream GPP and nutrient uptake, with uncertain impacts on nutrient loading to the Arctic Ocean.

  1. Remote sensing of vegetation and land-cover change in Arctic Tundra Ecosystems

    USGS Publications Warehouse

    Stow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.; Noyle, B.; Silapaswan, C.; Douglas, D.; Griffith, B.; Jia, G.; Epstein, H.; Walker, D.; Daeschner, S.; Petersen, A.; Zhou, L.; Myneni, R.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored. ?? 2003 Elsevier Inc. All rights reserved.

  2. Remote sensing of vegetation and land-cover change in Arctic tundra ecosystems

    USGS Publications Warehouse

    Checkstow, D.A.; Hope, A.; McGuire, D.; Verbyla, D.; Gamon, J.; Huemmrich, F.; Houston, S.; Racine, C.; Sturm, M.; Tape, K.; Hinzman, L.; Yoshikawa, K.; Tweedie, C.

    2004-01-01

    The objective of this paper is to review research conducted over the past decade on the application of multi-temporal remote sensing for monitoring changes of Arctic tundra lands. Emphasis is placed on results from the National Science Foundation Land-Air-Ice Interactions (LAII) program and on optical remote sensing techniques. Case studies demonstrate that ground-level sensors on stationary or moving track platforms and wide-swath imaging sensors on polar orbiting satellites are particularly useful for capturing optical remote sensing data at sufficient frequency to study tundra vegetation dynamics and changes for the cloud prone Arctic. Less frequent imaging with high spatial resolution instruments on aircraft and lower orbiting satellites enable more detailed analyses of land cover change and calibration/validation of coarser resolution observations. The strongest signals of ecosystem change detected thus far appear to correspond to expansion of tundra shrubs and changes in the amount and extent of thaw lakes and ponds. Changes in shrub cover and extent have been documented by modern repeat imaging that matches archived historical aerial photography. NOAA Advanced Very High Resolution Radiometer (AVHRR) time series provide a 20-year record for determining changes in greenness that relates to photosynthetic activity, net primary production, and growing season length. The strong contrast between land materials and surface waters enables changes in lake and pond extent to be readily measured and monitored.

  3. The response of aboveground plant productivity to earlier snowmelt and summer warming in an Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Livensperger, C.; Steltzer, H.; Darrouzet-Nardi, A.; Sullivan, P.; Wallenstein, M. D.; Weintraub, M. N.

    2012-12-01

    Plant communities in the Arctic are undergoing changes in structure and function due to shifts in seasonality from changing winters and summer warming. These changes will impact biogeochemical cycling, surface energy balance, and functioning of vertebrate and invertebrate communities. To examine seasonal controls on aboveground net primary production (ANPP) in a moist acidic tundra ecosystem in northern Alaska, we shifted the growing season by accelerating snowmelt (using radiation absorbing shadecloth) and warming air and soil temperature (using 1 m2 open-top chambers), individually and in combination. After three years, we measured ANPP by harvesting up to 16 individual ramets, tillers and rhizomes for each of 7 plant species, including two deciduous shrubs, two graminoids, two evergreen shrubs and one forb during peak season. Our results show that ANPP per stem summed across the 7 species increased when snow melt occurred earlier. However, standing biomass, excluding current year growth, was also greater. The ratio of ANPP/standing biomass decreased in all treatments compared to the control. ANPP per unit standing biomass summed for the four shrub species decreases due to summer warming alone or in combination with early snowmelt; however early snowmelt alone did not lead to lower ANPP for the shrubs. ANPP per tiller or rhizome summed for the three herbaceous species increased in response to summer warming. Understanding the differential response of plants to changing seasonality will inform predictions of future Arctic plant community structure and function.

  4. Are Hotspots Always Hotspots? The Relationship between Diversity, Resource and Ecosystem Functions in the Arctic

    PubMed Central

    Link, Heike; Piepenburg, Dieter; Archambault, Philippe

    2013-01-01

    The diversity-ecosystem function relationship is an important topic in ecology but has not received much attention in Arctic environments, and has rarely been tested for its stability in time. We studied the temporal variability of benthic ecosystem functioning at hotspots (sites with high benthic boundary fluxes) and coldspots (sites with lower fluxes) across two years in the Canadian Arctic. Benthic remineralisation function was measured as fluxes of oxygen, silicic acid, phosphate, nitrate and nitrite at the sediment-water interface. In addition we determined sediment pigment concentration and taxonomic and functional macrobenthic diversity. To separate temporal from spatial variability, we sampled the same nine sites from the Mackenzie Shelf to Baffin Bay during the same season (summer or fall) in 2008 and 2009. We observed that temporal variability of benthic remineralisation function at hotspots is higher than at coldspots and that taxonomic and functional macrobenthic diversity did not change significantly between years. Temporal variability of food availability (i.e., sediment surface pigment concentration) seemed higher at coldspot than at hotspot areas. Sediment chlorophyll a (Chl a) concentration, taxonomic richness, total abundance, water depth and abundance of the largest gallery-burrowing polychaete Lumbrineristetraura together explained 42% of the total variation in fluxes. Food supply proxies (i.e., sediment Chl a and depth) split hot- from coldspot stations and explained variation on the axis of temporal variability, and macrofaunal community parameters explained variation mostly along the axis separating eastern from western sites with hot- or coldspot regimes. We conclude that variability in benthic remineralisation function, food supply and diversity will react to climate change on different time scales, and that their interactive effects may hide the detection of progressive change, particularly at hotspots. Time-series of benthic functions and

  5. Climate change and Arctic ecosystems: 2. Modeling, paleodata-model comparisons, and future projections

    USGS Publications Warehouse

    Kaplan, J.O.; Bigelow, N.H.; Prentice, I.C.; Harrison, S.P.; Bartlein, P.J.; Christensen, T.R.; Cramer, W.; Matveyeva, N.V.; McGuire, A.D.; Murray, D.F.; Razzhivin, V.Y.; Smith, B.; Walker, D. A.; Anderson, P.M.; Andreev, A.A.; Brubaker, L.B.; Edwards, M.E.; Lozhkin, A.V.

    2003-01-01

    Large variations in the composition, structure, and function of Arctic ecosystems are determined by climatic gradients, especially of growing-season warmth, soil moisture, and snow cover. A unified circumpolar classification recognizing five types of tundra was developed. The geographic distributions of vegetation types north of 55??N, including the position of the forest limit and the distributions of the tundra types, could be predicted from climatology using a small set of plant functional types embedded in the biogeochemistry-biogeography model BIOME4. Several palaeoclimate simulations for the last glacial maximum (LGM) and mid-Holocene were used to explore the possibility of simulating past vegetation patterns, which are independently known based on pollen data. The broad outlines of observed changes in vegetation were captured. LGM simulations showed the major reduction of forest, the great extension of graminoid and forb tundra, and the restriction of low- and high-shrub tundra (although not all models produced sufficiently dry conditions to mimic the full observed change). Mid-Holocene simulations reproduced the contrast between northward forest extension in western and central Siberia and stability of the forest limit in Beringia. Projection of the effect of a continued exponential increase in atmospheric CO2 concentration, based on a transient ocean-atmosphere simulation including sulfate aerosol effects, suggests a potential for larger changes in Arctic ecosystems during the 21st century than have occurred between mid-Holocene and present. Simulated physiological effects of the CO2 increase (to > 700 ppm) at high latitudes were slight compared with the effects of the change in climate.

  6. Chamber and Diffusive Based Carbon Flux Measurements in an Alaskan Arctic Ecosystem

    NASA Astrophysics Data System (ADS)

    Wilkman, E.; Oechel, W. C.; Zona, D.

    2013-12-01

    Eric Wilkman, Walter Oechel, Donatella Zona Comprising an area of more than 7 x 106 km2 and containing over 11% of the world's organic matter pool, Arctic terrestrial ecosystems are vitally important components of the global carbon cycle, yet their structure and functioning are sensitive to subtle changes in climate and many of these functional changes can have large effects on the atmosphere and future climate regimes (Callaghan & Maxwell 1995, Chapin et al. 2002). Historically these northern ecosystems have acted as strong C sinks, sequestering large stores of atmospheric C due to photosynthetic dominance in the short summer season and low rates of decomposition throughout the rest of the year as a consequence of cold, nutrient poor, and generally water-logged conditions. Currently, much of this previously stored carbon is at risk of loss to the atmosphere due to accelerated soil organic matter decomposition in warmer future climates (Grogan & Chapin 2000). Although there have been numerous studies on Arctic carbon dynamics, much of the previous soil flux work has been done at limited time intervals, due to both the harshness of the environment and labor and time constraints. Therefore, in June of 2013 an Ultraportable Greenhouse Gas Analyzer (UGGA - Los Gatos Research Inc.) was deployed in concert with the LI-8100A Automated Soil Flux System (LI-COR Biosciences) in Barrow, AK to gather high temporal frequency soil CO2 and CH4 fluxes from a wet sedge tundra ecosystem. An additional UGGA in combination with diffusive probes, installed in the same location, provides year-round soil and snow CO2 and CH4 concentrations. When used in combination with the recently purchased AlphaGUARD portable radon monitor (Saphymo GmbH), continuous soil and snow diffusivities and fluxes of CO2 and CH4 can be calculated (Lehmann & Lehmann 2000). Of particular note, measuring soil gas concentration over a diffusive gradient in this way allows one to separate both net production and

  7. The Role of Remote Sensing in Modeling Landscape Change and Its Associated Carbon Cycle Impacts Across Terrestrial Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Hayes, D. J.; Goswami, S.; Jones, B. M.; Grosse, G.; Balser, A.; Wullschleger, S. D.

    2014-12-01

    Terrestrial ecosystems across the circumpolar Arctic region are undergoing unprecedented changes in structure and function as a result of rapid climate warming. Such changes have substantially altered energy, water and biogeochemical cycling in these regions, which has important global-scale consequences for climate and society. Recognizing the vulnerability of these ecosystems to change, scientists and decision-makers have identified a critical need for research that employs existing and new remote sensing technologies and methodologies to observe, monitor and understand changes in Arctic ecosystems. The unique capabilities provided by remote sensing imagery and data products have allowed us novel views of ecosystems and their dynamics over multiple scales in time and space across all regions of the globe. Here we offer a synthetic discussion of the recent and emerging science focused on understanding the dynamic landscape processes in Arctic terrestrial ecosystems using a variety of remotely-sensed information collected from passive and active sensors on ground-, aircraft- and satellite- based platforms. To consider the evolution of these technologies, methods and applications over recent decades, we look at key examples from the scientific literature that range from the use of radar sensors for local-scale characterization of active layer dynamics to the circumpolar-scale assessment of changes in vegetation productivity using long-term records of optical satellite imagery. This discussion has a particular focus on the use of remotely sensed data and products to parameterize, drive, evaluate and benchmark the modeling of Arctic ecosystem processes. We use these examples to demonstrate the opportunities for model-data integration, as well as to highlight the challenges of remote sensing studies in northern high latitude regions.

  8. Challenges in Modeling Disturbance Regimes and Their Impacts in Arctic and Boreal Ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    McGuire, A. D.; Rupp, T. S.; Kurz, W.

    2013-12-01

    Disturbances in arctic and boreal terrestrial ecosystems influence services provided by these ecosystems to society. In particular, changes in disturbance regimes in northern latitudes have uncertain consequences for the climate system. A major challenge for the scientific community is to develop the capability to predict how the frequency, severity and resultant impacts of disturbance regimes will change in response to future changes in climate projected for northern high latitudes. Here we compare what is known about drivers and impacts of wildfire, phytophagous insect pests, and thermokarst disturbance to illustrate the complexities in predicting future changes in disturbance regimes and their impacts in arctic and boreal regions. Much of the research on predicting fire has relied on the use of drivers related to fire weather. However, changes in vegetation, such as increases in broadleaf species, associated with intensified fire regimes have the potential to influence future fire regimes through negative feedbacks associated with reduced flammability. Phytophagous insect outbreaks have affected substantial portions of the boreal region in the past, but frequently the range of the tree host is larger than the range of the insect. There is evidence that a number of insect species are expanding their range in response to climate change. Major challenges to predicting outbreaks of phytophagous insects include modeling the effects of climate change on insect growth and maturation, winter mortality, plant host health, the synchrony of insect life stages and plant host phenology, and changes in the ranges of insect pests. Moreover, Earth System Models often simplify the representation of vegetation characteristics, e.g. the use of plant functional types, providing insufficient detail to link to insect population models. Thermokarst disturbance occurs when the thawing of ice-rich permafrost results in substantial ground subsidence. In the boreal forest, thermokarst can

  9. Ice Shelf Microbial Ecosystems in the High Arctic and Implications for Life on Snowball Earth

    NASA Astrophysics Data System (ADS)

    Vincent, W. F.; Gibson, J. A. E.; Pienitz, R.; Villeneuve, V.; Broady, P. A.; Hamilton, P. B.; Howard-Williams, C.

    The Ward Hunt Ice Shelf (83°N, 74°W) is the largest remaining section of thick (>10m) landfast sea ice along the northern coastline of Ellesmere Island, Canada. Extensive meltwater lakes and streams occur on the surface of the ice and are colonized by photosynthetic microbial mat communities. This High Arctic cryo-ecosystem is similar in several of its physical, biological and geochemical features to the McMurdo Ice Shelf in Antarctica. The ice-mats in both polar regions are dominated by filamentous cyanobacteria but also contain diatoms, chlorophytes, flagellates, ciliates, nematodes, tardigrades and rotifers. The luxuriant Ward Hunt consortia also contain high concentrations (107-108cm-2) of viruses and heterotrophic bacteria. During periods of extensive ice cover, such as glaciations during the Proterozoic, cryotolerant mats of the type now found in these polar ice shelf ecosystems would have provided refugia for the survival, growth and evolution of a variety of organisms, including multicellular eukaryotes.

  10. Ice shelf microbial ecosystems in the high arctic and implications for life on snowball earth.

    PubMed

    Vincent, W F; Gibson, J A; Pienitz, R; Villeneuve, V; Broady, P A; Hamilton, P B; Howard-Williams, C

    2000-03-01

    The Ward Hunt Ice Shelf (83 degrees N, 74 degrees W) is the largest remaining section of thick (> 10 m) land-fast sea ice along the northern coastline of Ellesmere Island, Canada. Extensive meltwater lakes and streams occur on the surface of the ice and are colonized by photosynthetic microbial mat communities. This High Arctic cryo-ecosystem is similar in several of its physical, biological and geochemical features to the McMurdo Ice Shelf in Antarctica. The ice-mats in both polar regions are dominated by filamentous cyanobacteria but also contain diatoms, chlorophytes, flagellates, ciliates, nematodes, tardigrades and rotifers. The luxuriant Ward Hunt consortia also contain high concentrations (10(7)-10(8) cm-2) of viruses and heterotrophic bacteria. During periods of extensive ice cover, such as glaciations during the Proterozoic, cryotolerant mats of the type now found in these polar ice shelf ecosystems would have provided refugia for the survival, growth and evolution of a variety of organisms, including multicellular eukaryotes. PMID:10798200

  11. Coupled ecosystem carbon and nutrient cycling in a High Arctic ecosystem are altered by long-term experimental warming and higher rainfall

    NASA Astrophysics Data System (ADS)

    Schaeffer, S. M.; Schimel, J.; Welker, J. M.

    2013-12-01

    The rapid changes in temperature and precipitation in High Arctic tundra ecosystems are altering the biogeochemical cycles of nitrogen (N) and carbon (C), but in ways that are difficult to anticipate. The challenge grows from the complexity of tundra soil organic matter, the uncertainty of N cycle responses and the extent to which shifts in soil N processes are coupled with the C cycle, including leaf-level photosynthesis, gross ecosystem photosynthesis (GEP-productivity) and net CO2 exchange (NEE-C sequestration). Understanding the processes that are leading to changes in High Arctic biogeochemical processes are especially important today as soil organic C pools in the High Arctic are up to 6 times greater than previously estimated, and are sensitive to being oxidized to the atmosphere through changes in microbial decomposition associated with warmer and wetter conditions. We used a long-term (since 2003) experiment of summer warming and supplemental summer water additions to a High Arctic ecosystem in NW Greenland to determine the impact of interactions between temperature, water availability, and microbial metabolism on the cycling of C and plant-available N in High Arctic tundra soil. We have found that water availability plays a critical role in these cycles in High Arctic tundra, over and above that from temperature increases. On seasonal time scales, we observed greater net N mineralization under both global change scenarios, yet water addition also significantly increased net nitrification rates, loss of NO3--N via leaching from surface soil layers, and lowered rates of labile organic C and N production. We also expected the chronic warming and watering would lead to long-term changes in soil N-cycling that would be reflected in soil δ15N values. However, we found that soil δ15N decreased under the different climate change scenarios. Our findings indicate that warmer, wetter High Arctic tundra will be cycling N and C in ways that may transform these

  12. Reviews and Syntheses: Effects of permafrost thaw on arctic aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Vonk, J. E.; Tank, S. E.; Bowden, W. B.; Laurion, I.; Vincent, W. F.; Alekseychik, P.; Amyot, M.; Billet, M. F.; Canário, J.; Cory, R. M.; Deshpande, B. N.; Helbig, M.; Jammet, M.; Karlsson, J.; Larouche, J.; MacMillan, G.; Rautio, M.; Anthony, K. M. Walter; Wickland, K. P.

    2015-07-01

    The Arctic is a water-rich region, with freshwater systems covering 16 % of the northern permafrost landscape. The thawing of this permafrost creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic and lotic systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas, vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying variables determine the degree to which permafrost thaw manifests as thermokarst, whether thermokarst leads to slumping or the formation of thermokarst lakes, and the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying variables determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted systems is also likely to change, with thaw-impacted lakes and streams having unique microbiological communities, and showing differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter and nutrient delivery. The degree to which thaw enables the delivery of

  13. Development of an advanced regional climate-ecosystem model for Arctic applications

    NASA Astrophysics Data System (ADS)

    Chaudhary, Nitin; Smith, Benjamin; Miller, Paul

    2013-04-01

    Cryospheric processes together with their feedbacks play a crucial role in determining rates and patterns of future warming over high-latitude regions. Cryospheric processes including permafrost as well as peatland and associated vegetation, hydrological and biogeochemical dynamics are not well represented in land surface schemes (LSS) of most climate models. As a step in this direction, we describe a scheme to include the coupled dynamics of vegetation, hydrology and peat accumulation under climate forcing within a detailed vegetation dynamics-biogeochemistry model, LPJ GUESS (Smith et al. 2001; Miller et al., in preparation). In the first step, a one-dimensional (1D) landscape scale peat accumulation and two dimensional (2D) micro-topographical models have been developed. For the parameterisation and validation of these models, good quality datasets are being used which are collected at various locations around the Arctic. Building on these, a three-dimensional (3D) scheme will be incorporated in a version of LPJ-GUESS that already includes patch-scale vegetation dynamics and soil carbon cycling, as well as a one-dimensional hydrology scheme. The patches in the 3D model will be treated as adjacent micro-patches in a grid and depending on underlying micro-topography water will flow from higher to lower patches. The 2D and 3D models will help in simulating hummock and hollow structure which is typical for Northern peatlands based on the cyclic regeneration theory (von Post and Sernander, 1910). The resulting models will be incorporated within the biospheric component of a regional climate-ecosystem model, RCA-GUESS (Smith et al., 2010) and used to investigate feedbacks related to the dynamics of peatlands, permafrost and emissions of the greenhouse gases, mainly CO2 and CH4 across the Arctic region. References- Smith B, Prentice IC, and Skyes MT. 2001. Representation of vegetation dynamics in modelling of European ecosystems: comparison of two contrasting

  14. Reviews and syntheses: Effects of permafrost thaw on Arctic aquatic ecosystems

    NASA Astrophysics Data System (ADS)

    Vonk, J. E.; Tank, S. E.; Bowden, W. B.; Laurion, I.; Vincent, W. F.; Alekseychik, P.; Amyot, M.; Billet, M. F.; Canário, J.; Cory, R. M.; Deshpande, B. N.; Helbig, M.; Jammet, M.; Karlsson, J.; Larouche, J.; MacMillan, G.; Rautio, M.; Anthony, K. M. Walter; Wickland, K. P.

    2015-12-01

    The Arctic is a water-rich region, with freshwater systems covering about 16 % of the northern permafrost landscape. Permafrost thaw creates new freshwater ecosystems, while at the same time modifying the existing lakes, streams, and rivers that are impacted by thaw. Here, we describe the current state of knowledge regarding how permafrost thaw affects lentic (still) and lotic (moving) systems, exploring the effects of both thermokarst (thawing and collapse of ice-rich permafrost) and deepening of the active layer (the surface soil layer that thaws and refreezes each year). Within thermokarst, we further differentiate between the effects of thermokarst in lowland areas vs. that on hillslopes. For almost all of the processes that we explore, the effects of thaw vary regionally, and between lake and stream systems. Much of this regional variation is caused by differences in ground ice content, topography, soil type, and permafrost coverage. Together, these modifying factors determine (i) the degree to which permafrost thaw manifests as thermokarst, (ii) whether thermokarst leads to slumping or the formation of thermokarst lakes, and (iii) the manner in which constituent delivery to freshwater systems is altered by thaw. Differences in thaw-enabled constituent delivery can be considerable, with these modifying factors determining, for example, the balance between delivery of particulate vs. dissolved constituents, and inorganic vs. organic materials. Changes in the composition of thaw-impacted waters, coupled with changes in lake morphology, can strongly affect the physical and optical properties of thermokarst lakes. The ecology of thaw-impacted lakes and streams is also likely to change; these systems have unique microbiological communities, and show differences in respiration, primary production, and food web structure that are largely driven by differences in sediment, dissolved organic matter, and nutrient delivery. The degree to which thaw enables the delivery

  15. FINAL ECOSYSTEM GOODS AND SERVICES CLASSIFICATION SYSTEM (FEGS-CS)

    EPA Science Inventory

    This document defines and classifies 338 Final Ecosystem Goods and Services (FEGS), each defined and uniquely numbered by a combination of environmental class or sub-class and a beneficiary category or sub-category. The introductory section provides the rationale and conceptual ...

  16. A case study of high Arctic anthropogenic disturbance to polar desert permafrost and ecosystems

    NASA Astrophysics Data System (ADS)

    Becker, M. S.; Pollard, W. H.

    2013-12-01

    One of the indirect impacts of climate change on Arctic ecosystems is the expected increase of industrial development in high latitudes. The scale of terrestrial impacts cannot be known ahead of time, particularly due to a lack of long-term impact studies in this region. With one of the slowest community recovery rates of any ecosystem, the high Artic biome will be under a considerable threat that is exacerbated by a high susceptibility to change in the permafrost thermal balance. One such area that provides a suitable location for study is an old airstrip near Eureka, Ellesmere Island, Nunavut (80.0175°N, 85.7340°W). While primarily used as an ice-runway for winter transport, the airstrip endured a yearly summer removal of vegetation that continued from 1947 until its abandonment in 1951. Since then, significant vegetative and geomorphic differences between disturbed and undisturbed areas have been noted in the literature throughout the decades (Bruggemann, 1953; Beschel, 1963; Couture and Pollard, 2007), but no system wide assessment of both the ecosystem and near-surface permafrost has been conducted. Key to our study is that the greatest apparent geomorphic and vegetative changes have occurred and persisted in areas where underlying ice-wedges have been disturbed. This suggests that the colonizing communities rapidly filled new available thermokarst niches and have produced an alternative ice-wedge stable state than the surrounding polar desert. We hypothesize that disturbed areas will currently have greater depths of thaw (deeper active layers) and degraded ice-wedges, with decreased vegetation diversity but higher abundance due to a changed hydrological balance. To test this a comprehensive set of near-surface active layer and ecosystem measurements were conducted. Permafrost dynamics were characterized using probing and high-frequency Ground Penetrating Radar (500 MHz) to map the near-surface details of ice-wedges and active layer. Vegetation was measured

  17. Relationships between ecosystem metabolism, benthic macroinvertebrate densities, and environmental variables in a sub-arctic Alaskan river

    USGS Publications Warehouse

    Benson, Emily R.; Wipfli, Mark S.; Clapcott, Joanne E.; Hughes, Nicholas F.

    2013-01-01

    Relationships between environmental variables, ecosystem metabolism, and benthos are not well understood in sub-arctic ecosystems. The goal of this study was to investigate environmental drivers of river ecosystem metabolism and macroinvertebrate density in a sub-arctic river. We estimated primary production and respiration rates, sampled benthic macroinvertebrates, and monitored light intensity, discharge rate, and nutrient concentrations in the Chena River, interior Alaska, over two summers. We employed Random Forests models to identify predictor variables for metabolism rates and benthic macroinvertebrate density and biomass, and calculated Spearman correlations between in-stream nutrient levels and metabolism rates. Models indicated that discharge and length of time between high water events were the most important factors measured for predicting metabolism rates. Discharge was the most important variable for predicting benthic macroinvertebrate density and biomass. Primary production rate peaked at intermediate discharge, respiration rate was lowest at the greatest time since last high water event, and benthic macroinvertebrate density was lowest at high discharge rates. The ratio of dissolved inorganic nitrogen to soluble reactive phosphorus ranged from 27:1 to 172:1. We found that discharge plays a key role in regulating stream ecosystem metabolism, but that low phosphorous levels also likely limit primary production in this sub-arctic stream.

  18. Arctic and boreal ecosystems of western North America as components of the climate system

    USGS Publications Warehouse

    Chapin, F. S., III; McGuire, A.D.; Randerson, J.; Pielke, R., Sr.; Baldocchi, D.; Hobbie, S.E.; Roulet, Nigel; Eugster, W.; Kasischke, E.; Rastetter, E.B.; Zimov, S.A.; Running, S.W.

    2000-01-01

    Synthesis of results from several Arctic and boreal research programmes provides evidence for the strong role of high-latitude ecosystems in the climate system. Average surface air temperature has increased 0.3??C per decade during the twentieth century in the western North American Arctic and boreal forest zones. Precipitation has also increased, but changes in soil moisture are uncertain. Disturbance rates have increased in the boreal forest; for example, there has been a doubling of the area burned in North America in the past 20 years. The disturbance regime in tundra may not have changed. Tundra has a 3-6-fold higher winter albedo than boreal forest, but summer albedo and energy partitioning differ more strongly among ecosystems within either tundra or boreal forest than between these two biomes. This indicates a need to improve our understanding of vegetation dynamics within, as well as between, biomes. If regional surface warming were to continue, changes in albedo and energy absorption would likely act as a positive feedback to regional warming due to earlier melting of snow and, over the long term, the northward movement of treeline. Surface drying and a change in dominance from mosses to vascular plants would also enhance sensible heat flux and regional warming in tundra. In the boreal forest of western North America, deciduous forests have twice the albedo of conifer forests in both winter and summer, 50-80% higher evapotranspiration, and therefore only 30-50% of the sensible heat flux of conifers in summer. Therefore, a warming-induced increase in fire frequency that increased the proportion of deciduous forests in the landscape, would act as a negative feedback to regional warming. Changes in thermokarst and the aerial extent of wetlands, lakes, and ponds would alter high-latitude methane flux. There is currently a wide discrepancy among estimates of the size and direction of CO2 flux between high-latitude ecosystems and the atmosphere. These

  19. Ecosystems on ice: the microbial ecology of Markham Ice Shelf in the high Arctic.

    PubMed

    Vincent, Warwick F; Mueller, Derek R; Bonilla, Sylvia

    2004-04-01

    Microbial communities occur throughout the cryosphere in a diverse range of ice-dominated habitats including snow, sea ice, glaciers, permafrost, and ice clouds. In each of these environments, organisms must be capable of surviving freeze-thaw cycles, persistent low temperatures for growth, extremes of solar radiation, and prolonged dormancy. These constraints may have been especially important during global cooling events in the past, including the Precambrian glaciations. One analogue of these early Earth conditions is the thick, landfast sea ice that occurs today at certain locations in the Arctic and Antarctic. These ice shelves contain liquid water for a brief period each summer, and support luxuriant microbial mat communities. Our recent studies of these mats on the Markham Ice Shelf (Canadian high Arctic) by high performance liquid chromatography (HPLC) showed that they contain high concentrations of chlorophylls a and b, and several carotenoids notably lutein, echinenone and beta-carotene. The largest peaks in the HPLC chromatograms were two UV-screening compounds known to be produced by cyanobacteria, scytonemin, and its decomposition product scytonemin-red. Microscopic analyses of the mats showed that they were dominated by the chlorophyte genera cf. Chlorosarcinopsis, Pleurastrum, Palmellopsis, and Bracteococcus, and cyanobacteria of the genera Nostoc, Phormidium, Leptolyngbya, and Gloeocapsa. From point transects and localized sampling we estimated a total standing stock on this ice shelf of up to 11,200 tonnes of organic matter. These observations underscore the ability of microbial communities to flourish despite the severe constraints imposed by the cryo-ecosystem environment. PMID:15094087

  20. Ecosystem Respiration Rates of Arctic Tundra Mesocosms in Response to Cold-Season Temperatures

    NASA Astrophysics Data System (ADS)

    Oberbauer, S. F.; Moser, J. G.; Olivas, P. C.; Starr, G.; Mortazavi, B.

    2013-12-01

    The cold season in the Arctic extends over 8 to 9 mo, during which air temperatures often reach as low as -40 °C. However, as a result of the insulating layer created by snow cover, temperatures seldom fall below -15 °C, and are likely warm enough to support some metabolism. Little research has been conducted on arctic plants and tundra during the cold season, despite its length and the fact that warming is predicted to be greatest during this period. The primary focus of cold-season research has been on rates of winter ecosystem respiration (ER) for estimates of annual carbon balance. The majority of these measurements during the winter or at winter temperatures indicate that some respiration is occurring. Although rates are low, they may contribute substantially to the annual carbon balance because of the length of the cold season. However, estimates of respiration at low temperatures differ substantially, have been taken at different temperatures using different methodologies, and importantly almost none provide quantitative relationships across a range of temperatures. We measured respiration rates of intact arctic tundra monoliths from 15 to -15 °C at 5 °C steps to facilitate improved model estimates of tundra respiration. Six tundra monoliths (~900 cm2) taken from Toolik Field Station, Alaska were conditioned for the cold season in growth chambers at shortened photoperiods and low, but above-freezing temperatures. Desired temperatures were obtained with a combination of growth chambers and a modified freezer. The average of five samplings of [CO2] at each temperature step was used to estimate the ER rates. Measurements were conducted with a closed system using incubation periods of 30 to 180 min, depending on the temperature. Carbon dioxide concentrations were measured by syringe samples injected into a N2 gas stream flowing through an infrared gas analyzer. Rates of ER calculated on an area basis were close to zero at -15 °C, but increased steadily with

  1. CONTAMINATION OF U. S. ARCTIC ECOSYSTEMS BY LONG-RANGE TRANSPORT OF ATMOSPHERIC CONTAMINANTS

    EPA Science Inventory

    Various kinds of atmospheric pollutants are found in Arctic environments, including organic contaminants, radionuclides, and pollutants associated with fossil fuel combustion, smelting, and industrial development. hile some of these contaminants originate in the Arctic itself, ot...

  2. Tracking Biological and Ecosystem Responses to Changing Environmental Conditions in the Pacific Arctic

    NASA Astrophysics Data System (ADS)

    Grebmeier, J. M.; Cooper, L. W.; Frey, K. E.; Moore, S. E.

    2014-12-01

    Changing seasonal sea ice conditions and seawater temperatures strongly influence biological processes and marine ecosystems at high latitudes. In the Pacific Arctic, persistent regions termed "hotspots", are localized areas with high benthic macroinfaunal biomass that have been documented over four decades (see Figure). These regions are now being more formally tracked to relate physical forcing and ecosystem response as an Arctic Distributed Biological Observatory (DBO) supported by the US National Ocean Policy Implementation Plan and international partners. These hotspots are important foraging areas for upper trophic level benthic feeders, such as marine mammals and seabirds. South of St. Lawrence Island (SLI) in the northern Bering Sea, benthic feeding spectacled eiders, bearded seals and walruses are important winter consumers of infauna, such as bivalves and polychaetes. Gray whales have historically been a major summer consumer of benthic amphipods in the Chirikov Basin to the north of SLI, although summertime sightings of gray whales declined in the Chirikov from the 1980s up until at least 2002. The SE Chukchi Sea hotspot, as are the other hotspots, is maintained by export of high chlorophyll a that is produced locally as well as advected by water masses transiting northward through the system. Both walrus and gray whales are known to forage in this hotspot seasonally on high biomass levels of benthic prey. Notably the center of the highest benthic biomass regions has shifted northward in three of the DBO hotspots in recent years. This has coincided with changing sediment grain size, an indicator of current speed, and is also likely a response to changes in primary production in the region. Studies of these broad biological responses to changing physical drivers have been facilitated through development of the DBO cooperative effort by both US and international scientists. The DBO includes a series of coordinated, multi-trophic level observations that

  3. Response of a tundra ecosystem to elevated atmospheric carbon dioxide and CO{sub 2}-induced climate change. Final report

    SciTech Connect

    Oechel, W.C.

    1996-11-01

    The overall objective of this research was to document current patterns of CO{sub 2} flux in selected locations of the circumpolar arctic, and to develop the information necessary to predict how these fluxes may be affected by climate change. In fulfillment of these objectives, net CO{sub 2} flux was measured at several sites on the North Slope of Alaska during the 1990--94 growing season (June--August) to determine the local and regional patterns of seasonal CO{sub 2} exchange. In addition, net CO{sub 2} flux was measured in the Russian and Icelandic Arctic to determine if the patterns of CO{sub 2} exchange observed in Arctic Alaska were representative of the circumpolar Arctic, while cold-season CO{sub 2} flux measurements were carried out during the 1993--94 winter season to determine the magnitude of CO{sub 2} efflux not accounted for by the growing season measurements. Manipulations of soil water table depth and surface temperature, which were identified from the extensive measurements as being the most important variables in determining the magnitude and direction of net CO{sub 2} exchange, were carried out during the 1993--94 growing seasons in tussock and wet sedge tundra ecosystems. Finally, measurements of CH{sub 4} flux were also measured at several of the North Slope study sites during the 1990--91 growing seasons.

  4. Marine ecosystem synthesis: From physics to whales in the Pacific Arctic

    NASA Astrophysics Data System (ADS)

    Sheffield Guy, Lisa; Moore, Sue E.; Stabeno, Phyllis

    2012-11-01

    Synthesis of Arctic Research (SOAR) Workshop; Anchorage, Alaska, 14-16 March 2012 The Synthesis of Arctic Research (SOAR) program brings together a multidisciplinary group of Arctic scientists and Alaskan coastal community residents to explore and integrate marine research information in the Pacific Arctic region. The goal of SOAR is to increase scientific understanding of the relationships among oceanographic conditions (physics, chemistry, sea ice), benthic organisms, lower trophic pelagic species (forage fish and zooplankton), and higher trophic species (i.e., seabirds, walrus, whales) in the Pacific Arctic, with particular emphasis on the Chukchi Sea oil and gas lease sale areas.

  5. Changing the seasonality of an Arctic tundra ecosystem: earlier snowmelt and warmer temperatures

    NASA Astrophysics Data System (ADS)

    Steltzer, H.; Weintraub, M. N.; Darrouzet-Nardi, A.; Melle, C.; Segal, A.; Sullivan, P.; Landry, C.; Wallenstein, M. D.

    2010-12-01

    In the Arctic and around the world, earlier plant growth is an indication that warmer temperatures or other global changes are changing the seasonality of the Earth’s ecosystems. To determine how changes in seasonality affect plant life histories and biogeochemical cycles in tussock tundra, we established a factorial experiment that includes two approaches to changing the seasonality of this ecosystem. In early May, we placed radiation absorbing fabric on the snow surface to accelerate the timing of snowmelt. We monitored the rate of snowmelt over a 10 day period and removed the fabric on the 10th day when the accelerated plots were 80% snowfree. Instrument arrays placed in the plots collected daily data that characterize an increase in energy absorption in these snowfree areas over the 4 day period prior to when control areas were snowfree. In addition, when the plots became snowfree we placed open-top-chambers in areas with and without accelerated snowmelt. The chambers increased air temperatures especially during mid-day early in the growing season. The instrument arrays included light sensors to monitor the plant community life history by observing surface greenness. Our results suggest that the plant community initiated growth earlier when snowmelt occurred earlier and that warming speeded the development of the plant canopy. However, plant species’ life history responses to these changes in seasonality were variable. Experimental alteration of the timing of plant life history events will provide a useful tool to examine controls on the seasonality of biogeochemical processes, such as nutrient availability to plants and nutrient limitation of decomposition. Accelerated snowmelt and warmer temperatures in tussock tundra, AK.

  6. Timing, Magnitude and Sources of Ecosystem Respiration in High Arctic Tundra of NW Greenland

    NASA Astrophysics Data System (ADS)

    Lupascu, M.; Xu, X.; Lett, C.; Maseyk, K. S.; Lindsey, D. S.; Thomas, J. S.; Welker, J. M.; Czimczik, C. I.

    2011-12-01

    High arctic ecosystems with low vegetation density contain significant stocks of organic carbon (C) in the form of soil organic matter that range in age from modern to ancient. How rapidly these C pools can be mineralized and lost to the atmosphere as CO2 (ecosystem respiration, ER) as a consequence of warming and, or changes in precipitation is a major uncertainty in our understanding of current and future arctic biogeochemistry and for predicting future levels of atmospheric CO2. In a 2-year study (2010-2011), we monitored seasonal changes in the magnitude, timing and sources of ER and soil pore space CO2 in the High Arctic of NW Greenland under current and simulated, future climate conditions. Measurements were taken from May to August at a multi-factorial, long-term climate change experiment in prostrate dwarf-shrub tundra on patterned ground with 5 treatments: (T1) +2oC warming, (T2) +4oC warming, (W) +50% summer precipitation, (T2W) +4oC + 50% summer precipitation, and (C) control. ER (using opaque chambers) and soil CO2 concentrations (wells) were monitored daily via infrared spectroscopy (LI-COR 800 & 840). The source of CO2 was inferred from its radiocarbon (14C) content analyzed at the AMS facility in UCI. CO2 was sampled monthly using molecular sieve traps (chambers) or evacuated canisters (wells). Highest rates of ER are observed on vegetated ground with a maximum in mid summer - reflecting a peak in plant productivity and soil temperature. Respiration rates from bare ground remain similar throughout the summer. Additional soil moisture, administered or due to precipitation events, strongly enhances ER from both vegetated and bare ground. Daily ER budget for the sampling period was of 53.1 mmol C m-2 day-1 for the (C) vegetated areas compared to the 60.0 for the (T2), 68.1 for the (T2W) or the 79.9 for the (W) treatment. ER was highly correlated to temperature (eg. C = 0.8; T2W = 0.8) until middle of July, when heavy precipitation started to occur. In

  7. Foliar Expression of Parent Lithologic Composition in the Sub-Arctic: Examples from Heath Ecosystems of Abisko, Sweden.

    NASA Astrophysics Data System (ADS)

    Heim, E. W.; Tomczyk, N.; Remiszewski, K.; Bryce, J. G.; Frey, S. D.; Prado, M. F.; Varner, R. K.

    2014-12-01

    Climatic evolution and its effect on ecosystem stability through macronutrient acquisition is of particular interest in the fringe ecosystems of the Arctic and Sub-Arctic, regions predicted to face the most extreme temperature increases in Earth's changing climate. Accordingly enhanced understanding of climate change impacts on nutrient mobilization in recently glaciated terrains will factor importantly into accurate predictive models for future ecosystem health. Lithologic variation can lead to differences in geomorphic processes and thus influence landscape evolution [1]. Heath ecosystems in the region are developed on thin soils which place them close to parent material bedrock. Given the abundance of thin soils mantling bedrock, we assessed how bedrock geochemical content links with foliar composition of key macronutrients. We focused our studies on four sites near Abisko, Sweden (68°21'N 19°02'E) in metamorphosed sedimentary bedrock. In our sites the average annual air temperature has crossed the 0o threshold and has been linked to many cryospheric and ecological impacts [2]. Sites were chosen at the same elevation (700 m absl) and shared similar vegetation coverage. Three dominant species across our sampling sites include Betula nana, Empetrum nigrum, and Salix lapponum. E. Nigrum had consistent concentrations of foliar magnesium (Mg) and phosphorus (P) across the bedrock compositional gradients. B. nana and S. lapponum had consistently higher foliar Mg and P concentrations than E. nigrum across the gradients. Across a soil calcium (Ca) gradient, dominant species had a weak correlation between soil Ca and foliar Ca contents, R2 = 0.106. Soil Mg and P gradients were similarly poorly correlated with foliar abundances, R2 = -0.0228, and R2= -0.034 respectively. Expansion of our work into other lithologies will contribute towards improved predictive biogeochemical models of macronutrient acquisition and ecological evolution across changing Arctic ecosystems.

  8. Hematology of southern Beaufort Sea polar bears (2005-2007): Biomarker for an arctic ecosystem health sentinel

    USGS Publications Warehouse

    Kirk, Cassandra M.; Amstrup, S.; Swor, Rhonda; Holcomb, Darce; O'Hara, T. M.

    2010-01-01

    Declines in sea-ice habitats have resulted in declining stature, productivity, and survival of polar bears in some regions. With continuing sea-ice declines, negative population effects are projected to expand throughout the polar bear's range. Precise causes of diminished polar bear life history performance are unknown, however, climate and sea-ice condition change are expected to adversely impact polar bear (Ursus maritimus) health and population dynamics. As apex predators in the Arctic, polar bears integrate the status of lower trophic levels and are therefore sentinels of ecosystem health. Arctic residents feed at the apex of the ecosystem, thus polar bears can serve as indicators of human health in the Arctic. Despite their value as indicators of ecosystem welfare, population-level health data for U.S. polar bears are lacking. We present hematological reference ranges for southern Beaufort Sea polar bears. Hematological parameters in southern Beaufort Sea polar bears varied by age, geographic location, and reproductive status. Total leukocytes, lymphocytes, monocytes, eosinophils, and serum immunoglobulin G were significantly greater in males than females. These measures were greater in nonlactating females ages ???5, than lactating adult females ages ???5, suggesting that females encumbered by young may be less resilient to new immune system challenges that may accompany ongoing climate change. Hematological values established here provide a necessary baseline for anticipated changes in health as arctic temperatures warm and sea-ice declines accelerate. Data suggest that females with dependent young may be most vulnerable to these changes and should therefore be a targeted cohort for monitoring in this sentinel. ?? 2010 International Association for Ecology and Health.

  9. Long-term experimentally deepened snow decreases growing-season respiration in a low- and high-arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Semenchuk, Philipp R.; Christiansen, Casper T.; Grogan, Paul; Elberling, Bo; Cooper, Elisabeth J.

    2016-05-01

    Tundra soils store large amounts of carbon (C) that could be released through enhanced ecosystem respiration (ER) as the arctic warms. Over time, this may change the quantity and quality of available soil C pools, which in-turn may feedback and regulate ER responses to climate warming. Therefore, short-term increases in ER rates due to experimental warming may not be sustained over longer periods, as observed in other studies. One important aspect, which is often overlooked, is how climatic changes affecting ER in one season may carry-over and determine ER in following seasons. Using snow fences, we increased snow depth and thereby winter soil temperatures in a high-arctic site in Svalbard (78°N) and a low-arctic site in the Northwest Territories, Canada (64°N), for 5 and 9 years, respectively. Deepened snow enhanced winter ER while having negligible effect on growing-season soil temperatures and soil moisture. Growing-season ER at the high-arctic site was not affected by the snow treatment after 2 years. However, surprisingly, the deepened snow treatments significantly reduced growing-season ER rates after 5 years at the high-arctic site and after 8-9 years at the low-arctic site. We speculate that the reduction in ER rates, that became apparent only after several years of experimental manipulation, may, at least in part, be due to prolonged depletion of labile C substrate as a result of warmer soils over multiple cold seasons. Long-term changes in winter climate may therefore significantly influence annual net C balance not just because of increased wintertime C loss but also because of "legacy" effects on ER rates during the following growing seasons.

  10. Importance of particle-associated bacterial heterotrophy in a coastal Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Garneau, Marie-Ève; Vincent, Warwick F.; Terrado, Ramon; Lovejoy, Connie

    2009-01-01

    estuarine stations with highest POM content. Particle-associated bacteria are an important functional component of this Arctic ecosystem. Under a warmer climate, they are likely to play an increasing role in coastal biogeochemistry and carbon fluxes as a result of permafrost melting and increased particle transport from the tundra to coastal waters.

  11. Net ecosystem exchange of CO2 with rapidly changing high Arctic landscapes.

    PubMed

    Emmerton, Craig A; St Louis, Vincent L; Humphreys, Elyn R; Gamon, John A; Barker, Joel D; Pastorello, Gilberto Z

    2016-03-01

    High Arctic landscapes are expansive and changing rapidly. However, our understanding of their functional responses and potential to mitigate or enhance anthropogenic climate change is limited by few measurements. We collected eddy covariance measurements to quantify the net ecosystem exchange (NEE) of CO2 with polar semidesert and meadow wetland landscapes at the highest latitude location measured to date (82°N). We coupled these rare data with ground and satellite vegetation production measurements (Normalized Difference Vegetation Index; NDVI) to evaluate the effectiveness of upscaling local to regional NEE. During the growing season, the dry polar semidesert landscape was a near-zero sink of atmospheric CO2 (NEE: -0.3 ± 13.5 g C m(-2) ). A nearby meadow wetland accumulated over 300 times more carbon (NEE: -79.3 ± 20.0 g C m(-2) ) than the polar semidesert landscape, and was similar to meadow wetland NEE at much more southerly latitudes. Polar semidesert NEE was most influenced by moisture, with wetter surface soils resulting in greater soil respiration and CO2 emissions. At the meadow wetland, soil heating enhanced plant growth, which in turn increased CO2 uptake. Our upscaling assessment found that polar semidesert NDVI measured on-site was low (mean: 0.120-0.157) and similar to satellite measurements (mean: 0.155-0.163). However, weak plant growth resulted in poor satellite NDVI-NEE relationships and created challenges for remotely detecting changes in the cycling of carbon on the polar semidesert landscape. The meadow wetland appeared more suitable to assess plant production and NEE via remote sensing; however, high Arctic wetland extent is constrained by topography to small areas that may be difficult to resolve with large satellite pixels. We predict that until summer precipitation and humidity increases enough to offset poor soil moisture retention, climate-related changes to productivity on polar semideserts may be restricted. PMID:26279166

  12. Possible Cretaceous Arctic terrestrial ecosystem dynamics based on a rich dinosaur record from Alaska

    NASA Astrophysics Data System (ADS)

    Fiorillo, A. R.; McCarthy, P. J.; Flaig, P. P.

    2010-12-01

    The widespread occurrence of large-bodied herbivores, specifically hadrosaurian and ceratopsian dinosaurs, in the Cretaceous of Alaska presents a proxy for understanding polar terrestrial ecosystem biological productivity in a warm Arctic world. These dinosaurs lived in Alaska at time when this region was at or near current latitudes. Thus these dinosaurs present a paradox. The warmer Cretaceous high-latitude climate, likely related to higher levels of CO2, may have increased plant productivity but the polar light regime fluctuations must have limited the available food during the winter months. The most detailed sedimentological data available regarding the paleoenvironments supporting these dinosaurs are from the Prince Creek Formation of northern Alaska and to a lesser extent the Cantwell Formation of the Alaska Range. The sediments of the Late Cretaceous Prince Creek Formation represent a continental succession deposited on a high-latitude, low-gradient, alluvial/coastal plain. The Prince Creek Formation records numerous paleosols that are consistent with seasonality and successional vegetative cover. Drab colors in fine-grained sediments, abundant carbonaceous plant material, and common siderite nodules and jarosite suggest widespread reducing conditions on poorly-drained floodplains influenced in more distal areas by marine waters. In addition, these rocks contain high levels of organic carbon and charcoal. Carbonaceous root-traces found ubiquitously within all distributary channels and most floodplain facies, along with common Fe-oxide mottles, indicate that the alluvial system likely experienced flashy, seasonal, or ephemeral flow and a fluctuating water table. The flashy nature of the alluvial system may have been driven by recurring episodes of vigorous seasonal snowmelt in the Brooks Range orogenic belt as a consequence of the high paleolatitude of northern Alaska in the Late Cretaceous. The presence of dinosaurian megaherbivores suggests that water was

  13. Late Pleistocene paleoecology of arctic ground squirrel ( Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA

    NASA Astrophysics Data System (ADS)

    Gaglioti, Benjamin V.; Barnes, Brian M.; Zazula, Grant D.; Beaudoin, Alwynne B.; Wooller, Matthew J.

    2011-11-01

    Botanical analyses of fossil and modern arctic ground squirrel ( Urocitellus parryii) caches and nests have been used to reconstruct the past vegetation from some parts of Beringia, but such archives are understudied in Alaska. Five modern and four fossil samples from arctic ground squirrel caches and nests provide information on late Pleistocene vegetation in Eastern Beringia. Modern arctic ground squirrel caches from Alaska's arctic tundra were dominated by willow and grass leaves and grass seeds and bearberries, which were widespread in the local vegetation as confirmed by vegetation surveys. Late Pleistocene caches from Interior Alaska were primarily composed of steppe and dry tundra graminoid and herb seeds. Graminoid cuticle analysis of fossil leaves identified Calamagrostis canadensis, Koeleria sp. and Carex albonigra as being common in the fossil samples. Stable carbon isotopes analysis of these graminoid specimens indicated that plants using the C 3 photosynthetic pathways were present and functioning with medium to high water-use efficiency. Fossil plant taxa and environments from ground squirrel caches in Alaska are similar to other macrofossil assemblages from the Yukon Territory, which supports the existence of a widespread mammoth steppe ecosystem type in Eastern Beringia that persisted throughout much of the late Pleistocene.

  14. Estimations of moisture content in the active layer in an Arctic ecosystem by using ground-penetrating radar profiling

    NASA Astrophysics Data System (ADS)

    Gacitúa, Guisella; Tamstorf, Mikkel Peter; Kristiansen, Søren Munch; Uribe, José Andrés

    2012-04-01

    We applied high-frequency GPR at a study site in the high arctic ecosystem of Northeast Greenland to evaluate its usefulness in assessing depth of, and water content in, the active layer at Zackenberg Valley (74°N; 20°W) to evaluate its usefulness in the high arctic ecosystems. The study site includes different vegetation types, and it well represents of the entire valley, for which we aimed to determine the conditions and characteristics that influence the GPR performance in the active layer. The spatial distribution of moisture content along the transect studied was estimated using GPR data (400 MHz antenna), depth to permafrost, soil samples and vegetation observations. Vertical distribution of the water content in the unfrozen soil bulk was predicted for several points on the transect by combining data that influence the behavior of the radar waves with that of capacitive moisture probes. The statistical models resulted to be highly significant, thus assuming common conditions of the soil to the classified vegetation, we can obtain from the GPR data, truthful estimations of water content, and, moreover, we can predict the distribution to the bottom of the active layer. Hence, we conclude that GPR is a viable option for improving active layer spatial quantification of water contents that can be used to assess changes in the active layer in arctic regions.

  15. Assessing the Utility of Alternate Digital Image Color Space for Deriving Phenological Dynamics in a High-Arctic Tundra Ecosystem

    NASA Astrophysics Data System (ADS)

    Vargas, S. A., Jr.; Oberbauer, S. F.; Ramirez, G.; Ramirez, G. A.; Tweedie, C. E.; Hollister, R. D.; Escarzaga, S. M.; Ochoa, E.

    2015-12-01

    The need to improve the spatial and temporal scaling and extrapolation of plot level ecosystem properties and processes to the landscape level remains a persistent research challenge in the Arctic. Plant and landscape phenology is sensitive to a number of spatiotemporally variable environmental factors such as soil moisture, temperature, and radiation. Seasonal and inter-annual differences in phenology can affect surface energy balance and land-atmosphere carbon flux. Considering the relative importance of the Arctic to global carbon balance, improved scaling and extrapolation of phenological dynamics from the plot level to the landscape level is important for advancing our understanding of the impact of climate and other environmental change in arctic terrestrial ecosystems. Seasonal and interannual landscape phenology was observed over the Mobile Instrumented Sensor Platform (MISP) grid (2 x 50 meters) located in Barrow and Atqasuk, Alaska using imagery acquired from kite aerial photography (KAP), a hyperspectral ground-based spectrometer, and a phenocam. These data were analyzed in RGB and non-traditional HSV and l*a*b*color spaces to determine site, plant community seasonal, and inter annual phenological dynamics. Results were also compared to high spatial resolution satellite imagery to determine optimal indices for scaling vegetation dynamics from plot to landscape level. These results show that greenness indices similar to those acquired from hyperspectral remote sensing platforms can be derived using low-cost and low-tech techniques that could be deployed at multiple sites at low cost.

  16. ARCTIC BIODIVERSITY: FROM DISCOVERY TO FAUNAL BASELINES-REVEALING THE HISTORY OF A DYNAMIC ECOSYSTEM

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of parasite biodiversity contributes to new and exciting approaches to understand the structure, history and future of the Arctic fauna. As a discovery- based process the Beringian Coevolution Project and activities under the umbrella of the Research Group for Arctic Parasitology serve as...

  17. Novel wildlife in the Arctic: the influence of changing riparian ecosystems and shrub habitat expansion on snowshoe hares.

    PubMed

    Tape, Ken D; Christie, Katie; Carroll, Geoff; O'Donnell, Jonathan A

    2016-01-01

    Warming during the 20th century has changed the arctic landscape, including aspects of the hydrology, vegetation, permafrost, and glaciers, but effects on wildlife have been difficult to detect. The primary aim of this study is to examine the physical and biological processes contributing to the expanded riparian habitat and range of snowshoe hares (Lepus americanus) in northern Alaska. We explore linkages between components of the riparian ecosystem in Arctic Alaska since the 1960s, including seasonality of stream flow, air temperature, floodplain shrub habitat, and snowshoe hare distributions. Our analyses show that the peak discharge during spring snowmelt has occurred on average 3.4 days per decade earlier over the last 30 years and has contributed to a longer growing season in floodplain ecosystems. We use empirical correlations between cumulative summer warmth and riparian shrub height to reconstruct annual changes in shrub height from the 1960s to the present. The effects of longer and warmer growing seasons are estimated to have stimulated a 78% increase in the height of riparian shrubs. Earlier spring discharge and the estimated increase in riparian shrub height are consistent with observed riparian shrub expansion in the region. Our browsing measurements show that snowshoe hares require a mean riparian shrub height of at least 1.24-1.36 m, a threshold which our hindcasting indicates was met between 1964 and 1989. This generally coincides with observational evidence we present suggesting that snowshoe hares became established in 1977 or 1978. Warming and expanded shrub habitat is the most plausible reason for recent snowshoe hare establishment in Arctic Alaska. The establishment of snowshoe hares and other shrub herbivores in the Arctic in response to increasing shrub habitat is a contrasting terrestrial counterpart to the decline in marine mammals reliant on decreasing sea ice. PMID:26527375

  18. Aboveground and belowground responses to nutrient additions and herbivore exclusion in Arctic tundra ecosystems in northern Alaska

    NASA Astrophysics Data System (ADS)

    Moore, J. C.; Gough, L.; Simpson, R.; Johnson, D. R.

    2011-12-01

    The Arctic has experienced significant increased regional warming over the past 30 years. Warming generally increases tundra soil nutrient availability by creating a more favorable environment for plant growth, decomposition and nutrient mineralization. Aboveground there has been a "greening" of the Arctic with increased net primary productivity (NPP), and an increase in woody vegetation. Concurrent with the changes aboveground has been an increase in root growth at lower depths and a loss of soil organic C (40 -100 g C m-2 yr-1). Given that arctic soils contain 14% of the global soil C pool, understanding the mechanisms behind shifts of this magnitude that are changing arctic soils from a net sink to a net source of atmospheric C is critical. We took an integrated multi-trophic level approach to examine how altering soil nutrients and mammalian herbivore activity affects vegetation, soil fauna, and microbial communities as well as soil physical characteristics in moist acidic (MAT) and dry heath (DH) tundra. Our work was conducted at the Arctic LTER site in northern Alaska. We sampled the nutrient (controls and annual N+P additions) and herbivore (controls and exclosures) manipulations established in 1996 after 10 years of treatment. Models that incorporated the biomass estimates from the field were used to characterize the trophic structure of the belowground food web and to estimate carbon flux among soil organisms and C-mineralization rates. Both MAT and DH exhibited significant increases in NPP and root growth and changes in vegetation structure with transitions from a mixed community to deciduous shrubs in MAT and from lichens to grasses and shrubs in DH, with nutrient additions and herbivore exclosures. Belowground responses to the treatments were dependent on ecosystem type, but exposed alterations in trophic structure that included changes in microbial biomass, the establishment of microbivorous enchytreaids, increases in root-feeding nematodes, and

  19. Characterizing subsurface controls on the Arctic ecosystem carbon cycling across scales using geophysical, in-situ and remote sensing datasets

    NASA Astrophysics Data System (ADS)

    Wainwright, H. M.; Hubbard, S. S.; Dafflon, B.; Ulrich, C.; Peterson, J. E.; Wu, Y.; Hahn, M. S.; Torn, M. S.; Gangodagamage, C.; Rowland, J. C.; Wilson, C. J.; Liljedahl, A.; Gusmeroli, A.; Wullschleger, S. D.

    2013-12-01

    Recent studies suggest that warming climate has significant impacts on the Arctic ecosystems, which could in turn create feedbacks to the climate system. Predicting Arctic ecosystem evolution and feedbacks requires a mechanistic understanding of complex subsurface processes (e.g., permafrost degradation and carbon decomposition) and characterization of key controls on those processes - such as soil moisture, active layer thickness and aqueous geochemistry - from native scales (where the processes occur) to landscape scales considered in climate models. Among others, developing such a predictive understanding requires two advances that we consider in this study: (1) approaches to characterize heterogeneous geocryological and hydrogeochemical properties in high resolution, and their uncertainties, inter-correlations, and correlations to land surface variables; (2) identification of possible zonation that can distinguish between suites of subsurface properties. Our study is carried out at the Department of Energy, Office of Science, Next Generation Ecosystem Experiment (NGEE-Arctic) Site in Barrow, Alaska. Given the importance of quantifying heterogeneous subsurface properties in both high resolution and over large spatial scales, we take advantage of geophysical datasets. We first develop and implement a multiscale Bayesian method to estimate subsurface properties using disparate datasets. We consider in-situ, surface geophysical and remote-sensing datasets along two 500m transects that traverse various ice-wedge polygon features. The method is based on site-specific correlations between geophysical datasets and in-situ measured subsurface properties. The Markov-chain Monte-Carlo sampling is used to compute the posterior distributions. For example, thaw depth and soil moisture are estimated by integrating ground-penetrating radar (GPR), electrical resistivity tomography and in-situ point data. Snow depth coverage is estimated by integrating GPR and point data. The

  20. The Barents and Chukchi Seas: Comparison of two Arctic shelf ecosystems

    NASA Astrophysics Data System (ADS)

    Hunt, George L.; Blanchard, Arny L.; Boveng, Peter; Dalpadado, Padmini; Drinkwater, Kenneth F.; Eisner, Lisa; Hopcroft, Russ R.; Kovacs, Kit M.; Norcross, Brenda L.; Renaud, Paul; Reigstad, Marit; Renner, Martin; Skjoldal, Hein Rune; Whitehouse, Andy; Woodgate, Rebecca A.

    2013-01-01

    This paper compares and contrasts the ecosystems of the Barents and Chukchi Seas. Despite their similarity in a number of features, the Barents Sea supports a vast biomass of commercially important fish, but the Chukchi does not. Here we examine a number of aspects of these two seas to ascertain how they are similar and how they differ. We then indentify processes and mechanisms that may be responsible for their similarities and differences. Both the Barents and Chukchi Seas are high latitude, seasonally ice covered, Arctic shelf-seas. Both have strongly advective regimes, and receive water from the south. Water entering the Barents comes from the deep, ice-free and "warm" Norwegian Sea, and contains not only heat, but also a rich supply of zooplankton that supports larval fish in spring. In contrast, Bering Sea water entering the Chukchi in spring and early summer is cold. In spring, this Bering Sea water is depleted of large, lipid-rich zooplankton, thus likely resulting in a relatively low availability of zooplankton for fish. Although primary production on average is similar in the two seas, fish biomass density is an order of magnitude greater in the Barents than in the Chukchi Sea. The Barents Sea supports immense fisheries, whereas the Chukchi Sea does not. The density of cetaceans in the Barents Sea is about double that in the Chukchi Sea, as is the density of nesting seabirds, whereas, the density of pinnipeds in the Chukchi is about double that in the Barents Sea. In the Chukchi Sea, export of carbon to the benthos and benthic biomass may be greater. We hypothesize that the difference in fish abundance in the two seas is driven by differences in the heat and plankton advected into them, and the amount of primary production consumed in the upper water column. However, we suggest that the critical difference between the Chukchi and Barents Seas is the pre-cooled water entering the Chukchi Sea from the south. This cold water, and the winter mixing of the

  1. Microbial Biomass and Population Densities of Non-Sorted Circles in High Arctic Ecosystems

    NASA Astrophysics Data System (ADS)

    Rivera-Figueroa, F.; González, G.; Gould, W. A.; Cantrell, S.; Pérez, J.

    2006-12-01

    Non-sorted circles are small patterned-ground features that occur in arctic soils as a result of intensive frost heave action. This tundra feature has been extensively described. However, little is known about the ecological relationships between this pattern and above- and belowground organisms. In this study, we compare the biomass and populaton densities of microbes in non-sorted circles and the vegetated surrounding soils (inter-circles) in the High Arctic. We collected soil samples during the summer of 2004 and 2005 on Banks and Prince Patrick and Ellef Ringnes Islands, Canada. Soil samples (0-10 cm) were gathered from non- sorted circles and inter-circles along a topographic sequence: dry (ridge), mesic (mid slope) and wet (valley) and along three transects in zonal (mesic) sites on each island. We estimated total microbial biomass and bacterial population densities using substrate induce respiration (SIR) and the most probable number method (MPN), respectively. We also isolated soil fungi using Rose Bengal and Saboraud Dextrose culture media. We are in the process of analyzing the catena samples using a terminal restriction fragment length polymorphism (TRFLP) technique of PCR-amplified 16S rRNA. Based on the SIR trials, the average microbial biomass at the mid slope position in the Banks site (Green Cabin) was 0.49 mg C g-1 dry soil in the non- sorted circles and 0.95 mg C g-1 dry soil in the inter-circles. At Prince Patrick Island (Mould Bay) the microbial biomass was 0.54 mg C g-1 dry soil in the non-sorted circles and 0.74 mg C g-1 dry soil in the inter-circles. In Ellef Ringnes (Isachsen) the microbial biomass was 0.09 mg C g-1 dry soil in the non- sorted circles and 0.14 mg C g-1 dry soil in the inter-circles. At the mesic site at Green Cabin, bacteria vary from 2.92 x 106 cell g-1 dry soil in the non-sorted circles to 6.74 x 106 cell g-1 dry soil in the inter-circles. At Mould Bay the range was 7.67 x 105 cells g-1 dry soil in the non-sorted circles

  2. Changing Arctic ecosystems--measuring and forecasting the response of Alaska's terrestrial ecosystem to a warming climate

    USGS Publications Warehouse

    Pearce, John; DeGange, Anthony R.; Flint, Paul; Fondell, Tom F.; Gustine, David; Holland-Bartels, Leslie; Hope, Andrew G.; Hupp, Jerry; Koch, Josh; Schmutz, Joel; Talbot, Sandra; Ward, David; Whalen, Mary

    2012-01-01

    The Arctic Coastal Plain of northern Alaska is a complex landscape of lakes, streams, and wetlands scattered across low relief tundra that is underlain by permafrost. This region of the Arctic has experienced a warming trend over the past three decades, leading to thawing of on-shore permafrost and the disappearance of sea ice at an unprecedented rate. The loss of sea ice has increased ocean wave action, leading to higher rates of erosion and salt water inundation of coastal habitats. Warming temperatures also have advanced the overall phenology of the region, including earlier snowmelt, lake ice thaw, and plant growth. As a result, many migratory species now arrive in the Arctic several days earlier in spring than in the 1970s. Predicted warming trends for the future will continue to alter plant growth, ice thaw, and other basic landscape processes. These changes will undoubtedly result in different responses by wildlife (fish, birds, and mammals) and the food they rely upon (plants, invertebrates, and fish). However, the type of response by different wildlife populations and their habitats-either positively or negatively-remains largely unknown.

  3. The nearshore western Beaufort Sea ecosystem: Circulation and importance of terrestrial carbon in arctic coastal food webs

    NASA Astrophysics Data System (ADS)

    Dunton, Kenneth H.; Weingartner, Thomas; Carmack, Eddy C.

    2006-10-01

    . Calculations from isotopic mixing equations indicate cod from lagoons may derive 70% of their carbon from terrestrial sources. The δ15N values of lagoon fish were also 4‰ lower than coastal specimens, reflective of the lower δ15N values of terrestrially derived nitrogen (0-1.5‰ compared to 5-7‰ for phytoplankton). The role of terrestrial carbon in arctic estuarine food webs is especially important in view of the current warming trend in the arctic environment and the role of advective processes that transport carbon along the nearshore shelf. Biogeochemical studies of the arctic coastal estuarine environment may provide more insights into the function of these biologically complex ecosystems.

  4. Increases in Growing Season Length and Changes in Precipitation at Six Different Arctic and Subarctic Ecosystems from 1906-Present

    NASA Astrophysics Data System (ADS)

    Culler, L. E.; Finger, R.; Plane, E.; Ayres, M.; Virginia, R. A.

    2015-12-01

    Ecological dynamics across the Arctic are responding to rapid changes in climate. As a whole, the Arctic has warmed at approximately twice the rate of the rest of the world, but changes in temperature and precipitation experienced at regional and local scales are most important for coupled human-natural systems. In addition, biologically-relevant climate indices are necessary for quantifying ecological responses of terrestrial and aquatic systems to varying climate. We compared climatic changes at six different Arctic and sub-Arctic locations, including two in Greenland (Kangerlussuaq, Sisimiut), one in Sweden (Abisko), and three in Alaska (Barrow, Nome, Fairbanks). We amassed weather data (daily temperature and precipitation), dating as far back as 1906, from public-access databases and used these data to calculate indices such as length of growing season, growing season degree days (GDD), and growing season precipitation. Annual GDD increased at all locations (average of 13% increase in GDD since 1980), but especially in western Greenland (16 and 37% in Kangerlussuaq and Sisimiut, respectively). Changes in growing season precipitation were more variable, with only Barrow, AK and Abisko, Sweden experiencing increased precipitation. All other sites experienced stable or slightly declining precipitation. Increasing temperatures and relatively stable precipitation translates to increased evapotranspiration potential, which influences soil moisture, lake depth, vegetation, carbon emissions, and fire susceptibility. Understanding local and regional trends in temperature and precipitation can help explain observed phenological changes and other processes at population, community, and ecosystem levels. In addition, identification of locations most susceptible to future change will allow scientists to closely monitor their ecological dynamics, anticipate changes in coupled human-natural systems, and consider adaptation plans for the most rapidly changing systems.

  5. Spatial and temporal variation of an ice-adapted predator's feeding ecology in a changing Arctic marine ecosystem.

    PubMed

    Yurkowski, David J; Ferguson, Steven H; Semeniuk, Christina A D; Brown, Tanya M; Muir, Derek C G; Fisk, Aaron T

    2016-03-01

    Spatial and temporal variation can confound interpretations of relationships within and between species in terms of diet composition, niche size, and trophic position (TP). The cause of dietary variation within species is commonly an ontogenetic niche shift, which is a key dynamic influencing community structure. We quantified spatial and temporal variations in ringed seal (Pusa hispida) diet, niche size, and TP during ontogeny across the Arctic-a rapidly changing ecosystem. Stable carbon and nitrogen isotope analysis was performed on 558 liver and 630 muscle samples from ringed seals and on likely prey species from five locations ranging from the High to the Low Arctic. A modest ontogenetic diet shift occurred, with adult ringed seals consuming more forage fish (approximately 80 versus 60 %) and having a higher TP than subadults, which generally decreased with latitude. However, the degree of shift varied spatially, with adults in the High Arctic presenting a more restricted niche size and consuming more Arctic cod (Boreogadus saida) than subadults (87 versus 44 %) and adults at the lowest latitude (29 %). The TPs of adult and subadult ringed seals generally decreased with latitude (4.7-3.3), which was mainly driven by greater complexity in trophic structure within the zooplankton communities. Adult isotopic niche size increased over time, likely due to the recent circumpolar increases in subarctic forage fish distribution and abundance. Given the spatial and temporal variability in ringed seal foraging ecology, ringed seals exhibit dietary plasticity as a species, suggesting adaptability in terms of their diet to climate change. PMID:26210748

  6. Final Technical Report for Project "Improving the Simulation of Arctic Clouds in CCSM3"

    SciTech Connect

    Stephen J. Vavrus

    2008-11-15

    the CCSM3 climate model. J. Climate, 21, 5673-5687.). The article also provides a novel synthesis of surface- and satellite-based Arctic cloud observations that show how much the new freezedry parameterization improves the simulated cloud amount in high latitudes (Fig. 3). Freezedry has been incorporated into the CCSM3.5 version, in which it successfully limits the excessive polar clouds, and may be used in CCSM4. Material from this work is also appearing in a synthesis article on future Arctic cloud changes (Vavrus, D. Waliser, J. Francis, and A. Schweiger, 'Simulations of 20th and 21st century Arctic cloud amount in the global climate models assessed in the IPCC AR4', accepted in Climate Dynamics) and was used in a collaborative paper on Arctic cloud-sea ice coupling (Schweiger, A., R. Lindsay, S. Vavrus, and J. Francis, 2008: Relationships between Arctic sea ice and clouds during autumn. J. Climate, 21, 4799-4810.). This research was presented at the 2007 CCSM Annual Workshop, as well as the CCSM's 2007 Atmospheric Model Working Group and Polar Working Group Meetings. The findings were also shown at the 2007 Climate Change Prediction Program's Science Team Meeting. In addition, I served as an instructor at the International Arctic Research Center's (IARC) Summer School on Arctic Climate Modeling in Fairbanks this summer, where I presented on the challenges and techniques used in simulating polar clouds. I also contributed to the development of a new Arctic System Model by attending a workshop in Colorado this summer on this fledgling project. Finally, an outreach activity for the general public has been the development of an interactive web site () that displays Arctic cloud amount in the CMIP3 climate model archive under present and future scenarios. This site allows users to make polar and global maps of a variety of climate variables to investigate the individual and ensemble-mean GCM response to greenhouse

  7. Mercury in freshwater ecosystems of the Canadian Arctic: recent advances on its cycling and fate.

    PubMed

    Chételat, John; Amyot, Marc; Arp, Paul; Blais, Jules M; Depew, David; Emmerton, Craig A; Evans, Marlene; Gamberg, Mary; Gantner, Nikolaus; Girard, Catherine; Graydon, Jennifer; Kirk, Jane; Lean, David; Lehnherr, Igor; Muir, Derek; Nasr, Mina; Poulain, Alexandre J; Power, Michael; Roach, Pat; Stern, Gary; Swanson, Heidi; van der Velden, Shannon

    2015-03-15

    The Canadian Arctic has vast freshwater resources, and fish are important in the diet of many Northerners. Mercury is a contaminant of concern because of its potential toxicity and elevated bioaccumulation in some fish populations. Over the last decade, significant advances have been made in characterizing the cycling and fate of mercury in these freshwater environments. Large amounts of new data on concentrations, speciation and fluxes of Hg are provided and summarized for water and sediment, which were virtually absent for the Canadian Arctic a decade ago. The biogeochemical processes that control the speciation of mercury remain poorly resolved, including the sites and controls of methylmercury production. Food web studies have examined the roles of Hg uptake, trophic transfer, and diet for Hg bioaccumulation in fish, and, in particular, advances have been made in identifying determinants of mercury levels in lake-dwelling and sea-run forms of Arctic char. In a comparison of common freshwater fish species that were sampled across the Canadian Arctic between 2002 and 2009, no geographic patterns or regional hotspots were evident. Over the last two to four decades, Hg concentrations have increased in some monitored populations of fish in the Mackenzie River Basin while other populations from the Yukon and Nunavut showed no change or a slight decline. The different Hg trends indicate that the drivers of temporal change may be regional or habitat-specific. The Canadian Arctic is undergoing profound environmental change, and preliminary evidence suggests that it may be impacting the cycling and bioaccumulation of mercury. Further research is needed to investigate climate change impacts on the Hg cycle as well as biogeochemical controls of methylmercury production and the processes leading to increasing Hg levels in some fish populations in the Canadian Arctic. PMID:24993511

  8. Effects of Disturbances on Vegetation Composition and Permafrost Thaw in Boreal Forests and Tundra Ecosystems of the Siberian Arctic

    NASA Astrophysics Data System (ADS)

    Ramos, E.; Alexander, H. D.; Natali, S.

    2014-12-01

    In Arctic ecosystems, climate-driven changes to the thermal regime of permafrost soils have the potential to create surface disturbances that influence vegetation dynamics and underlying soil properties. Disturbance-mediated changes in vegetation are important because vegetation and the accumulation of soil organic matter drive ecosystem carbon (C) dynamics and contribute to the insulation of soils and protection of permafrost from thaw. We examined the effect of two disturbance types—thermokarsts and frost boils—to determine disturbance effects on the vegetation community and soil properties in northeast Siberia. In summer 2014, we measured vegetation cover, soil moisture, soil temperature, and thaw depth in two thermokarst sites within boreal forests, two frost boil sites in tundra, and in adjacent undisturbed sites within both ecosystems. Both thermokarst and frost boils resulted in decreased vegetation cover and greater exposure of mineral soils (10-40% bare soils vs. 0% in undisturbed), and consequently, 2-3 times higher soil temperature and deeper thaw depth. Compared to undisturbed areas, soil moisture was 3-4 times higher in thermokarst areas but 1.2-2 times lower in frost boil areas, which reflected differences in microtopography between these two disturbance types. In both thermokarst and frost boil disturbed areas, deciduous and evergreen shrubs covered only 5 and 10%, respectively, compared to approximately 10 and 20%, respectively, in undisturbed areas. In general, graminoids were substantially more abundant (2-20 times) in disturbed areas than in those undisturbed. These results highlight important linkages between disturbances, vegetation communities, and permafrost soils, and contribute to our understanding of how changes in arctic vegetation dynamics as direct and/or indirect consequences of climate change have the potential to impact permafrost C pools.

  9. Interacting effects of elevated temperature and additional water on plant physiology and net ecosystem carbon fluxes in a high Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Maseyk, Kadmiel; Seibt, Ulrike; Lett, Céline; Lupascu, Massimo; Czimczik, Claudia; Sullivan, Patrick; Welker, Jeff

    2013-04-01

    Arctic ecosystems are experiencing temperature increases more strongly than the global average, and increases in precipitation are also expected amongst the climate impacts on this region in the future. These changes are expected to strongly influence plant physiology and soil biogeochemistry with subsequent implications for system carbon balance. We have investigated the effects of a long-term (10 years) increase in temperature, soil water and the combination of both on a tundra ecosystem at a field manipulation experiment in NW Greenland. Leaf gas exchange, chlorophyll fluorescence, carbon (C) and nitrogen (N) content and leaf isotopic composition, and leaf morphology were measured on Salix arctica plants in treatment and control plots in June-July 2011, and continuous measurements of net plant and soil fluxes of CO2 and water were made using automatic chambers coupled to a trace gas laser analyzer. Plants in the elevated temperature (T2) treatment had the highest photosynthetic capacity in terms of net CO2 assimilation rates and photosystem II efficiencies, and lowest rates of non-photochemical energy dissipation during photosynthesis. T2 plants also had the highest leaf N content, specific leaf area (SLA) and saturation light level of photosynthesis. It appears that warming increases soil N availability, which the plants direct towards increasing photosynthetic capacity and producing larger thinner leaves. On the other hand, the plants in the plots with both elevated temperatures and additional water (T2W) had the lowest photosystem II efficiencies and the highest rates of non-photochemical energy dissipation, due more to higher levels of constitutive energy dissipation than regulated thermal quenching. Watering, both in combination with higher temperatures and alone (W treatment), also reduced leaf SLA and leaf N relative to control plots. However, net photosynthetic rates remained similar to control plants, due in part to higher stomatal conductance (W) and

  10. Deglacial and Holocene Evolution of Climate and Terrestrial Ecosystems in the Western Arctic.

    NASA Astrophysics Data System (ADS)

    Edwards, M. E.

    2006-12-01

    The late- and post-glacial history of the Western Arctic land area is distinguished by the region being largely unglaciated (away from the coastal cordillera), and by a considerable reduction in areal extent due to sea-level rise. Between ca. 15 and 10 cal ka B.P. rising summer temperatures and increasing precipitation related to orbital forcing and adjustments in the hemispheric circulation resulted in widespread replacement of herbaceous vegetation with deciduous woody plants, rising lake levels, reduction of eolian activity, and the onset of thermokarst erosion. These changes had impacts at both global and regional levels, e.g., reduced atmospheric dust loading, increased carbon flux to the atmosphere, and feedbacks to the surface energy balance. The Younger Dryas event (ca. 12.9-11.6 cal ka B.P.) is not strongly expressed in terrestrial records. Some localities near the Pacific coast and in eastern Siberia record a weak to moderate climatic reversal, but central, northern, and eastern areas show no consistent signal. This suggests a muted response of the North Pacific and/or adjacent lands to events in the North Atlantic. However, the nearly coincident flooding and eventual breaching of the Bering land bridge probably reduced continentality in adjacent regions and may be linked to early-Holocene increases in effective moisture in both summer and winter. At ca. 10 cal ka B.P. evergreen conifers expanded to dominance or co-dominance much of the forest zone on both sides of the Bering Strait. This appears to be an example of a moisture-driven vegetation change in a region normally expected to respond largely to temperature. Particularly in Alaska and NW Canada, it likely led to two significant ecosystem changes: a vegetation-driven shift in the fire regime and enhanced paludification. The former could have influenced atmospheric chemistry and the latter nutrient availability, the status of permafrost, and the export of organic carbon and other nutrients to

  11. Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    ScienceCinema

    Wullschleger, Stan [ORNL

    2013-01-22

    Stan Wullschleger of Oak Ridge National Laboratory on "Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems" on March 22, 2012 at the 7th Annual Genomics of Energy & Environment Meeting in Walnut Creek, California.

  12. Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems (JGI Seventh Annual User Meeting 2012: Genomics of Energy and Environment)

    SciTech Connect

    Wullschleger, Stan

    2012-03-22

    Stan Wullschleger of Oak Ridge National Laboratory on "Omics in the Arctic: Genome-enabled Contributions to Carbon Cycle Research in High-Latitude Ecosystems" on March 22, 2012 at the 7th Annual Genomics of Energy & Environment Meeting in Walnut Creek, California.

  13. USING LAKE SEDIMENT MERCURY FLUX RATIOS TO EVALUATE THE REGIONAL AND CONTINENTAL DIMENSIONS OF MERCURY DEPOSITION IN ARCTIC AND BOREAL ECOSYSTEMS

    EPA Science Inventory

    Anthropogenically elevated Hg deposition in arctic and subarctic ecosystems is potentially a serious environmental problem, particularly in northern Europe and North America. To determine the magnitude of this concern, it is necessary to make an evaluation over a broad spatial sc...

  14. Inclusion of Additional Plant Species and Trait Information in Dynamic Vegetation Modeling of Arctic Tundra and Boreal Forest Ecosystem

    NASA Astrophysics Data System (ADS)

    Euskirchen, E. S.; Patil, V.; Roach, J.; Griffith, B.; McGuire, A. D.

    2015-12-01

    Dynamic vegetation models (DVMs) have been developed to model the ecophysiological characteristics of plant functional types in terrestrial ecosystems. They have frequently been used to answer questions pertaining to processes such as disturbance, plant succession, and community composition under historical and future climate scenarios. While DVMs have proved useful in these types of applications, it has often been questioned if additional detail, such as including plant dynamics at the species-level and/or including species-specific traits would make these models more accurate and/or broadly applicable. A sub-question associated with this issue is, 'How many species, or what degree of functional diversity, should we incorporate to sustain ecosystem function in modeled ecosystems?' Here, we focus on how the inclusion of additional plant species and trait information may strengthen dynamic vegetation modeling in applications pertaining to: (1) forage for caribou in northern Alaska, (2) above- and belowground carbon storage in the boreal forest and lake margin wetlands of interior Alaska, and (3) arctic tundra and boreal forest leaf phenology. While the inclusion of additional information generally proved valuable in these three applications, this additional detail depends on field data that may not always be available and may also result in increased computational complexity. Therefore, it is important to assess these possible limitations against the perceived need for additional plant species and trait information in the development and application of dynamic vegetation models.

  15. Nonlinear responses to nitrogen and strong interactions with nitrogen and phosphorus additions drastically alter the structure and function of a high arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Arens, Seth J. T.; Sullivan, Patrick F.; Welker, Jeffrey M.

    2008-09-01

    Significant changes in ecosystem CO2 exchange and vegetation characteristics were observed following multiple additions of nitrogen (N) and factorial additions of N and phosphorus (P) to prostrate dwarf-shrub, herb tundra in Northwest Greenland. Ecosystem CO2 exchange and vegetation cover and composition were very sensitive to low rates of N inputs (0.5 g m-2 y-1), indicating that even low rates of atmospheric N deposition may alter high arctic ecosystem structure and function. Increasing N addition from 1 to 5 g N m-2 y-1 did not alter CO2 exchange or vegetation characteristics, suggesting the ecosystem had become N saturated. Factorial additions of both N and P released the ecosystem from N saturation and dramatically increased gross ecosystem photosynthesis (+500%) and ecosystem respiration (+250%), such that the ecosystem switched from a small source of CO2 to a small sink for CO2 at midday during the 2005 growing season. Changes in the component fluxes of CO2 exchange were largely explained by a doubling of the normalized difference vegetation index, a 100% increase in vascular plant cover and dramatic increases in the abundance of several previously rare grass species. Our results clearly demonstrate that high arctic prostrate dwarf-shrub, herb tundra is highly sensitive to low levels of N addition and that future increases in N deposition or N mineralization will likely lead to change in carbon cycling and vegetation characteristics, but the magnitude of the response will be constrained by P availability.

  16. Remote Sensing of Arctic-Boreal Terrestrial and Freshwater Ecosystems - Recent Progress and Current and Future Challenges

    NASA Astrophysics Data System (ADS)

    Kasischke, E. S.; Goetz, S. J.

    2015-12-01

    NASA is in the process of starting its next major terrestrial field campaign, the Arctic-Boreal Vulnerability Experiment (ABoVE), with field-based research beginning in 2016 at sites in high northern latitude regions of western North America. In this presentation, we will review the research that is being planned for ABoVE that involves the use of remotely-sensed data, including the development of information products required by end users to assess the societal impacts of environmental change. These plans included taking advantage of recent advances in mapping of key surface and atmospheric characteristics using both airborne and spaceborne remote sensing data. We will also identify current and future challenges for the collection and analysis of additional data needed to assess key ecosystem changes, including the need for use of medium resolution optical and SAR data, and fine resolution optical data.

  17. Plankton ecosystem functioning and nitrogen fluxes in the most oligotrophic waters of the Beaufort Sea, Arctic Ocean: a modeling study

    NASA Astrophysics Data System (ADS)

    Le Fouest, V.; Zakardjian, B.; Xie, H.; Raimbault, P.; Joux, F.; Babin, M.

    2012-10-01

    The Arctic Ocean (AO) undergoes profound changes of its physical and biotic environments due to climate change. The greater light exposure and stratification alter its plankton ecosystem structure, functioning and productivity promoting oligotrophy in some areas as the Beaufort Sea. A one-dimension (1-D) physical-biological coupled model based on the large multiparametric database of the Malina project in the Beaufort Sea was used (i) to infer the functioning and nitrogen fluxes within the summer plankton ecosystem and (ii) to assess the model sensitivity to key light-associated processes involved in nutrient recycling and phytoplankton growth. The coupled model suggested that ammonium photochemically produced from photosensitive dissolved organic nitrogen (i.e. photoammonification process) was a necessary nitrogen source to achieve the observed levels of microbial biomass and production. It contributed to ca. two-thirds and one-third of the simulated surface (0-10 m) and depth-integrated primary and bacterial production, respectively. The model also suggested that carbon to chlorophyll ratios for small (< 5 μm) phytoplankton (ca. 15-45 g g-1) lower than those commonly used in biogeochemical models applied to the AO were required to simulate the observed herbivorous versus microbial food web competition and realistic nitrogen fluxes in the Beaufort Sea oligotrophic waters. In face of accelerating Arctic warming, more attention should be paid in the future to the mechanistic processes involved in food webs and functional groups competition, nutrient recycling and primary production in poorly productive waters of the AO as they are expected to expand rapidly.

  18. Integration of Measurements and Models Across Spatial Scales for Improved Process Understanding in Arctic and Boreal Ecosystems

    NASA Astrophysics Data System (ADS)

    Wullschleger, S. D.; Collier, N.; Kumar, J.; Painter, S. L.; Thornton, P. E.; Wilson, C. J.

    2014-12-01

    Characterizing the spatial variability of properties and processes in Arctic and boreal landscapes is critical for gaining an understanding of ecosystem functioning and for parameterizing process-rich models that simulate feedbacks to a changing climate. However, large-scale models are often poorly informed by process studies and new approaches are needed if we are to better link field and laboratory investigations to climate models. A fundamental goal of the Next-Generation Ecosystem Experiments (NGEE Arctic) project is to accelerate improvements in climate prediction through close integration of field, laboratory, and modeling activities. Geomorphological units, including thaw lakes, drained thaw lake basins, and ice-rich polygonal ground provide the organizing framework for our integrated framework for the coastal plains of the North Slope of Alaska. Process studies and observations of hydrology, geomorphology, biogeochemistry, vegetation patterns, and energy exchange and their couplings are being conducted across nested scales to populate a modeling framework and to achieve a broader goal of optimally informing process representations in global-scale models. We investigate the soil thermal regimes and their control on local scale hydrology for sites near Barrow, Alaska, through simulations at sub-meter scale resolution for low-centered, high-centered and transition polygons. We use high-resolution LiDAR and high-fidelity simulations using several models to couple surface-subsurface processes. A central focus of this challenge is to advance process understanding and predicting the evolution of permafrost thaw, degradation (i.e., thermokarst), and disturbance, and their impact on topography in a warming world and how these changes control the availability of water for biogeochemical, ecological, and physical feedbacks to the climate system.

  19. Effects of increased snow cover on the rates and sources of ecosystem respiration from high arctic tundra

    NASA Astrophysics Data System (ADS)

    Lupascu, M.; Welker, J. M.; Cooper, E.; Xu, X.; Czimczik, C. I.

    2013-12-01

    A key driver of carbon (C) cycling in arctic ecosystems is the amount, onset and duration of snow cover. Arctic tundra is covered in snow for 8-10 months of the year, although spatial and internannual variability of snow cover is high. Anticipated changes in the amount and timing of snow cover as a consequence of climate warming and their implications for regional C budget and biogeochemistry are highly uncertain. Here, we investigated the effects of increased winter snow depth on the rates and sources of ecosystem respiration (Reco) of a polar semi-desert and mesic meadow at two long-term snowpack manipulation experiments in NW Greenland and Svalbard, Norway. We monitored Reco, the concentrations of CO2 in the soil pore space and their radiocarbon (14C) contents (as an age proxy) over the course of three summers in Greenland and one winter in Svalbard. Preliminary results show that wintertime Reco fluxes were 45% higher in areas of deep as compared to ambient snow. Summertime Reco fluxes were positively correlated to total water-year precipitation (summer rain plus winter snow). However, due to the shorter, snow-free vegetation period, cumulative summertime Reco fluxes under increased snow cover were reduced by up to -34.1×5.4% compared to the control. The mean age of soil CO2 was always older during both the winter- and summertime under increased snow cover. Similarly, the mean age of Reco was older under increased snowpack during the wintertime. However, summertime Reco was dominated by decomposition of younger C and plant respiration, and we found no effect of snow cover. Our results demonstrate the vulnerability of permafrost C to increasing snow cover and the strong potential to serve as a positive feedback to global climate change.

  20. Two years with extreme and little snowfall: effects on energy partitioning and surface energy exchange in a high-Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Stiegler, Christian; Lund, Magnus; Røjle Christensen, Torben; Mastepanov, Mikhail; Lindroth, Anders

    2016-07-01

    Snow cover is one of the key factors controlling Arctic ecosystem functioning and productivity. In this study we assess the impact of strong variability in snow accumulation during 2 subsequent years (2013-2014) on the land-atmosphere interactions and surface energy exchange in two high-Arctic tundra ecosystems (wet fen and dry heath) in Zackenberg, Northeast Greenland. We observed that record-low snow cover during the winter 2012/2013 resulted in a strong response of the heath ecosystem towards low evaporative capacity and substantial surface heat loss by sensible heat fluxes (H) during the subsequent snowmelt period and growing season. Above-average snow accumulation during the winter 2013/2014 promoted summertime ground heat fluxes (G) and latent heat fluxes (LE) at the cost of H. At the fen ecosystem a more muted response of LE, H and G was observed in response to the variability in snow accumulation. Overall, the differences in flux partitioning and in the length of the snowmelt periods and growing seasons during the 2 years had a strong impact on the total accumulation of the surface energy balance components. We suggest that in a changing climate with higher temperature and more precipitation the surface energy balance of this high-Arctic tundra ecosystem may experience a further increase in the variability of energy accumulation, partitioning and redistribution.

  1. Historical and contemporary imagery to assess ecosystem change on the Arctic coastal plain of northern Alaska

    USGS Publications Warehouse

    Tape, Ken D.; Pearce, John M.; Walworth, Dennis; Meixell, Brandt W.; Fondell, Tom F.; Gustine, David D.; Flint, Paul L.; Hupp, Jerry W.; Schmutz, Joel A.; Ward, David H.

    2014-01-01

    In this report, we describe and make available a set of 61 georectified aerial images of the Arctic Coastal Plain (taken from 1948 to 2010) that were obtained by the USGS to inform research objectives of the USGS CAE Initiative. Here, we describe the origins, metadata, and public availability of these images that were obtained within four main study areas on the Arctic Coastal Plain: Teshekpuk Lake Special Area, Chipp River, the Colville River Delta, and locations along the Dalton Highway Corridor between the Brooks Range and Deadhorse. We also provide general descriptions of observable changes to the geomorphology of landscapes that are apparent by comparing historical and contemporary images. These landscape changes include altered river corridors, lake drying, coastal erosion, and new vegetation communities. All original and georectified images and metadata are available through the USGS Alaska Science Center Portal (search under ‘Project Name’ using title of this report) or by contacting ascweb@usgs.gov.

  2. Using paleolimnology to track the impacts of early Arctic peoples on freshwater ecosystems from southern Baffin Island, Nunavut

    NASA Astrophysics Data System (ADS)

    Michelutti, Neal; McCleary, Kathryn M.; Antoniades, Dermot; Sutherland, Patricia; Blais, Jules M.; Douglas, Marianne S. V.; Smol, John P.

    2013-09-01

    Paleolimnological approaches can be used to determine the ways in which past Arctic peoples have affected the ecosystems in which they live, and simultaneously to reconstruct the climate and other aspects of the environment that may have influenced local populations. Here we analyze sediment cores from seven ponds on the south-western coast of Baffin Island, Nunavut, in order to assess the impacts of early Arctic peoples on freshwater ecosystems. Prior to the historic Inuit occupation, the study area was extensively inhabited by Thule culture Inuit (ca 1200-1600 AD) and by an earlier Arctic group, the Dorset culture Palaeo-Eskimos (ca 500 BC-1500 AD) and their predecessors from as early as 2500 BC. The study ponds were selected to cover a gradient of the intensity of human activity in their catchments. The ecological impacts of early hunting societies can be detected using paleolimnology because the butchering of marine mammals released nutrients that eutrophied nearby ponds and left distinct geochemical signals in the sediments. The degree of eutrophication in the small freshwater ponds depended on the length of the occupation, as well as the amount and type of marine mammals taken as primary prey items (eg, whales, walrus, or seals). All sediment cores were AMS 14C dated to establish their chronologies, and analyzed for diatoms and stable isotopes of nitrogen (δ15N). Both diatoms and sedimentary δ15N have been previously demonstrated to respond sensitively to nutrient enrichment from Inuit whalers. Our δ15N and diatom data record nutrient enrichment in lakes surrounded by either long-term Thule or Dorset settlements. The Dorset sites that were the locations of periodic seasonal gatherings did not register any evidence of eutrophication in the nearby ponds, reflecting the shorter, less intensive nature of these occupations. Similarly, nearby control ponds with no evidence of significant human activity in their catchments showed little-to-no changes in δ15N

  3. Seasonal and spatial variation in soil chemistry and anaerobic processes in an Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Lipson, D.; Mauritz, M.; Bozzolo, F.; Raab, T. K.; Santos, M. J.; Friedman, E. F.; Rosenbaum, M.; Angenent, L.

    2009-12-01

    Drained thaw lake basins (DTLB) are the dominant landform in the Arctic coastal plain near Barrow, Alaska. Our previous work in a DTLB showed that Fe(III) and humic substances are important electron acceptors in anaerobic respiration, and play a significant role in the C cycle of these organic-rich soils. In the current study, we investigated seasonal and spatial patterns of availability of electron acceptors and labile substrate, redox conditions and microbial activity. Landscapes within DTLB contain complex, fine-scale topography arising from ice wedge polygons, which produce raised and lowered areas. One goal of our study was to determine the effects of microtopographic variation on the potential for Fe(III) reduction and other anaerobic processes. Additionally, the soil in the study site has a complex vertical structure, with an organic peat layer overlying a mineral layer, overlying permafrost. We described variations in soil chemistry across depth profiles into the permafrost. Finally, we installed an integrated electrode/potentiostat system to electrochemically monitor microbial activity in the soil. Topographically low areas differed from high areas in most of the measured variables: low areas had lower oxidation-reduction potential, higher pH and electrical conductivity. Soil pore water from low areas had higher concentrations of Fe(III), Fe(II), dissolved organic C (DOC), and aromaticity (UV absorbance at 260nm, “A260”). Low areas also had higher concentrations of dissolve CO2 and CH4 in soil pore water. Laboratory incubations of soil showed a trend toward higher potentials for Fe(III) reduction in topographically low areas. Clearly, ice wedge-induced microtopography exerts a strong control on microbial processes in this DTLB landscape, with increased anaerobic activity occurring in the wetter, depressed areas. Soil water extracted from 5-15 cm depth had higher concentrations of Fe(III), Fe(II), A260, and DOC compared to soil water sampled from 0-5cm

  4. Growing season fluxes and sources of CO2 and CH4 in high arctic ecosystems, NW Greenland

    NASA Astrophysics Data System (ADS)

    Lupascu, M.; Seibt, U.; Stills, A. K.; Xu, X.; Lindsey, D. S.; Welker, J. M.; Czimczik, C. I.

    2010-12-01

    Arctic tundra soils store vast amounts of organic carbon. Understanding how rapidly this pool can be mineralized as a consequence of warming and changes in the magnitude and timing of precipitation is a major uncertainty in predicting future levels of carbon dioxide in the atmosphere. We quantified the magnitudes and patterns of ecosystem-atmosphere fluxes of carbon dioxide (CO2) and methane (CH4) from polar semi-desert landscapes in NW Greenland. The measurements were undertaken from May to August 2010 at a multi-factorial, long-term climate change experiment started in 2003. In each treatment, fluxes were monitored from vegetated and barren soils. The experimental treatments consist of +2oC warming (T1), +4oC warming (T2), +50% summer precipitation (W), +4oC × +50% summer precipitation (T2W), and control (C). We used radiocarbon analysis to investigate the sources of carbon contributing to ecosystem carbon respiration under current and future climate conditions. Net ecosystem exchange (NEE) of CO2 and CH4 was measured continuously from four clear, automated chambers using cavity ring-down spectroscopy (Picarro 1301) under ambient and under conditions of high warming and added summer water (T2W). In all treatments, ecosystem respiration (R) from opaque chambers and soil pore space CO2 concentrations from soil wells were monitored daily via infrared spectroscopy (LI-COR 800 & 840) and sampled monthly for radiocarbon analysis. NEE fluxes were higher in vegetated than in bare soils and showed a clear seasonal pattern: both C and T2W treatments were a source of CO2 to the atmosphere in the spring and a net CO2 sink during summer. During the summer, NEE fluxes from vegetated soil were up to 5 times higher in the T2W (-11 µmol m-2 s-1) than ambient conditions (~ - 2 µmol m-2 s-1). Bare soils were a net source of CO2 at all times. All plots were a net sink of CH4 and showed a maximum in mid summer (-3 µmol m-2 s-1) when soil moisture was at a minimum. In the T2W

  5. SOUTH FLORIDA ECOSYSTEM ASSESSMENT PROJECT: FINAL TECHNICAL REPORT - PHASE I

    EPA Science Inventory

    The South Florida Ecosystem Assessment Project is an innovative, large-scale monitoring and assessment program designed to measure current and changing conditions of ecological resources in South Florida using an integrated holistic approach. Using the United States Environmenta...

  6. Potential indicators of final ecosystem services in wetlands

    EPA Science Inventory

    Numerous and inconsistent lists of wetland ecosystem services exist because services are identified using ambiguous definitions or categorization schemes based around divergent or ambiguous objectives. A consistent and scientific approach would provide clarity and provide greater...

  7. Methane turnover and methanotrophic communities in arctic aquatic ecosystems of the Lena Delta, Northeast Siberia.

    PubMed

    Osudar, Roman; Liebner, Susanne; Alawi, Mashal; Yang, Sizhong; Bussmann, Ingeborg; Wagner, Dirk

    2016-08-01

    Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a flood plain area. Though, in all aquatic systems, we detected both, Type I and II MOB, in lake systems, we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity. PMID:27230921

  8. Lepidoptera Larvae as an Indicator of Multi-trophic Level Responses to Changing Seasonality in an Arctic Tundra Ecosystem

    NASA Astrophysics Data System (ADS)

    Daly, K. M.; Steltzer, H.; Boelman, N.; Weintraub, M. N.; Darrouzet-Nardi, A.; Wallenstein, M. D.; Sullivan, P.; Gough, L.; Rich, M.; Hendrix, C.; Kielland, K.; Philip, K.; Doak, P.; Ferris, C.; Sikes, D.

    2011-12-01

    Earlier snowmelt and warming temperatures in the Arctic will impact multiple trophic levels through the timing and availability of food resources. Lepidoptera are a vital link within the ecosystem; their roles include pollinator, parasitized host for other pollinating insects, and essential food source for migrating birds and their fledglings. Multiple environmental cues including temperature initiate plant growth, and in turn, trigger the emergence of Lepidoptera and the migrations of birds. If snowmelt is accelerated and temperature is increased, it is expected that the Lepidoptera larvae will respond to early plant growth by increasing their abundance within areas that have accelerated snowmelt and warmer conditions. In May of 2011 in a moist acidic tussock tundra system, we accelerated snowmelt by 15 days through the use of radiation-absorbing fabric and warmed air and soil temperatures using open-top chambers, individually and in combination. Every 1-2 days from May 27th to July 8th, 2 minute searches were performed for Lepidoptera larvae in all treatments; when an animal was found, their micro-habitat, surface temperature, behavior, food source, and time of day were noted. The length, body and head width were measured, and the animals were examined for braconid wasp and tachinid fly parasites. Lepidoptera larvae collected in pitfall traps from May 26th to July 7th were also examined and measured. Total density of parasitized larvae accounted for 54% of observed specimens and 50% of pitfall specimens, indicating that Lepidoptera larvae serve an integral role as a host for other pollinators. Total larvae density was highest within the accelerated snowmelt plots compared to the control plots; 66% of observed live specimens and 63% of pitfall specimens were found within the accelerated snowmelt plots. Ninety percent of the total observed animals were found within the open-top warming chambers. Peak density of animals occurred at Solar Noon between 14:00 -15

  9. Ecosystem approach: Healthy ecosystems and sustainable economies. Volume 3. Case studies. Final report

    SciTech Connect

    1996-03-01

    The case study report of the Interagency Ecosystem Management Task Force presents findings and recommendations from seven survey teams, details the nature, history, and current status of each ecosystem, and summarizes survey team interviews with many participating parties. The volume targets those interested in how ecosystem partnerships work. Ecosystems include: Anacostia River watershed--state and local agencies are restoring components of this system of marshes, rivers, forests in urban environments: Coastal Louisiana--a federal task force and the state of Louisiana are restoring wetlands to reverse the trend of losses; Great Lakes basin--local communities joined with governmental agencies to reverse pollution and habitat degradation; Pacific Northwest forests--an interagency effort is protecting both forest ecosystems and the region`s economic health; Prince William Sound--a state/federal trustee council is restoring the ecosystem following the Exxon Valdez oil spill: South Florida--a federal task force is restoring habitat in the Everglades; and Southern Appalachians--the Man and Biosphere program is working with communities to restore habitats.

  10. [A data collection program focused on hydrologic and meteorologic parameters in an Arctic ecosystem

    SciTech Connect

    Kane, D.

    1992-12-31

    The hydrologic cycle of an arctic watershed is dominated by such physical elements as snow, ice, permafrost, seasonally frozen soils, wide fluctuations in surface energy balance and phase change of snow and ice to water. At Imnavait basin, snow accumulation begins in September or early October and maximum snowpack water equivalent is reached just prior to the onset of ablation in mid May. No significant mid winter melt occurs in this basin. Considerable snowfall redistribution by wind to depressions and valley bottom is evident. Spring snowmelt on the North Slope of Alaska is the dominant hydrologic event of the year.This event provides most of the moisture for use by vegetation in the spring and early summer period. The mechanisms and timing of snowmelt are important factors in predicting runoff, the migrations of birds and large mammals and the diversity of plant communities. It is important globally due to the radical and abrupt change in the surface energy balance over vast areas. We were able to explore the trends and differences in the snowmelt process along a transect from the Brooks Range to the Arctic Coastal plain. Snowpack ablation was monitored at three sites. These data were analyzed along with meteorologic data at each site. The initiation of ablation was site specific being largely controlled by the complementary addition of energy from radiation and sensible heat flux. Although the research sites were only 115 km apart, the rates and mechanisms of snowmelt varied greatly. Usually, snowmelt begins at the mid-elevations in the foothills and progresses northerly toward the coast and southerly to the mountains. In the more southerly areas snowmelt progressed much faster and was more influenced by sensible heat advected from areas south of the Brooks Range. In contrast snowmelt in the more northerly areas was slower and the controlled by net radiation.

  11. [A data collection program focused on hydrologic and meteorologic parameters in an Arctic ecosystem

    SciTech Connect

    Kane, D.

    1992-01-01

    The hydrologic cycle of an arctic watershed is dominated by such physical elements as snow, ice, permafrost, seasonally frozen soils, wide fluctuations in surface energy balance and phase change of snow and ice to water. At Imnavait basin, snow accumulation begins in September or early October and maximum snowpack water equivalent is reached just prior to the onset of ablation in mid May. No significant mid winter melt occurs in this basin. Considerable snowfall redistribution by wind to depressions and valley bottom is evident. Spring snowmelt on the North Slope of Alaska is the dominant hydrologic event of the year.This event provides most of the moisture for use by vegetation in the spring and early summer period. The mechanisms and timing of snowmelt are important factors in predicting runoff, the migrations of birds and large mammals and the diversity of plant communities. It is important globally due to the radical and abrupt change in the surface energy balance over vast areas. We were able to explore the trends and differences in the snowmelt process along a transect from the Brooks Range to the Arctic Coastal plain. Snowpack ablation was monitored at three sites. These data were analyzed along with meteorologic data at each site. The initiation of ablation was site specific being largely controlled by the complementary addition of energy from radiation and sensible heat flux. Although the research sites were only 115 km apart, the rates and mechanisms of snowmelt varied greatly. Usually, snowmelt begins at the mid-elevations in the foothills and progresses northerly toward the coast and southerly to the mountains. In the more southerly areas snowmelt progressed much faster and was more influenced by sensible heat advected from areas south of the Brooks Range. In contrast snowmelt in the more northerly areas was slower and the controlled by net radiation.

  12. The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Cassidy, A. E.; Christen, A.; Henry, G. H. R.

    2015-12-01

    Soil carbon stored in high-latitude permafrost landscapes is threatened by warming, and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, have increased in frequency and magnitude across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season the undisturbed tundra was a small net sink (NEE = -0.12 g C m-2 d-1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE = +0.39 g C m-2 d-1). Over the measurement period, the undisturbed tundra sequestered 3.84 g C m-2, while the disturbed tundra released 12.48 g C m-2. Before full leaf out in early July, the undisturbed tundra was a small source of CO2, but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.41 μmol m-2 s-1 and +0.50 μmol m-2 s-1, respectively) than those found in undisturbed tundra (+1.21 μmol m-2 s-1 and +1.00 μmol m-2 s-1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the growing season.

  13. The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Cassidy, Alison E.; Christen, Andreas; Henry, Gregory H. R.

    2016-04-01

    Soil carbon stored in high-latitude permafrost landscapes is threatened by warming and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Thermokarst and permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, are present across the Fosheim Peninsula, Ellesmere Island, Canada. To determine the effects of retrogressive thaw slumps on net ecosystem exchange (NEE) of CO2 in high Arctic tundra, we used two eddy covariance (EC) tower systems to simultaneously and continuously measure CO2 fluxes from a disturbed site and the surrounding undisturbed tundra. During the 32-day measurement period in the 2014 growing season, the undisturbed tundra was a small net sink (NEE = -0.1 g C m-2 d-1); however, the disturbed terrain of the retrogressive thaw slump was a net source (NEE = +0.4 g C m-2 d-1). Over the measurement period, the undisturbed tundra sequestered 3.8 g C m-2, while the disturbed tundra released 12.5 g C m-2. Before full leaf-out in early July, the undisturbed tundra was a small source of CO2 but shifted to a sink for the remainder of the sampling season (July), whereas the disturbed tundra remained a source of CO2 throughout the season. A static chamber system was also used to measure daytime fluxes in the footprints of the two towers, in both disturbed and undisturbed tundra, and fluxes were partitioned into ecosystem respiration (Re) and gross primary production (GPP). Average GPP and Re found in disturbed tundra were smaller (+0.40 µmol m-2 s-1 and +0.55 µmol m-2 s-1, respectively) than those found in undisturbed tundra (+1.19 µmol m-2 s-1 and +1.04 µmol m-2 s-1, respectively). Our measurements indicated clearly that the permafrost disturbance changed the high Arctic tundra system from a sink to a source for CO2 during the majority of the growing season (late June and July).

  14. Simulating carbon and water fluxes at Arctic and boreal ecosystems in Alaska by optimizing the modified BIOME-BGC with eddy covariance data

    NASA Astrophysics Data System (ADS)

    Ueyama, M.; Kondo, M.; Ichii, K.; Iwata, H.; Euskirchen, E. S.; Zona, D.; Rocha, A. V.; Harazono, Y.; Nakai, T.; Oechel, W. C.

    2013-12-01

    To better predict carbon and water cycles in Arctic ecosystems, we modified a process-based ecosystem model, BIOME-BGC, by introducing new processes: change in active layer depth on permafrost and phenology of tundra vegetation. The modified BIOME-BGC was optimized using an optimization method. The model was constrained using gross primary productivity (GPP) and net ecosystem exchange (NEE) at 23 eddy covariance sites in Alaska, and vegetation/soil carbon from a literature survey. The model was used to simulate regional carbon and water fluxes of Alaska from 1900 to 2011. Simulated regional fluxes were validated with upscaled GPP, ecosystem respiration (RE), and NEE based on two methods: (1) a machine learning technique and (2) a top-down model. Our initial simulation suggests that the original BIOME-BGC with default ecophysiological parameters substantially underestimated GPP and RE for tundra and overestimated those fluxes for boreal forests. We will discuss how optimization using the eddy covariance data impacts the historical simulation by comparing the new version of the model with simulated results from the original BIOME-BGC with default ecophysiological parameters. This suggests that the incorporation of the active layer depth and plant phenology processes is important to include when simulating carbon and water fluxes in Arctic ecosystems.

  15. Assessment of Pan-Arctic Soil Moisture, Surface Temperature, and Net Ecosystem Carbon Exchange

    NASA Astrophysics Data System (ADS)

    Nirala, M. L.; Kimball, J.; Njoku, E.; McDonald, K.; Chan, S.; Jones, L.; Oechel, W.; Running, S.

    2006-05-01

    In this paper, we discuss the application of Moderate Resolution Imaging Spectroradiometer (MODIS), Leaf Area Index (LAI), Gross Primary Production (GPP), and Advanced Microwave Scanning Radiometer - EOS (AMSR-E) brightness temperature and soil moisture to derived Net Ecosystem Carbon Exchange (NEE). We also compare the satellite-derived results with ground-based tower CO2 eddy flux observations and Biome- BGC ecosystem process model simulations using site meteorology. We found that AMSR-E brightness temperature-derived surface temperatures compare favorably with site-based temperatures and that sensitivity to air and soil temperatures depend on wavelength, snow cover, freeze-thaw conditions, and the sub-grid scale extent of open water. The surface temperature estimations using the emissivity lookup table approach showed good agreement, as compared to observations on most sites. AMSR-E L3 soil moisture data showed large discrepancies relative to site-based ecosystem model simulations and limited site observations. The soil moisture differences were larger in winter than summer. Satellite-derived carbon model results were consistent with site-based CO2 flux tower observations and detailed ecosystem process model (BIOME-BGC) simulations. The carbon model represents NEE seasonal variability and regional patterns, and the NEE is highly sensitive to LAI, which determines the optimal soil decomposition rate. NEE is a residual of two fluxes: GPP and respiration. Small changes in component fluxes yielded large changes in annual NEE and predicted carbon source/sink behavior, especially for relatively low productivity sites, such as tundra. This work was performed at The University of Montana and the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  16. Beyond arctic and alpine: the influence of winter climate on temperate ecosystems.

    PubMed

    Ladwig, Laura M; Ratajczak, Zak R; Ocheltree, Troy W; Hafich, Katya A; Churchill, Amber C; Frey, Sarah J K; Fuss, Colin B; Kazanski, Clare E; Muñoz, Juan D; Petrie, Matthew D; Reinmann, Andrew B; Smith, Jane G

    2016-02-01

    Winter climate is expected to change under future climate scenarios, yet the majority of winter ecology research is focused in cold-climate ecosystems. In many temperate systems, it is unclear how winter climate relates to biotic responses during the growing season. The objective of this study was to examine how winter weather relates to plant and animal communities in a variety of terrestrial ecosystems ranging from warm deserts to alpine tundra. Specifically, we examined the association between winter weather and plant phenology, plant species richness, consumer abundance, and consumer richness in 11 terrestrial ecosystems associated with the U.S. Long-Term Ecological Research (LTER) Network. To varying degrees, winter precipitation and temperature were correlated with all biotic response variables. Bud break was tightly aligned with end of winter temperatures. For half the sites, winter weather was a better predictor of plant species richness than growing season weather. Warmer winters were correlated with lower consumer abundances in both temperate and alpine systems. Our findings suggest winter weather may have a strong influence on biotic activity during the growing season and should be considered in future studies investigating the effects of climate change on both alpine and temperate systems. PMID:27145612

  17. The resilience and functional role of moss in boreal and arctic ecosystems.

    PubMed

    Turetsky, M R; Bond-Lamberty, B; Euskirchen, E; Talbot, J; Frolking, S; McGuire, A D; Tuittila, E-S

    2012-10-01

    Mosses in northern ecosystems are ubiquitous components of plant communities, and strongly influence nutrient, carbon and water cycling. We use literature review, synthesis and model simulations to explore the role of mosses in ecological stability and resilience. Moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories. Simulations from two process-based models suggest that northern ecosystems would need to experience extreme perturbation before mosses were eliminated. But simulations with two other models suggest that loss of moss will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. It seems clear that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species. We highlight several issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, and parameter vs conceptual uncertainty in models. Mosses play an important role in several ecosystem processes that play out over centuries - permafrost formation and thaw, peat accumulation, development of microtopography - and there is a need for studies that increase our understanding of slow, long-term dynamical processes. PMID:22924403

  18. The resilience and functional role of moss in boreal and arctic ecosystems

    USGS Publications Warehouse

    Turetsky, M.; Bond-Lamberty, B.; Euskirchen, E.S.; Talbot, J. J.; Frolking, S.; McGuire, A.D.; Tuittila, E.S.

    2012-01-01

    Mosses in northern ecosystems are ubiquitous components of plant communities, and strongly influence nutrient, carbon and water cycling. We use literature review, synthesis and model simulations to explore the role of mosses in ecological stability and resilience. Moss community responses to disturbance showed all possible responses (increases, decreases, no change) within most disturbance categories. Simulations from two process-based models suggest that northern ecosystems would need to experience extreme perturbation before mosses were eliminated. But simulations with two other models suggest that loss of moss will reduce soil carbon accumulation primarily by influencing decomposition rates and soil nitrogen availability. It seems clear that mosses need to be incorporated into models as one or more plant functional types, but more empirical work is needed to determine how to best aggregate species. We highlight several issues that have not been adequately explored in moss communities, such as functional redundancy and singularity, relationships between response and effect traits, and parameter vs conceptual uncertainty in models. Mosses play an important role in several ecosystem processes that play out over centuries – permafrost formation and thaw, peat accumulation, development of microtopography – and there is a need for studies that increase our understanding of slow, long-term dynamical processes.

  19. Impacts of a recent storm surge on an Arctic delta ecosystem examined in the context of the last millennium.

    PubMed

    Pisaric, Michael F J; Thienpont, Joshua R; Kokelj, Steven V; Nesbitt, Holly; Lantz, Trevor C; Solomon, Steven; Smol, John P

    2011-05-31

    One of the most ominous predictions related to recent climatic warming is that low-lying coastal environments will be inundated by higher sea levels. The threat is especially acute in polar regions because reductions in extent and duration of sea ice cover increase the risk of storm surge occurrence. The Mackenzie Delta of northwest Canada is an ecologically significant ecosystem adapted to freshwater flooding during spring breakup. Marine storm surges during the open-water season, which move saltwater into the delta, can have major impacts on terrestrial and aquatic systems. We examined growth rings of alder shrubs (Alnus viridis subsp. fruticosa) and diatoms preserved in dated lake sediment cores to show that a recent marine storm surge in 1999 caused widespread ecological changes across a broad extent of the outer Mackenzie Delta. For example, diatom assemblages record a striking shift from freshwater to brackish species following the inundation event. What is of particular significance is that the magnitude of this recent ecological impact is unmatched over the > 1,000-year history of this lake ecosystem. We infer that no biological recovery has occurred in this lake, while large areas of terrestrial vegetation remain dramatically altered over a decade later, suggesting that these systems may be on a new ecological trajectory. As climate continues to warm and sea ice declines, similar changes will likely be repeated in other coastal areas of the circumpolar Arctic. Given the magnitude of ecological changes recorded in this study, such impacts may prove to be long lasting or possibly irreversible. PMID:21576496

  20. Present and Future Carbon Balance of Russia's Northern Ecosystems. Final report

    SciTech Connect

    Chapin, F. Stuart III; Zimov, Sergei A.

    2000-08-28

    Recent increases in the seasonal amplitude of atmospheric CO{sub 2} at high latitudes suggest a widespread biospheric response to high-latitude warming. We have shown that the seasonal amplitude of net ecosystem carbon exchange by northern Siberian ecosystems is greater in disturbed than undisturbed sites, due to increased summer influx and increased winter efflux. Net carbon gain in summer and respiration in winter were greater in a cool than in a warm year, especially in disturbed sites and did not differ between high-arctic and treeline sites, suggesting that high-latitude warming, if it occurred, would have little effect or would reduce seasonal amplitude of carbon exchange. We suggest that increased disturbance contributes significantly to the amplified seasonal cycle of atmospheric CO{sub 2} at high latitudes.

  1. Experiences in multiyear combined state-parameter estimation with an ecosystem model of the North Atlantic and Arctic Oceans using the Ensemble Kalman Filter

    NASA Astrophysics Data System (ADS)

    Simon, Ehouarn; Samuelsen, Annette; Bertino, Laurent; Mouysset, Sandrine

    2015-12-01

    A sequence of one-year combined state-parameter estimation experiments has been conducted in a North Atlantic and Arctic Ocean configuration of the coupled physical-biogeochemical model HYCOM-NORWECOM over the period 2007-2010. The aim is to evaluate the ability of an ensemble-based data assimilation method to calibrate ecosystem model parameters in a pre-operational setting, namely the production of the MyOcean pilot reanalysis of the Arctic biology. For that purpose, four biological parameters (two phyto- and two zooplankton mortality rates) are estimated by assimilating weekly data such as, satellite-derived Sea Surface Temperature, along-track Sea Level Anomalies, ice concentrations and chlorophyll-a concentrations with an Ensemble Kalman Filter. The set of optimized parameters locally exhibits seasonal variations suggesting that time-dependent parameters should be used in ocean ecosystem models. A clustering analysis of the optimized parameters is performed in order to identify consistent ecosystem regions. In the north part of the domain, where the ecosystem model is the most reliable, most of them can be associated with Longhurst provinces and new provinces emerge in the Arctic Ocean. However, the clusters do not coincide anymore with the Longhurst provinces in the Tropics due to large model errors. Regarding the ecosystem state variables, the assimilation of satellite-derived chlorophyll concentration leads to significant reduction of the RMS errors in the observed variables during the first year, i.e. 2008, compared to a free run simulation. However, local filter divergences of the parameter component occur in 2009 and result in an increase in the RMS error at the time of the spring bloom.

  2. Predicting ecosystem carbon balance in a warming Arctic: the importance of long-term thermal acclimation potential and inhibitory effects of light on respiration.

    PubMed

    McLaughlin, Blair C; Xu, Cheng-Yuan; Rastetter, Edward B; Griffin, Kevin L

    2014-06-01

    The carbon balance of Arctic ecosystems is particularly sensitive to global environmental change. Leaf respiration (R), a temperature-dependent key process in determining the carbon balance, is not well-understood in Arctic plants. The potential for plants to acclimate to warmer conditions could strongly impact future global carbon balance. Two key unanswered questions are (1) whether short-term temperature responses can predict long-term respiratory responses to growth in elevated temperatures and (2) to what extent the constant daylight conditions of the Arctic growing season inhibit leaf respiration. In two dominant Arctic species Eriophorum vaginatum (tussock grass) and Betula nana (woody shrub), we assessed the extent of respiratory inhibition in the light (RL/RD), respiratory response to short-term temperature change, and respiratory acclimation to long-term warming treatments. We found that R of both species is strongly inhibited by light (averaging 35% across all measurement temperatures). In E. vaginatum both RL and RD acclimated to the long-term warming treatment, reducing the magnitude of respiratory response relative to the short-term response to temperature increase. In B. nana, both RL and RD responded to short-term temperature increase but showed no acclimation to the long-term warming. The ability to predict plant respiratory response to global warming with short-term temperature responses will depend on species-specific acclimation potential and the differential response of RL and RD to temperature. With projected woody shrub encroachment in Arctic tundra and continued warming, changing species dominance between these two functional groups, may impact ecosystem respiratory response and carbon balance. PMID:24677488

  3. Modelling carbon responses of tundra ecosystems to historical and projected climate: Sensitivity of pan-Arctic carbon storage to temporal and spatial variation in climate

    USGS Publications Warehouse

    McGuire, A.D.; Clein, J.S.; Melillo, J.M.; Kicklighter, D.W.; Meier, R.A.; Vorosmarty, C.J.; Serreze, M.C.

    2000-01-01

    Historical and projected climate trends for high latitudes show substantial temporal and spatial variability. To identify uncertainties in simulating carbon (C) dynamics for pan-Arctic tundra, we compare the historical and projected responses of tundra C storage from 1921 to 2100 between simulations by the Terrestrial Ecosystem Model (TEM) for the pan-Arctic and the Kuparuk River Basin, which was the focus of an integrated study of C dynamics from 1994 to 1996. In the historical period from 1921 to 1994, the responses of net primary production (NPP) and heterotrophic respiration (RH) simulated for the Kuparuk River Basin and the pan-Arctic are correlated with the same factors; NPP is positively correlated with net nitrogen mineralization (NMIN) and RH is negatively correlated with mean annual soil moisture. In comparison to the historical period, the spatially aggregated responses of NPP and RH for the Kuparuk River Basin and the pan-Arctic in our simulations for the projected period have different sensitivities to temperature, soil moisture and NMIN. In addition to being sensitive to soil moisture during the projected period, RH is also sensitive to temperature and there is a significant correlation between RH and NMIN. We interpret the increases in NPP during the projected period as being driven primarily by increases in NMIN, and that the correlation between NPP and temperature in the projected period is a result primarily of the causal linkage between temperature, RH, and NMIN. Although similar factors appear to be controlling simulated regional-and biome-scale C dynamics, simulated C dynamics at the two scales differ in magnitude with higher increases in C storage simulated for the Kuparuk River Basin than for the pan-Arctic at the end of the historical period and throughout the projected period. Also, the results of the simulations indicate that responses of C storage show different climate sensitivities at regional and pan-Arctic spatial scales and that

  4. Vegetation Feedbacks Explain Recent High-latitude Summer Warming in Alaskan Arctic and Boreal Ecosystems

    NASA Astrophysics Data System (ADS)

    Chapin, F. S.; Beringer, J.; Copass, C.; Epstein, H.; Lloyd, A.; Lynch, A.; McGuire, A. D.; Sturm, M.

    2002-12-01

    Although General Circulation Models predict the observed winter and spring warming at high latitudes, there is no obvious physical mechanism in the climate system that can account for the significant increase in summer temperatures that has occurred at high latitudes during the past 30 years. We demonstrate that vegetation-induced feedbacks in snow properties and summer energy exchange with the atmosphere explain this recent summer warming. A combination of stand-age reconstructions, repeat photography, and satellite measures of vegetation greenness demonstrate an expansion of the distribution and an infilling of shrubs in moist tundra and of trees in forest tundra. These vegetation changes increase the depth and thermal resistance of the snow pack, causing a 3oC increase in winter soil temperature and an increase in winter decomposition and nutrient mineralization, which enhance plant growth. These vegetation changes also increase summer heat transport to the atmosphere by increasing radiation absorption (lower albedo) and the proportion of absorbed energy that is transferred to the atmosphere as sensible heat. The resulting increase in atmospheric heating, on a unit-area basis, is similar to effects of a doubling of atmospheric carbon dioxide or a 2% change in solar constant, such as occurred at the last glacial-interglacial boundary. Simulations with the regional climate model ARCSyM indicate that a change from shrubless tundra to shrub-dominated tundra on the North Slope of Alaska would increase July mean temperature by 1.5 to 3.5 degrees C, with the warming effects extending south into the boreal forest of interior Alaska. If these vegetation feedbacks to regional warming are widespread, as suggested by indigenous knowledge and the satellite record, they are of sufficient magnitude to explain the summer warming that has recently been observed in northern Alaska and other regions of the circumpolar Arctic.

  5. Modern to millennium-old greenhouse gases emitted from freshwater ecosystems of the eastern Canadian Arctic

    NASA Astrophysics Data System (ADS)

    Bouchard, F.; Laurion, I.; Preskienis, V.; Fortier, D.; Xu, X.; Whiticar, M. J.

    2015-07-01

    Ponds and lakes are widespread across the rapidly changing permafrost environments. Aquatic systems play an important role in global biogeochemical cycles, especially in greenhouse gas (GHG) exchanges between terrestrial systems and the atmosphere. The source, speciation and emission of carbon released from permafrost landscapes are strongly influenced by local specific conditions rather than general environmental setting. This study reports on GHG ages and emission rates from aquatic systems on Bylot Island in the eastern Canadian Arctic. Dissolved and ebullition gas samples were collected during the summer season from different types of water bodies located in a highly dynamic periglacial valley: polygonal ponds, collapsed ice-wedge trough ponds, and larger lakes overlying unfrozen soils (talik). The results showed strikingly different ages and fluxes depending on aquatic system types. Polygonal ponds were net sinks of dissolved CO2, but variable sources of dissolved CH4. They presented the highest ebullition fluxes, one or two orders of magnitude higher than from other ponds and lakes. Trough ponds appeared as substantial GHG sources, especially when their edges were actively eroding. Both types of ponds produced modern to hundreds of years old (<550 yr BP) GHG, even if trough ponds could contain much older carbon (>2000 yr BP) derived from freshly eroded peat. Lakes had small dissolved and ebullition fluxes, however they released much older GHG, including millennium-old CH4 (up to 3500 yr BP) sampled from lake central areas. Acetoclastic methanogenesis dominated at all study sites and there was minimal, if any, methane oxidation in gas emitted through ebullition. These findings provide new insights on the variable role of permafrost aquatic systems as a positive feedback mechanism on climate.

  6. Ecosystem characteristics and processes facilitating persistent macrobenthic biomass hotspots and associated benthivory in the Pacific Arctic

    NASA Astrophysics Data System (ADS)

    Grebmeier, Jacqueline M.; Bluhm, Bodil A.; Cooper, Lee W.; Danielson, Seth L.; Arrigo, Kevin R.; Blanchard, Arny L.; Clarke, Janet T.; Day, Robert H.; Frey, Karen E.; Gradinger, Rolf R.; Kędra, Monika; Konar, Brenda; Kuletz, Kathy J.; Lee, Sang H.; Lovvorn, James R.; Norcross, Brenda L.; Okkonen, Stephen R.

    2015-08-01

    The northern Bering and Chukchi Seas are areas in the Pacific Arctic characterized by high northward advection of Pacific Ocean water, with seasonal variability in sea ice cover, water mass characteristics, and benthic processes. In this review, we evaluate the biological and environmental factors that support communities of benthic prey on the continental shelves, with a focus on four macrofaunal biomass "hotspots." For the purpose of this study, we define hotspots as macrofaunal benthic communities with high biomass that support a corresponding ecological guild of benthivorous seabird and marine mammal populations. These four benthic hotspots are regions within the influence of the St. Lawrence Island Polynya (SLIP), the Chirikov Basin between St. Lawrence Island and Bering Strait (Chirikov), north of Bering Strait in the southeast Chukchi Sea (SECS), and in the northeast Chukchi Sea (NECS). Detailed benthic macrofaunal sampling indicates that these hotspot regions have been persistent over four decades of sampling due to annual reoccurrence of seasonally consistent, moderate-to-high water column production with significant export of carbon to the underlying sediments. We also evaluate the usage of the four benthic hotspot regions by benthic prey consumers to illuminate predator-prey connectivity. In the SLIP hotspot, spectacled eiders and walruses are important winter consumers of infaunal bivalves and polychaetes, along with epibenthic gastropods and crabs. In the Chirikov hotspot, gray whales have historically been the largest summer consumers of benthic macrofauna, primarily feeding on ampeliscid amphipods in the summer, but they are also foraging further northward in the SECS and NECS hotspots. Areas of concentrated walrus foraging occur in the SLIP hotspot in winter and early spring, the NECS hotspot in summer, and the SECS hotspot in fall. Bottom up forcing by hydrography and food supply to the benthos influences persistence and composition of benthic prey

  7. Chemosynthetic ecosystems study. Final report. Volume 1. Executive summary

    SciTech Connect

    MacDonald, I.R.; Sager, W.W.; Lee, C.; Schroeder, W.W.; Kennicutt, M.C.

    1995-06-01

    Volume I presents a brief summary of the findings of a three year investigation of the geology, chemistry, and biology of chemosynthetic ecosystems in the Gulf of Mexico. These dense assemblages of tube worms, mussels and/or clams are primarily dependent upon chemical conditions generated by natural oils and gas seeps. Hydrocarbon seeps produce a variety of distinctive geological features including carbonate rock, mud volcanoes, and hydrate mounds, which tend to be localized to areas less than 1 km. The interaction of the sediment bacteria with the hydrocarbons in the seafloor yields a highly specialized chemical environment featuring high levels of hydrogen sulfide and degraded oils.

  8. The Role of Disturbance in Arctic Ecosystem Response to a Changing Climate

    NASA Astrophysics Data System (ADS)

    Hinzman, L. D.

    2014-12-01

    Wildfires in the tundra regions and the boreal forest project an immediate effect upon the surface energy and water budget by drastically altering the surface albedo, roughness, infiltration rates, and moisture absorption capacity in organic soils. Although fires create a sudden and drastic change to the landcover, it is only the beginning of a long process of recovery and perhaps a shift to a different successional pathway. In permafrost regions, these effects become part of a process of long-term (20-50 years) cumulative impacts. Burn severity may largely determine immediate impacts and long-term disturbance trajectories. As transpiration decreases or ceases, soil moisture increases markedly, remaining quite wet throughout the year. Because the insulating quality of the organic layer is removed during fires, permafrost begins to thaw near the surface and warm to greater depths. Within a few years, it may thaw to the point where it can no longer completely refreeze every winter, creating a permanently thawed layer in the soil called a talik. After formation of a talik, soils can drain internally throughout the year. At this point, soils may become quite dry, as the total precipitation received annually in the Arctic is quite low. The local ecological community must continuously adapt to the changing soil thermal and moisture regimes. The wet soils found over shallow permafrost favor black spruce forests. After a fire creates a deeper permafrost table (thicker active layer) the invading tree species tend to be birch or alder. The hydrologic and thermal regime of the soil is the primary factor controlling these vegetation trajectories and the subsequent changes in surface mass and energy fluxes. The complexities of a changing climate accentuate these processes of change and complicate predictions of the resulting vegetation trajectories. Understanding these shifts in vegetative communities and quantifying the consequences of thawing permafrost can only be

  9. Chemosynthetic ecosystems study. Final report. Volume 3. Appendices

    SciTech Connect

    MacDonald, I.R.; Sager, W.W.; Lee, C.; Schroeder, W.W.; Kennicutt, M.C.

    1995-06-01

    Volume III presents ancillary materials from the findings of a three year investigation of the geology, chemistry and biology of chemosynthetic ecosystems in the Gulf of Mexico. These dense assemblages of tube worms, mussels and/or clams are primarily dependent upon chemical conditions generated by natural oil and gas seeps. Hydrocarbon seeps produce a variety of distinctive geological features including carbonate rock, mud volcanoes and hydrate mounds, which tend to be localized to areas less than 1 km. The interaction of the sediment bacteria with the hydrocarbons in the seafloor yields a highly specialized chemical environment featuring high levels of hydrogen sulfide and degraded oils. The biological community is supported by chemoautotrophic bacteria that live symbiotically with tube worms, mussels and clams.

  10. Chemosynthetic ecosystems study. Final report. Volume 2. Technical report

    SciTech Connect

    MacDonald, I.R.; Sager, W.W.; Lee, C.; Schroeder, W.W.; Kennicutt, M.C.

    1995-06-01

    Volume II presents detailed findings of a three year investigation of the geology, chemistry and biology of chemosynthetic ecosystems in the Gulf of Mexico. These dense assemblages of tube worms, mussels and/or clams are primarly dependent upon chemical conditions generated by natural oil and gas seeps. Hydrocarbon seeps produce a variety of distinctive geological features including carbonate rock, mud volcanoes and hydrate mounds, which tend to be localized to areas less than 1 km. The interaction of the sediment bacteria with the hydrocarbons in the seafloor yields a highly specialized chemical environment featuring high levels of hydrogen sulfide and degraded oils. The biological community is supported by chemoautotrophic bacteria that live symbiotically with tube worms, mussels and clams. The bacteria derive energy for fixing new carbon by oxidizing sulfides or methane.

  11. Extremotrophs, extremophiles and broadband pigmentation strategies in a high arctic ice shelf ecosystem.

    PubMed

    Mueller, Derek R; Vincent, Warwick F; Bonilla, Sylvia; Laurion, Isabelle

    2005-06-01

    Remnant ice shelves along the northern coast of Ellesmere Island, Nunavut, Canada ( approximately 83 degrees N) provide a habitat for cryo-tolerant microbial mat communities. Bioassays of bacterial and primary production were undertaken to quantify the short-term physiological response of the mats to changes in key variables that characterize this cryo-ecosystem (salinity, irradiance and temperature). The heterotrophic versus autotrophic community responses to these stressors differed markedly. The heterotrophic bacteria were extremophilic and specifically adapted to ambient conditions on the ice shelf, whereas the autotrophic community had broader tolerance ranges and optima outside the ambient range. This latter, extremotrophic response may be partly due to a diverse suite of pigments including oligosaccharide mycosporine-like amino acids, scytonemins, carotenoids, phycobiliproteins and chlorophylls that absorb from the near UV-B to red wavelengths. These pigments provide a comprehensive broadband strategy for coping with the multiple stressors of high irradiance, variable salinity and low temperatures in this extreme cryo-environment. PMID:16329931

  12. Staunton 1 reclamation demonstration project. Aquatic ecosystems. Final report

    SciTech Connect

    Vinikour, W. S.

    1981-02-01

    To provide long-term indications of the potential water quality improvements following reclamation efforts at the Staunton 1 Reclamation Demonstration Project, macroinvertebrates were collected from three on-site ponds and from the receiving stream (Cahokia Creek) for site drainage. Implications for potential benthic community differences resulting from site runoff were disclosed, but macroinvertebrate diversity throughout Cahokia Creek was limited due to an unstable, sandy substrate. The three ponds sampled were the New Pond, which was created as part of the reclamation activities; the Shed Pond, which and the Old Pond, which, because it was an existing, nonimpacted pond free of site runoff, served as a control. Comparisons of macroinvertebrates from the ponds indicated the potential for the New Pond to develop into a productive ecosystem. Macroinvertebrates in the New Pond were generally species more tolerant of acid mine drainage conditions. However, due to the present limited faunal densities and the undesirable physical and chemical characteristics of the New Pond, the pond should not be stocked with fish at this time.

  13. Response of Sea Ice and Marine Ecosystems to the Observed Warming Trends in the Arctic

    NASA Technical Reports Server (NTRS)

    Cota, Glenn F.; Comiso, Joey C.

    2004-01-01

    Our third (final) year activities have focused on two elements: 1) Creating and evaluating panarctic weekly climatologies of ocean color products for 1998 through 2002, 2) Interacting to assess image databases, submit and revise publications. Comiso and his programmer have principal responsibility for assembling and archiving the monthly and weekly image database at GSFC. There are now five year's (1998-2002) of climatologies. In addition to email correspondence, the PIs have met to prepare a series of publications ranging from panarctic physical-biological interactions to more focused regional studies.

  14. Deeper winter snow reduces ecosystem C losses but increases the global warming potential of Arctic tussock tundra over the growing season.

    NASA Astrophysics Data System (ADS)

    Blanc-Betes, E.; Welker, J. M.; Gomez-Casanovas, N.; Gonzalez-Meler, M. A.

    2015-12-01

    Arctic winter precipitation is projected to increase globally over the next decades, spatial variability encompassing areas with increases and decreases in winter snow. Changes in winter precipitation strongly affect C dynamics in Arctic systems and may lead to major positive climate forcing feedbacks. However, impacts of predicted changes in snowfall and accumulation on the rate and form of C fluxes (CO2 and CH4) and associated forcing feedbacks from Arctic tundra remain uncertain. We investigated how changes in winter precipitation affect net ecosystem CO2 and CH4 fluxes and budgets of moist acidic tundra in an 18-yrs snow fence experiment over a complete growing season at Toolik Lake, AK. Arctic tundra under ambient winter precipitation (CTL) was a net source of CO2 and CH4, yielding net C losses over the growing season. Reduced snow (-15-30% snow depth; RS) switched the system to a net CO2 sink mostly by limiting SOC decomposition within colder soils. Snow additions progressively reduced net ecosystem CO2 losses compared to CTL, switching the system into a weaker net CO2 source with medium additions (+20-45% snow depth; MS) and into a small net CO2 sink with high additions (+70-100% snow depth; HS). Increasingly wetter soils with snow additions constrained the temperature sensitivity of aerobic decomposition and favored the anaerobic metabolism, buffering ecosystem CO2 losses despite substantial soil warming. Accordingly, Arctic tundra switched from a sustained CH4 sink at RS site to an increasingly stronger CH4 source with snow additions. Accounting for both CO2 and CH4, the RS site became a net C sink over the growing season, overall reducing the global warming potential (CO2 equiv.; GWP) of the system relative to CTL. Snow additions progressively reduced net C losses at the MS site compared to CTL and the system transitioned into a net C sink at HS plots, partly due to the slower metabolism of anaerobic decomposition. However, given the greater radiative

  15. Mississippi/Alabama Pinnacle Trend Ecosystem Monitoring Final Synthesis Report

    USGS Publications Warehouse

    Continental Shelf Associates Inc.; Texas A&M University, Geochemical and Environmental Research Group

    2001-01-01

    This Final Synthesis Report summarizes a four-year program to characterize and monitor carbonate mounds on the Mississippi/Alabama outer continental shelf (OCS). The study area is shown in Fig.ES.1. The study was conducted by Continental Shelf Associates, Inc. and the Geochemical and Environmental Research Group (GERG) of Texas A&M University (TAMU), for the U.S. Geological Survey (USGS), Biological Resources Division.

  16. Carbon cycling in a high-arctic marine ecosystem - Young Sound, NE Greenland

    NASA Astrophysics Data System (ADS)

    Rysgaard, Søren; Nielsen, Torkel Gissel

    2006-10-01

    Young Sound is a deep-sill fjord in NE Greenland (74°N). Sea ice usually begins to form in late September and gains a thickness of ∼1.5 m topped with 0-40 cm of snow before breaking up in mid-July the following year. Primary production starts in spring when sea ice algae begin to flourish at the ice-water interface. Most biomass accumulation occurs in the lower parts of the sea ice, but sea ice algae are observed throughout the sea ice matrix. However, sea ice algal primary production in the fjord is low and often contributes only a few percent of the annual phytoplankton production. Following the break-up of ice, the immediate increase in light penetration to the water column causes a steep increase in pelagic primary production. Usually, the bloom lasts until August-September when nutrients begin to limit production in surface waters and sea ice starts to form. The grazer community, dominated by copepods, soon takes advantage of the increased phytoplankton production, and on an annual basis their carbon demand (7-11 g C m -2) is similar to phytoplankton production (6-10 g C m -2). Furthermore, the carbon demand of pelagic bacteria amounts to 7-12 g C m -2 yr -1. Thus, the carbon demand of the heterotrophic plankton is approximately twice the estimated pelagic primary production, illustrating the importance of advected carbon from the Greenland Sea and from land in fuelling the ecosystem. In the shallow parts of the fjord (<40 m) benthic primary producers dominate primary production. As a minimum estimate, a total of 41 g C m -2 yr -1 is fixed by primary production, of which phytoplankton contributes 15%, sea ice algae <1%, benthic macrophytes 62% and benthic microphytes 22%. A high and diverse benthic infauna dominated by polychaetes and bivalves exists in these shallow-water sediments (<40 m), which are colonized by benthic primary producers and in direct contact with the pelagic phytoplankton bloom. The annual benthic mineralization is 32 g C m -2 yr -1 of

  17. Depletion of stratospheric ozone over the Antarctic and Arctic: responses of plants of polar terrestrial ecosystems to enhanced UV-B, an overview.

    PubMed

    Rozema, Jelte; Boelen, Peter; Blokker, Peter

    2005-10-01

    Depletion of stratospheric ozone over the Antarctic has been re-occurring yearly since 1974, leading to enhanced UV-B radiation. Arctic ozone depletion has been observed since 1990. Ozone recovery has been predicted by 2050, but no signs of recovery occur. Here we review responses of polar plants to experimentally varied UV-B through supplementation or exclusion. In supplementation studies comparing ambient and above ambient UV-B, no effect on growth occurred. UV-B-induced DNA damage, as measured in polar bryophytes, is repaired overnight by photoreactivation. With UV exclusion, growth at near ambient may be less than at below ambient UV-B levels, which relates to the UV response curve of polar plants. UV-B screening foils also alter PAR, humidity, and temperature and interactions of UV with environmental factors may occur. Plant phenolics induced by solar UV-B, as in pollen, spores and lignin, may serve as a climate proxy for past UV. Since the Antarctic and Arctic terrestrial ecosystems differ essentially, (e.g. higher species diversity and more trophic interactions in the Arctic), generalization of polar plant responses to UV-B needs caution. PMID:16005756

  18. Microbial life in cold, sulfur-rich environments: Investigations of an Arctic ecosystem and implications for life detection at Europa

    NASA Astrophysics Data System (ADS)

    Gleeson, Damhnait Fagan

    2009-12-01

    Exobiological investigations require a detailed understanding of life's interactions with its environment here on Earth before we can confidently recognize signs of these interactions at other worlds such as Europa. Using a cold, sulfur-based ecosystem at Borup Fiord pass in the Canadian High Arctic as a study site, I investigated how the supraglacial non-ice materials are represented across different scales in spectral data, how microbiology is influencing the mineralogy of the site, and whether the products of microbial sulfide oxidation preserve indications of their biogenic origin. A systematic scale-integrated approach was applied to query orbital (Hyperion), field, and laboratory spectra to identify sulfur-rich materials precipitated on a glacier. While sulfur, the main constituent of the deposits, is well represented in Hyperion data, minor constituents such as calcite and gypsum are partially or entirely masked. Absorption features of sulfates, where present, are shifted in wavelength due to the effects of mixing or temperature. Autonomous detection methods were successfully applied to monitor the generation and extent of the deposits, which show spectral similarities to Europa's non-ice materials. Geomicrobiological cultivation of sulfide oxidizing bacteria succeeded in demonstrating that the microbiological community present at the site has the potential to catalyze the generation of sulfur deposits. Sulfur generated in culture is present as biomineralized structures comprised of microbial filaments and sheaths along which sulfur globules are deposited. Consortia producing these structures are dominated by gamma-Proteobacteria closely related to Marinobacter, not previously known to oxidize sulfide. The sulfur structures produced by these consortia are not observed in abiotic controls and have the potential to serve as morphological biosignatures. Investigations into the biogenicity of field deposits reveal mineral assemblages with similar morphologies to

  19. Approaches to determining Final Ecosystem Goods and Services: Benefits and Beneficiaries

    EPA Science Inventory

    By nature, the concept of ‘Final’ Ecosystem Goods and Services (FEGS) poses the question; to what or to whom are these goods and services final? We identify two main approaches theoreticians and practitioners are using to define and perceive FEGS (note: we recognize t...

  20. Observed and Potential Responses of Upland Tundra Ecosystems to a Changing Climate: Results from the Arctic Long-Term Ecological Research Project, North Slope, Alaska, USA

    NASA Astrophysics Data System (ADS)

    Bowden, W. B.

    2014-12-01

    permafrost in the arctic region approaches the 0ºC tipping point, the combination of presses and pulses may radically and rapidly alter upland tundra terrestrial and aquatic ecosystems. These changes will almost certainly occur more rapidly than would be the case if the region were influenced by the press of warming temperature alone.

  1. Modeling plankton ecosystem functioning and nitrogen fluxes in the oligotrophic waters of the Beaufort Sea, Arctic Ocean: a focus on light-driven processes

    NASA Astrophysics Data System (ADS)

    Le Fouest, V.; Zakardjian, B.; Xie, H.; Raimbault, P.; Joux, F.; Babin, M.

    2013-07-01

    The Arctic Ocean (AO) undergoes profound changes of its physical and biotic environments due to climate change. In some areas of the Beaufort Sea, the stronger haline stratification observed in summer alters the plankton ecosystem structure, functioning and productivity, promoting oligotrophy. A one-dimension (1-D) physical-biological coupled model based on the large multiparametric database of the Malina project in the Beaufort Sea was used (i) to infer the plankton ecosystem functioning and related nitrogen fluxes and (ii) to assess the model sensitivity to key light-driven processes involved in nutrient recycling and phytoplankton growth. The coupled model suggested that ammonium photochemically produced from photosensitive dissolved organic nitrogen (i.e., photoammonification process) was a necessary nitrogen source to achieve the observed levels of microbial biomass and production. Photoammonification directly and indirectly (by stimulating the microbial food web activity) contributed to 70% and 18.5% of the 0-10 m and whole water column, respectively, simulated primary production (respectively 66% and 16% for the bacterial production). The model also suggested that variable carbon to chlorophyll ratios were required to simulate the observed herbivorous versus microbial food web competition and realistic nitrogen fluxes in the Beaufort Sea oligotrophic waters. In face of accelerating Arctic warming, more attention should be paid in the future to the mechanistic processes involved in food webs and functional group competition, nutrient recycling and primary production in poorly productive waters of the AO, as they are expected to expand rapidly.

  2. Soil-plant N processes in a High Arctic ecosystem, NW Greenland are altered by long-term experimental warming and higher rainfall.

    PubMed

    Schaeffer, Sean M; Sharp, Elizabeth; Schimel, Joshua P; Welker, Jeffery M

    2013-11-01

    Rapid temperature and precipitation changes in High Arctic tundra ecosystems are altering the biogeochemical cycles of carbon (C) and nitrogen (N), but in ways that are difficult to predict. The challenge grows from the uncertainty of N cycle responses and the extent to which shifts in soil N are coupled with the C cycle and productivity of tundra systems. We used a long-term (since 2003) experiment of summer warming and supplemental summer water additions to a High Arctic ecosystem in NW Greenland, and applied a combination of discrete sampling and in situ soil core incubations to measure C and N pools and seasonal microbial processes that might control plant-available N. We hypothesized that elevated temperature and increased precipitation would stimulate microbial activity and net inorganic N mineralization, thereby increasing plant N-availability through the growing season. While we did find increased N mineralization rates under both global change scenarios, water addition also significantly increased net nitrification rates, loss of NO3 (-) -N via leaching, and lowered rates of labile organic N production. We also expected the chronic warming and watering would lead to long-term changes in soil N-cycling that would be reflected in soil δ(15) N values. We found that soil δ(15) N decreased under the different climate change scenarios. Our results suggest that temperature accelerates biological processes and existing C and N transformations, but moisture increases soil hydraulic connectivity and so alters the pathways, and changes the fate of the products of C and N transformations. In addition, our findings indicate that warmer, wetter High Arctic tundra will be cycling N and C in ways that may transform these landscapes in part leading to greater C sequestration, but simultaneously, N losses from the upper soil profile that may be transported to depth dissolved in water and or transported off site in lateral flow. PMID:23843128

  3. Rates and radiocarbon content of summer ecosystem respiration in response to long-term deeper snow in the High Arctic of NW Greenland

    NASA Astrophysics Data System (ADS)

    Lupascu, M.; Welker, J. M.; Xu, X.; Czimczik, C. I.

    2014-06-01

    The amount and timing of snow cover control the cycling of carbon (C), water, and energy in arctic ecosystems. The implications of changing snow cover for regional C budgets, biogeochemistry, hydrology, and albedo due to climate change are rudimentary, especially for the High Arctic. In a polar semidesert of NW Greenland, we used a ~10 year old snow manipulation experiment to quantify how deeper snow affects magnitude, seasonality, and 14C content of summer C emissions. We monitored ecosystem respiration (Reco), soil CO2, and their 14C contents over three summers in vegetated and bare areas. Additional snowpack, elevated soil water content (SWC), and temperature throughout the growing season in vegetated, but not in bare, areas. Daily Reco was positively correlated to temperature, but negatively correlated to SWC; consequently, we found no effect of increased snow on daily flux. Cumulative summertime Reco was not related to annual snowfall, but to water year precipitation (winter snow plus summer rain). Experimentally increased snowpack shortened the growing season length and reduced summertime Reco up to 40%. Soil CO2 was older under increased snow. However, we found no effect of snow depth on the Reco age because older C emissions were masked by younger CO2 produced from the litter layer or plant respiration. In the High Arctic, anticipated changes in precipitation regime associated with warming are a key uncertainty for understanding future C cycling. In polar semideserts, water year precipitation is an important driver of summertime Reco. Permafrost C is vulnerable to changes in snowpack, with a deeper snowpack-promoting decomposition of older soil C.

  4. Rich and cold: diversity, distribution and drivers of fungal communities in patterned-ground ecosystems of the North American Arctic.

    PubMed

    Timling, I; Walker, D A; Nusbaum, C; Lennon, N J; Taylor, D L

    2014-07-01

    Fungi are abundant and functionally important in the Arctic, yet comprehensive studies of their diversity in relation to geography and environment are not available. We sampled soils in paired plots along the North American Arctic Transect (NAAT), which spans all five bioclimatic subzones of the Arctic. Each pair of plots contrasted relatively bare, cryoturbated patterned-ground features (PGFs) and adjacent vegetated between patterned-ground features (bPGFs). Fungal communities were analysed via sequencing of 7834 ITS-LSU clones. We recorded 1834 OTUs - nearly half the fungal richness previously reported for the entire Arctic. These OTUs spanned eight phyla, 24 classes, 75 orders and 120 families, but were dominated by Ascomycota, with one-fifth belonging to lichens. Species richness did not decline with increasing latitude, although there was a decline in mycorrhizal taxa that was offset by an increase in lichen taxa. The dominant OTUs were widespread even beyond the Arctic, demonstrating no dispersal limitation. Yet fungal communities were distinct in each subzone and were correlated with soil pH, climate and vegetation. Communities in subzone E were distinct from the other subzones, but similar to those of the boreal forest. Fungal communities on disturbed PGFs differed significantly from those of paired stable areas in bPGFs. Indicator species for PGFs included lichens and saprotrophic fungi, while bPGFs were characterized by ectomycorrhizal and pathogenic fungi. Our results suggest that the Arctic does not host a unique mycoflora, while Arctic fungi are highly sensitive to climate and vegetation, with potential to migrate rapidly as global change unfolds. PMID:24689939

  5. Seasonal snow of arctic Alaska R4D investigations. Final report

    SciTech Connect

    Benson, C.S.

    1993-02-01

    Seasonal snow is present on the Arctic Slope of Alaska for nine months each year. Its presence or absence determines whether 80% of the solar radiation is reflected or absorbed, respectively. Although life on the Arctic Slope is adapted to, and in some cases dependent upon seasonal snow, little is known about it from a scientific point of view. Its quantity has been grossly underestimated, and knowledge of its distribution and the extent of wind transport and redistribution is very limited. This research project dealt with the amount, regional distribution and physical properties of wind blown snow and its biological role in the R4D area of the Arctic Slope. Physical processes which operate within the snow that were studied included the flux of heat and vapor and the fractionation of stable isotopes through it during fall and winter, and the complex heat and mass transfer within the snow and between snow, its substrate and the overlying atmosphere during the melt period.

  6. Handbook for nuclear weapons effects under arctic conditions. sanitized. Final report, June 1979-April 1980

    SciTech Connect

    Keith, J.R.; Wallace, W.E.

    1980-04-30

    This report describes the changes to be expected in nuclear weapons effects in arctic conditions as compared with the temperature regions of the works. Previous research in this area was reviewed, and relevant information is presented. The emphasis was placed on low-altitude and underwater bursts and effects. Inadequacies and uncertainties in current prediction techniques are given. The characteristics of the arctic region of importance in nuclear-effect calculations are given. The effects considered include air blast, cratering, thermal radiation, nuclear radiation, EMP, HF communication degradation, water shock, water waves, and acoustic effects.

  7. NASA's Arctic Voyage 2010

    NASA Video Gallery

    NASA's first oceanographic research expedition left Alaska on June 15, 2010. The ICESCAPE mission will head into the Arctic to study sea ice and the changing ocean ecosystem. Listen to the scientis...

  8. Life in a temperate Polar sea: a unique taphonomic window on the structure of a Late Cretaceous Arctic marine ecosystem

    PubMed Central

    Chin, Karen; Bloch, John; Sweet, Arthur; Tweet, Justin; Eberle, Jaelyn; Cumbaa, Stephen; Witkowski, Jakub; Harwood, David

    2008-01-01

    As the earth faces a warming climate, the rock record reminds us that comparable climatic scenarios have occurred before. In the Late Cretaceous, Arctic marine organisms were not subject to frigid temperatures but still contended with seasonal extremes in photoperiod. Here, we describe an unusual fossil assemblage from Devon Island, Arctic Canada, that offers a snapshot of a ca 75 Myr ago marine palaeoecosystem adapted to such conditions. Thick siliceous biogenic sediments and glaucony sands reveal remarkably persistent high primary productivity along a high-latitude Late Cretaceous coastline. Abundant fossil faeces demonstrate that this planktonic bounty supported benthic invertebrates and large, possibly seasonal, vertebrates in short food chains. These ancient organisms filled trophic roles comparable to those of extant Arctic species, but there were fundamental differences in resource dynamics. Whereas most of the modern Arctic is oligotrophic and structured by resources from melting sea ice, we suggest that forested terrestrial landscapes helped support the ancient marine community through high levels of terrigenous organic input. PMID:18713718

  9. Linking Biological Responses of Terrestrial N Eutrophication to the Final Ecosystem Goods and Services Classification System

    NASA Astrophysics Data System (ADS)

    Bell, M. D.; Clark, C.; Blett, T.

    2015-12-01

    The response of a biological indicator to N deposition can indicate that an ecosystem has surpassed a critical load and is at risk of significant change. The importance of this exceedance is often difficult to digest by policy makers and public audiences if the change is not linked to a familiar ecosystem endpoint. A workshop was held to bring together scientists, resource managers, and policy makers with expertise in ecosystem functioning, critical loads, and economics in an effort to identify the ecosystem services impacted by air pollution. This was completed within the framework of the Final Ecosystem Goods and Services (FEGS) Classification System to produce a product that identified distinct interactions between society and the effects of nitrogen pollution. From each change in a biological indicator, we created multiple ecological production functions to identify the cascading effects of the change to a measureable ecosystem service that a user interacts with either by enjoying, consuming, or appreciating the good or service, or using it as an input in the human economy. This FEGS metric was then linked to a beneficiary group that interacts with the service. Chains detailing the links from the biological indicator to the beneficiary group were created for aquatic and terrestrial acidification and eutrophication at the workshop, and here we present a subset of the workshop results by highlighting for 9 different ecosystems affected by terrestrial eutrophication. A total of 213 chains that linked to 37 unique FEGS metrics and impacted 15 beneficiary groups were identified based on nitrogen deposition mediated changes to biological indicators. The chains within each ecosystem were combined in flow charts to show the complex, overlapping relationships among biological indicators, ecosystem services, and beneficiary groups. Strength of relationship values were calculated for each chain based on support for the link in the scientific literature. We produced the

  10. Aircraft Emissions Deposited in the Stratosphere and Within the Arctic Polar Vortex. Final report

    SciTech Connect

    Baughcum, S.L.

    1996-04-01

    This report describes an analysis of the quantity of emissions (water vapor, NO(x)) projected to be deposited directly within the Arctic polar vortex by projected fleets of Mach 2.4 high speed civil transports (HSCT`s). It also evaluates the amount of emissions from subsonic aircraft which are emitted into the lower stratosphere using aircraft emission inventories developed earlier for May 1990 as representative of the annual average.

  11. Final deglaciation of the Barents Sea at 12.9 ka and potential trigger of the Arctic atmospheric dipole

    NASA Astrophysics Data System (ADS)

    Hormes, Anne; Briner, Jason

    2016-04-01

    The specific configuration and history of the marine-based Barents Sea ice sheet has been under dispute for decades. Bjørnøya is situated between northern Fennoscandia and the Svalbard archipelago and therefore lies in a key position for understanding the maximum configuration and final retreat of the ice sheet. Bjørnøya also lies between two important trough systems that contributed to the ice sheet drainage: the Bjørnøya and Storfjorden palaeo-ice streams. We obtained 24 cosmogenic 10Be exposure ages from glacial erratics on southern Bjørnøya to 1) investigate the timing of initial deglaciation of the Barents Sea ice sheet, and 2) determine the timing of complete deglaciation of the island. The 10Be ages are from glacially transported sandstone and conglomerate boulders situated in the southern part of the island, calculated using the Arctic 10Be production rate, and presented with analytical uncertainty. 18 10Be ages exhibit a very strong mode from 11.9 to 14.5 ka, averaging 12.9 ± 0.6 ka, a much smaller mode from 24.6 to 26.2 ka (averaging 25.6 ± 1.2 ka), and three samples were excluded as outliers scattering at different times (3.6 ± 0.2 ka, 16.3 ± 0.7 ka and 19.6 ± 1.0 ka). Boulders between 17 and 293 m a.s.l. and the highest samples from Antarcticafjellet (340-351 m a.s.l.) indicate ages averaging 12.9 ± 0.6 ka. These boulders indicate the final deglaciation of restricted local remnants of ice covering the higher Antarctic and Alfred mountains and leaving well-preserved moraine sequences in the lowlands. We will discuss the ice-free Barents Sea as a potential precondition to build up low pressure in this region needed for a strong Arctic atmospheric dipole. In turn a strong Arctic atmospheric dipole causes increase in Meridional winds succeeding in transport of Arctic sea ice into the North Atlantic with the trans-polar drift.

  12. a New Japanese Project for Arctic Climate Change Research - Grene Arctic - (Invited)

    NASA Astrophysics Data System (ADS)

    Enomoto, H.

    2013-12-01

    A new Arctic Climate Change Research Project 'Rapid Change of the Arctic Climate System and its Global Influences' has started in 2011 for a five years project. GRENE-Arctic project is an initiative of Arctic study by more than 30 Japanese universities and institutes as the flame work of GRENE (Green Network of Excellence) of MEXT (Ministry of Education, Culture, Sports, Science and Technology, Japan). The GRENE-Arctic project set four strategic research targets: 1. Understanding the mechanism of warming amplification in the Arctic 2. Understanding the Arctic system for global climate and future change 3. Evaluation of the effects of Arctic change on weather in Japan, marine ecosystems and fisheries 4. Prediction of sea Ice distribution and Arctic sea routes This project aims to realize the strategic research targets by executing following studies: -Improvement of coupled general circulation models based on validations of the Arctic climate reproducibility and on mechanism analyses of the Arctic climate change and variability -The role of Arctic cryosphere in the global change -Change in terrestrial ecosystem of pan-Arctic and its effect on climate -Studies on greenhouse gas cycles in the Arctic and their responses to climate change -Atmospheric studies on Arctic change and its global impacts -Ecosystem studies of the Arctic ocean declining Sea ice -Projection of Arctic Sea ice responding to availability of Arctic sea route (* ** ***) *Changes in the Arctic ocean and mechanisms on catastrophic reduction of Arctic sea ice cover **Coordinated observational and modeling studies on the basic structure and variability of the Arctic sea ice-ocean system ***Sea ice prediction and construction of ice navigation support system for the Arctic sea route. Although GRENE Arctic project aims to product scientific contribution in a concentrated program during 2011-2016, Japanese Arctic research community established Japan Consortium for Arctic Environmental Research (JCAR) in May

  13. The contribution of Fe(III) and humic acid reduction to ecosystem respiration in drained thaw lake basins of the Arctic Coastal Plain

    NASA Astrophysics Data System (ADS)

    Lipson, David A.; Raab, Theodore K.; Goria, Dominic; Zlamal, Jaime

    2013-04-01

    research showed that anaerobic respiration using iron (Fe) oxides as terminal electron acceptor contributed substantially to ecosystem respiration (ER) in a drained thaw lake basin (DTLB) on the Arctic coastal plain. As DTLBs age, the surface organic layer thickens, progressively burying the Fe-rich mineral layers. We therefore hypothesized that Fe(III) availability and Fe reduction would decline with basin age. We studied four DTLBs across an age gradient, comparing seasonal changes in the oxidation state of dissolved and extractable Fe pools and the estimated contribution of Fe reduction to ER. The organic layer thickness did not strictly increase with age for these four sites, though soil Fe levels decreased with increasing organic layer thickness. However, there were surprisingly high levels of Fe minerals in organic layers, especially in the ancient basin where cryoturbation may have transported Fe upward through the profile. Net reduction of Fe oxides occurred in the latter half of the summer and contributed an estimated 40-45% to ecosystem respiration in the sites with the thickest organic layers and 61-63% in the sites with the thinnest organic layers. All sites had high concentrations of soluble Fe(II) and Fe(III), explained by the presence of siderophores, and this pool became progressively more reduced during the first half of the summer. Redox titrations with humic acid (HA) extracts and chelated Fe support our view that this pattern indicates the reduction of HA during this interval. We conclude that Fe(III) and HA reductions contribute broadly to ER in the Arctic coastal plain.

  14. Changing Arctic Ecosystems: Updated forecast: Reducing carbon dioxide (CO2) emissions required to improve polar bear outlook

    USGS Publications Warehouse

    Oakley, Karen L.; Atwood, Todd C.; Mugel, Douglas N.; Rode, Karyn D.; Whalen, Mary E.

    2015-01-01

    The Arctic is warming faster than other regions of the world due to the loss of snow and ice, which increases the amount of solar energy absorbed by the region. The most visible consequence has been the rapid decline in sea ice over the last 3 decades-a decline projected to bring long ice-free summers if greenhouse gas (GHG) emissions are not significantly reduced. The polar bear (Ursus maritimus) depends on sea ice over the biologically productive continental shelves of the Arctic Ocean as a platform for hunting seals. In 2008, the U.S. Fish and Wildlife Service listed the polar bear as threatened under the Endangered Species Act (ESA) due to the threat posed by sea ice loss. The polar bear was the first species to be listed due to forecasted population declines from climate change.

  15. Decadal Arctic ice simulations: 1986-1995. Final report, September 1993--November 1997

    SciTech Connect

    Piacsek, S.; Preller, R.; Posey, P.

    1997-05-01

    The Arctic ice cover has been simulated for the period 1986-1995 with two coupled ice-ocean models, one with low resolution on a small polar stereographic plane (PIPS1/O), and one with high resolution on a rotated spherical grid (PIPS2), covering all northern hemispheric sea ice. The ice model used was the Hibler ice model, and the ocean models were both z-level types with rigid lid. Atmospheric forcing were derived from surface fluxes computed by the Navy`s NOGAPS global atmospheric prediction model.

  16. Mediation of Fire-Climate Linkages by Vegetation Types in Alaskan Arctic Tundra Ecosystems: Impacts of Model Uncertainty on GCM-Based Forecasts of Future Fire Activity

    NASA Astrophysics Data System (ADS)

    Duffy, P.; Higuera, P. E.; Young, A. M.; Hu, F.; Dietze, M.

    2014-12-01

    Fire is a powerful landscape scale disturbance agent in tundra ecosystems. Impacts on biophysical properties (e.g. albedo) and biogeochemical function (e.g. carbon flux) underscore the need to better quantify fire-climate linkages in tundra ecosystems as climate change accelerates at northern high latitudes. In this context, a critical question is "How does the functional linkage between climate and fire vary across spatial domains dominated by different vegetation types?" We address this question with BLM-Alaska Fire Service area burned data (http://fire.ak.blm.gov/predsvcs/maps.php) used in conjunction with downscaled historical climate data from the Scenarios Network for Alaska Planning (http://www.snap.uaf.edu/data.php) to develop gradient boosting models of annual area burned in Alaska tundra ecosystems. The sparse historical fire records in the Arctic necessitate explicit quantification of model uncertainty associated with the development of statistical analyses. In this work, model uncertainty is depicted through the construction of separate models depicting fire-climate relationships for regions defined by the graminoid, shrub, and wetland tundra vegetation classes (Circumpolar Arctic Vegetation Map: http://www.geobotany.uaf.edu/cavm/). Non-linear relationships between annual area burned and climate variables are depicted with partial dependence functions. Our results show that vegetation-specific models result in different non-linear relationships between climate and fire. Precipitation variables generally had higher relative influence scores than temperature; however, differences between the magnitude of the scores were greater when models were built with monthly (versus seasonal) explanatory variables. Key threshold values for climate variables are identified. The impact of model uncertainty on forecasts of future fire activity was quantified using output from five different AR5/CMIP5 General Circulation Models. Model uncertainty corresponding to

  17. Arctic climate tipping points.

    PubMed

    Lenton, Timothy M

    2012-02-01

    There is widespread concern that anthropogenic global warming will trigger Arctic climate tipping points. The Arctic has a long history of natural, abrupt climate changes, which together with current observations and model projections, can help us to identify which parts of the Arctic climate system might pass future tipping points. Here the climate tipping points are defined, noting that not all of them involve bifurcations leading to irreversible change. Past abrupt climate changes in the Arctic are briefly reviewed. Then, the current behaviour of a range of Arctic systems is summarised. Looking ahead, a range of potential tipping phenomena are described. This leads to a revised and expanded list of potential Arctic climate tipping elements, whose likelihood is assessed, in terms of how much warming will be required to tip them. Finally, the available responses are considered, especially the prospects for avoiding Arctic climate tipping points. PMID:22270703

  18. Modeling permafrost thaw and ecosystem carbon cycle under annual and seasonal warming at an Arctic tundra site in Alaska

    NASA Astrophysics Data System (ADS)

    Li, Jianwei; Luo, Yiqi; Natali, Susan; Schuur, Edward A. G.; Xia, Jianyang; Kowalczyk, Eva; Wang, Yingping

    2014-06-01

    Permafrost thaw and its impacts on ecosystem carbon (C) dynamics are critical for predicting global climate change. It remains unclear whether annual and seasonal warming (winter or summer) affect permafrost thaw and ecosystem C balance differently. It is also required to compare the short-term stepwise warming and long-term gradual warming effects. This study validated a land surface model, the Community Atmosphere Biosphere Land Exchange model, at an Alaskan tundra site, and then used it to simulate permafrost thaw and ecosystem C flux under annual warming, winter warming, and summer warming. The simulations were conducted under stepwise air warming (2°C yr-1) during 2007-2011, and gradual air warming (0.04°C yr-1) during 2007-2056. We hypothesized that all warming treatments induced greater permafrost thaw, and larger ecosystem respiration than plant growth thus shifting the ecosystem C sink to C source. Results only partially supported our hypothesis. Climate warming further enhanced C sink under stepwise (6-15%) and gradual (1-8%) warming scenarios as followed by annual warming, winter warming, and summer warming. This is attributed to disproportionally low temperature increase in soil (0.1°C) in comparison to air warming (2°C). In a separate simulation, a greater soil warming (1.5°C under winter warming) led to a net ecosystem C source (i.e., 18 g C m-2 yr-1). This suggests that warming tundra can potentially provide positive feedbacks to global climate change. As a key variable, soil temperature and its dynamics, especially during wintertime, need to be carefully studied under global warming using both modeling and experimental approaches.

  19. Modeling the Pan-Arctic terrestrial and atmospheric water cycle. Final report

    SciTech Connect

    Gutowski, W.J., Jr.

    2001-03-30

    This report describes results of DOE grant DE-FG02-96ER61473 to Iowa State University (ISU). Work on this grant was performed at Iowa State University and at the University of New Hampshire in collaboration with Dr. Charles Vorosmarty and fellow scientists at the University of New Hampshire's (UNH's) Institute for the Study of the Earth, Oceans, and Space, a subcontractor to the project. Research performed for the project included development, calibration and validation of a regional climate model for the pan-Arctic, modeling river networks, extensive hydrologic database development, and analyses of the water cycle, based in part on the assembled databases and models. Details appear in publications produced from the grant.

  20. Ecosystem CO2 and CH4 Exchange in a Mixed Tundra and a Fen Within an Arctic Landscape: Modeled Impacts of Climate Change

    NASA Astrophysics Data System (ADS)

    Grant, R. F.

    2015-12-01

    Climate change will have important effects on arctic productivity and greenhouse gas exchange. These changes were projected by the model ecosys under an SRES A2 scenario over the 21st century for a landscape including an upland tundra and a lowland fen at Daring Lake, NWT. Rising temperatures and precipitation caused increases in active layer depths (ALD) and eventual formation of taliks, particularly in the fen, which were attributed to heat advection from warmer and more intense precipitation and downslope flow. These changes raised net primary productivity from more rapid N mineralization and uptake, driven by more rapid heterotrophic respiration and increasing deciduous vs. evergreen plant functional types. Consequently gains in net ecosystem productivity (NEP) of 29 and 10 g C m-2 y-1 were modelled in the tundra and fen after 90 years. However CH4 emissions modelled from the fen rose sharply from direct effects of increasing soil temperatures and greater ALD on fermenter and methanogenic populations, and from indirect effects of increasing sedge growth which hastened transfer of CH4 through porous roots to the atmosphere. After 90 years, landscape CH4 emissions increased from 1.1 to 5.2 g C m-2 y-1 while landscape NEP increased from 34 to 46 g C m-2 y-1. Positive feedback to radiative forcing from increases in CH4 emissions more than offset negative feedback from increases in NEP. This feedback was largely attributed to rises in CH4 emission caused by heat advection from increasing precipitation, the impacts of which require greater attention in arctic climate change studies.

  1. Ecosystem CO2 and CH4 exchange in a mixed tundra and a fen within a hydrologically diverse Arctic landscape: 2. Modeled impacts of climate change

    NASA Astrophysics Data System (ADS)

    Grant, R. F.

    2015-07-01

    Climate change will have important effects on arctic productivity and greenhouse gas exchange. These changes were projected by the model ecosys under an Special Report on Emissions Scenarios (SRES) A2 scenario over the 21st century for a landscape including an upland tundra and a lowland fen at Daring Lake, NWT. Rising temperatures and precipitation caused increases in active layer depths (ALD) and eventual formation of taliks, particularly in the fen, which were attributed to heat advection from warmer and more intense precipitation and downslope flow. These changes raised net primary productivity from more rapid N mineralization and uptake, driven by more rapid heterotrophic respiration and increasing deciduous versus evergreen plant functional types. Consequently, gains in net ecosystem productivity (NEP) of 29 and 10 g C m-2 yr-1 were modeled in the tundra and fen after 90 years. However, CH4 emissions modeled from the fen rose sharply from direct effects of increasing soil temperatures and greater ALD on fermenter and methanogenic populations and from indirect effects of increasing sedge growth, which hastened transfer of CH4 through porous roots to the atmosphere. After 90 years, landscape CH4 emissions increased from 1.1 to 5.2 g C m-2 yr-1 while landscape NEP increased from 34 to 46 g C m-2 yr-1. Positive feedback to radiative forcing from increases in CH4 emissions more than offset negative feedback from increases in NEP. This feedback was largely attributed to rises in CH4 emission caused by heat advection from increasing precipitation, the impacts of which require greater attention in arctic climate change studies.

  2. Last Deglacial Arctic to Pacific Transgressions via the Bering Strait: Implications for Climate, Meltwater Source, Ecosystems and Southern Ocean Wind Strength

    NASA Astrophysics Data System (ADS)

    Nwaodua, Emmanuel C.

    The main goal of this research is to provide physical evidence of reverse flow(s), from the Arctic to the North Pacific Ocean, after the Last Glacial Maximum (LGM). This is primarily essential to studies concerned with understanding how the fluctuations in strength of the Southern Ocean Wind (SOW), in conjunction with an open Bering Strait, alter the direction of water flow through the Bering Strait. Visible and Near Infrared (VNIR) derivative spectroscopy; quotient normalization and varimax rotated principal component analysis of diffuse spectral reflectance (DSR) measurements from 234 surface core samples and 2 piston cores, in addition to the USGS spectral library, were used to extract and identify these lithological compositions (in order of importance) within the study location. These compositions are chlorite + muscovite; goethite + phycoerythrin + phycocyanin; smectite; calcite+dolomite; and illite + Chlorophyll a. The Geostatistical tool, kriging, was utilized in creating the sedimentary maps of all the components. These maps were used to determine these components' modern spatial patterns. This aided in the evaluation and downcore interpretation of the component most suited for this study. The illite in illite + Chlorophyll a assemblage was deemed to be the appropriate water mass tracer for a reverse flow from the Arctic into the North Pacific; this is because of its prominence and abundance in the Mackenzie River drainage basin and on the west Arctic Sea shelf. The illite denotes these periods of meltwater pulses (MWP): MWP 1A, ˜14,600 and 13,800 Cal yrs. BP, separated by the Older Dryas; MWP 1B, ˜11,000--9,200 Cal yrs. BP; and MWP 1C, ˜8,000 Cal yrs. BP. The timing of these pulses along with previously published data on the Bering Sea shelf and the North Pacific Ocean enabled these deductions: 1) the initial opening of the Bering Strait and the flow direction after the LGM; 2) the source of these meltwater pulses and the mechanism that might drive

  3. Integrating Research and Education in a Study of Biocomplexity in Arctic Tundra Ecosystems: Costs, Results, and Benefits to the Research Agenda

    NASA Astrophysics Data System (ADS)

    Gould, W. A.; González, G.; Walker, D. A.

    2006-12-01

    The integration of research and education is one of the fundamental goals of our national science policy. There is strong interest to improve this integration at the graduate and undergraduate levels, with the general public, and with local and indigenous people. Efforts expended in integrating research and education can occur at the expense of research productivity and represent a cost. Results may include number of personnel involved, activities accomplished, research or other products produced. Benefits are difficult to quantify and may be short term and tangible, e.g. education-research projects enhancing research productivity with publications, or long-term and include intangibles such as personal interactions and experiences influencing career choices, the perception of research activities, enhanced communication, and direct or indirect influence on related research and educational projects. We have integrated the University field course Arctic Field Ecology with an interdisciplinary research project investigating the interactions of climate, vegetation, and permafrost in the study Biocomplexity of Arctic Tundra Ecosystems. The integration is designed to give students background in regional ecology; introduce students to the project objectives, methods, and personnel; provide for interaction with participating scientists; conduct research initiated by the class and instructors; and provide the opportunity to interact with indigenous people with interests in traditional ecological knowledge and land management. Our costs included increased logistical complexity and time-demands on the researchers and staff managing the integration. The educational component increased the size of the research group with the addition of 55 participants over the 4 field seasons of the study. Participants came from 7 countries and included 20 enrolled university students, 18 Inuit non student participants, 9 Inuit students, 3 visiting scientists, 3 staff, and 2 scientist

  4. A systematic approach for quantifying final ecosystems services at regional and national scales

    EPA Science Inventory

    Since the development of the Millennium Ecosystem Assessment (2005), there have been a myriad of proposals regarding how to apply ecosystem services concepts in routine, systematic ways to support standards, markets and assessments of ecosystems services. The key question being ...

  5. Effects of short term and long term soil warming on ecosystem phenology of a sub-arctic grassland: an NDVI-based approach

    NASA Astrophysics Data System (ADS)

    Leblans, Niki; Sigurdsson, Bjarni D.; Janssens, Ivan A.

    2014-05-01

    % greening was advanced by 23 days at +5°C and by 32 days at +10°C Ts. However, no difference in the date of maximum greening or in the onset of senescence occurred. In contrast, in the long-term warmed grassland, the start of the growing season was not affected by Ts and the 50% greening point occurred only 10 days earlier at +5°C and 15 days earlier at +10°C Ts. However, the timing of maximum greening was advanced by 19 days at +5°C and even by 32 days at +10°C Ts. Again, the onset of senescence did not change with Ts. Significant Ts effects on ecosystem phenology of subarctic grasslands only occurred at warming of 5°C or higher. This study also demonstrates that short-term Ts effects on ecosystem phenology are not necessarily good predictors for long-term changes in sub-arctic grasslands. In the short-term (5 years warming), soil warming induced an early onset of the growing season, which was later compensated by faster greening on colder soils, so that maximum greenness was reached simultaneously irrespective of Ts. In contrast, the long-term Ts warming did not induce earlier onset of the growing season, but it led to faster greening on warm soils, which again led to an advance in timing of maximum greenness. This difference between short- and long-term responses in phenology might be caused by either phenotypic plasticity (acclimation) or by a genetic selection (evolution) of the grass populations where the warming has been ongoing for centuries. Such processes are at present not included in modelling predictions of climate change responses of natural ecosystems, but may offer important negative feedback mechanisms to warming which will reduce its effects.

  6. The future of Arctic benthos: Expansion, invasion, and biodiversity

    NASA Astrophysics Data System (ADS)

    Renaud, Paul E.; Sejr, Mikael K.; Bluhm, Bodil A.; Sirenko, Boris; Ellingsen, Ingrid H.

    2015-12-01

    One of the logical predictions for a future Arctic characterized by warmer waters and reduced sea-ice is that new taxa will expand or invade Arctic seafloor habitats. Specific predictions regarding where this will occur and which taxa are most likely to become established or excluded are lacking, however. We synthesize recent studies and conduct new analyses in the context of climate forecasts and a paleontological perspective to make concrete predictions as to relevant mechanisms, regions, and functional traits contributing to future biodiversity changes. Historically, a warmer Arctic is more readily invaded or transited by boreal taxa than it is during cold periods. Oceanography of an ice-free Arctic Ocean, combined with life-history traits of invading taxa and availability of suitable habitat, determine expansion success. It is difficult to generalize as to which taxonomic groups or locations are likely to experience expansion, however, since species-specific, and perhaps population-specific autecologies, will determine success or failure. Several examples of expansion into the Arctic have been noted, and along with the results from the relatively few Arctic biological time-series suggest inflow shelves (Barents and Chukchi Seas), as well as West Greenland and the western Kara Sea, are most likely locations for expansion. Apparent temperature thresholds were identified for characteristic Arctic and boreal benthic fauna suggesting strong potential for range constrictions of Arctic, and expansions of boreal, fauna in the near future. Increasing human activities in the region could speed introductions of boreal fauna and reduce the value of a planktonic dispersal stage. Finally, shelf regions are likely to experience a greater impact, and also one with greater potential consequences, than the deep Arctic basin. Future research strategies should focus on monitoring as well as compiling basic physiological and life-history information of Arctic and boreal taxa, and

  7. Patterns and controls of winter carbon dioxide emissions and microbial biomass C and N, in two arctic ecosystem types under varying snow regimes

    NASA Astrophysics Data System (ADS)

    Larsen, K. S.

    2003-04-01

    In a manipulative study, snow fences were put up in sub arctic birch forest and dry heath areas near Abisko, Northern Sweden, increasing the natural snow-cover by 5-35 cm. In early March, CO2 fluxes were 77% and 157% higher in the snow-fenced areas (birch and heath, respectively) and in the snowmelt period from April to May there was a tendency to higher effluxes of CO2 in patches with increased snow-cover. This indicates that small increases in winter snowfall have the potential to increase the CO2 loss substantially from these ecosystems during the off-season. CO2 fluxes integrated over 22 days in April-May at the heath site constituted 8% of growing season net primary production at a nearby heath site, showing that a substantial part of annual CO2 loss may take place during the early spring. In a second study, measurements of CO2 emissions from birch and heath ecosystems situated across a natural snow-cover gradient were performed. The results of this study corroborates with the findings in the snow fence study, showing consistently higher fluxes from sites with higher snow depths. The microbial biomass N and P were determined in both studies and were consistently high in the sub nivean soils compared to summer estimates, indicating that microbes provide a significant buffer limiting the export of mineral nutrients in the snowmelt period. A significant decrease in microbial biomass was observed as plots became snow free at the heath site. Although such decreases have been suggested to be caused by freeze-thaw cycles, this cannot fully explain the observation in this study. The first spring thaw and the transition from constant, sub-zero temperatures and a constant water regime to more variable conditions, and possibly increased grazing by nematodes and protozoans, may also play and important role controlling the microbial population during and after snowmelt.

  8. Final ecosystem services for stream ecosystems and the metrics, methods and challenges to apply them in a national monitoring context

    EPA Science Inventory

    The challenge of translating notions of ecosystem services from the theoretical arena to practical application at large scales (e.g. national) requires an interdisciplinary approach. To meet this challenge, we convened a workshop involving a broad suite of natural and social scie...

  9. Microsatellite and mtDNA analysis of lake trout, Salvelinus namaycush, from Great Bear Lake, Northwest Territories: impacts of historical and contemporary evolutionary forces on Arctic ecosystems

    PubMed Central

    Harris, Les N; Howland, Kimberly L; Kowalchuk, Matthew W; Bajno, Robert; Lindsay, Melissa M; Taylor, Eric B

    2013-01-01

    Resolving the genetic population structure of species inhabiting pristine, high latitude ecosystems can provide novel insights into the post-glacial, evolutionary processes shaping the distribution of contemporary genetic variation. In this study, we assayed genetic variation in lake trout (Salvelinus namaycush) from Great Bear Lake (GBL), NT and one population outside of this lake (Sandy Lake, NT) at 11 microsatellite loci and the mtDNA control region (d-loop). Overall, population subdivision was low, but significant (global FST θ = 0.025), and pairwise comparisons indicated that significance was heavily influenced by comparisons between GBL localities and Sandy Lake. Our data indicate that there is no obvious genetic structure among the various basins within GBL (global FST = 0.002) despite the large geographic distances between sampling areas. We found evidence of low levels of contemporary gene flow among arms within GBL, but not between Sandy Lake and GBL. Coalescent analyses suggested that some historical gene flow occurred among arms within GBL and between GBL and Sandy Lake. It appears, therefore, that contemporary (ongoing dispersal and gene flow) and historical (historical gene flow and large founding and present-day effective population sizes) factors contribute to the lack of neutral genetic structure in GBL. Overall, our results illustrate the importance of history (e.g., post-glacial colonization) and contemporary dispersal ecology in shaping genetic population structure of Arctic faunas and provide a better understanding of the evolutionary ecology of long-lived salmonids in pristine, interconnected habitats. PMID:23404390

  10. Importance of soil moisture and N availability to larch growth and distribution in the Arctic taiga-tundra boundary ecosystem, northeastern Siberia

    NASA Astrophysics Data System (ADS)

    Liang, Maochang; Sugimoto, Atsuko; Tei, Shunsuke; Bragin, Ivan V.; Takano, Shinya; Morozumi, Tomoki; Shingubara, Ryo; Maximov, Trofim C.; Kiyashko, Serguei I.; Velivetskaya, Tatiana A.; Ignatiev, Alexander V.

    2014-12-01

    To better understand the factors controlling the growth of larch trees in Arctic taiga-tundra boundary ecosystem, we conducted field measurements of photosynthesis, tree size, nitrogen (N) content, and isotopic ratios in larch needles and soil. In addition, we observed various environmental parameters, including topography and soil moisture at four sites in the Indigirka River Basin, near Chokurdakh, northeastern Siberia. Most living larch trees grow on mounds with relatively high elevations and dry soils, indicating intolerance of high soil moisture. We found that needle δ13C was positively correlated with needle N content and needle mass, and these parameters showed spatial patterns similar to that of tree size. These results indicate that trees with high needle N content achieved higher rates of photosynthesis, which resulted in larger amounts of C assimilation and larger C allocation to needles and led to larger tree size than trees with lower needle N content. A positive correlation was also found between needle N content and soil NH 4 + pool. Thus, soil inorganic N pool may indicate N availability, which is reflected in the needle N content of the larch trees. Microtopography plays a principal role in N availability, through a change in soil moisture. Relatively dryer soil of mounds with higher elevation and larger extent causes higher rates of soil N production, leading to increased N availability for plants, in addition to larger rooting space for trees to uptake more N.

  11. Flight destinations and foraging behaviour of northern gannets ( Sula bassana) preying on a small forage fish in a low-Arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Garthe, Stefan; Montevecchi, William A.; Davoren, Gail K.

    2007-02-01

    We applied data loggers (temperature-depth and GPS-temperature-depth) on individual birds in combination with dietary sampling and a vessel survey of prey availability to assess the foraging behaviour of northern gannets ( Sula bassana, Linnaeus 1758) in a low-Arctic ecosystem in the NW Atlantic. We demonstrate that the gannets foraged almost exclusively on inshore and coastal aggregations of capelin. There was a strong correspondence between the distributions of capelin and foraging gannets, and gannets exhibited persistence in successive foraging trips to the same foraging areas. The diving activity of gannets was highest during the early morning and evening, when capelin are known to be primarily available in the upper water column. Most of the gannets dive depths were less than 5 m. Flight speeds recorded by GPS were 9% higher than those estimated by previous methods and were shown to benefit from tail wind. This study shows how a combination of ship-based surveys and individually tagged birds can help understanding predator-prey intersection in a three-dimensional space in the marine environment.

  12. Arctic hydroclimatology

    NASA Astrophysics Data System (ADS)

    Cherry, Jessica Ellen

    Arctic air temperature, precipitation, ground temperature, river runoff, clouds, and radiation are all changing quickly in a warming climate. Interactions and feedbacks between these features are not well understood. In particular, the relative role of local climate processes and large-scale ocean-atmosphere dynamics in driving observed Arctic changes is difficult to ascertain because of the sparsity of observations, inaccuracy of those that do exist, biases in global circulation models and analyses, and fundamental physics of the Arctic region. Four studies of Arctic hydroclimatology herein attempt to overcome these challenges. The first study, analysis of the Lena river basin hydroclimatology, shows canonical acceleration of the hydrologic cycle and amplification of global warming. Winter and spring are warming and increased frozen precipitation is contributing to permafrost melting by increasing soil insulation. Increasing runoff and soil moisture is leading to increasing evapotranspiration and changes in clouds. Changes in clouds are cooling summer days but warming summer nights, melting additional permafrost. Model simulations suggests that a deepening active layer will lead to an increasingly wet Arctic. The second two studies describe the development of the Pan-Arctic Snowfall Reconstruction (PASR). This product addresses the problem of cold season precipitation gauge biases for 1940-1999. The NASA Interannual-to-Seasonal Prediction Project Catchment-based Land Surface Model is used to reconstruct solid precipitation from observed snow depth and surface air temperatures. Error estimation is done via controlled simulations at Reynolds Creek Experimental Watershed, in Idaho. The method is then applied to stations in the pan-Arctic hydrological catchment. Comparison with existing products suggests that the PASR is a better estimate of actual snowfall for hydroclimatological studies. The final chapter is a case study on hydroclimatological variability driven by

  13. Energy and water additions give rise to simple responses in plant canopy and soil microclimates of a high arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Sullivan, Patrick F.; Welker, Jeffrey M.; Steltzer, Heidi; Sletten, Ronald S.; Hagedorn, Birgit; Arens, Seth J. T.; Horwath, Jennifer L.

    2008-09-01

    Energy and water inputs were increased during the snow-free season to test the sensitivity of a cold, dry ecosystem to climate change. Infrared radiators were used to provide two levels of supplemental radiation (T1 and T2) to prostrate dwarf-shrub, herb tundra in northwest Greenland. The higher radiation addition was combined with supplemental water in a factorial design. Radiation additions increased midday canopy temperatures by up to 4.0°C and 6.0°C and growing season mean shallow soil temperatures by 1.3°C and 2.4°C in T1 and T2 plots, respectively. Soil warming was measured at and probably exceeded 10 cm in depth. There was no evidence of soil drying in plots that received additional radiation, in contrast with other studies, nor was there evidence that supplemental water interacted with radiation additions to affect soil temperatures. Water additions were generally undetectable against a background of large seasonal changes in soil water content. We suggest that well-drained soils and strong seasonal controls on soil water contents (e.g., soil thaw and evapotranspiration) limit the system's sensitivity to changes in precipitation during the brief growing season. In general, multifactor changes in climate gave rise to simple changes in the vegetation microclimate of this cold, dry ecosystem.

  14. Ecosystem function and particle flux dynamics across the Mackenzie Shelf (Beaufort Sea, Arctic Ocean): an integrative analysis of spatial variability and biophysical forcings

    NASA Astrophysics Data System (ADS)

    Forest, A.; Babin, M.; Stemmann, L.; Picheral, M.; Sampei, M.; Fortier, L.; Gratton, Y.; Bélanger, S.; Devred, E.; Sahlin, J.; Doxaran, D.; Joux, F.; Ortega-Retuerta, E.; Jeffrey, W. H.; Martín, J.; Gasser, B.; Miquel, J. C.

    2012-08-01

    A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here, we combine mooring times-series, ship-based measurements and remote-sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their biophysical determinants in summer. Flux data were obtained with sediment traps and via a regional empirical algorithm applied to particle size-distributions (17 classes from 0.08-4.2 mm) measured by an Underwater Vision Profiler 5. Redundancy analyses and forward selection of abiotic/biotic parameters, linear trends, and spatial structures (i.e. principal coordinates of neighbor matrices, PCNM), were conducted to partition the variation of POC flux size-classes. Flux variability was explained at 69.5 % by the addition of a linear temporal trend, 7 significant PCNM and 9 biophysical variables. The interaction of all these factors explained 27.8 % of the variability. The first PCNM canonical axis (44.4 % of spatial variance) reflected a shelf-basin gradient controlled by bottom depth and ice concentration (p < 0.01), but a complex assemblage of fine-to-broad scale patterns was also identified. Among biophysical parameters, bacterial production and northeasterly wind (upwelling-favorable) were the two strongest explanatory variables (r2 cum. = 0.37), suggesting that bacteria were associated with sinking material, which was itself partly linked to upwelling-induced productivity. The second most important spatial structure corresponded actually to the two areas where shelf break upwelling is known to occur under easterlies. Copepod biomass was negatively correlated (p < 0.05) with vertical POC fluxes, implying that metazoans played a significant role in the regulation of export fluxes. The low fractal dimension of settling particles (1

  15. Pacific Northwest Laboratory Alaska (ARCTIC) research program

    SciTech Connect

    Hanson, W.C.; Eberhardt, L.E.

    1980-03-01

    The current program continues studies of arctic ecosystems begun in 1959 as part of the Cape Thompson Program. Specific ecosystem aspects include studies of the ecology of arctic and red foxes, small mammel and bird population studies, lichen studies, and radiation ecology studies. (ACR)

  16. Modelling regulation of decomposition and related root/mycorrhizal processes in arctic tundra soils. Final report

    SciTech Connect

    Linkins, A.E.

    1992-09-01

    Since this was the final year of this project principal activities were directed towards either collecting data needed to complete existing incomplete data sets or writing manuscripts. Data sets on Imnaviat Creek watershed basin are functionally complete and data finialized on the cellulose mineralizaiton and dust impact on soil organic carbon and phsophorus decomposition. Seven manuscripts were prepared, and are briefly outlined.

  17. A Binary Approach to Define and Classify Final Ecosystem Goods and Services

    EPA Science Inventory

    The ecosystem services literature decries the lack of consistency and standards in the application of ecosystem services as well as the inability of current approaches to explicitly link ecosystem services to human well-being. Recently, SEEA and CICES have conceptually identifie...

  18. Coupling of continuous in situ ecosystem water vapor, precipitation, plant and soil water isotope (δ2H, δ18O and d-excess) measurements in Arctic Alaska to understand a changing water cycle

    NASA Astrophysics Data System (ADS)

    Welker, J. M.; Klein, E. S.; Leffler, J.; Cherry, J. E.; Young, J. M.

    2013-12-01

    A changing Arctic water cycle is focusing our efforts on the patterns and processes governing the exchange of water between the land surface and the atmosphere. We initiated a NSF EAGER study of the changing Arctic water cycle with a cross-scale water isotope (ecosystem-landscape and region) study employing tower, aircraft and satellite measurements in N Alaska. At the land surface, we measured in situ, continuous ecosystem δ2H and δ18O in water vapor isotopes along a vertical profile (0.1 to 3 m) in late winter, spring, and summer of 2013 at the Toolik Lake Field Station in Arctic Alaska. The continuous water vapor measurements are being combined with soil, plant and precipitation water isotope measurements, and species-level transpiration rates. Diurnal patterns of δ2H values in water vapor vary systematically from the soil surface, through the plant canopy and in the near boundary layer ranging between -200 ‰ at the surface to -240 ‰ at 3 m. These vertical patterns were also observed in d-excess ranging from 5 ‰ near the soil surface to -15 ‰ at 3 m. These patterns disappeared at night indicating their link with evapotranspiration. These data will serve as the foundation for a Bayesian model to articulate the sources, species, and processes governing the exchange of H2O with the lower boundary layer; and will also help to calibrate ecosystem, landscape (aircraft) and regional (satellite) measurements of the water vapor isotopes above different vegetation types (tussock tundra, riparian tundra, and recently burned tundra) and regions (Northern Foothills of the Brooks Range and the Arctic Coastal Plain). Continuous water vapor isotope traits in Arctic Tundra from the soil surface (0.02 m) to 3 m above the tundra for a window of time during the 2013 growing season. The diurnal patterns depict the evidence for transpiration and evaporation as the values above the soil (0.02 m) and in the canopy (0.2m) are enriched during the day and become depleted during

  19. State of the Arctic Coast 2010: Scientific Review and Outlook

    NASA Astrophysics Data System (ADS)

    Rachold, V.; Forbes, D. L.; Kremer, H.; Lantuit, H.

    2010-12-01

    The coast is a key interface in the Arctic environment. It is a locus of human activity, a rich band of biodiversity, critical habitat, and high productivity, and among the most dynamic components of the circumpolar landscape. The Arctic coastal interface is a sensitive and important zone of interaction between land and sea, a region that provides essential ecosystem services and supports indigenous human lifestyles; a zone of expanding infrastructure investment and growing security concerns; and an area in which climate warming is expected to trigger landscape instability, rapid responses to change, and increased hazard exposure. Starting with a collaborative workshop in October 2007, the International Arctic Science Committee (IASC), the Land-Ocean Interactions in the Coastal Zone (LOICZ) Project and the International Permafrost Association (IPA) decided to jointly initiate an assessment of the state of the Arctic coast. The goal of this report is to draw on initial findings regarding climate change and human dimensions for the Arctic as a whole provided by the Arctic Climate Impact Assessment (ACIA) and Arctic Human Development Report (AHDR) to develop a comprehensive picture of status and current and anticipated change in the most sensitive Arctic coastal areas. Underlying is the concept of a social ecological system perspective that explores the implications of change for the interaction of humans with nature. The report is aimed to be a first step towards a continuously updated coastal assessment and to identify key issues seeking future scientific concern in an international Earth system research agenda. The report titled “State of the Arctic Coast 2010: Scientific Review and Outlook” is the outcome of this collaborative effort. It is organized in three parts: the first provides an assessment of the state of Arctic coastal systems under three broad disciplinary themes - physical systems, ecological systems, and human concerns in the coastal zone; the

  20. Connecting nitrogen deposition and Final Ecosystem Goods and Services for air quality standards review

    EPA Science Inventory

    There has been a great deal of effort to document changes in ecosystem structure and function in response to increasing or decreasing N deposition, yet less work connects the specific effects on the value to people of these changes in the ecosystem. Although there are studies ta...

  1. Ecosystem function and particle flux dynamics across the Mackenzie Shelf (Beaufort Sea, Arctic Ocean): an integrative analysis of spatial variability and biophysical forcings

    NASA Astrophysics Data System (ADS)

    Forest, A.; Babin, M.; Stemmann, L.; Picheral, M.; Sampei, M.; Fortier, L.; Gratton, Y.; Bélanger, S.; Devred, E.; Sahlin, J.; Doxaran, D.; Joux, F.; Ortega-Retuerta, E.; Martín, J.; Jeffrey, W. H.; Gasser, B.; Miquel, J. Carlos

    2013-05-01

    A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here we combine mooring times series, ship-based measurements and remote sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their determinants in summer. Flux data were obtained with sediment traps moored around 125 m and via a regional empirical algorithm applied to particle size distributions (17 classes from 0.08-4.2 mm) measured by an Underwater Vision Profiler 5. The low fractal dimension (i.e., porous, fluffy particles) derived from the algorithm (1.26 ± 0.34) and the dominance (~ 77%) of rapidly sinking small aggregates (< 0.5 mm) in total fluxes suggested that settling material was the product of recent aggregation processes between marine detritus, gel-like substances, and ballast minerals. Modeled settling velocity of small and large aggregates was, respectively, higher and lower than in previous studies within which a high fractal dimension (i.e., more compact particles) was consequential of deep-trap collection (~400-1300 m). Redundancy analyses and forward selection of abiotic/biotic parameters, linear trends, and spatial structures (i.e., principal coordinates of neighbor matrices, PCNM) were conducted to partition the variation of the 17 POC flux size classes. Flux variability was explained at 69.5% by the addition of a temporal trend, 7 significant PCNM, and 9 biophysical variables. The first PCNM canonical axis (44.5% of spatial variance) reflected the total magnitude of POC fluxes through a shelf-basin gradient controlled by bottom depth and sea ice concentration (p < 0.01). The second most important spatial structure (5.0%) corresponded to areas where shelf break upwelling is known to occur under easterlies and where phytoplankton was

  2. Response of plants and ecosystems to CO{sub 2} and climate change. Final technical report

    SciTech Connect

    Reynolds, J.F.

    1993-12-31

    In recognition of the important role of vegetation in the bio-geosphere carbon cycle, the Carbon Dioxide Research Program of the US Department of Energy established the research program: Direct Effects of increasing Carbon Dioxide on Vegetation. The ultimate goal is to develop a general ecosystem model to investigate, via hypothesis testing, the potential responses of different terrestrial ecosystems to changes in the global environment over the next century. The approach involves the parallel development of models at several hierarchical levels, from the leaf to the ecosystem. At the plant level, mechanism and the direct effects of CO{sub 2} in the development of a general plant growth model, GEPSI - GEneral Plant SImulator has been stressed. At the ecosystem level, we have stressed the translation Of CO{sub 2} effects and other aspects of climate change throughout the ecosystem, including feedbacks and constraints to system response, in the development of a mechanistic, general ecosystem model SERECO - Simulation of Ecosystem Response to Elevated CO{sub 2} and Climate Change has been stressed.

  3. Modeling the response of plants and ecosystems to CO{sub 2} and climate change. Final technical report, September 1, 1992--August 31, 1996

    SciTech Connect

    Reynolds, J.F.

    1998-04-10

    Objectives can be divided into those for plant modeling and those for ecosystem modeling and experimental work in support of both. The author worked in a variety of ecosystem types, including pine, arctic, desert, and grasslands. Plant modeling objectives are: (1) to construct generic models of leaf, canopy, and whole-plant response to elevated CO{sub 2} and climate change; (2) to validate predictions of whole-plant response against various field studies of elevated CO{sub 2} and climate change; (3) to use these models to test specific hypotheses and to make predictions about primary, secondary and tertiary effects of elevated CO{sub 2} and climate change on individual plants for conditions and time frames beyond those used to calibrate the model; and (4) to provide information to higher-level models, such as community models and ecosystem models. Ecosystem level modeling objectives are: (1) to incorporate models of plant responses to elevated CO{sub 2} into a generic ecosystem model in order to predict the direct and indirect effects of elevated CO{sub 2} and climate change on ecosystems; (2) to validate model predictions of total system-level response (including decomposition) against various ecosystem field studies of elevated CO{sub 2} and climate change; (3) to use the ecosystem model to test specific hypotheses and to make predictions about primary, secondary and tertiary effects of elevated CO{sub 2} and climate change on ecosystems for conditions and time frames beyond those used to calibrate the model; and (4) to use the ecosystem model to study effects of change in CO{sub 2} and climate at regional and global scales. Occasionally the author conducted some experimental work that was deemed important to the development of the models. This work was mainly physiological work that could be performed in the Duke University Phytotron, using existing facilities.

  4. Hydrological Controls on Ecosystem CO2 and CH4 Exchange in a MIXED Tundra and a FEN within an Arctic Landscape UNDER Current and Future Climates

    NASA Astrophysics Data System (ADS)

    Grant, R. F.; Humphreys, E.; Lafleur, P.

    2014-12-01

    Variation in CO2 and CH4 exchange in years with contrasting weather is strongly affected by hydrology in landscapes underlain by permafrost. Hypotheses for this variation were incorporated into the ecosystem model ecosys which simulated CO2 and CH4 fluxes along a topographic gradient within an arctic landscape at Daring Lake, NWT, Canada. Fluxes modelled at mixed tundra and fen sites within the gradient were compared with CO2 fluxes measured at eddy covariance towers from 2006 to 2009, and with CH4 fluxes measured with surface chambers in 2008. Slopes and correlation coefficients from regressions of modelled vs. measured CO2 fluxes were 1.0 ± 0.1 and 0.7 - 0.8 for both sites in all years. At the mixed tundra site, rises in net CO2 uptake in warmer years with earlier snowmelt were constrained by midafternoon declines in CO2 influxes when vapor pressure deficits (D) exceeded 1.5 kPa, and by rises in CO2 effluxes with greater active layer depth (ALD). Consequently annual net CO2 uptake at this site rose little with warming. At the fen site, CO2 influxes declined less with D and CO2 effluxes rose less with warming, so that rises in net CO2 uptake in warmer years were greater than those at the mixed tundra site. The greater declines in CO2 influxes with warming at the mixed tundra site were modelled from greater soil-plant-atmosphere water potential gradients that developed in drier soil, and the smaller rises in CO2 effluxes with warming at the fen site were modelled from O2 constraints to heterotrophic and below-ground autotrophic respiration that limited their responses to greater ALD. Modelled and measured CH4 exchange during July and August indicated very small influxes at the mixed tundra site, and larger emissions at the fen site. Emissions of CH4 modelled during soil freezing in October - November contributed about one-third of the annual total, and so should be included in estimates of annual emissions. These contrasting responses to warming under current

  5. USGS Arctic science strategy

    USGS Publications Warehouse

    Shasby, Mark; Smith, Durelle

    2015-01-01

    The United States is one of eight Arctic nations responsible for the stewardship of a polar region undergoing dramatic environmental, social, and economic changes. Although warming and cooling cycles have occurred over millennia in the Arctic region, the current warming trend is unlike anything recorded previously and is affecting the region faster than any other place on Earth, bringing dramatic reductions in sea ice extent, altered weather, and thawing permafrost. Implications of these changes include rapid coastal erosion threatening villages and critical infrastructure, potentially significant effects on subsistence activities and cultural resources, changes to wildlife habitat, increased greenhouse-gas emissions from thawing permafrost, threat of invasive species, and opening of the Arctic Ocean to oil and gas exploration and increased shipping. The Arctic science portfolio of the U.S. Geological Survey (USGS) and its response to climate-related changes focuses on landscapescale ecosystem and natural resource issues and provides scientific underpinning for understanding the physical processes that shape the Arctic. The science conducted by the USGS informs the Nation's resource management policies and improves the stewardship of the Arctic Region.

  6. SCARS operations final report for the NORESS and ARCESS arrays. [System Control And Receiving Station (SCARS), Norwegian Experimental Seismic System (NORESS), Arctic Experimental Seismic System (ARCESS)

    SciTech Connect

    Harrer, S.J.

    1992-05-01

    This SCARS (System Control and Receiving Station) Operations Final Report for the Norwegian Experimental Seismic System (NORESS) and Arctic Experimental Seismic System (ARCESS) Arrays is a history of the operations of these projects. It is intended for those who were directly involved in the NORESS and ARCESS projects, as well as for those who are involved in similar projects. Included is a description of the locations and configuration of each array, the function and performance of the field systems, and a summation of the wide range of tasks performed at SCARS.

  7. FINAL REPORT. ENVIRONMENTAL ANALYSIS OF ENDOCRINE DISRUPTING EFFECTS FROM HYDROCARBON CONTAMINANTS IN THE ECOSYSTEM

    EPA Science Inventory

    The objective of this project was to determine howenvironmental contaminants, namely hydrocarbons, act as hormones or anti- hormones in different species present in aquatic ecosystems. The three major components of the research included:1)a biotechnology based screening system ...

  8. Final Technical Report: Response of Mediterranean-Type Ecosystems to Elevated Atmospheric CO2 and Associated Climate Change

    SciTech Connect

    Oechel, Walter C

    2002-08-15

    This research incorporated an integrated hierarchical approach in space, time, and levels of biological/ecological organization to help understand and predict ecosystem response to elevated CO{sub 2} and concomitant environmental change. The research utilized a number of different approaches, and collaboration of both PER and non-PER investigators to arrive at a comprehensive, integrative understanding. Central to the work were the CO{sub 2}-controlled, ambient Lit, Temperature controlled (CO{sub 2}LT) null-balance chambers originally developed in the arctic tundra, which were re-engineered for the chaparral with treatment CO{sub 2} concentrations of from 250 to 750 ppm CO{sub 2} in 100 ppm increments, replicated twice to allow for a regression analysis. Each chamber was 2 meters on a side and 2 meters tall, which were installed over an individual shrub reprouting after a fire. This manipulation allowed study of the response of native chaparral to varying levels of CO{sub 2}, while regenerating from an experimental burn. Results from these highly-controlled manipulations were compared against Free Air CO{sub 2} Enrichment (FACE) manipulations, in an area adjacent to the CO{sub 2}LT null balance greenhouses. These relatively short-term results (5-7 years) were compared to long-term results from Mediterranean-type ecosystems (MTEs) surrounding natural CO{sub 2} springs in northern Italy, near Laiatico, Italy. The springs lack the controlled experimental rigor of our CO{sub 2}LT and FACE manipulation, but provide invaluable validation of our long-term predictions.

  9. Arctic Clouds

    Atmospheric Science Data Center

    2013-04-19

    ...     View Larger Image Stratus clouds are common in the Arctic during the summer months, and are ... formats available at JPL August 23, 2000 - Stratus clouds help modulate the arctic climate. project:  ...

  10. A coupled approach to spatially derived parameters necessary for ecosystem modeling on the North Slope of Alaska: Appendix A. Final report, March 1, 1989--February 28, 1993

    SciTech Connect

    Petersen, G.W.; Day, R.L.; Pollack, J.

    1993-12-01

    This study concerned an investigation of ecosystem dynamics in several small study sites in the North Slope region of Alaska. The scope of the proposed research is to quantitatively determine spatial interrelationships between landform geometry within these study areas and such ecologically important factors as vegetation type, depth-to-permafrost, hydraulic conductivity and incoming solar radiation. Extrapolation techniques developed and terrain-related data generated as a result of this research will augment R4D Phase II goals which relate to running the General Arctic Simulac (GAS) model (and associated ecosystem models) at different locations on the North Slope. In particular, Penn State has contributed significantly to extrapolation efforts by developing techniques which can be used to initialize conditions for model input either through direct measurement (e.g., slope and aspect) and GIS-based simulation models (e.g., drainage basin characterization). As stated in the R4D Phase II Research Plan, the long-term objectives of this program are: (1) to determine effects and to develop models based on ecosystem disturbances commonly created by energy development so that appropriate, cost-effective measures can be utilized to minimize deleterious disturbances; and (2) to extend the results to other arctic and alpine areas which are important because of likely impact from energy development. It is this second long-term objective which relates most directly to Penn State`s work.