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Sample records for alaska arctic tundra

  1. Tundra Rehabilitation in Alaska's Arctic

    NASA Astrophysics Data System (ADS)

    Lynn, L. A.

    2012-12-01

    Oil exploration in Alaska's Arctic has been conducted for more than 40 years, resulting in over 3,640 ha of gravel fill placed for roads, pads, and airstrips to support the industry. Likewise, tundra disturbance from burying power lines and by tundra vehicle travel are also common. Rehabilitation of disturbed sites began around 2002, with well over 150 ha that has been previously treated or is currently being rehabilitated. Two primary goals of rehabilitation efforts have been 1) revegetation by indigenous species, and 2) limiting thermokarst. Early efforts were concerned that removing gravel and having exposed bare ground would lead to extensive subsidence and eolian erosion. Native grass cultivars (e.g. Poa glauca, Arctagrostis latifolia, and Festuca rubra) were seeded to create vegetation cover quickly with the expectation that these grasses would survive only temporarily. The root masses and leaf litter were also expected to trap indigenous seed to enhance natural recolonization by indigenous plants. Due to the remote location of these sites, many of which are only accessible by helicopter, most are visited only two to three times following cultivation treatments, providing a limited data pool. At many sites, the total live seeded grass cover declined about 15% over the first 5¬-6 years (from around 30% to 15% cover), while total live indigenous vascular cover increased from no or trace cover to an average of 10% cover in that time. Cover of indigenous vascular plants at sites that were not seeded with native grass cultivars averaged just less than 10% after 10 years, showing no appreciable difference between the two approaches. Final surface elevations at the sites affect local hydrology and soil moisture. Other factors that influence the success of vegetation cover are proximity to the Arctic coast (salt effects), depth of remaining gravel, and changes in characteristics of the near-surface soil. Further development of rehabilitation techniques and the

  2. Willow Shrub Expansion Following Tundra Fires in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Racine, C.

    2010-12-01

    Climate warming in the Arctic is predicted to result in the expansion of woody shrubs and increased frequency and size of tundra fires. How will fire influence this shrub expansion? Over a period of 32 years, following a 1977 tundra fire in the central Seward Peninsula, we sampled seven times the post-fire vegetation at eight permanently marked sites on a long (2 Km) hillslope (Nimrod Hill). We had previously sampled vegetation here in 1973 prior to the fire. By 2001, 24 years post-fire conspicuous willow shrubs (mostly Salix pulchra) had increased in numbers, size and cover over the entire slope in moist tussock-shrub tundra, well-drained heath, and wet meadow. Prior to fire, willow on this slope was largely restricted to small drainages or watertracks. Willows here have originated from both seed and vegetative resprouting - the latter mostly in moist tussock-shrub tundra from willows resprouting within one to three years post-fire. With fire-induced removal of vascular plant competition and Spagnum moss cover and litter in tussock-shrub tundra, both seedling and resprouting willows have grown rapidly to overtop tussocks by 30-40 cm. Similar rapid post-fire resprouting of willows has been observed in tussock-shrub tundra after the 2007 Anaktuvuk River tundra fire and after the 1977 tundra fires in the Noatak River basin. On Nimrod Hill the most striking willow expansion has occurred on the severely burned and well-drained backslope where willow establishment from seed 5-10 years after fire has resulted in up to 40% cover of rapidly growing willows of both upright and spreading growth form. At several sites along the slope there is evidence of continuing willow expansion from seedlings 24 to 32 years post-fire, when we might expect the effects of fire on seedbeds would have ceased. We conclude that tundra fire may promote shrub expansion in the Arctic.

  3. Analysis of state of vehicular scars on Arctic Tundra, Alaska

    NASA Technical Reports Server (NTRS)

    Lathram, E. H.

    1974-01-01

    Identification on ERTS images of severe vehicular scars in the northern Alaska tundra suggests that, if such scars are of an intensity or have spread to a dimension such that they can be resolved by ERTS sensors (20 meters), they can be identified and their state monitored by the use of ERTS images. Field review of the state of vehicular scars in the Umiat area indicates that all are revegetating at varying rates and are approaching a stable state.

  4. 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

  5. Initial Conceptualization and Simulation of Arctic Tundra Landscape Evolution Using the Alaska Thermokarst Model

    NASA Astrophysics Data System (ADS)

    Bolton, W. R.; Romanovsky, V. E.; McGuire, A. D.; Grosse, G.; Lara, M. J.

    2014-12-01

    Thermokarst topography forms whenever ice-rich permafrost thaws and the ground subsides due to the volume loss when excess ground ice transitions to water. The Alaska Thermokarst Model (ATM) is a large-scale, state-and-transition model designed to simulate transitions between [non-]thermokarst landscape units, or cohorts. The ATM uses a frame-based methodology to track transitions and proportion of cohorts within a 1-km2 grid cell. In the arctic tundra environment, the ATM tracks thermokarst-related transitions between wetland tundra, graminoid tundra, shrub tundra, and thermokarst lakes. The transition from one cohort to another due to thermokarst processes can take place if thaw reaches ice-rich ground layers either due to pulse disturbance events such as a large precipitation event or fires or due to gradual active layer deepening that eventually results in penetration of the protective layer. The protective layer buffers the ice-rich soils from the land surface and is critical to determine how susceptible an area is to thermokarst degradation. The rate of terrain transition in our model is determined by the ice-content of the soil, the drainage efficiency (or ability of the landscape to store or transport water), and a cumulative probability of thermokarst initiation. Tundra types are allowed to transition from one type to another (ie wetland tundra to a graminoid tundra) under favorable climatic conditions. In this study, we present our conceptualization and initial simulation results from the ATM model for an 1792 km2 area on the Barrow Peninsula, Alaska. The area selected for simulation is located in a polygonal tundra landscape under varying degrees of thermokarst degradation. The goal of this modeling study is to simulate landscape evolution in response to thermokarst disturbance as a result of climate change. The ATM will eventually be incorporated into the Integrated Ecosystem Model (IEM) for Alaska and Northwest Canada for use in management decisions

  6. Succession Stages of Tundra Plant Communities Following Wildfire Disturbance in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Breen, A. L.; Hollingsworth, T. N.; Mack, M. C.; Jones, B. M.

    2015-12-01

    Rapid climate change is affecting climate-sensitive disturbance regimes throughout the world. In particular, the impacts of climate change on Arctic disturbance regimes are poorly understood because landscape-scale disturbances are infrequent or occur in remote localities. Wildfire in Arctic Alaska is presently limited by ignition source and favorable burn weather. With rapid climate change, a lengthening growing season, and subsequent increase in plant biomass and productivity, wildfire frequency and annual area burned in tundra ecosystems is expected to increase over the next century. Yet, post-fire tundra vegetation succession is inadequately characterized except at a few point locations. We identify succession stages of tussock tundra communities following wildfire using a chronosequence of 65 relevés in 10 tundra fire scars (1971-2011) and nearby unburned tundra from sites on the Seward Peninsula and northern foothills of the Brooks Range. We used the Braun-Blanquét approach to classify plant communities, and applied nonmetric multidimentional scaling (NMDS) to identify ecological gradients underlying community differentiation. The ordination revealed a clear differentiation between unburned and burned tundra communities. Ecological gradients, reflected by ordination axes, correspond to fire history (e.g., time since last fire, number of times burned, burn severity) and a complex productivity gradient. Post-fire species richness is less than unburned tundra; primarily reflected as a decrease in lichen species and turnover of bryophyte species immediately post-fire. Species richness of grasses increases post-fire and is greatest in communities that burned more than once in the past 30 years. Shrub cover and total aboveground biomass are greatest in repeat burn sites. We review and discuss our results focusing on the implications of a changing tundra fire regime, its effect on vegetation succession trajectories, and subsequent rates of carbon sequestration and

  7. THE HYDRAULIC CHARACTERISTICS AND GEOCHEMISTRY OF HYPORHEIC AND PARAFLUVIAL ZONES IN ARCTIC TUNDRA STREAMS, NORTH SLOPE, ALASKA

    EPA Science Inventory

    Sodium bromide and Rhodamine WT were used as conservative tracers to examine the hydrologic characteristics of seven tundra streams in Arctic Alaska, during the summers of 1994-1996. Continuous tracer additions were conducted in seven rivers ranging from 1st to 5th order with sam...

  8. Methane emissions from Alaska Arctic tundra - An assessment of local spatial variability

    NASA Technical Reports Server (NTRS)

    Morrissey, L. A.; Livingston, G. P.

    1992-01-01

    The findings of an extensive midsummer survey of CH4 emissions measurements representing the Alaska Arctic tundra are presented. Variability in rates of emissions was similar in magnitude on local and regional scales, ranging from 0 to 286.5 mg/sq m/d overall and often varying across two orders of magnitude within 0.5 m distances. Primary control on rates of emission was determined by the substrate and position of the water table relative to the surface. Emission rates in the Arctic Foothills ranged from 0.2 mg/sq m/d for tussock tundra to 55.53 mg/sq m/d over wet meadows. Plant-mediated release of CH4 to the atmosphere was directly proportional to green leaf area and represented 92-98 percent of the total emission rates over vegetated sites. The results suggest the current published emission rates may have overestimated the contribution of boreal ecosystems to the global CH4 budget by several fold.

  9. Long-Term Perspectives of Shrub Expansions and Peat Initiation in Arctic Tundra on the North Slope of Alaska

    NASA Astrophysics Data System (ADS)

    Cleary, K.; Yu, Z.

    2014-12-01

    The ongoing climate warming in the Arctic has caused rapid terrestrial ecosystem changes, including shrub expansion and permafrost thaw. Here we used results from a peat-accumulating permafrost tundra in upper Imnavait Creek on the Arctic foothills of Alaska (68° 36' N, 149° 18' W) to investigate ecological responses to recent climate warming in the context of the last millennium. Six peat soil cores were collected from Sphagnum mosaics along an elevational gradient from 906 m to 950 m on a hillslope covered by Eriophorum-dominated tussock tundra. Macrofossil analysis documents a consistent development sequence among all cores from a mineral soil to a minerotrophic sedge peat and finally to an ombrotrophic Sphagnum peat. The 14C dating results show the ages of peat initiation range from about 900 to 140 cal BP, but do not follow the elevation gradient, suggesting the dominant control of local factors. The Sphagnum onset begins at 1820 AD near the ridge top, and subsequently propagates downslope to the floodplain at 2008 AD. This transition (ombrotrophication) was likely in response to Arctic warming, and subsequent permafrost thaw and active layer thickening, leading to drying initiating at the ridge top and facilitating Sphagnum colonization. Pollen analysis of the master core UIC13-3 at 916 m elevation (basal age 700 cal BP) shows that the vegetation was dominated by sedges (up to 84%) during the cool Little Ice Age until 1800 AD, followed by increases in shrubs first from dwarf birch (Betula nana) (up to 57%) and then willows (Salix spp.) up to 62% in the 1960s. These results indicate that shrub expansion of willows, due to accelerated warming in recent decades, was preceded by birch expansion over the last two centuries. Our new results provide a long-term perspective on ecological transformations in the Arctic, in particular the history of recent shrub expansions and the process of peatland initiation and expansion across Arctic tundra.

  10. Two-source energy balance model implementation in the Alaska Arctic tundra

    NASA Astrophysics Data System (ADS)

    Cristóbal-Rosselló, J.; Prakash, A.; Anderson, M. C.; Kustas, W. P.; Kane, D. L.

    2014-12-01

    Evaporation and transpiration are the two main processes involved in water transfer from vegetated and non-vegetated areas to the atmosphere. Evapotranspiration (ET) from the Earth's vegetation constitutes 88% of the total terrestrial ET, and returns more than 50% of terrestrial precipitation to the atmosphere (Oki and Kane, 2006); therefore it plays a key role in both the hydrological cycle and the energy balance of the land surface. In Arctic regions, surface-atmosphere exchanges due to ET are estimated from water balance computations to be about 74% of summer precipitation or 50% of annual precipitation. Even though ET is a significant component of the hydrologic cycle in this region, these bulk estimates do not accurately account for spatial and temporal variability due to vegetation type, topography, etc. (Kane and Yang, 2004). In this work we present the implementation of the Two-Source Energy Balance method, TSEB (Norman et al., 1995), in two Alaska Arctic tundra settings, as a base-line to retrieve energy fluxes at the regional scale from remote sensing imagery. In order to calibrate and validate the model, four flux towers located at the Imanvait Creek and the Anaktuvuk river were used. The TSEB model mainly requires meteorological inputs as well as land surface temperature (LST) and leaf area index (LAI) data. In this study, TSEB was run from late May to early September from 2008 to 2011 in all sky conditions using half hour intervals of meteorological data from the flux tower, and the LST derived from the four component net radiation instrument. TERRA/AQUA MODIS LAI daily product (MOD15/MYD15) was used as LAI input data. Results show an acceptable agreement between the TSEB model and flux tower data. RMSE obtained in the case of net radiation, latent heat, sensible heat and soil heat fluxes was 12, 51, 60 and 27 W/m2. Further efforts will be focused on the daily energy flux integration through implementation of the DTD model (Norman et al., 2000).

  11. Effect of thaw depth on fluxes of CO₂ and CH₄ in manipulated Arctic coastal tundra of Barrow, Alaska.

    PubMed

    Kim, Yongwon

    2015-02-01

    Changes in CO₂ and CH₄ emissions represent one of the most significant consequences of drastic climate change in the Arctic, by way of thawing permafrost, a deepened active layer, and decline of thermokarst lakes in the Arctic. This study conducted flux-measurements of CO₂ and CH₄, as well as environmental factors such as temperature, moisture, and thaw depth, as part of a water table manipulation experiment in the Arctic coastal plain tundra of Barrow, Alaska during autumn. The manipulation treatment consisted of draining, controlling, and flooding treated sections by adjusting standing water. Inundation increased CH₄ emission by a factor of 4.3 compared to non-flooded sections. This may be due to the decomposition of organic matter under a limited oxygen environment by saturated standing water. On the other hand, CO₂ emission in the dry section was 3.9-fold higher than in others. CH₄ emission tends to increase with deeper thaw depth, which strongly depends on the water table; however, CO₂ emission is not related to thaw depth. Quotients of global warming potential (GWPCO₂) (dry/control) and GWPCH₄ (wet/control) increased by 464 and 148%, respectively, and GWPCH₄ (dry/control) declined by 66%. This suggests that CO₂ emission in a drained section is enhanced by soil and ecosystem respiration, and CH₄ emission in a flooded area is likely stimulated under an anoxic environment by inundated standing water. The findings of this manipulation experiment during the autumn period demonstrate the different production processes of CO₂ and CH₄, as well as different global warming potentials, coupled with change in thaw depth. Thus the outcomes imply that the expansion of tundra lakes leads the enhancement of CH₄ release, and the disappearance of the lakes causes the stimulated CO₂ production in response to the Arctic climate change. PMID:25461040

  12. Effect of Thaw Depth on Fluxes of CO2 and CH4 in Manipulated Arctic Coastal Tundra of Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Kim, Y.

    2014-12-01

    Changes in CO2 and CH4 emissions represent one of the most significant consequences of drastic climate change in the Arctic, by way of thawing permafrost, a deepened active layer, and decline of thermokarst lakes in the Arctic. This study conducted flux-measurements of CO2 and CH4, as well as environmental factors such as temperature, moisture, and thaw depth, as part of a water table manipulation experiment in the Arctic coastal plain tundra of Barrow, Alaska during autumn. The manipulation treatment consisted of draining, controlling, and flooding treated sections by adjusting standing water. Inundation increased CH4 emission by a factor of 4.3 compared to non-flooded sections. This may be due to the decomposition of organic matter under a limited oxygen environment by saturated standing water. On the other hand, CO2 emission in the dry section was 3.9-fold higher than in others. CH4 emission tends to increase with deeper thaw depth, which strongly depends on the water table; however, CO2 emission is not related to thaw depth. Quotients of global warming potential (GWPCO2) (dry/control) and GWPCH4 (wet/control) increased by 464 and 148 %, respectively, and GWPCH4 (dry/control) declined by 66 %. This suggests that CO2 emission in a drained section is enhanced by soil and ecosystem respiration, and CH4 emission in a flooded area is likely stimulated under an anoxic environment by inundated standing water. The findings of this manipulation experiment during the autumn period demonstrate the different production processes of CO2 and CH4, as well as different global warming potentials, coupled with change in thaw depth. Thus the outcomes imply that the expansion of tundra lakes leads the enhancement of CH4 release, and the disappearance of the lakes causes the stimulated CO2 production in response to the Arctic climate change.

  13. 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

  14. Net carbon exchange across the Arctic tundra-boreal forest transition in Alaska 1981-2000

    USGS Publications Warehouse

    Thompson, Catharine Copass; McGuire, A.D.; Clein, J.S.; Chapin, F. S., III; Beringer, J.

    2006-01-01

    Shifts in the carbon balance of high-latitude ecosystems could result from differential responses of vegetation and soil processes to changing moisture and temperature regimes and to a lengthening of the growing season. Although shrub expansion and northward movement of treeline should increase carbon inputs, the effects of these vegetation changes on net carbon exchange have not been evaluated. We selected low shrub, tall shrub, and forest tundra sites near treeline in northwestern Alaska, representing the major structural transitions expected in response to warming. In these sites, we measured aboveground net primary production (ANPP) and vegetation and soil carbon and nitrogen pools, and used these data to parameterize the Terrestrial Ecosystem Model. We simulated the response of carbon balance components to air temperature and precipitation trends during 1981-2000. In areas experiencing warmer and dryer conditions, Net Primary Production (NPP) decreased and heterotrophic respiration (R H ) increased, leading to a decrease in Net Ecosystem Production (NEP). In warmer and wetter conditions NPP increased, but the response was exceeded by an increase in R H ; therefore, NEP also decreased. Lastly, in colder and wetter regions, the increase in NPP exceeded a small decline in R H , leading to an increase in NEP. The net effect for the region was a slight gain in ecosystem carbon storage over the 20 year period. This research highlights the potential importance of spatial variability in ecosystem responses to climate change in assessing the response of carbon storage in northern Alaska over the last two decades. ?? Springer 2005.

  15. Disappearing Arctic Tundra Ponds: Assessing 60 Years of Change in the Barrow Peninsula, Alaska

    NASA Astrophysics Data System (ADS)

    Andresen, C.; Lougheed, V.

    2012-12-01

    Decadal hydrological changes of closed-basin tundra ponds in continuous permafrost fills a missing gap in arctic fresh water research. Furthermore, the lack of historic datasets and high resolution historical imagery adds to the challenge of understanding the long-term trends of these ecosystems. Given the dominance of these aquatic ecosystems in the Arctic landscape, documenting hydrological changes is important to understand carbon and energy balance, trophic energy flow, and biodiversity. We utilized historic aerial imagery from USGS archives of 1948 and modern high-resolution Quickbird imagery from 2008 to assess areal changes in arctic ponds over the past 60 years. Object-oriented classification was used to extract the areal extent of ponds and validated using a combination of ground-based measurements such as Kite Aerial Photography (KAP) and Differential Geographic Positioning System (DGPS). A total of 1120 ponds in different drained thaw lake basins (DTLB) distributed across the Barrow Peninsula were assessed. Analysis indicated a decline in total pond area and a decrease of 36% in the number of ponds, with change more pronounced in smaller ponds (<100m2). Aquatic plant cover data collected over a 40 year period (1970-2012) indicate that expansion of vegetation into the ponds may be a primary mechanism whereby ponds may experience infilling. Other mechanisms may include increased evaporation due to warmer and longer summers, transpiration from encroaching aquatic grasses and changes in precipitation patterns. However, images from additional years will be analyzed to separate out the roles of these variables on inter- versus intra-annual variability in pond surface area.

  16. Correlations between the Heterogeneity of Permafrost Thaw Depth and Vegetation in Boreal Forests and Arctic Tundra in Alaska.

    NASA Astrophysics Data System (ADS)

    Uy, K. L. Q.; Natali, S.; Kholodov, A. L.; Loranty, M. M.

    2015-12-01

    Global climate change induces rapid large scale changes in the far Northern regions of the globe, which include the thickening of the active layer of arctic and subarctic soils. Active layer depth, in turn, drives many changes to the hydrology and geochemistry of the soil, making an understanding of this layer essential to boreal forest and arctic tundra ecology. Because the structure of plant communities can affect the thermal attributes of the soil, they may drive variations in active layer depth. For instance, trees and tussocks create shade, which reduces temperatures, but also hold snow, which increases temperature through insulation; these aspects of vegetation can increase or decrease summer thaw. The goal of this project is to investigate correlations between the degree of heterogeneity of active layer depths, organic layer thickness, and aboveground vegetation to determine how these facets of Northern ecosystems interact at the ecosystem scale. Permafrost thaw and organic layer depths were measured along 20m transects in twenty-four boreal forest and tundra sites in Alaska. Aboveground vegetation along these transects was characterized by measuring tree diameter at breast height (DBH), tussock dimensions, and understory biomass. Using the coefficient of variation as a measure of heterogeneity, we found a positive correlation between thaw depth variability and tussock volume variability, but little correlation between the former and tree DBH variability. Soil organic layer depth variability was also positively correlated with thaw depth variability, but weakly correlated with tree and tussock heterogeneity. These data suggest that low vegetation and organic layer control the degree of variability in permafrost thaw at the ecosystem scale. Vegetation can thus affect the microtopography of permafrost and future changes in the plant community that affect vegetation heterogeneity will drive corresponding changes in the variability of the soil.

  17. Community Land Model (CLM) Assessment on Simulating and Analyzing Water, Carbon and Nitrogen Cycles in Arctic Coastal Tundra at Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Yuan, F.; Thornton, P. E.; King, A. W.; Ricciuto, D. M.; Post, W. M.

    2012-12-01

    Recent climate warming has been widely hypothesized to be one of primary contributors to shifting both biophysical and biological conditions of Arctic tundra ecosystem and thus water, carbon and nitrogen cycles. Both constrains on integrating multiple-scale observations scattered in various sources and comprehensive process-based model assessments on those may hinder our further and/or deepen understanding of climate impacts on Arctic tundra and their feedbacks. This preliminary study is to assess and improve, as needed, the Community Land Model (CLM-CN mode) on simulating soil water, temperature, nitrogen nutrient and other factors and their effects on soil-plant C stocks and/or fluxes in Arctic tundra at Barrow, Alaska. The model assessment is carried out by exploring and using data compiled from various researches, e.g., AmeriFlux, US/IBP, ITEX and others during past few decades in the area. We add a simple N emission subroutine in the current released CLM4 (in CESM1.0.4) and modify soil water drainage boundary conditions so that model can partially capture the landscape position effects of hydrological process on thermal and biogeochemical processes. We initially parameterize and initialize the model for Arctic tundra at Barrow, AK with 4 new plant functional types (PFTs): mosses, forbs, graminoids, and shrubs, based on literature study. It shows strong inter-annual variance of C fluxes, which tightly coupled with water, temperature and N nutrient dynamics. We then conduct a factory model experiments with drainage classes and varying PFT compositions in order to understand possible water, C and N cycle variations if vegetation changes over landscape. This preliminary analysis is of importance to apply for CLM model in this highly heterogeneous coastal Arctic tundra region under historical and projected climate changes.

  18. Changes in Algal Trends and Nutrient Budgets in Arctic Tundra Ponds Over the Past 40 Years in Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Hernandez, C.; Lougheed, V.

    2011-12-01

    In the 1970's, Barrow, Alaska was host to a detailed ecological study, the International Biological Program (IBP), which examined physical, chemical and biological characteristics of Arctic tundra ponds. Forty years later, this area has experienced warming and potential release of nutrients from permafrost; however, there have been no follow up studies since the 1970's and biological changes in these ponds remain unknown. The 1970's IBP research suggested that algae had warmer temperature optima than ambient temperatures and that phosphorus was the limiting nutrient. The goal of this study was to understand algal growth trends during the 2010 growing season, the role of limiting nutrients, and how both these have changed through time in light of shifting climate regimes. Algae was collected and quantified weekly from periphyton (attached to sediment) and phytoplankton (free-floating algae) from several IBP ponds over the summer of 2010. Nutrient addition and release experiments with known quantities of nitrogen (N) and phosphorus (P) were utilized to determine algal nutrient limitation. Algal biomass was significantly greater in 2010 than in the 1970s. Nutrient addition experiments showed a shift from phosphorus limitation in the 1970s to nitrogen limitation of periphyton in 2010, while phytoplankton was co-limited by nitrogen and phosphorus in 2010. These preliminary results indicate substantial changes have occurred over the past 40 years. Further studies are being completed in Summer 2011 to understand inter-annual variability in these trends and to reveal the implications of these trends in algal production and nutrient budgets in the Arctic.

  19. The Role of Explicitly Modeling Bryophytes in Simulating Carbon Exchange and Permafrost Dynamics of an Arctic Coastal Tundra at Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Yuan, F.; Thornton, P. E.; McGuire, A. D.; Oechel, W. C.; Yang, B.; Tweedie, C. E.; Rogers, A.; Norby, R. J.

    2013-12-01

    Bryophyte cover is greater than 50% in many Arctic tundra ecosystems. In regions of the Arctic where shrubs are expanding it is expected that bryophyte cover will be substantially reduced. Such a loss in cover could influence the hydrological, biogeochemical, and permafrost dynamics of Arctic tundra ecosystems. The explicit representation of bryophyte physiological and biophysical processes in large-scale ecological and land surface models is rare, and we hypothesize that the representation of bryophytes has consequences for estimates of the exchange of water, energy, and carbon by these models. This study explicitly represents the effects of bryophyte function and structure on the exchange of carbon (e.g., summer photosynthesis effects) and energy (e.g., summer insulation effects) with the atmosphere in the Community Land Model (CLM-CN). The modified model was evaluated for its ability to simulate C exchange, soil temperature, and soil moisture since the 1970s at Barrow, Alaska through comparison with data from AmeriFlux sites, USDA Soil Climate Networks observation sites at Barrow, and other sources. We also compare the outputs of the CLM-CN simulations with those of the recently developed Dynamical Organic Soil coupled Terrestrial Ecosystem Model (DOS-TEM). Overall, our evaluation indicates that bryophytes are important contributors to land-atmospheric C exchanges in Arctic tundra and that they play an important role to permafrost thermal and hydrological processes which are critical to permafrost stability. Our next step in this study is to examine the climate system effects of explicitly representing bryophyte dynamics in the land surface model. Key Words: Bryophytes, Arctic coastal tundra, Vegetation composition, Net Ecosystem Exchange, Permafrost, Land Surface Model, Terrestrial Ecosystem Model

  20. Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska

    PubMed Central

    Morgado, Luis N; Semenova, Tatiana A; Welker, Jeffrey M; Walker, Marilyn D; Smets, Erik; Geml, József

    2015-01-01

    Arctic regions are experiencing the greatest rates of climate warming on the planet and marked changes have already been observed in terrestrial arctic ecosystems. While most studies have focused on the effects of warming on arctic vegetation and nutrient cycling, little is known about how belowground communities, such as fungi root-associated, respond to warming. Here, we investigate how long-term summer warming affects ectomycorrhizal (ECM) fungal communities. We used Ion Torrent sequencing of the rDNA internal transcribed spacer 2 (ITS2) region to compare ECM fungal communities in plots with and without long-term experimental warming in both dry and moist tussock tundra. Cortinarius was the most OTU-rich genus in the moist tundra, while the most diverse genus in the dry tundra was Tomentella. On the diversity level, in the moist tundra we found significant differences in community composition, and a sharp decrease in the richness of ECM fungi due to warming. On the functional level, our results indicate that warming induces shifts in the extramatrical properties of the communities, where the species with medium-distance exploration type seem to be favored with potential implications for the mobilization of different nutrient pools in the soil. In the dry tundra, neither community richness nor community composition was significantly altered by warming, similar to what had been observed in ECM host plants. There was, however, a marginally significant increase in OTUs identified as ECM fungi with the medium-distance exploration type in the warmed plots. Linking our findings of decreasing richness with previous results of increasing ECM fungal biomass suggests that certain ECM species are favored by warming and may become more abundant, while many other species may go locally extinct due to direct or indirect effects of warming. Such compositional shifts in the community might affect nutrient cycling and soil organic C storage. PMID:25156129

  1. Summer temperature increase has distinct effects on the ectomycorrhizal fungal communities of moist tussock and dry tundra in Arctic Alaska.

    PubMed

    Morgado, Luis N; Semenova, Tatiana A; Welker, Jeffrey M; Walker, Marilyn D; Smets, Erik; Geml, József

    2015-02-01

    Arctic regions are experiencing the greatest rates of climate warming on the planet and marked changes have already been observed in terrestrial arctic ecosystems. While most studies have focused on the effects of warming on arctic vegetation and nutrient cycling, little is known about how belowground communities, such as fungi root-associated, respond to warming. Here, we investigate how long-term summer warming affects ectomycorrhizal (ECM) fungal communities. We used Ion Torrent sequencing of the rDNA internal transcribed spacer 2 (ITS2) region to compare ECM fungal communities in plots with and without long-term experimental warming in both dry and moist tussock tundra. Cortinarius was the most OTU-rich genus in the moist tundra, while the most diverse genus in the dry tundra was Tomentella. On the diversity level, in the moist tundra we found significant differences in community composition, and a sharp decrease in the richness of ECM fungi due to warming. On the functional level, our results indicate that warming induces shifts in the extramatrical properties of the communities, where the species with medium-distance exploration type seem to be favored with potential implications for the mobilization of different nutrient pools in the soil. In the dry tundra, neither community richness nor community composition was significantly altered by warming, similar to what had been observed in ECM host plants. There was, however, a marginally significant increase in OTUs identified as ECM fungi with the medium-distance exploration type in the warmed plots. Linking our findings of decreasing richness with previous results of increasing ECM fungal biomass suggests that certain ECM species are favored by warming and may become more abundant, while many other species may go locally extinct due to direct or indirect effects of warming. Such compositional shifts in the community might affect nutrient cycling and soil organic C storage. PMID:25156129

  2. 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

    The Arctic is one of the most rapidly changing biomes on earth. Research at the Toolik Field Station by the Arctic Long-Term Ecological Research project provides a perspective on changes that are impacting the upland tussock tundra region of the North Slope of Alaska, a region that is typical of ~15% of the arctic region. The arctic is responding to a combination of long-term, gradual changes (presses) and short-term, event-driven changes (pulses). The most important press, of course, is the persistent rise in average annual air temperature observed in most places (though not at Toolik). Associated with this increase in SAT is a well-documented increase in shallow permafrost temperature (which is observed around Toolik). Our long-term research shows that this trend will favor taller and more productive shrub and grass vegetation. Higher SAT translates to earlier spring breakup and later onset of winter. This change in seasonality is affecting interactions between shrub leaf-out, insect emergence, and bird nesting. Persistent and more frequent droughts are having important impacts on the ability of Arctic grayling - the top consumer is most upland tundra streams - to survive and has the potential to block their ability to migrate to essential overwintering lakes. The interaction between temperature (which is changing) and light (which is not) creates a "seasonal asynchrony" that may be increasing the loading of nutrients - notably nitrate - to upland tundra streams late in the season, with impacts that we do not fully understand yet. The upland tundra environment is also responding to an increasing frequency of pulses, most notably wildfires and the development of thermo-erosional failures (TEFs). Wildfires transfer large quantities of carbon and nitrogen directly to the atmosphere. TEFs may deliver large quantities of sediment and nutrients to streams and lakes. Currently these pulse disturbances seem to be having only limited, local impacts. However, as shallow

  3. Potential NEE Budget and Prediction of Future Emissions under Climate Change in an Arctic Wet Sedge Tundra, Barrow, Alaska .

    NASA Astrophysics Data System (ADS)

    Kalhori, A. A. M.; Oechel, W. C.; Burba, G. G.; Gioli, B.; Zona, D.; Murphy, P.; Goodrich, J. P.

    2015-12-01

    Arctic ecosystems are critically affected by climate change and also play an important role in the global carbon budget. Presented here is a 14-year study of growing season CO2 fluxes in an Alaskan wet sedge tundra ecosystem -which is about 2 km south of the Arctic Ocean and is adjacent to the NOAA Climate Monitoring & Diagnostic Laboratory (CMDL)- and the key environmental controls on these fluxes. We have measured net ecosystem exchange of CO2 (NEE) using the eddy covariance technique from 1998 to 2014 in order to quantify the long-term seasonal and inter-annual variability in the CO2 budget over this period. The WPL correction and the surface heating correction were applied to all CO2 flux data from the open-path instrument (Burba et al., 2008). Despite several gaps in measurement years, we found that growing season net CO2 uptake has significantly increased since the 2000s and that NEE is sensitive to dry conditions in tundra. Our data suggest this increase in CO2 uptake (larger than -6 μmol m-2 s-1) occurred during the initial thawing period and during the June-August growing season. However, there is a decreasing trend in total summer uptake beginning in 2011, continuing until the end of 2014. The mean diurnal pattern for the summer period over the course of 14 years (Figure below), indicates inter-annual variability associated with the key environmental controls on these CO2 fluxes. Monthly trends in Photosynthetically Active Radiation (PAR), net radiation, relative humidity as well as air temperature and soil temperature have consistently simultaneous effects on the variation in NEE. More significant effect of PAR than temperature on summer NEE had been observed for the first period of this study, however our ANOVA, multiple regression and t-test results showed a stronger effect of temperature than PAR in the recent years assuming that Arctic warming will be greater than average global warming. Also the diurnal pattern shows that the maximum daily carbon

  4. Future distribution of tundra refugia in northern Alaska

    USGS Publications Warehouse

    Hope, Andrew G.; Waltari, Eric; Payer, David C.; Cook, Joseph A.; Talbot, Sandra L.

    2013-01-01

    Climate change in the Arctic is a growing concern for natural resource conservation and management as a result of accelerated warming and associated shifts in the distribution and abundance of northern species. We introduce a predictive framework for assessing the future extent of Arctic tundra and boreal biomes in northern Alaska. We use geo-referenced museum specimens to predict the velocity of distributional change into the next century and compare predicted tundra refugial areas with current land-use. The reliability of predicted distributions, including differences between fundamental and realized niches, for two groups of species is strengthened by fossils and genetic signatures of demographic shifts. Evolutionary responses to environmental change through the late Quaternary are generally consistent with past distribution models. Predicted future refugia overlap managed areas and indicate potential hotspots for tundra diversity. To effectively assess future refugia, variable responses among closely related species to climate change warrants careful consideration of both evolutionary and ecological histories.

  5. Soil and Plant Mercury Concentrations and Pools in the Arctic Tundra of Northern Alaska by Hedge Christine, Obrist Daniel, Agnan Yannick, Moore Christopher, Biester Harald, Helmig Detlev

    NASA Astrophysics Data System (ADS)

    Hedge, C.; Agnan, Y.

    2015-12-01

    We present vegetation, soil and runoff mercury (Hg) concentrations and pool sizes in vegetation and soils at several arctic tundra sites, an area that represents <7 x 106 km2 of land surface globally. The primary measurement location is at Toolik Field Station (TFS, 68° 38' N) in northern Alaska, with additional samples collected along a transect from TFS to the Arctic Ocean, and in Noatak National Preserve to be collected in August 2015. Soil and vegetation samples from all sites will be analyzed for total Hg concentration, pH, soil texture, bulk density, soil moisture content, organic and total carbon (C), nitrogen, along with major and trace elements. Initial results already obtained from TFS (characterized as moist to wet tundra with Typic Aquiturbel soils) show Hg concentrations in tundra vegetation (112±15 μg kg-1) and organic soil (140±8 μg kg-1) similar to those found in temperate sites. Calculation of plant-based Hg deposition rates by litterfall of 17.3 μg kg-1 yr-1 were surprisingly high, exceeding all other Hg deposition fluxes at this site. Hg concentrations in mineral soils (95±3 μg kg-1) were 2-3 times higher than those found at temperate sites. Hg concentrations showed weak relationships to organic C concentrations contrasting patterns from temperate soils where concentrations typically decline with depth following lower organic carbon contents. In fact, vertical mass profiles of Hg showed a strong increase with depth, with mineral layers storing over 90% (200-500 g ha-1) of Hg within these soils. A principle component analysis including major and trace elements indicated that soil Hg was not of lithogenic origin but from atmospheric sources, possibly by long-range transport. Carbon-14 dating results showed over 7,000 years old organic carbon in mineral soils of the active layer where highest concentrations of soil Hg were observed, suggesting long term retention of atmospheric Hg. These patterns suggest vertical translocation of Hg from the

  6. Impacts of Arctic Climate Change on Tundra Fire Regimes at Interannual to Millennial Timescales

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Tundra burning is emerging as a key process in the rapidly changing Arctic, and knowledge of tundra fire-regime responses to climate change is essential for projecting Earth system dynamics. This presentation will focus on climate-fire relationships in the Arctic, spatiotemporal patterns of Holocene tundra burning, and the effects of tundra burning on carbon cycling. Analysis of historical records reveals that across the Arctic, tundra burning occurred primarily in areas where mean summer temperature exceeded 9 °C and total summer precipitation was below 115 mm. In Alaska, summer temperature and precipitation explain >90% of the interannual variability in tundra area burned from AD 1950-2009, with thresholds of 10.5 °C and 140 mm. These patterns imply tipping points in tundra fire-regime responses to climate change. The frequency of tundra fires has varied greatly across space and through time. Approximately 1.0% of the circum-Arctic tundra burned from AD 2002-2013, and 4.5% of the Alaskan tundra burned from AD 1950-2009. The latter encompassed ecoregions with fire rotation periods ranging from ~400 to 13,640 years. Charcoal analysis of lake sediments also shows that Arctic tundra can sustain a wide range of fire regimes. Fires were rare on the Alaskan North Slope throughout the Holocene, implying that the climate thresholds evident in the historical records have seldom been crossed. In contrast, in areas of NW Alaska, tundra has burned regularly at 100-250 year intervals during the late Holocene. Tundra burning may cause sudden releases of the enormous amount of Arctic soil C. Charcoal particles from recent burns yielded 14C ages of AD 1952-2006. Thus the C consumed in recent fires may recover through vegetation succession. However, our results suggest that in areas that have burned multiple times in recent decades, old soil C is vulnerable to future fires.

  7. Coastal geomorphology of arctic Alaska

    USGS Publications Warehouse

    Barnes, Peter W.; Rawlinson, Stuart E.; Reimnitz, Erk

    1988-01-01

    The treeless, tundra-plain of northern Alaska merges with the Arctic Ocean along a coastal area characterized by low tundra bluffs, and sparse coastal and delta dunes. Coastal engineering projects that aggrade or degrade permafrost will alter the geomorphology and rates of coastal processes by changing coastal stability. Similarly, projects that modify the ice environment (artificial islands) or the coastal configuration (causeways) will cause nature to readjust to the new process regime, resulting in modification of the coast. In this paper the authors describe the coastal geomorphology from Barrow to the Canadian border. In addition, they provide a general outline and extensive references of the major coastal processes operating in this environment that will be useful on coastal environments elsewhere in the Arctic.

  8. 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.

  9. Climate Variations and Alaska Tundra Vegetation Productivity Declines in Spring

    NASA Astrophysics Data System (ADS)

    Bhatt, U. S.; Walker, D. A.; Bieniek, P.; Raynolds, M. K.; Epstein, H. E.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2015-12-01

    While sea ice has continued to decline, vegetation productivity increases have declined particularly during spring in Alaska as well as many parts of the Arctic tundra. To understand the processes behind these features we investigate spring climate variations that includes temperature, circulation patterns, and snow cover to determine how these may be contributing to spring browning. This study employs remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2014. Maximum NDVI (MaxNDVI, Maximum Normalized Difference Vegetation Index), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), atmospheric reanalysis data, dynamically downscaled climate data, meteorological station data, and snow water equivalent (GlobSnow, assimilated snow data set). We analyzed the data for the full period (1982-2014) and for two sub-periods (1982-1998 and 1999-2014), which were chosen based on the declining Alaska SWI since 1998. MaxNDVI has increased from 1982-2014 over most of the Arctic but has declined from 1999 to 2014 southwest Alaska. TI-NDVI has trends that are similar to those for MaxNDVI for the full period but display widespread declines over the 1999-2014 period. Therefore, as the MaxNDVI has continued to increase overall for the Arctic, TI-NDVI has been declining since 1999 and these declines are particularly noteworthy during spring in Alaska. Spring declines in Alaska have been linked to increased spring snow cover that can delay greenup (Bieniek et al. 2015) but recent ground observations suggest that after an initial warming and greening, late season freezing temperature are damaging the plants. The late season freezing temperature hypothesis will be explored with meteorological climate/weather data sets for Alaska tundra regions. References P.A. Bieniek, US Bhatt, DA Walker, MK Raynolds, JC Comiso, HE Epstein, JE Pinzon, CJ Tucker, RL Thoman, H Tran, N M

  10. DRILLING FLUIDS AND THE ARCTIC TUNDRA OF ALASKA: ASSESSING CONTAMINATION OF WETLANDS HABITAT AND THE TOXICITY TO AQUATIC INVERTEBRATES AND FISH (JOURNAL VERSION)

    EPA Science Inventory

    Drilling for oil on the North Slope of Alaska results in the release of large volumes of used drilling fluids into arctic wetlands. These releases usually come from regulated discharges or seepage from reserve pits constructed to hold used drilling fluids. A study of five drill s...

  11. Will Arctic ground squirrels impede or accelerate climate-induced vegetation changes to the Arctic tundra?

    NASA Astrophysics Data System (ADS)

    Dalton, J.; Flower, C. E.; Brown, J.; Gonzalez-Meler, M. A.; Whelan, C.

    2014-12-01

    Considerable attention has been given to the climate feedbacks associated with predicted vegetation shifts in the Arctic tundra in response to global environmental change. However, little is known regarding the extent to which consumers can facilitate or respond to shrub expansion. Arctic ground squirrels, the largest and most northern ground squirrel, are abundant and widespread throughout the North American tundra. Their broad diet of seeds, flowers, herbage, bird's eggs and meat speaks to the need to breed, feed, and fatten in a span of some 12-16 weeks that separate their 8-9 month bouts of hibernation with the potential consequence to impact ecosystem dynamics. Therefore Arctic ground squirrels are a good candidate to evaluate whether consumers are mere responders (bottom-up effects) or drivers (top-down) of the observed and predicted vegetation changes. As a start towards this question, we measured the foraging intensity (giving-up densities) of Arctic ground squirrels in experimental food patches within which the squirrels experience diminishing returns as they seek the raisins and peanuts that we provided at the Toolik Lake field station in northern Alaska. If the squirrels show their highest feeding intensity in the shrubs, they may impede vegetation shifts by slowing the establishment and expansion of shrubs in the tundra. Conversely, if they show their lowest feeding intensity within shrub dominated areas, they may accelerate vegetation shifts. We found neither. Feeding intensity varied most among transects and times of day, and least along a tundra-to-shrub vegetation gradient. This suggests that the impacts of squirrels will be heterogeneous - in places responders and in others drivers. We should not be surprised then to see patches of accelerated and impeded vegetation changes in the tundra ecosystem. Some of these patterns may be predictable from the foraging behavior of Arctic ground squirrels.

  12. Distinct temperature sensitivity among taiga and tundra shrubs in Alaska

    NASA Astrophysics Data System (ADS)

    Andreu-Hayles, L.; Anchukaitis, K. J.; D'Arrigo, R.

    2014-12-01

    Shrub expansion into Arctic and alpine tundra ecosystems is well documented, mostly over the last 50 years, based on remote sensing data, aerial photography, and in-situ observations. Warming temperatures are considered the main driver of the observed change in shrub vegetation patterns. Here, we assess the relationship between temperatures and shrub growth from five populations of Salix spp. (willow) and Alnus spp. (alder) in Alaska growing within the tundra and the boreal forest (~taiga) using dendrochronological techniques. The three tundra shrub sites are located on the Dalton Highway north from Toolik Lake (~69ºN 148ºW), whereas the two taiga shrub sites are located closer to Fairbanks at the Twelve Mile Summit site (~65ºN 146ºW). Because shrub ages vary among the studied populations lead to different time spans for the ring-width chronologies generated, a common period with available satellite data spanning from 1982 to 2010 was selected for this study. All tundra shrub chronologies shared a strong positive response to summer temperatures despite growing in heterogeneous site conditions and belonging to different species. In contrast, in the taiga, summer temperatures enhance willow growth, whereas alder growth appears almost insensitive to temperature over the interval studied. Extending the analyses back in time, a very strong positive relationship was found between alder ring-width and June temperatures prior to 1970. This phenomenon, a weakening of the previously existing relationship between growth and temperatures, was also detected in white spruce (Picea glauca) growing at the same site, and it is known in the literature as the 'divergence problem'. Thus, at this taiga location, alder shrubs and trees seem to have similar growth patterns. Summer temperatures no longer seem to enhance taiga alder growth. Shrubs of different species exposed to the same climatic conditions can exhibit varied growth responses. The distinct temperature sensitivities

  13. Late-Summer Tundra Methane Concentrations and Fluxes on the North Slope of Alaska

    NASA Astrophysics Data System (ADS)

    Smith, J. P.; Suriben, R. S.; Coffin, R. B.; Boyd, T. J.; Rose, P. S.; Douglas, T. A.; Millholland, L. C., IV; Boudart, E. R.; Woods, J. E.

    2014-12-01

    Scientific evidence indicates wide-scale changes in Arctic climate. The Arctic contains large expanses of tundra with permafrost, or permanently frozen subsoil. Climate change impacts on the tundra have the potential to enhance biogenic methane (CH4) production in thawed, active soils or release CH4 trapped in or below the permafrost. Methane is a highly effective greenhouse gas so CH4 released from thawing tundra or melting massive ice features constitutes a potential positive feedback to Arctic climate change. In August, 2013 the U.S. Naval Research Laboratory (NRL-6114) led an expedition to investigate late-summer tundra CH4 concentrations and fluxes on the North Slope of Alaska near Prudhoe Bay. Permafrost cores were collected to measure tundra CH4 concentrations and soil parameters and a series of gas traps were deployed to measure tundra CH4 flux at 9 locations spread across a study area of ~1800 km2. Thaw probe measurements at each site provided information on the depth of the seasonally-thawed (active) layer. Results show large differences in tundra CH4 concentrations with depth through the active layer and into the upper permafrost terrain and fine-scale variability in daily CH4 flux over a relatively small spatial area. It is likely that variations in biogeochemical and geomorphological characteristics such as soil composition, microbial activity, moisture type, active layer composition and extent from site-to-site control the CH4 regime. In order to provide more accurate estimates of permafrost tundra CH4 storage and fluxes, controls on CH4 variability from location to location must be better understood. Further research is required to quantify and predict tundra CH4 flux in order to better understand the potential impact it will have on Arctic climate, particularly if, as predicted, climate warming leads to the liberation of permafrost carbon in these landscapes.

  14. Frequent fires in ancient shrub tundra: implications of paleorecords for arctic environmental change.

    PubMed

    Higuera, Philip E; Brubaker, Linda B; Anderson, Patricia M; Brown, Thomas A; Kennedy, Alison T; Hu, Feng Sheng

    2008-01-01

    Understanding feedbacks between terrestrial and atmospheric systems is vital for predicting the consequences of global change, particularly in the rapidly changing Arctic. Fire is a key process in this context, but the consequences of altered fire regimes in tundra ecosystems are rarely considered, largely because tundra fires occur infrequently on the modern landscape. We present paleoecological data that indicate frequent tundra fires in northcentral Alaska between 14,000 and 10,000 years ago. Charcoal and pollen from lake sediments reveal that ancient birch-dominated shrub tundra burned as often as modern boreal forests in the region, every 144 years on average (+/- 90 s.d.; n = 44). Although paleoclimate interpretations and data from modern tundra fires suggest that increased burning was aided by low effective moisture, vegetation cover clearly played a critical role in facilitating the paleofires by creating an abundance of fine fuels. These records suggest that greater fire activity will likely accompany temperature-related increases in shrub-dominated tundra predicted for the 21(st) century and beyond. Increased tundra burning will have broad impacts on physical and biological systems as well as on land-atmosphere interactions in the Arctic, including the potential to release stored organic carbon to the atmosphere. PMID:18320025

  15. Quantitative Interpretation of Arctic Tundra Attributes Using Remote Sensing: Leveraging Field Data, Modern- and Legacy Landsat Data, and Commercial Imagery in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Frost, G. V., Jr.; Macander, M. J.; Nelson, P. R.

    2014-12-01

    Integrated analysis of ground-based vegetation data and remote sensing supports vegetation mapping, landscape-change detection, wildlife habitat assessment, and tracking of phenological events such as green-up and senescence. The life-cycles of tundra plants occur within a highly compressed seasonal window, making the quantitative assessment of vegetation and landscape attributes from ≤30m resolution remotely-sensed imagery, such as above-ground biomass, % shrub cover, and % surface water, a difficult task when applied across large study domains. To support mapping of vegetation and landscape attributes across ~100,000 km2 of Alaska's North Slope, we obtained ground data for tundra vegetation using a point-intercept sampling approach across a network of 107 field plots spanning gradients of bioclimate, landscape position (upland, lowland, riverine), and geomorphic setting (foothills, coastal plain). At each plot, vegetation data were collected along three 50-m linear transects, compatible with 30-m Landsat imagery. We summarized live vegetation, litter, and non-vegetated surfaces using three terms: top cover (uppermost "hit"), percent cover (total areal cover along transect), and hit density (all "hits" at a point). We then evaluated a suite of data models (e.g., General Additive Models, classification tree, clustering) and data-mining approaches (e.g., neural networks, random forest) using midsummer Landsat TM/ETM+ acquisitions since 1985, and OLI acquisitions for 2013-2014. The large size, frequent cloudiness, and interannual variability of the study area necessitated the compositing of a multitude of Landsat scenes. A median NDVI compositing technique was used to select Landsat observations from cloud- and shadow-free pixels that met day-of-year and year constraints. This technique produced seamless, phenologically consistent composites that are largely free of artifacts and suitable for regional-scale analysis. Ground-based training data and an archive of

  16. Using Discriminant Analysis to Examine Spectral Differences Among Four Tundra Vegetation Communities at Ivotuk, Alaska

    NASA Astrophysics Data System (ADS)

    Bratsch, S.; Epstein, H. E.

    2014-12-01

    Warming in the Arctic has resulted in changes in the distribution and composition of tundra vegetation in addition to a lengthening of the growing season. Past studies have mapped tundra vegetation at relatively coarse spatial scales; however, vegetation changes in the Arctic are occurring at spatial scales within a few meters. This research uses hyperspectral remote sensing data to differentiate among four vegetation communities at Ivotuk, Alaska (68.49°N, 155.74°W). Ivotuk is located on the North Slope, and is dominated by four plant communities including moist acidic tundra (MAT), moist nonacidic tundra (MNT), mossy tussock tundra (MT), and shrub tundra (ST). Hand-held hyperspectral data were collected during the 1999 growing season (5 June-27 August) at biweekly intervals using narrow, ~1.42 nm wavebands. Only wavebands within 400-1060 nm were used in analysis. Two sets of comparisons were conducted using stepwise discriminant analysis: 1) MNT and ST, and 2) all four tundra plant communities. MNT and ST classification accuracy ranged from 91.3-100%, with 100% classification and cross-validated accuracy occurring on 27 July. Classification accuracy for the overall growing season was 97.9% for MNT and 98.1% for ST. The stepwise function indicated 18 significant bands including 8 near infrared (NIR) and 4 blue bands. MAT, MNT, MT, and ST classification accuracy ranged from 58-100%, with greatest classification accuracy (100%) also occurring during peak growing season on 27 July. Overall classification accuracy for the growing season was 97.6% for MNT, 92% for MT, 84% for ST, and 70.8% for MAT. There were 14 significant bands including 6 NIR and 3 blue bands. The results presented here demonstrate that discriminant analysis can be useful in distinguishing among the dominant tundra vegetation communities in the Arctic, and can potentially help us to better understand and monitor arctic vegetation and ecosystem responses to environmental changes.

  17. Alaska North Slope Tundra Travel Model and Validation Study

    SciTech Connect

    Harry R. Bader; Jacynthe Guimond

    2006-03-01

    The Alaska Department of Natural Resources (DNR), Division of Mining, Land, and Water manages cross-country travel, typically associated with hydrocarbon exploration and development, on Alaska's arctic North Slope. This project is intended to provide natural resource managers with objective, quantitative data to assist decision making regarding opening of the tundra to cross-country travel. DNR designed standardized, controlled field trials, with baseline data, to investigate the relationships present between winter exploration vehicle treatments and the independent variables of ground hardness, snow depth, and snow slab thickness, as they relate to the dependent variables of active layer depth, soil moisture, and photosynthetically active radiation (a proxy for plant disturbance). Changes in the dependent variables were used as indicators of tundra disturbance. Two main tundra community types were studied: Coastal Plain (wet graminoid/moist sedge shrub) and Foothills (tussock). DNR constructed four models to address physical soil properties: two models for each main community type, one predicting change in depth of active layer and a second predicting change in soil moisture. DNR also investigated the limited potential management utility in using soil temperature, the amount of photosynthetically active radiation (PAR) absorbed by plants, and changes in microphotography as tools for the identification of disturbance in the field. DNR operated under the assumption that changes in the abiotic factors of active layer depth and soil moisture drive alteration in tundra vegetation structure and composition. Statistically significant differences in depth of active layer, soil moisture at a 15 cm depth, soil temperature at a 15 cm depth, and the absorption of photosynthetically active radiation were found among treatment cells and among treatment types. The models were unable to thoroughly investigate the interacting role between snow depth and disturbance due to a lack

  18. Recent Arctic tundra fire initiates widespread thermokarst development.

    PubMed

    Jones, Benjamin M; Grosse, Guido; Arp, Christopher D; Miller, Eric; Liu, Lin; Hayes, Daniel J; Larsen, Christopher F

    2015-01-01

    Fire-induced permafrost degradation is well documented in boreal forests, but the role of fires in initiating thermokarst development in Arctic tundra is less well understood. Here we show that Arctic tundra fires may induce widespread thaw subsidence of permafrost terrain in the first seven years following the disturbance. Quantitative analysis of airborne LiDAR data acquired two and seven years post-fire, detected permafrost thaw subsidence across 34% of the burned tundra area studied, compared to less than 1% in similar undisturbed, ice-rich tundra terrain units. The variability in thermokarst development appears to be influenced by the interaction of tundra fire burn severity and near-surface, ground-ice content. Subsidence was greatest in severely burned, ice-rich upland terrain (yedoma), accounting for ~50% of the detected subsidence, despite representing only 30% of the fire disturbed study area. Microtopography increased by 340% in this terrain unit as a result of ice wedge degradation. Increases in the frequency, magnitude, and severity of tundra fires will contribute to future thermokarst development and associated landscape change in Arctic tundra regions. PMID:26511650

  19. Recent Arctic tundra fire initiates widespread thermokarst development

    PubMed Central

    Jones, Benjamin M.; Grosse, Guido; Arp, Christopher D.; Miller, Eric; Liu, Lin; Hayes, Daniel J.; Larsen, Christopher F.

    2015-01-01

    Fire-induced permafrost degradation is well documented in boreal forests, but the role of fires in initiating thermokarst development in Arctic tundra is less well understood. Here we show that Arctic tundra fires may induce widespread thaw subsidence of permafrost terrain in the first seven years following the disturbance. Quantitative analysis of airborne LiDAR data acquired two and seven years post-fire, detected permafrost thaw subsidence across 34% of the burned tundra area studied, compared to less than 1% in similar undisturbed, ice-rich tundra terrain units. The variability in thermokarst development appears to be influenced by the interaction of tundra fire burn severity and near-surface, ground-ice content. Subsidence was greatest in severely burned, ice-rich upland terrain (yedoma), accounting for ~50% of the detected subsidence, despite representing only 30% of the fire disturbed study area. Microtopography increased by 340% in this terrain unit as a result of ice wedge degradation. Increases in the frequency, magnitude, and severity of tundra fires will contribute to future thermokarst development and associated landscape change in Arctic tundra regions. PMID:26511650

  20. The unseen iceberg: Plant roots in arctic tundra

    DOE PAGESBeta

    Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F.; Euskirchen, Eugenie S; McGuire, A. David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey; Wullschleger, Stan D

    2015-01-01

    Arctic tundra is characterized by short-statured plant communities underlain by carbon (C)-rich soils and permafrost. Ecosystem C and nutrient cycles in tundra are driven by complex interactions between plants and their environment. However, root dynamics are one of the least understood aspects of plant growth in the Arctic. We synthesized available literature on tundra roots and discussed their representation in terrestrial biosphere models. Belowground biomass in tundra ecosystems can be an order of magnitude larger than aboveground biomass. Data on root production and turnover in tundra is sparse, limiting our understanding of the controls over root dynamics in these systems.more » Roots are shallowly distributed in the thin layer of soil that thaws each year, and are often found in the organic horizon at the soil surface. Species-specific differences in root distribution, mycorrhizal colonization, and resource partitioning may affect plant species competition under changing climatic conditions. Model representation of belowground processes has increased in complexity over recent years, but data are desperately needed to fill the gaps in model treatment of tundra roots. Future research should focus on estimates of root production and lifespan, and interactions between roots and the surrounding soil across the diversity of tundra ecosystems in the Arctic.« less

  1. The unseen iceberg: Plant roots in arctic tundra

    SciTech Connect

    Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F.; Euskirchen, Eugenie S; McGuire, A. David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey; Wullschleger, Stan D

    2015-01-01

    Arctic tundra is characterized by short-statured plant communities underlain by carbon (C)-rich soils and permafrost. Ecosystem C and nutrient cycles in tundra are driven by complex interactions between plants and their environment. However, root dynamics are one of the least understood aspects of plant growth in the Arctic. We synthesized available literature on tundra roots and discussed their representation in terrestrial biosphere models. Belowground biomass in tundra ecosystems can be an order of magnitude larger than aboveground biomass. Data on root production and turnover in tundra is sparse, limiting our understanding of the controls over root dynamics in these systems. Roots are shallowly distributed in the thin layer of soil that thaws each year, and are often found in the organic horizon at the soil surface. Species-specific differences in root distribution, mycorrhizal colonization, and resource partitioning may affect plant species competition under changing climatic conditions. Model representation of belowground processes has increased in complexity over recent years, but data are desperately needed to fill the gaps in model treatment of tundra roots. Future research should focus on estimates of root production and lifespan, and interactions between roots and the surrounding soil across the diversity of tundra ecosystems in the Arctic.

  2. Changes in tundra vascular plant biomass over thirty years at Imnavait Creek, Alaska.

    NASA Astrophysics Data System (ADS)

    Bret-Harte, M. S.; Euskirchen, E. S.; Edgar, C.; Huebner, D. C.; Okano, K.; Tucker, C.; Genet, H.; Ray, P. M.; Shaver, G. R.

    2014-12-01

    Understanding the magnitude of, and controls over, CO2 and water fluxes in arctic ecosystems is essential for accurate assessment and prediction of their responses to climate change. In 2013, we harvested vegetation and soils in the most common plant community types located in the source areas for fluxes measured by eddy covariance towers located in three representative Alaska tundra ecosystems along a toposequence (a ridge site composed of heath tundra and moist non-acidic tundra, a mid-slope site composed of moist acidic tussock tundra, and a valley bottom fen site composed of wet sedge tundra and moist acidic tundra) at Imnavait Creek, Alaska. While the purpose of this harvest was to relate biomass and production to estimates of overall net ecosystem CO2 exchange (NEE), gross primary productivity (GPP) and ecosystem respiration (ER) obtained by micrometeorological methods, it also afforded an opportunity to compare with biomass harvests done in the 1980s in moist acidic tundra at Imnavait Creek; there have been no other harvests than ours at Imnavait since then. Our data showed that plant biomass and production were greatest in the tussock tundra at the mid-slope tower, and least in the wet sedge community at the fen tower, while plant diversity was greatest in the communities at the ridge site. Aboveground biomass of vascular plants in our 2013 harvest in moist acidic tundra was nearly three times higher than that measured approximately thirty years earlier in three harvests of nearby areas at Imnavait Creek, due to an increase in the biomass of shrubs and graminoids. Comparison with other biomass harvests from the vicinity of Toolik Field Station indicate that vascular plant biomass in moist acidic tundra has increased over this time period, with the greatest increase evident by the mid-1990s, and a more gradual increase through to the present time, despite no obvious increase in air temperature as seen in data from nearby climate stations. These data will be

  3. The unseen iceberg: Plant roots in arctic tundra

    USGS Publications Warehouse

    Iverson, Colleen M.; Sloan, Victoria L.; Sullivan, Patrick F.; Euskirchen, E.S.; McGuire, Anthony; Norby, Richard J.; Walker, Anthony P.; Warren, Jeffrey M.; Wullschleger, Stan D.

    2015-01-01

    Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits – including distribution, chemistry, anatomy and resource partitioning – play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions.

  4. Winter and early spring CO2 efflux from tundra communities of northern Alaska

    NASA Astrophysics Data System (ADS)

    Fahnestock, J. T.; Jones, M. H.; Brooks, P. D.; Walker, D. A.; Welker, J. M.

    1998-11-01

    Carbon dioxide concentrations through snow were measured in different arctic tundra communities on the North Slope of Alaska during winter and early spring of 1996. Subnivean CO2 concentrations were always higher than atmospheric CO2. A steady state diffusion model was used to generate conservative estimates of CO2 flux to the atmosphere. The magnitude of CO2 efflux differed with tundra community type, and rates of carbon release increased from March to May. Winter CO2 efflux was highest in riparian and snow bed communities and lowest in dry heath, upland tussock, and wet sedge communities. Snow generally accrues earlier in winter and is deeper in riparian and snow bed communities compared with other tundra communities, which are typically windswept and do not accumulate much snow during the winter. These results support the hypothesis that early and deep snow accumulation may insulate microbial populations from very cold temperatures, allowing sites with earlier snow cover to sustain higher levels of activity throughout winter compared to communities that have later developing snow cover. Extrapolating our estimates of CO2 efflux to the entire snow-covered season indicates that total carbon flux during winter in the Arctic is 13-109 kg CO2-C ha-1, depending on the vegetation community type. Wintertime CO2 flux is a potentially important, yet largely overlooked, part of the annual carbon cycle of tundra, and carbon release during winter should be accounted for in estimates of annual carbon balance in arctic ecosystems.

  5. Mapping wildfire burn severity in the Arctic Tundra from downsampled MODIS data

    USGS Publications Warehouse

    Kolden, Crystal A.; Rogan, John

    2013-01-01

    Wildfires are historically infrequent in the arctic tundra, but are projected to increase with climate warming. Fire effects on tundra ecosystems are poorly understood and difficult to quantify in a remote region where a short growing season severely limits ground data collection. Remote sensing has been widely utilized to characterize wildfire regimes, but primarily from the Landsat sensor, which has limited data acquisition in the Arctic. Here, coarse-resolution remotely sensed data are assessed as a means to quantify wildfire burn severity of the 2007 Anaktuvuk River Fire in Alaska, the largest tundra wildfire ever recorded on Alaska's North Slope. Data from Landsat Thematic Mapper (TM) and downsampled Moderate-resolution Imaging Spectroradiometer (MODIS) were processed to spectral indices and correlated to observed metrics of surface, subsurface, and comprehensive burn severity. Spectral indices were strongly correlated to surface severity (maximum R2 = 0.88) and slightly less strongly correlated to substrate severity. Downsampled MODIS data showed a decrease in severity one year post-fire, corroborating rapid vegetation regeneration observed on the burned site. These results indicate that widely-used spectral indices and downsampled coarse-resolution data provide a reasonable supplement to often-limited ground data collection for analysis and long-term monitoring of wildfire effects in arctic ecosystems.

  6. CO2 and CH4 fluxes along a latitudinal transect in Northern Alaska using eddy covariance technique in challenging conditions: first results of a long term experiment in the Arctic tundra

    NASA Astrophysics Data System (ADS)

    Moreaux, V.; Oechel, W. C.; Losacco, S.; McEwing, R.; Murphy, P.; Zona, D.

    2013-12-01

    Being one of the most sensitive regions on earth, the Arctic is likely to be one of the most affected by global change. Physical changes (drying, snow cover, active layer depth, permafrost thawing, etc.) could create feedbacks in the release of greenhouse gas to the atmosphere. Correlated to the significant increase in air temperature, changes in trace gas balance have already been reported (Oechel et al. 1998). Carbon (C) is currently trapped as organic matter in the permafrost that underlies much of the Arctic. C represents about 30-50% of the global belowground organic carbon pool (Tarnocai et al.2009, Zona et al. 2012). Stored organic matter can form the substrate for significant release of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Ubiquitous arctic wetlands are additional sources of CH4 and CO2 to the atmosphere (Melton et al. 2013). CO2 is important because of the magnitude of its fluxes, and CH4 is of interest since its global warming potential is 23 times higher than the CO2 over a 100-year time horizon. CH4 is produced by the decomposition of dead plant material in anaerobic soils, especially in tundra ponds. Methane release is mostly influenced by temperature, water table, and active layer depth. The spatial and temporal variability results in very large uncertainties of current CH4 fluxes from the Arctic. The sporadic studies available create a generally inadequate baseline from which to determine a change in emissions from this critical and sensitive environment. Here we initiate a large scale, continuously monitored, study of CO2 and CH4 budgets from tundra ecosystems across a latitudinal gradient of more than 400 km. Our main questions for this study are: (i) does the release of CO2 and CH4 from biological and geothermal processes exceed the sink of greenhouse gases from active vegetation and surface organisms? (ii) How does this balance behave over latitudinal and environmental gradients? The observations presented are the result of

  7. Alaska tundra vegetation trends and their links to the large-scale climate

    NASA Astrophysics Data System (ADS)

    Bieniek, P. A.; Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Comiso, J. C.

    2011-12-01

    The arctic Normalized Vegetation Index (NDVI) data set (a measure of vegetation photosynthetic capacity) has been used to document coherent temporal relationships between near-coastal sea ice, summer tundra land surface temperatures, and vegetation productivity throughout the Arctic (Bhatt et al. 2010). Land warming over North America has displayed larger trends (+30%) when compared to Eurasia (+16%) since 1982. In the tundra of northern Alaska the greatest change was found in absolute maximum NDVI along the Beaufort Sea coast (+14%). In contrast, tundra areas in southwest Alaska along the Bering Sea have seen a decline (-4%). Greenup date in these regions has been occurring as much as 1-4 days earlier per decade, but trends are mixed. Winter snow water equivalent (SWE) has only increased slightly (+0.1 mm/yr) in the Arctic region of Alaska since 1987 (R. Muskett, personal communication). These findings suggest that there have been changes in the seasonal climate in Alaska during the NDVI record. The tundra trends are further investigated by evaluating remotely sensed sea ice, surface air temperature, SWE, daily snow cover, and NDVI3g. While the snow data has a relatively short record (1999-2010), notable trends can be observed in snow melt, occurring as much 15 days earlier per decade in northern Alaska. Unfortunately, other snow data sets have been found to be problematic and could not be used to extend our analysis. This highlights the need for a long-term pan-arctic snow data set that is suitable for climate analysis. Possible climate drivers are also investigated. Results show that the summer tundra, in terms of NDVI and summer warmth index (SWI), has few direct links with the large-scale climate. However, the sea ice concentration along the coast of the tundra regions has strong preseason links to the large-scale climate. This suggests that the large-scale climate influences the sea ice concentration which then affects the NDVI and SWI. Three tundra regions

  8. InSAR detects increase in surface subsidence caused by an Arctic tundra fire

    USGS Publications Warehouse

    Liu, Lin; Jafarov, Elchin E.; Schaefer, Kevin M.; Jones, Benjamin M.; Zebker, Howard A.; Williams, Christopher A.; Rogan, John; Zhang, Tingjun

    2014-01-01

    Wildfire is a major disturbance in the Arctic tundra and boreal forests, having a significant impact on soil hydrology, carbon cycling, and permafrost dynamics. This study explores the use of the microwave Interferometric Synthetic Aperture Radar (InSAR) technique to map and quantify ground surface subsidence caused by the Anaktuvuk River fire on the North Slope of Alaska. We detected an increase of up to 8 cm of thaw-season ground subsidence after the fire, which is due to a combination of thickened active layer and permafrost thaw subsidence. Our results illustrate the effectiveness and potential of using InSAR to quantify fire impacts on the Arctic tundra, especially in regions underlain by ice-rich permafrost. Our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice-rich permafrost terrain than changes in active layer thickness alone.

  9. InSAR detects increase in surface subsidence caused by an Arctic tundra fire

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Jafarov, Elchin E.; Schaefer, Kevin M.; Jones, Benjamin M.; Zebker, Howard A.; Williams, Christopher A.; Rogan, John; Zhang, Tingjun

    2014-06-01

    Wildfire is a major disturbance in the Arctic tundra and boreal forests, having a significant impact on soil hydrology, carbon cycling, and permafrost dynamics. This study explores the use of the microwave Interferometric Synthetic Aperture Radar (InSAR) technique to map and quantify ground surface subsidence caused by the Anaktuvuk River fire on the North Slope of Alaska. We detected an increase of up to 8 cm of thaw-season ground subsidence after the fire, which is due to a combination of thickened active layer and permafrost thaw subsidence. Our results illustrate the effectiveness and potential of using InSAR to quantify fire impacts on the Arctic tundra, especially in regions underlain by ice-rich permafrost. Our study also suggests that surface subsidence is a more comprehensive indicator of fire impacts on ice-rich permafrost terrain than changes in active layer thickness alone.

  10. Methane Suppression: The Impacts of Fe(III) and Humic Acids on Net Methane Flux from Arctic Tundra Wetlands in Alaska and Finland (Invited)

    NASA Astrophysics Data System (ADS)

    Lipson, D.; Miller, K.; Lai, C.

    2013-12-01

    Arctic soils contain large reservoirs of carbon (C) that are vulnerable to loss from climatic warming. However the potential global impacts of this C depend on whether it is lost primarily in the form of methane (CH4) or carbon dioxide (CO2), two gases with very different greenhouse warming potentials. In anaerobic environments, the relative production of CH4 vs. CO2 may be controlled by the presence of alternative terminal electron acceptors, which allow more thermodynamically favorable anaerobic respiratory pathways to dominate over methanogenesis. This work investigated how the addition of terminal electron acceptors, ferric iron (Fe(III)) and humic acids, affected net CH4 fluxes from high-latitude wetland ecosystems. We conducted two manipulative field experiments in Barrow, Alaska (71° N) and Finnish Lapland (69° N). The ecosystem in Barrow was known from previous studies to be rich in Fe(III) and to harbor a microbial community that is dominated by Fe(III)- and humic acid-reducing microorganisms. The role of these alternative electron acceptors had not previously been studied at the Finnish site. CH4 and CO2 fluxes were measured using a portable trace gas analyzer from experimental plots, before and after amendments with Fe(III) (in the chelated form, ferric nitrilotriacetic acid), humic acids, or water as a control. Both in the ecosystem with permafrost and naturally high levels of soil Fe (Barrow, AK) and in the ecosystem with no permafrost and naturally low levels of soil Fe (Petsikko, Finland), the addition of the alternative electron acceptors Fe(III) and humic acids significantly reduced net CH4 flux. CO2 fluxes were not significantly altered by the treatments. The reduction in CH4 flux persisted for at least several weeks post-treatment. There was no significant difference between the reduction caused by humic acids versus that from Fe(III). These results show that the suppression of CH4 flux by Fe(III) and humic acids is a widespread phenomenon that

  11. The temperature response of methane emission in Arctic wet sedge tundra

    NASA Astrophysics Data System (ADS)

    Lim, Edward; Zona, Donatella

    2015-04-01

    Since the last glacial maximum Arctic tundra soils have acted as an important carbon sink, having accumulated carbon under cold, anaerobic conditions (Zona et al. 2009). Several studies indicate that recent climate warming has altered this balance, with the Arctic tundra now posited to be a significant annual source of atmospheric methane (CH4) (McGuire et al. 2012). Nonetheless, the response of Arctic tundra CH4 fluxes to continued climate warming remains uncertain. Laboratory and field studies indicate that CH4 fluxes are temperature sensitive, thus accurate calculation of the temperature sensitivity is vital for the prediction of future CH4 emission. For this, the increase in reaction rate over a 10°C range (Q10) is frequently used, with single fixed Q10 values (between 2 and 4) commonly incorporated into climate-carbon cycle models. However, the temperature sensitivity of CH4 emission can vary considerably depending on factors such as vegetation composition, water table and season. This promotes the use of spatially and seasonally variable Q10 values for accurate CH4 flux estimation under different future climate change scenarios. This study investigates the temperature sensitivity (Q10) of Arctic tundra methane fluxes, using an extensive number of soil cores (48) extracted from wet sedge polygonal tundra (Barrow Experimental Observatory, Alaska). 'Wet' and 'dry' cores were taken from the centre and raised perimeter of ice-wedge polygons, where the water tables are 0cm and -15cm respectively. Cores were incubated in two controlled environment chambers (University of Sheffield, UK) for 12 weeks under different thaw depth treatments (control and control + 6.8cm), water tables (surface and -15cm), and CO2 concentrations (400ppm and 850ppm) in a multifactorial manner. Chamber temperature was gradually increased from -5°C to 20°C, then gradually decreased to -5°C, with each temperature stage lasting one week. Average CH4 fluxes from 'dry' cores were consistently

  12. Long-term recovery patterns of arctic tundra after winter seismic exploration.

    PubMed

    Jorgenson, Janet C; Ver Hoef, Jay M; Jorgenson, M T

    2010-01-01

    In response to the increasing global demand for energy, oil exploration and development are expanding into frontier areas of the Arctic, where slow-growing tundra vegetation and the underlying permafrost soils are very sensitive to disturbance. The creation of vehicle trails on the tundra from seismic exploration for oil has accelerated in the past decade, and the cumulative impact represents a geographic footprint that covers a greater extent of Alaska's North Slope tundra than all other direct human impacts combined. Seismic exploration for oil and gas was conducted on the coastal plain of the Arctic National Wildlife Refuge, Alaska, USA, in the winters of 1984 and 1985. This study documents recovery of vegetation and permafrost soils over a two-decade period after vehicle traffic on snow-covered tundra. Paired permanent vegetation plots (disturbed vs. reference) were monitored six times from 1984 to 2002. Data were collected on percent vegetative cover by plant species and on soil and ground ice characteristics. We developed Bayesian hierarchical models, with temporally and spatially autocorrelated errors, to analyze the effects of vegetation type and initial disturbance levels on recovery patterns of the different plant growth forms as well as soil thaw depth. Plant community composition was altered on the trails by species-specific responses to initial disturbance and subsequent changes in substrate. Long-term changes included increased cover of graminoids and decreased cover of evergreen shrubs and mosses. Trails with low levels of initial disturbance usually improved well over time, whereas those with medium to high levels of initial disturbance recovered slowly. Trails on ice-poor, gravel substrates of riparian areas recovered better than those on ice-rich loamy soils of the uplands, even after severe initial damage. Recovery to pre-disturbance communities was not possible where trail subsidence occurred due to thawing of ground ice. Previous studies of

  13. Vegetation shifts observed in arctic tundra 17 years after fire

    USGS Publications Warehouse

    Barrett, Kirsten; Rocha, Adrian V.; van de Weg, Martine Janet; Shaver, Gaius

    2012-01-01

    With anticipated climate change, tundra fires are expected to occur more frequently in the future, but data on the long-term effects of fire on tundra vegetation composition are scarce. This study addresses changes in vegetation structure that have persisted for 17 years after a tundra fire on the North Slope of Alaska. Fire-related shifts in vegetation composition were assessed from remote-sensing imagery and ground observations of the burn scar and an adjacent control site. Early-season remotely sensed imagery from the burn scar exhibits a low vegetation index compared with the control site, whereas the late-season signal is slightly higher. The range and maximum vegetation index are greater in the burn scar, although the mean annual values do not differ among the sites. Ground observations revealed a greater abundance of moss in the unburned site, which may account for the high early growing season normalized difference vegetation index (NDVI) anomaly relative to the burn. The abundance of graminoid species and an absence of Betula nana in the post-fire tundra sites may also be responsible for the spectral differences observed in the remotely sensed imagery. The partial replacement of tundra by graminoid-dominated ecosystems has been predicted by the ALFRESCO model of disturbance, climate and vegetation succession.

  14. Cold season emissions dominate the Arctic tundra methane budget

    NASA Astrophysics Data System (ADS)

    Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

    2016-01-01

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y-1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming.

  15. Cold season emissions dominate the Arctic tundra methane budget.

    PubMed

    Zona, Donatella; Gioli, Beniamino; Commane, Róisín; Lindaas, Jakob; Wofsy, Steven C; Miller, Charles E; Dinardo, Steven J; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y-W; Henderson, John M; Murphy, Patrick C; Goodrich, Jordan P; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D; Kimball, John S; Lipson, David A; Oechel, Walter C

    2016-01-01

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥ 50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the "zero curtain" period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y(-1), ∼ 25% of global emissions from extratropical wetlands, or ∼ 6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming. PMID:26699476

  16. Impact of permafrost thaw on Arctic tundra pond geochemistry

    NASA Astrophysics Data System (ADS)

    Reyes, F.; Lougheed, V.

    2012-12-01

    Increasing evidence indicates the arctic tundra is changing physically, biologically, and chemically due to climate warming. With a warmer climate, permafrost is expected to thaw and influence the chemistry of arctic aquatic ecosystems. However, knowledge is limited on how geochemistry of arctic tundra pond ecosystems will respond. By re-sampling historical IBP ponds in Barrow, AK first sampled in the 1970s, previous studies have shown an increase in water temperature, nutrients and algal biomass through time. Results from this study indicate an increase of Ca, Mg, and Na in the water column, and a decrease in pH relative to the 1970s, suggesting an increased rate and magnitude of carbonate and Mg release. Seasonal trends were also examined to understand what processes, such as mineral weathering, peat decomposition and evaporation, were currently most influential in determining pond geochemistry. An increase in Ca/Na molar ratios, and carbonate and magnesium concentrations indicates that these tundra ponds are experiencing greater carbonate weathering compared to the 1970s and the rate of carbonate weathering increases in ponds as the summer progresses. However, increasing dissolved organic carbon (DOC) concentrations originating from peat decomposition are likely neutralizing additional inputs of carbonate, causing pond pH to decrease and exacerbating mineral weathering. A strong positive relationship between element concentrations and active layer pond thaw depth suggests that the origin of these additional solutes is likely from permafrost thaw. Active layer thaw depth has increased substantially over the past 40 years in the IBP ponds. Chloride/Bromide molar ratios and Deuterium/ 18-Oxygen isotope ratios will be used to determine the degree of evaporation occurring in tundra ponds. Ultimately, this study provides evidence for how geochemistry can identify the sources of chemical inputs to Arctic ponds affected by climate change and permafrost thaw.

  17. Cold season emissions dominate the Arctic tundra methane budget

    PubMed Central

    Zona, Donatella; Gioli, Beniamino; Lindaas, Jakob; Wofsy, Steven C.; Miller, Charles E.; Dinardo, Steven J.; Dengel, Sigrid; Sweeney, Colm; Karion, Anna; Chang, Rachel Y.-W.; Henderson, John M.; Murphy, Patrick C.; Goodrich, Jordan P.; Moreaux, Virginie; Liljedahl, Anna; Watts, Jennifer D.; Kimball, John S.; Lipson, David A.; Oechel, Walter C.

    2016-01-01

    Arctic terrestrial ecosystems are major global sources of methane (CH4); hence, it is important to understand the seasonal and climatic controls on CH4 emissions from these systems. Here, we report year-round CH4 emissions from Alaskan Arctic tundra eddy flux sites and regional fluxes derived from aircraft data. We find that emissions during the cold season (September to May) account for ≥50% of the annual CH4 flux, with the highest emissions from noninundated upland tundra. A major fraction of cold season emissions occur during the “zero curtain” period, when subsurface soil temperatures are poised near 0 °C. The zero curtain may persist longer than the growing season, and CH4 emissions are enhanced when the duration is extended by a deep thawed layer as can occur with thick snow cover. Regional scale fluxes of CH4 derived from aircraft data demonstrate the large spatial extent of late season CH4 emissions. Scaled to the circumpolar Arctic, cold season fluxes from tundra total 12 ± 5 (95% confidence interval) Tg CH4 y−1, ∼25% of global emissions from extratropical wetlands, or ∼6% of total global wetland methane emissions. The dominance of late-season emissions, sensitivity to soil environmental conditions, and importance of dry tundra are not currently simulated in most global climate models. Because Arctic warming disproportionally impacts the cold season, our results suggest that higher cold-season CH4 emissions will result from observed and predicted increases in snow thickness, active layer depth, and soil temperature, representing important positive feedbacks on climate warming. PMID:26699476

  18. Pathways of anaerobic organic matter decomposition in tundra soils from Barrow, Alaska

    DOE PAGESBeta

    Herndon, Elizabeth M.; Mann, Benjamin F.; Chowdhury, Taniya Roy; Wullschleger, Stan D.; Graham, David E.; Liang, Liyuan; Gu, Baohua; Yang, Ziming

    2015-11-23

    Arctic tundra soils store a large quantity of organic carbon that is susceptible to decomposition and release to the atmosphere as methane (CH4) and carbon dioxide (CO2) under a warming climate. Anaerobic processes that generate CH4 and CO2 remain unclear because previous studies have focused on aerobic decomposition pathways. To predict releases of CO2 and CH4 from tundra soils, it is necessary to identify pathways of soil organic matter decomposition under the anoxic conditions that are prevalent in Arctic ecosystems. Here molecular and spectroscopic techniques were used to monitor biological degradation of water-extractable organic carbon (WEOC) during anoxic incubation ofmore » tundra soils from a region of continuous permafrost in northern Alaska. Organic and mineral soils from the tundra active layer were incubated at –2, +4, or +8°C for up to 60 days to mimic the short-term thaw season. Results suggest that, under anoxic conditions, fermentation converted complex organic molecules into simple organic acids that were used in concomitant Fe-reduction and acetoclastic methanogenesis reactions. Nonaromatic compounds increased over time as WEOC increased. Organic acid metabolites initially accumulated in soils but were mostly depleted by day 60 because organic acids were consumed to produce Fe(II), CO2, and CH4. We conclude that fermentation of nonprotected organic matter facilitates methanogenesis and Fe reduction reactions, and that the proportion of organic acids consumed by methanogenesis increases relative to Fe reduction with increasing temperature. As a result, the decomposition pathways observed in this study are important to consider in numerical modeling of greenhouse gas production in the Arctic.« less

  19. Pathways of anaerobic organic matter decomposition in tundra soils from Barrow, Alaska

    SciTech Connect

    Herndon, Elizabeth M.; Mann, Benjamin F.; Chowdhury, Taniya Roy; Wullschleger, Stan D.; Graham, David E.; Liang, Liyuan; Gu, Baohua; Yang, Ziming

    2015-11-23

    Arctic tundra soils store a large quantity of organic carbon that is susceptible to decomposition and release to the atmosphere as methane (CH4) and carbon dioxide (CO2) under a warming climate. Anaerobic processes that generate CH4 and CO2 remain unclear because previous studies have focused on aerobic decomposition pathways. To predict releases of CO2 and CH4 from tundra soils, it is necessary to identify pathways of soil organic matter decomposition under the anoxic conditions that are prevalent in Arctic ecosystems. Here molecular and spectroscopic techniques were used to monitor biological degradation of water-extractable organic carbon (WEOC) during anoxic incubation of tundra soils from a region of continuous permafrost in northern Alaska. Organic and mineral soils from the tundra active layer were incubated at –2, +4, or +8°C for up to 60 days to mimic the short-term thaw season. Results suggest that, under anoxic conditions, fermentation converted complex organic molecules into simple organic acids that were used in concomitant Fe-reduction and acetoclastic methanogenesis reactions. Nonaromatic compounds increased over time as WEOC increased. Organic acid metabolites initially accumulated in soils but were mostly depleted by day 60 because organic acids were consumed to produce Fe(II), CO2, and CH4. We conclude that fermentation of nonprotected organic matter facilitates methanogenesis and Fe reduction reactions, and that the proportion of organic acids consumed by methanogenesis increases relative to Fe reduction with increasing temperature. As a result, the decomposition pathways observed in this study are important to consider in numerical modeling of greenhouse gas production in the Arctic.

  20. Pathways of anaerobic organic matter decomposition in tundra soils from Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Herndon, Elizabeth M.; Mann, Benjamin F.; Roy Chowdhury, Taniya; Yang, Ziming; Wullschleger, Stan D.; Graham, David; Liang, Liyuan; Gu, Baohua

    2015-11-01

    Arctic tundra soils store a large quantity of organic carbon that is susceptible to decomposition and release to the atmosphere as methane (CH4) and carbon dioxide (CO2) under a warming climate. Anaerobic processes that generate CH4 and CO2 remain unclear because previous studies have focused on aerobic decomposition pathways. To predict releases of CO2 and CH4 from tundra soils, it is necessary to identify pathways of soil organic matter decomposition under the anoxic conditions that are prevalent in Arctic ecosystems. Here molecular and spectroscopic techniques were used to monitor biological degradation of water-extractable organic carbon (WEOC) during anoxic incubation of tundra soils from a region of continuous permafrost in northern Alaska. Organic and mineral soils from the tundra active layer were incubated at -2, +4, or +8°C for up to 60 days to mimic the short-term thaw season. Results suggest that, under anoxic conditions, fermentation converted complex organic molecules into simple organic acids that were used in concomitant Fe-reduction and acetoclastic methanogenesis reactions. Nonaromatic compounds increased over time as WEOC increased. Organic acid metabolites initially accumulated in soils but were mostly depleted by day 60 because organic acids were consumed to produce Fe(II), CO2, and CH4. We conclude that fermentation of nonprotected organic matter facilitates methanogenesis and Fe reduction reactions, and that the proportion of organic acids consumed by methanogenesis increases relative to Fe reduction with increasing temperature. The decomposition pathways observed in this study are important to consider in numerical modeling of greenhouse gas production in the Arctic.

  1. Shrub Abundance Mapping in Arctic Tundra with Misr

    NASA Astrophysics Data System (ADS)

    Duchesne, R.; Chopping, M. J.; Wang, Z.; Schaaf, C.; Tape, K. D.

    2013-12-01

    Over the last 60 years an increase in shrub abundance has been observed in the Arctic tundra in connection with a rapid surface warming trend. Rapid shrub expansion may have consequences in terms of ecosystem structure and function, albedo, and feedbacks to climate; however, its rate is not yet known. The goal of this research effort is thus to map large scale changes in Arctic tundra vegetation by exploiting the structural signal in moderate resolution satellite remote sensing images from NASA's Multiangle Imaging SpectroRadiometer (MISR), mapped onto a 250m Albers Conic Equal Area grid. We present here large area shrub mapping supported by reference data collated using extensive field inventory data and high resolution panchromatic imagery. MISR Level 1B2 Terrain radiance scenes from the Terra satellite from 15 June-31 July, 2000 - 2010 were converted to surface bidirectional reflectance factors (BRF) using MISR Toolkit routines and the MISR 1 km LAND product BRFs. The red band data in all available cameras were used to invert the RossThick-LiSparse-Reciprocal BRDF model to retrieve kernel weights, model-fitting RMSE, and Weights of Determination. The reference database was constructed using aerial survey, three field campaigns (field inventory for shrub count, cover, mean radius and height), and high resolution imagery. Tall shrub number, mean crown radius, cover, and mean height estimates were obtained from QuickBird and GeoEye panchromatic image chips using the CANAPI algorithm, and calibrated using field-based estimates, thus extending the database to over eight hundred locations. Tall shrub fractional cover maps for the North Slope of Alaska were constructed using the bootstrap forest machine learning algorithm that exploits the surface information provided by MISR. The reference database was divided into two datasets for training and validation. The model derived used a set of 19 independent variables(the three kernel weights, ratios and interaction terms

  2. Prevalence, transmission, and genetic diversity of blood parasites infecting tundra-nesting geese in Alaska

    USGS Publications Warehouse

    Ramey, Andy M.; Reed, John A.; Schmutz, Joel A.; Fondell, Tom F.; Meixell, Brandt W.; Hupp, Jerry W.; Ward, David H.; Terenzi, John; Ely, Craig R.

    2014-01-01

    A total of 842 blood samples collected from five species of tundra-nesting geese in Alaska was screened for haemosporidian parasites using molecular techniques. Parasites of the generaLeucocytozoon Danilewsky, 1890, Haemoproteus Kruse, 1890, and Plasmodium Marchiafava and Celli, 1885 were detected in 169 (20%), 3 (<1%), and 0 (0%) samples, respectively. Occupancy modeling was used to estimate prevalence of Leucocytozoon parasites and assess variation relative to species, age, sex, geographic area, year, and decade. Species, age, and decade were identified as important in explaining differences in prevalence of Leucocytozoonparasites. Leucocytozoon parasites were detected in goslings sampled along the Arctic Coastal Plain using both historic and contemporary samples, which provided support for transmission in the North American Arctic. In contrast, lack of detection of Haemoproteus and Plasmodiumparasites in goslings (n = 238) provided evidence to suggest that the transmission of parasites of these genera may not occur among waterfowl using tundra habitats in Alaska, or alternatively, may only occur at low levels. Five haemosporidian genetic lineages shared among different species of geese sampled from two geographic areas were indicative of interspecies parasite transmission and supported broad parasite or vector distributions. However, identicalLeucocytozoon and Haemoproteus lineages on public databases were limited to waterfowl hosts suggesting constraints in the range of parasite hosts.

  3. Phytomass patterns across a temperature gradient of the North American arctic tundra

    NASA Astrophysics Data System (ADS)

    Epstein, Howard E.; Walker, Donald A.; Raynolds, Martha K.; Jia, Gensuo J.; Kelley, Alexia M.

    2008-09-01

    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. An additional complicating factor for studying vegetation of arctic tundra is the high spatial variability associated with small patterned-ground features, 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°C of mean July temperatures. Vegetation biomass was analyzed as functions of the summer warmth index (SWI-sum of mean monthly temperatures > 0°C). The total absolute biomass (g m-2) and biomass of shrubs increased monotonically with SWI, however, biomass of nonvascular species (mosses and lichens), were a parabolic function of SWI, with greatest values at the ends of the gradient. The components of plant biomass on patterned-ground features (i.e., on nonsorted circles or within small polygons) were constrained to a greater degree with colder climate than undisturbed tundra, likely due to the effect of frost heave disturbances on the vegetation. There were also clear differences in the relative abundances of vascular versus nonvascular plants on and off patterned-ground features along the SWI gradient. The spatial patterns of biomass differ among plant functional groups and suggest that plant community responses to temperature, and land-surface processes that produce patterned-ground features, are quite complex.

  4. Increasing Dissolved Organic Carbon (DOC) in Arctic tundra ponds over the past 40 years

    NASA Astrophysics Data System (ADS)

    Lougheed, V.; Contreras, G.; Andresen, C. G.; Miller, N. A.; Reyes, F. R.

    2013-12-01

    With a warming Arctic, permafrost is expected to thaw and active layer depth to increase, thus releasing organic material and nutrients into aquatic environments; however, there are few long-term datasets with which to test these predictions in aquatic ecosystems. The Arctic tundra ponds at the International Biological Program (IBP) site in Barrow, Alaska, studied for the first time in the 1970s, represent one of the very few locations in the Arctic where long-term data are available on freshwater ecosystem structure and function. The objective of this study was to determine whether Dissolved Organic Carbon (DOC) concentrations in Arctic tundra ponds had changed over time, how changes in thaw depth and temperature have impacted DOC quantity, and what the consequences of any changes have been for aquatic ecosystems. Over the summers of 2010-13 we collected water samples and measured thaw depth from 5 IBP ponds and compared these with data from the 1970s. Ponds were 2°C warmer and thaw depth was up to 19cm deeper in the 2000s as compared to the 1970s. Release of organic (e.g. DOC) and inorganic compounds (e.g.nitrogen) from formerly frozen organic ground into the ponds was associated with the increased thaw depth. For example, DOC was significantly higher in 2009-2012 compared to the 1970s; this was most notable later in the growing season. Similarly, incubations experiments indicate a steady rise in DOC released from permafrost with warming. DOC is likely a relatively conservative tracer of permafrost thaw in aquatic systems, and thus was a better predictor of increased phytoplankton levels than inorganic nutrients. This study will add to our understanding of the changes that warmer temperatures and altered aquatic environments bring to the Arctic and the consequences for carbon budgets in northern latitudes.

  5. Fourfold higher tundra volatile emissions due to arctic summer warming

    NASA Astrophysics Data System (ADS)

    Lindwall, Frida; Schollert, Michelle; Michelsen, Anders; Blok, Daan; Rinnan, Riikka

    2016-03-01

    Biogenic volatile organic compounds (BVOCs), which are mainly emitted by vegetation, may create either positive or negative climate forcing feedbacks. In the Subarctic, BVOC emissions are highly responsive to temperature, but the effects of climatic warming on BVOC emissions have not been assessed in more extreme arctic ecosystems. The Arctic undergoes rapid climate change, with air temperatures increasing at twice the rate of the global mean. Also, the amount of winter precipitation is projected to increase in large areas of the Arctic, and it is unknown how winter snow depth affects BVOC emissions during summer. Here we examine the responses of BVOC emissions to experimental summer warming and winter snow addition—each treatment alone and in combination—in an arctic heath during two growing seasons. We observed a 280% increase relative to ambient in BVOC emissions in response to a 4°C summer warming. Snow addition had minor effects on growing season BVOC emissions after one winter but decreased BVOC emissions after the second winter. We also examined differences between canopy and air temperatures and found that the tundra canopy surface was on average 7.7°C and maximum 21.6°C warmer than air. This large difference suggests that the tundra surface temperature is an important driver for emissions of BVOCs, which are temperature dependent. Our results demonstrate a strong response of BVOC emissions to increasing temperatures in the Arctic, suggesting that emission rates will increase with climate warming and thereby feed back to regional climate change.

  6. The response of Arctic vegetation and soils following an unusually severe tundra fire

    PubMed Central

    Bret-Harte, M. Syndonia; Mack, Michelle C.; Shaver, Gaius R.; Huebner, Diane C.; Johnston, Miriam; Mojica, Camilo A.; Pizano, Camila; Reiskind, Julia A.

    2013-01-01

    Fire causes dramatic short-term changes in vegetation and ecosystem function, and may promote rapid vegetation change by creating recruitment opportunities. Climate warming likely will increase the frequency of wildfire in the Arctic, where it is not common now. In 2007, the unusually severe Anaktuvuk River fire burned 1039 km2 of tundra on Alaska's North Slope. Four years later, we harvested plant biomass and soils across a gradient of burn severity, to assess recovery. In burned areas, above-ground net primary productivity of vascular plants equalled that in unburned areas, though total live biomass was less. Graminoid biomass had recovered to unburned levels, but shrubs had not. Virtually all vascular plant biomass had resprouted from surviving underground parts; no non-native species were seen. However, bryophytes were mostly disturbance-adapted species, and non-vascular biomass had recovered less than vascular plant biomass. Soil nitrogen availability did not differ between burned and unburned sites. Graminoids showed allocation changes consistent with nitrogen stress. These patterns are similar to those seen following other, smaller tundra fires. Soil nitrogen limitation and the persistence of resprouters will likely lead to recovery of mixed shrub–sedge tussock tundra, unless permafrost thaws, as climate warms, more extensively than has yet occurred. PMID:23836794

  7. 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

  8. Vegetation biomass, leaf area index, and NDVI patterns and relationships along two latitudinal transects in arctic tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Walker, D. A.; Raynolds, M. K.; Kelley, A. M.; Jia, G.; Ping, C.; Michaelson, G.; Leibman, M. O.; Kaarlejärvi, E.; Khomutov, A.; Kuss, P.; Moskalenko, N.; Orekhov, P.; Matyshak, G.; Forbes, B. C.; Yu, Q.

    2009-12-01

    Analyses of vegetation properties along climatic gradients provide first order approximations as to how vegetation might respond to a temporally dynamic climate. Until recently, no systematic study of tundra vegetation had been conducted along bioclimatic transects that represent the full latitudinal extent of the arctic tundra biome. Since 1999, we have been collecting data on arctic tundra vegetation and soil properties along two such transects, the North American Arctic Transect (NAAT) and the Yamal Arctic Transect (YAT). The NAAT spans the arctic tundra from the Low Arctic of the North Slope of Alaska to the polar desert of Cape Isachsen on Ellef Ringnes Island in the Canadian Archipelago. The Yamal Arctic Transect located in northwest Siberia, Russia, presently ranges from the forest-tundra transition at Nadym to the High Arctic tundra on Belyy Ostrov off the north coast of the Yamal Peninsula. The summer warmth indices (SWI - sum of mean monthly temperatures greater than 0°C) range from approximately 40 °C months to 3 °C months from south to north. For largely zonal sites along these transects, we systematically collected leaf area index (LAI-2000 Plant Canopy Analyzer), normalized difference vegetation index (NDVI - PSII hand-held spectro-radiometer), and vegetation biomass (clip harvests). Site-averaged LAI ranges from 1.08 to 0 along the transects, yet can be highly variable at the landscape scale. Site-averaged NDVI ranges from 0.67 to 0.26 along the transects, and is less variable than LAI at the landscape scale. Total aboveground live biomass ranges from approximately 700 g m-2 to < 50 g m-2 along the NAAT, and from approximately 1100 g m-2 to < 400 g m-2 along the YAT (not including tree biomass at Nadym). LAI and NDVI are highly correlated logarithmically (r = 0.80) for the entire dataset. LAI is significantly related to total aboveground (live plus dead) vascular plant biomass, although there is some variability in the data (r = 0.63). NDVI is

  9. Changes in tundra vascular plant biomass over thirty years at Imnavait Creek, Alaska, and current ecosystem C and N dynamics.

    NASA Astrophysics Data System (ADS)

    Bret-Harte, M. S.; Shaver, G. R.; Euskirchen, E. S.; Huebner, D. C.; Drew, J. W.; Cherry, J. E.; Edgar, C.

    2015-12-01

    Understanding the magnitude of, and controls over, carbon fluxes in arctic ecosystems is essential for accurate assessment and prediction of their responses to climate change. In 2013, we harvested vegetation and soils in the most common plant community types in source areas for fluxes measured by eddy covariance towers located in three representative Alaska tundra ecosystems along a toposequence (a ridge site of heath tundra and moist non-acidic tundra, a mid-slope site of moist acidic tussock tundra, and a valley bottom site of wet sedge tundra and moist acidic tussock tundra) at Imnavait Creek, Alaska. This harvest sought to relate biomass, production, composition, and C and N stocks in soil and vegetation, to estimates of net ecosystem CO2 exchange obtained by micrometeorological methods. Soil C and N stocks in the seasonally unfrozen soil layer were greatest in the wet sedge community, and least in the heath community. In contrast, moist acidic tussock tundra at the valley bottom site had the highest C and N stocks in vascular plant biomass, while nearby wet sedge tundra had the lowest. Overall, soil C:N ratio was highest in moist acidic tussock tundra at the mid-slope site. Aboveground biomass of vascular plants in moist acidic tundra at the mid-slope site was nearly three times higher than that measured thirty years earlier in vegetation harvests of nearby areas at Imnavait Creek. Other harvests from sites near Toolik Field Station suggest that vascular plant biomass in moist acidic tundra has increased in multiple sites over this time period. Increased biomass in the mid-1990s corresponds with a switch from mostly negative to mostly positive spatially-averaged air temperature anomalies in the climate record. All our sites have been annual net sources of CO2 to the atmosphere over nine years of measurement, but in the last two years, the valley bottom site has been a particularly strong source, due to CO2 losses in fall and winter that correspond with a

  10. Modelling tundra vegetation response to recent arctic warming.

    PubMed

    Miller, Paul A; Smith, Benjamin

    2012-01-01

    The Arctic land area has warmed by > 1 °C in the last 30 years and there is evidence that this has led to increased productivity and stature of tundra vegetation and reduced albedo, effecting a positive (amplifying) feedback to climate warming. We applied an individual-based dynamic vegetation model over the Arctic forced by observed climate and atmospheric CO(2) for 1980-2006. Averaged over the study area, the model simulated increases in primary production and leaf area index, and an increasing representation of shrubs and trees in vegetation. The main underlying mechanism was a warming-driven increase in growing season length, enhancing the production of shrubs and trees to the detriment of shaded ground-level vegetation. The simulated vegetation changes were estimated to correspond to a 1.75 % decline in snow-season albedo. Implications for modelling future climate impacts on Arctic ecosystems and for the incorporation of biogeophysical feedback mechanisms in Arctic system models are discussed. PMID:22864701

  11. 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

  12. Spatial Heterogeneity in Arctic Tundra Snow: Processes, Patterns, and Problems

    NASA Astrophysics Data System (ADS)

    Sturm, M.; Liston, G. E.; Wagner, A. M.; Hiemstra, C. A.

    2014-12-01

    Tundra snow (exclusive of drifts) tends to be a thin veneer (<1 m) modified by extensive aeolian features like dunes and barchans. These features are on the order of 0.2 to 1.0 m high, and the substrate beneath the veneer snow (often various types of tundra) can have similar local relief. Consequently, veneer snow depths exhibit a high degree of spatial heterogeneity. Lateral variations of depth as high as 50% or more can be observed over a few meters. Even greater depth variations occur where the topography creates traps that hold drifts as thick as 5 m. We have been measuring and modeling the tundra snow in a nested series of basins ranging from 1 to 200 km in northern Alaska for 30 years. These efforts show that while modeling can produce reasonably accurate simulations of the deeper drifts, in many cases it does not do a good job in capturing the more subtle aspects of the snow distribution, being hampered by limited precipitation and wind data. More accurate and detailed patterns of snow distribution can be revealed through direct measurement or through melt period sequential imagery. These can improve the accuracy of weather-driven model depth distributions, but producing pattern maps remains labor- and time-intensive. Both approaches tend to do poorly at scales of 100-m or less where surface features like sastrugi and dunes alter the snow depth. These small-scale variations in depth and snow water equivalent might not seem important, but comparison of point values of snow depth from observing stations with spatial maps of the snow surrounding the stations suggests that significant differences can exist. A more comprehensive understanding of drifting and drift features is needed in order to improve our ability to model and understand this dynamic and fascinating class of snow.

  13. Dynamics of Aboveground Phytomass of the Circumpolar Arctic Tundra During the Past Three Decades

    NASA Technical Reports Server (NTRS)

    Epstein, Howard E.; Raynolds, Martha K.; Walker, Donald A.; Bhatt, Uma S.; Tucker, Compton J.; Pinzon, Jorge E.

    2012-01-01

    Numerous studies have evaluated the dynamics of Arctic tundra vegetation throughout the past few decades, using remotely sensed proxies of vegetation, such as the normalized difference vegetation index (NDVI). While extremely useful, these coarse-scale satellite-derived measurements give us minimal information with regard to how these changes are being expressed on the ground, in terms of tundra structure and function. In this analysis, we used a strong regression model between NDVI and aboveground tundra phytomass, developed from extensive field-harvested measurements of vegetation biomass, to estimate the biomass dynamics of the circumpolar Arctic tundra over the period of continuous satellite records (1982-2010). We found that the southernmost tundra subzones (C-E) dominate the increases in biomass, ranging from 20 to 26%, although there was a high degree of heterogeneity across regions, floristic provinces, and vegetation types. The estimated increase in carbon of the aboveground live vegetation of 0.40 Pg C over the past three decades is substantial, although quite small relative to anthropogenic C emissions. However, a 19.8% average increase in aboveground biomass has major implications for nearly all aspects of tundra ecosystems including hydrology, active layer depths, permafrost regimes, wildlife and human use of Arctic landscapes. While spatially extensive on-the-ground measurements of tundra biomass were conducted in the development of this analysis, validation is still impossible without more repeated, long-term monitoring of Arctic tundra biomass in the field.

  14. 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.

  15. Isotopic identification of soil and permafrost nitrate sources in an Arctic tundra ecosystem

    DOE PAGESBeta

    Heikoop, Jeffrey M.; Throckmorton, Heather M.; Newman, Brent D.; Perkins, George B.; Iversen, Colleen M.; Chowdhury, Taniya Roy; Romanovsky, Vladimir; Graham, David E.; Norby, Richard J.; Wilson, Cathy J.; et al

    2015-05-13

    The nitrate (NO3–) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, to distinguish between NO3– derived from atmospheric deposition versus that derived from microbial nitrification.

  16. Measurements of NO(x) and NO(y) concentrations and fluxes over Arctic tundra

    NASA Technical Reports Server (NTRS)

    Bakwin, Peter S.; Wofsy, Steven C.; Fan, Song-Miao; Fitzjarrald, David R.

    1992-01-01

    Measurements of the atmospheric concentrations of NO, NO2, total NO(y), and O3 were made during the NASA Arctic Boundary Layer Expedition (ABLE 3A) at a remote location in a tundra bog ecosystem in southeastern Alaska during the growing season (July-August 1988). Concentrations of NO(x) and NO(y) were found to be very low compared to other remote continental sites, indicating that anthropogenic influences were small at this site during this time of year. The NO(y) emission rate from the soil were 0.13 +/- 0.05 x 10 exp 9 molecules/sq cm/s. Direct measurements of the flux of total NO(y) were made for the first time, indicating downward flux of NO(y) at all times of day, with maximum deposition of 2.5 +/- 0.9 x 10 exp 9 molecules/sq cm/s in the afternoon. Deposition of HNO3 appears to dominate the atmosphere/surface exchange of NO(y). The mean dry deposition rate of NO(y) to the tundra was 1.8 +/- 1.0 x 10 exp 9 molecules/sq cm/s.

  17. Diversification of Nitrogen Sources in Various Tundra Vegetation Types in the High Arctic

    PubMed Central

    Skrzypek, Grzegorz; Wojtuń, Bronisław; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

    2015-01-01

    Low nitrogen availability in the high Arctic represents a major constraint for plant growth, which limits the tundra capacity for carbon retention and determines tundra vegetation types. The limited terrestrial nitrogen (N) pool in the tundra is augmented significantly by nesting seabirds, such as the planktivorous Little Auk (Alle alle). Therefore, N delivered by these birds may significantly influence the N cycling in the tundra locally and the carbon budget more globally. Moreover, should these birds experience substantial negative environmental pressure associated with climate change, this will adversely influence the tundra N-budget. Hence, assessment of bird-originated N-input to the tundra is important for understanding biological cycles in polar regions. This study analyzed the stable nitrogen composition of the three main N-sources in the High Arctic and in numerous plants that access different N-pools in ten tundra vegetation types in an experimental catchment in Hornsund (Svalbard). The percentage of the total tundra N-pool provided by birds, ranged from 0–21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by atmospheric N2-fixation. The stable nitrogen isotope mixing mass balance, in contrast to direct methods that measure actual deposition, indicates the ratio between the actual N-loads acquired by plants from different N-sources. Our results enhance our understanding of the importance of different N-sources in the Arctic tundra and the used methodological approach can be applied elsewhere. PMID:26376204

  18. Expansion of forest stands into tundra in the Noatak National Preserve, northwest Alaska

    USGS Publications Warehouse

    Suarez, F.; Binkley, D.; Kaye, M.W.; Stottlemyer, R.

    1999-01-01

    Temperatures across the northern regions of North America have been increasing for 150 years, and forests have responded to this increase. In the Noatak National Preserve in Alaska, white spruce (Picea glauca [Moench] Voss) forests reach their northern limit, occurring primarily on well-drained sites and as gallery forests along streams. Rolling plateaus of tundra separate the white spruce forests into disjunct stands. We examined patterns of tree age, tree growth, and tree encroachment into tundra ecosystems in six stands along the Agashashok River. Warming over the past 150 years appears to have increased tree growth and resulted in forest expansion into adjacent tundra ecosystems. The forest/tundra ecotone shifted by about 80 to 100 m into the tundra in the past 200 years, as evidenced by declining maximum tree age with distance towards the tundra. The decadal-scale pattern of tree establishment at the farthest extent of trees into the tundra (the tundra-forest ecotone) correlated with the detrended growth index for trees within the forests; climate conditions that led to higher tree growth appeared to foster tree establishment in the tundra. This recent forest expansion has occurred across topographic boundaries, from well-drained soils on slopes onto poorly drained, flatter areas of tundra. Further expansion of the forests may be limited by more severe wind exposure and poor drainage that make the majority of tundra less suitable for trees.

  19. Shrub expansion and climate feedbacks in Arctic tundra

    NASA Astrophysics Data System (ADS)

    Loranty, Michael M.; Goetz, Scott J.

    2012-03-01

    Arctic tundra ecosystems stand to play a substantial role in both the magnitude and rate of global climate warming over the coming decades and centuries. The exact nature of this role will be determined by the combined effects of currently amplified rates of climate warming in the Arctic (Serreze et al 2000) and a series of related positive climate feedbacks that include mobilization of permafrost carbon (Schuur et al 2008), decreases in surface albedo (Chapin et al 2005) and evapotranspiration (ET) mediated increases in atmospheric water vapor (Swann et al 2010). Conceptually, these feedback mechanisms are intuitive and readily comprehensible: warming-induced permafrost thaw will make new soil carbon pools accessible for microbial respiration, and increased vegetation productivity, expansion of shrubs in particular, will lower surface reflectance and increase ET. However, our current understanding of these feedback mechanisms relies largely on limited and local field studies and, as such, the quantitative estimates of feedback effects on regional and global climate require spatial upscaling and uncertainty estimates derived from models. Moreover, the feedback mechanisms interact and their combined net effect on climate is highly variable and not well characterized. A recent study by Bonfils et al (2012) is among the first to explicitly examine how shrub expansion in tundra ecosystems will impact regional climate. Using an Earth system model, Bonfils et al find that an idealized 20% increase in shrub cover north of 60°N latitude will lead to annual temperature increases of 0.66 °C and 1.84 °C, respectively, when the shrubs are 0.5 m and 2 m tall. The modeled temperature increases arise from atmospheric heating as a combined consequence of decreased albedo and increased ET. The primary difference between the two cases is associated with the fact that tall shrubs protrude above the snow, thus reducing albedo year round, whereas short shrubs are completely

  20. 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

  1. Spatiotemporal patterns of tundra fires: late-Quaternary charcoal records from Alaska

    NASA Astrophysics Data System (ADS)

    Chipman, M. L.; Hudspith, V.; Higuera, P. E.; Duffy, P. A.; Kelly, R.; Oswald, W. W.; Hu, F. S.

    2015-07-01

    Anthropogenic climate change has altered many ecosystem processes in the Arctic tundra and may have resulted in unprecedented fire activity. Evaluating the significance of recent fires requires knowledge from the paleofire record because observational data in the Arctic span only several decades, much shorter than the natural fire rotation in Arctic tundra regions. Here we report results of charcoal analysis on lake sediments from four Alaskan lakes to infer the broad spatial and temporal patterns of tundra-fire occurrence over the past 35 000 years. Background charcoal accumulation rates are low in all records (range is 0-0.05 pieces cm-2 yr-1), suggesting minimal biomass burning across our study areas. Charcoal peak analysis reveals that the mean fire-return interval (FRI; years between consecutive fire events) ranged from ca. 1650 to 6050 years at our sites, and that the most recent fire events occurred from ca. 880 to 7030 years ago, except for the CE 2007 Anaktuvuk River Fire. These mean FRI estimates are longer than the fire rotation periods estimated for the past 63 years in the areas surrounding three of the four study lakes. This result suggests that the frequency of tundra burning was higher over the recent past compared to the late Quaternary in some tundra regions. However, the ranges of FRI estimates from our paleofire records overlap with the expected values based on fire-rotation-period estimates from the observational fire data, and the differences are statistically insignificant. Together with previous tundra-fire reconstructions, these data suggest that the rate of tundra burning was spatially variable and that fires were extremely rare in our study areas throughout the late Quaternary. Given the rarity of tundra burning over multiple millennia in our study areas and the pronounced effects of fire on tundra ecosystem processes such as carbon cycling, dramatic tundra ecosystem changes are expected if anthropogenic climate change leads to more

  2. Could 4 degrees warming change Arctic tundra from carbon sink to carbon source?

    NASA Astrophysics Data System (ADS)

    Torn, M. S.; Abramoff, R. Z.; Chafe, O.; Curtis, J. B.; Smith, L. J.; Wullschleger, S. D.

    2015-12-01

    We have set up a controlled, active warming experiment in permafrost tundra on the North Slope of Alaska. The aim of this micro-warming experiment is to investigate the direct effect of soil warming on microbial decomposition of soil organic matter. We are testing the feasibility of small, short-term, in situ warming that can be run off batteries for distributed deployment and that preserves plant-soil relations and natural variability in wind, temperature, and precipitation. Based on preliminary results, the approach looks promising. One resistance heater cable per plot (25 cm diameter plots) was inserted vertically to 50 cm, spanning the full active layer (maximum thaw depth was 40 cm in 2014). Heaters were turned on August 1, 2015, and heated plots reached the 4ºC warming target within 1-3 days. We are measuring soil microclimate, thaw depth, CO2 and CH4 fluxes, and 14CO2, and microbial composition, as part of the DOE Next Generation Ecosystem Experiments (NGEE-Arctic). Ecosystem respiration increased immediately in the heated plots, and net ecosystem exchange under clear chambers changed from net uptake to net CO2 source in two of the four plots. CH4 flux shifted toward reduced net emissions or greater net uptake in all plots. These rapid responses demonstrate direct changes in decomposition without complications from microbial acclimation, altered community structure or changes in substrate availability. However, future Arctic tundra carbon balance will depend on both short term and long term microbial responses, as well as the links between warming, decomposition, nitrogen mineralization, and plant growth. Thus, we envision that distributed micro-warming plots could be combined with new approaches to aboveground passive warming being developed in NGEE, gradient studies, and modeling.

  3. Geochemical drivers of organic matter decomposition in Arctic tundra soils

    DOE PAGESBeta

    Herndon, Elizabeth M.; Yang, Ziming; Graham, David E.; Wullschleger, Stan D.; Gu, Baohua; Liang, Liyuan; Bargar, John; Janot, Noemie; Regier, Tom Z.

    2015-12-07

    Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO2) and methane (CH4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonal patterns ofmore » dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH4 increased relative to dissolved CO2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.« less

  4. Geochemical drivers of organic matter decomposition in Arctic tundra soils

    SciTech Connect

    Herndon, Elizabeth M.; Yang, Ziming; Graham, David E.; Wullschleger, Stan D.; Gu, Baohua; Liang, Liyuan; Bargar, John; Janot, Noemie; Regier, Tom Z.

    2015-12-07

    Climate change is warming tundra ecosystems in the Arctic, resulting in the decomposition of previously-frozen soil organic matter (SOM) and release of carbon (C) to the atmosphere; however, the processes that control SOM decomposition and C emissions remain highly uncertain. In this study, we evaluate geochemical factors that influence anaerobic production of carbon dioxide (CO2) and methane (CH4) in the active layers of four ice-wedge polygons. Surface and soil pore waters were collected during the annual thaw season over a two-year period in an area containing waterlogged, low-centered polygons and well-drained, high-centered polygons. We report spatial and seasonal patterns of dissolved gases in relation to the geochemical properties of Fe and organic C as determined using spectroscopic and chromatographic techniques. Iron was present as Fe(II) in soil solution near the permafrost boundary but enriched as Fe(III) in the middle of the active layer, similar to dissolved aromatic-C and organic acids. Dissolved CH4 increased relative to dissolved CO2 with depth and varied with soil moisture in the middle of the active layer in patterns that were positively correlated with the proportion of dissolved Fe(III) in transitional and low-centered polygon soils but negatively correlated in the drier flat- and high-centered polygons. These results suggest that microbial-mediated Fe oxidation and reduction influence respiration/fermentation of SOM and production of substrates (e.g., low-molecular-weight organic acids) for methanogenesis. As a result, we infer that geochemical differences induced by water saturation dictate microbial products of SOM decomposition, and Fe geochemistry is an important factor regulating methanogenesis in anoxic tundra soils.

  5. Determining Regional Arctic Tundra Carbon Exchange: A Bottom-Up Approach

    NASA Technical Reports Server (NTRS)

    Huemmrich, Fred

    2006-01-01

    This viewgraph presentation reviews the carbon atmospheric exchange with Arctic tundra. In the Arctic the ecosystem has been a net carbon sink. The project investigates the question of how might climate warming effect high latitude ecosystems and the Earth ecosystems and how to measure the changes.

  6. Backscatter from ice growing on shallow tundra lakes near Barrow, Alaska, winter 1991-1992

    NASA Technical Reports Server (NTRS)

    Jeffries, M. O.; Wakabayashi, H.; Weeks, W. F.; Morris, K.

    1993-01-01

    The timing of freeze-up and break-up of Arctic lake ice is a potentially useful environmental indicator that could be monitored using SAR. In order to do this, it is important to understand how the properties and structure of the ice during its growth and decay affect radar backscatter and thus lake ice SAR signatures. The availability of radiometrically and geometrically calibrated digital SAR data time series from the Alaska SAR Facility has made it possible for the first time to quantify lake ice backscatter intensity (sigma(sup o)) variations. This has been done for ice growing on shallow tundra lakes near Barrow, NW Alaska, from initial growth in September 1991 until thawing and decay in June 1992. Field and laboratory observations and measurements of the lake ice were made in late April 1992. The field investigations of the coastal lakes near Barrow confirmed previous findings that, (1) ice frozen to the lake bottom had a dark signature in SAR images, indicating weak backscatter, while, (2) ice that was floating had a bright signature, indicating strong backscatter. At all sites, regardless of whether the ice was grounded or floating, there was a layer of clear, inclusion-free ice overlaying a layer of ice with dense concentrations of vertically oriented tubular bubbles. At some sites, there was a third layer of porous, snow-ice overlaying the clear ice.

  7. Can antibrowsing defense regulate the spread of woody vegetation in arctic tundra?

    USGS Publications Warehouse

    Bryant, John P.; Joly, Kyle; Chapin, F. Stuart, III; DeAngelis, Donald L.; Kielland, Knut

    2014-01-01

    Global climate warming is projected to promote the increase of woody plants, especially shrubs, in arctic tundra. Many factors may affect the extent of this increase, including browsing by mammals. We hypothesize that across the Arctic the effect of browsing will vary because of regional variation in antibrowsing chemical defense. Using birch (Betula) as a case study, we propose that browsing is unlikely to retard birch expansion in the region extending eastward from the Lena River in central Siberia across Beringia and the continental tundra of central and eastern Canada where the more effectively defended resin birches predominate. Browsing is more likely to retard birch expansion in tundra west of the Lena to Fennoscandia, Iceland, Greenland and South Baffin Island where the less effectively defended non-resin birches predominate. Evidence from the literature supports this hypothesis. We further suggest that the effect of warming on the supply of plant-available nitrogen will not significantly change either this pan-Arctic pattern of variation in antibrowsing defense or the resultant effect that browsing has on birch expansion in tundra. However, within central and east Beringia warming-caused increases in plant-available nitrogen combined with wildfire could initiate amplifying feedback loops that could accelerate shrubification of tundra by the more effectively defended resin birches. This accelerated shrubification of tundra by resin birch, if extensive, could reduce the food supply of caribou causing population declines. We conclude with a brief discussion of modeling methods that show promise in projecting invasion of tundra by woody plants.

  8. Airborne Spectral Measurements of Surface-Atmosphere Anisotropy for Arctic Sea Ice and Tundra

    NASA Technical Reports Server (NTRS)

    Arnold, G. Thomas; Tsay, Si-Chee; King, Michael D.; Li, Jason Y.; Soulen, Peter F.

    1999-01-01

    Angular distributions of spectral reflectance for four common arctic surfaces: snow-covered sea ice, melt-season sea ice, snow-covered tundra, and tundra shortly after snowmelt were measured using an aircraft based, high angular resolution (1-degree) multispectral radiometer. Results indicate bidirectional reflectance is higher for snow-covered sea ice than melt-season sea ice at all wavelengths between 0.47 and 2.3 pm, with the difference increasing with wavelength. Bidirectional reflectance of snow-covered tundra is higher than for snow-free tundra for measurements less than 1.64 pm, with the difference decreasing with wavelength. Bidirectional reflectance patterns of all measured surfaces show maximum reflectance in the forward scattering direction of the principal plane, with identifiable specular reflection for the melt-season sea ice and snow-free tundra cases. The snow-free tundra had the most significant backscatter, and the melt-season sea ice the least. For sea ice, bidirectional reflectance changes due to snowmelt were more significant than differences among the different types of melt-season sea ice. Also the spectral-hemispherical (plane) albedo of each measured arctic surface was computed. Comparing measured nadir reflectance to albedo for sea ice and snow-covered tundra shows albedo underestimated 5-40%, with the largest bias at wavelengths beyond 1 pm. For snow-free tundra, nadir reflectance underestimates plane albedo by about 30-50%.

  9. Estimating carbon and energy fluxes in arctic tundra

    NASA Astrophysics Data System (ADS)

    Gokkaya, K.; Jiang, Y.; Rastetter, E.; Shaver, G. R.; Rocha, A. V.

    2013-12-01

    Arctic ecosystems are undergoing a very rapid change due to climate change and their response to climate change has important implications for the global energy budget and carbon (C) cycling. Therefore, it is important to understand how (C) and energy fluxes in the Arctic will respond to climate change. However, attribution of these responses to climate is challenging because measured fluxes are the sum of multiple processes that respond differently to environmental factors. For example, net ecosystem exchange of CO2 (NEE) is the net result of gross (C) uptake by plant photosynthesis (GPP) and (C) loss by ecosystem respiration (ER) and similarly, evapotranspiration (i.e. latent energy, LE) is the sum of transpiration and evaporation. Partitioning of NEE into GPP and ER requires nighttime measurements of NEE, when photosynthesis does not take place, to be extrapolated to daytime. This is challenging in the Arctic because of the long photoperiod during the growing season and the errors involved during the extrapolation. Transpiration (energy), photosynthesis (carbon), and vegetation phenology are inherently coupled because leaf stomata are the primary regulators of gas exchange. Our objectives in this study are to i) estimate canopy resistance (Rc) based on a light use efficiency model, ii) utilize the estimated Rc to predict GPP and transpiration using a coupled C and energy model and thus improve the partitioning of NEE and LE, and iii) to test ensemble Kalman filter (EnKF) to estimate model parameters and improve model predictions. Results from one growing season showed that the model predictions can explain 75 and 71% of the variance in GPP and LE in the Arctic tundra ecosystem, respectively. When the model was embedded within the EnKF for estimating Rc, the amount of variance explained for GPP increased to 81% but there was no improvement for the prediction of LE. This suggests that the factors controlling LE are not fully integrated in the model such as the

  10. Geochemical characterization of Arctic tundra and implications for organic matter degradation

    NASA Astrophysics Data System (ADS)

    Gu, B.; Herndon, E.; Graham, D. E.; Phelps, T. J.; Wullschleger, S. D.; Liang, L.

    2013-12-01

    Tundra soils are uniquely cold terrestrial environments that face irrevocable change under warming climate conditions. Specifically, many tundra soils store large quantities of organic carbon that may rapidly degrade with increasing temperature, releasing C into drainage systems or to the atmosphere as greenhouse gases (CH4, CO2). In order to predict rates of C release from tundra soils, it is necessary to quantify how biogeochemical factors such as pore water chemistry, terminal electron acceptor availability, and mineral adsorption regulate rates and pathways of soil organic carbon (SOC) degradation. In this study, we examine spatial and seasonal patterns of aqueous geochemistry and SOC characteristics from across an area of tundra landscape in the Arctic. We aim to identify factors that increase or decrease rates of SOC degradation, including: 1) the composition of organic substrates, 2) abundance of terminal electron acceptors, 3) vertical transport and spatial variability of both organic and inorganic compounds, and 4) adsorption to mineral surfaces. Soil and water samples were obtained from the Barrow Environmental Observatory (BEO) in northern Alaska as part of the Next Generation Ecosystem Experiment (NGEE) Arctic project. Tundra at the BEO is characterized by permafrost below ~60 cm and polygonal features that induce topographic gradients of water saturation. Soils are organic-rich and store large amounts of slowly decomposing plant material. Chemical and physical extractions were used to obtain operationally-defined pools of SOC to evaluate their mineral associations. Water samples collected in early and late summers were analyzed for pH, electrical conductivity, and dissolved concentrations of anions, cations, organic carbon, inorganic carbon, and ferrous iron, as well as dissolved and soil gases (CH4 and CO2). We observe a steep pH gradient, with acidic pH in surface waters and near neutral pH in pore waters >20 cm below the surface. Dissolved organic

  11. NOAA Atmospheric Baseline Observatories in the Arctic: Alaska & Greenland

    NASA Astrophysics Data System (ADS)

    Vasel, B. A.; Butler, J. H.; Schnell, R. C.; Crain, R.; Haggerty, P.; Greenland, S.

    2013-12-01

    The National Oceanic and Atmospheric Administration (NOAA) operates two year-round, long-term climate research facilities, known as Atmospheric Baseline Observatories (ABOs), in the Arctic Region. The Arctic ABOs are part of a core network to support the NOAA Global Monitoring Division's mission to acquire, evaluate, and make available accurate, long-term records of atmospheric gases, aerosol particles, and solar radiation in a manner that allows the causes of change to be understood. The observatory at Barrow, Alaska (BRW) was established in 1973 and is now host to over 200 daily measurements. Located a few kilometers to the east of the village of Barrow at 71.3° N it is also the northernmost point in the United States. Measurement records from Barrow are critical to our understanding of the Polar Regions including exchange among tundra, atmosphere, and ocean. Multiple data sets are available for carbon cycle gases, halogenated gases, solar radiation, aerosol properties, ozone, meteorology, and numerous others. The surface, in situ carbon dioxide record alone consists of over 339,000 measurements since the system was installed in July 1973. The observatory at Summit, Greenland (SUM) has been a partnership with the National Science Foundation (NSF) Division of Polar Programs since 2004, similar to that for South Pole. Observatory data records began in 1997 from this facility located at the top of the Greenland ice sheet at 72.58° N. Summit is unique as the only high-altitude (3200m), mid-troposphere, inland, Arctic observatory, largely free from outside local influences such as thawing tundra or warming surface waters. The measurement records from Summit help us understand long-range transport across the Arctic region, as well as interactions between air and snow. Near-real-time data are available for carbon cycle gases, halogenated gases, solar radiation, aerosol properties, meteorology, ozone, and numerous others. This poster will highlight the two facilities

  12. 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

  13. Mycorrhizal colonization mediated by species interactions in arctic tundra.

    PubMed

    Urcelay, Carlos; Bret-Harte, M Syndonia; Díaz, Sandra; Chapin, F Stuart

    2003-11-01

    The Alaskan tussock tundra is a strongly nutrient-limited ecosystem, where almost all vascular plant species are mycorrhizal. We established a long-term removal experiment to document effects of arctic plant species on ecto- and ericoid mycorrhizal fungi and to investigate whether species interactions and/or nutrient availability affect mycorrhizal colonization. The treatments applied were removal of Betula nana ( Betulaceae, dominant deciduous shrub species), removal of Ledum palustre ( Ericaceae, dominant evergreen shrub species), control (no removal), and each of these three treatments with the addition of fertilizer. After 3 years of Ledum removal and fertilization, we found that overall ectomycorrhizal colonization in Betula was significantly reduced. Changes in ectomycorrhizal morphotype composition in removal and fertilized treatments were also observed. These results suggest that the effect of Ledum on Betula's mycorrhizal roots is due to sequestration of nutrients by Ledum, leading to reduced nutrient availability in the soil. In contrast, ericoid mycorrhizal colonization was not affected by fertilization, but the removal of Betula and to a lower degree of Ledum resulted in a reduction of ericoid mycorrhizal colonization suggesting a direct effect of these species on ericoid mycorrhizal colonization. Nutrient availability was only higher in fertilized treatments, but caution should be taken with the interpretation of these data as soil microbes may effectively compete with the ion exchange resins for the nutrients released by plant removal in these nutrient-limited soils. PMID:12905060

  14. Identifying nitrogen limitations to organic sediments accumulation in various vegetation types of arctic tundra (Hornsund, Svalbard)

    NASA Astrophysics Data System (ADS)

    Skrzypek, G.; Wojtuń, B.; Hua, Q.; Richter, D.; Jakubas, D.; Wojczulanis-Jakubas, K.; Samecka-Cymerman, A.

    2015-12-01

    Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) deficiency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of the relative contributions from different N-sources is critical for understanding the constraints that limit tundra growth. The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in ten tundra types in the Fuglebekken catchment (Hornsund Fjord, Svalbard, 77°N 15°E). The percentage of the total tundra N-pool provided by seabirds' feces (colonially breeding, planktivorous Alle alle), ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment was built in 36% by birds, 38% by atmospheric deposition, and 26% by N2-fixation. The results clearly show that N-pool in the tundra is significantly supplemented by nesting seabirds. Thus, if they experienced substantial negative environmental pressure associated with climate change, it would adversely influence the tundra N-budget [1]. The growth rates and the sediment thickness (<15 cm) in different tundra types varied considerably but the tundra age was similar, <450 cal BP. The only exception was Ornithocoprophilous tundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110cm. The growth rates for this tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and then substantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additional argument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds' contribution to the tundra N-pool. [1] Skrzypek G, Wojtuń B, Richter D, Jakubas D, Wojczulanis-Jakubas K, Samecka-Cymerman A, 2015. Diversification of nitrogen sources in various tundra vegetation types in the high Arctic. PLoS ONE

  15. Tundra vegetation change near Barrow, Alaska (1972-2010)

    NASA Astrophysics Data System (ADS)

    Villarreal, S.; Hollister, R. D.; Johnson, D. R.; Lara, M. J.; Webber, P. J.; Tweedie, C. E.

    2012-03-01

    Knowledge of how arctic plant communities will respond to change has been largely derived from plot level experimental manipulation, not from trends of decade time scale environmental observations. This study documents plant community change in 330 marked plots at 33 sites established during the International Biological Program near Barrow, Alaska in 1972. Plots were resampled in 1999, 2008 and 2010 for species cover and presence. Cluster analysis identified nine plant communities in 1972. Non-metric multidimensional scaling (NMS) indicates that plant communities have changed in different ways over time, and that wet communities have changed more than dry communities. The relative cover of lichens increased over time, while the response of other plant functional groups varied. Species richness and diversity also increased over time. The most dramatic changes in the cover of bryophytes, graminoids and bare ground coincided with a lemming high in 2008.

  16. Long-term Nutrient Fertilization Increases CO2 Loss in Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Graham, L. M.; Natali, S.; Rastetter, E. B.; Shaver, G. R.; Risk, D. A.; Loranty, M. M.; Jastrow, J. D.

    2015-12-01

    As anthropogenic climate change warms the Arctic, organic carbon (C) trapped in permafrost is at an increased risk of being released to the atmosphere as carbon dioxide (CO2). At the same time, higher rates of decomposition may increase nutrient availability and enhance plant growth, leading to an uptake of C that may offset respiratory losses. Arctic tundra ecosystems are highly nitrogen (N) limited, and the indirect effects of warming on nutrient availability will be the most likely outcome of increased temperature on plant productivity. This study aims to understand the effects of nutrient addition on arctic CO2 and H2O exchange in a tundra ecosystem at Toolik Lake Field Station, Alaska. The nutrient addition experiment, which began in 2006, is comprised of 7 fertilization treatments: 0.5, 1, 2, 5, and 10 g m-2 of N as NO3- and NH4+ (1:1) with 0.25, 0.5, 1, 2.5, and 5 g m-2 of phosphorus as PO43-; 5 g m-2 of N as NO3-; 5 g m-2 of N as NH4+, and one control plot. Plot-level CO2 and H2O exchange was measured at 5 light levels 7 times over a four-week period in June and July 2015. We measured ecosystem CO2 and H2O exchange using a rectangular plexiglass chamber (0.49 m2) that was connected to an infrared gas analyzer (LI-840). Other ecosystem variables measured include thaw depth, soil moisture and temperature, and normalized difference vegetation index. After 10 years of nutrient addition, fertilization significantly altered ecosystem C cycling. Soil respiration was greatest in the highest fertilization treatment (2.97 μmol m-2 s-1), increasing linearly with nutrient level at a rate of 0.133 μmol m-2 s-1 per g m-2 of N added (R2=0.914). Net CO2 uptake was greatest under highest fertilization (-2.06 μmol m-2 s-1), decreasing linearly with nutrient addition at a rate of -0.068 μmol m-2 s-1 per g m-2 of N added (R2=0.687). These results suggest that as nutrients become more available under a warmer climate, plant productivity increases may not offset respiratory

  17. Microbial iron oxidation in the Arctic tundra and its implications for biogeochemical cycling.

    PubMed

    Emerson, David; Scott, Jarrod J; Benes, Joshua; Bowden, William B

    2015-12-01

    The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long -149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. PMID:26386054

  18. Microbial Iron Oxidation in the Arctic Tundra and Its Implications for Biogeochemical Cycling

    PubMed Central

    Scott, Jarrod J.; Benes, Joshua; Bowden, William B.

    2015-01-01

    The role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long −149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance of Proteobacteria, with Betaproteobacteria and members of the family Comamonadaceae being the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides. PMID:26386054

  19. Alaska's Living Tundra. Alaska Wildlife Week, 25-29 April 1988. Unit 6: Primary Teacher's Guide; Upper Elementary Teacher's Guide; Junior/Senior High School Teacher's Guide; Supplement.

    ERIC Educational Resources Information Center

    Quinlan, Susan E.

    Despite its cold and barren appearance, Alaska's tundra supports a surprising variety of insects, birds, and mammals. In this document, three teacher's guides (for primary, upper elementary, and junior and senior high schools) and a supplementary resource packet present a comprehensive unit of study on Alaska's living tundra. The five lessons in…

  20. 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

  1. Improving understanding of controls on spatial variability in methane fluxes in Arctic tundra

    NASA Astrophysics Data System (ADS)

    Davidson, Scott J.; Sloan, Victoria; Phoenix, Gareth; Wagner, Robert; Oechel, Walter; Zona, Donatella

    2015-04-01

    The Arctic is experiencing rapid climate change relative to the rest of the globe, and this increase in temperature has feedback effects across hydrological and thermal regimes, plant community distribution and carbon stocks within tundra soils. Arctic wetlands account for a significant amount of methane emissions from natural ecosystems to the atmosphere and with further permafrost degradation under a warming climate, these emissions are expected to increase. Methane (CH4) is an extremely important component of the global carbon cycle with a global warming potential 28.5 times greater than carbon dioxide over a 100 year time scale (IPCC, 2013). In order to validate carbon cycle models, modelling methane at broader landscape scales is needed. To date direct measurements of methane have been sporadic in time and space which, while capturing some key controls on the spatial heterogeneity, make it difficult to accurately upscale methane emissions to the landscape and regional scales. This study investigates what is controlling the spatial heterogeneity of methane fluxes across Arctic tundra. We combined over 300 portable chamber observations from 13 micro-topographic positions (with multiple vegetation types) across three locations spanning a 300km latitudinal gradient in Northern Alaska from Barrow to Ivotuk with synchronous measurements of environmental (soil temperature, soil moisture, water table, active layer thaw depth, pH) and vegetation (plant community composition, height, sedge tiller counts) variables to evaluate key controls on methane fluxes. To assess the diurnal variation in CH4 fluxes, we also performed automated chamber measurements in one study site (Barrow) location. Multiple statistical approaches (regression tree and multiple linear regression) were used to identify key controlling variables and their interactions. Methane emissions across all sites ranged from -0.08 to 15.3 mg C-CH4 m-2 hr-1. As expected, soil moisture was the main control

  2. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils.

    PubMed

    Lipson, David A; Raab, Theodore K; Parker, Melanie; Kelley, Scott T; Brislawn, Colin J; Jansson, Janet

    2015-08-01

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes). PMID:26034016

  3. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    SciTech Connect

    Lipson, David A.; Raab, Theodore K.; Parker, Melanie; Kelley, Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-08-01

    Summary This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes,

  4. Changes in microbial communities along redox gradients in polygonized Arctic wet tundra soils

    SciTech Connect

    Lipson, David A.; Raab, Theodore K.; Parker, Melanie; Kelley, Scott T.; Brislawn, Colin J.; Jansson, Janet K.

    2015-07-21

    This study investigated how microbial community structure and diversity varied with depth and topography in ice wedge polygons of wet tundra of the Arctic Coastal Plain in northern Alaska, and what soil variables explain these patterns. We observed strong changes in community structure and diversity with depth, and more subtle changes between areas of high and low topography, with the largest differences apparent near the soil surface. These patterns are most strongly correlated with redox gradients (measured using the ratio of reduced Fe to total Fe in acid extracts as a proxy): conditions grew more reducing with depth and were most oxidized in shallow regions of polygon rims. Organic matter and pH also changed with depth and topography, but were less effective predictors of the microbial community structure and relative abundance of specific taxa. Of all other measured variables, lactic acid concentration was the best, in combination with redox, for describing the microbial community. We conclude that redox conditions are the dominant force in shaping microbial communities in this landscape. Oxygen and other electron acceptors allowed for the greatest diversity of microbes: at depth the community was reduced to a simpler core of anaerobes, dominated by fermenters (Bacteroidetes and Firmicutes).

  5. Geochemical drivers of organic matter decomposition in the active layer of Arctic tundra

    NASA Astrophysics Data System (ADS)

    Herndon, E.; Roy Chowdhury, T.; Mann, B.; Graham, D. E.; Wullschleger, S. D.; Gu, B.; Liang, L.

    2014-12-01

    Arctic tundra soils store large quantities of organic carbon that are susceptible to decomposition and release to the atmosphere as CO2 and CH4. Decomposition rates are limited by cold temperatures and widespread anoxia; however, ongoing changes in soil temperature, thaw depth, and water saturation are expected to influence rates and pathways of organic matter decomposition. In order to predict greenhouse gas releases from high-latitude ecosystems, it is necessary to identify how geochemical factors (e.g. terminal electron acceptors, carbon substrates) influence CO2 and CH4 production in tundra soils. This study evaluates spatial patterns of aqueous geochemistry in the active layer of low- to high-centered polygons located at the Barrow Environmental Observatory in northern Alaska. Pore waters from saturated soils were low in sulfate and nitrate but contained abundant Fe which may serve a major terminal electron acceptor for anaerobic microbial metabolism. Relatively high concentrations of soluble Fe accumulated in the middle of the active layer near the boundary between the organic and mineral horizon, and we infer that Fe-oxide reduction and dissolution in the mineral horizon produced soluble Fe that diffused upwards and was stabilized by complexation with dissolved organic matter. Fe concentrations in the bulk soil were higher in organic than mineral horizons due to the presence of these organic-Fe complexes and Fe-oxide precipitates. Dissolved CH4 increased with increasing proportions of dissolved Fe(III) in saturated soils from transitional and low-centered polygons. The opposite trend was observed in drier soils from flat- and high-centered polygons where deeper oxidation fronts may inhibit methanogenesis. Using multiple spectroscopic and molecular methods (e.g. UV-Vis, Fourier transform infrared, ultrahigh resolution mass spectrometry), we also observed that pore waters from the middle of the active layer contained more aromatic organics than in mineral

  6. Fire behavior, weather, and burn severity of the 2007 anaktuvuk river tundra fire, North Slope, Alaska

    USGS Publications Warehouse

    Jones, B.; Kolden, C.; Jandt, R.; Abatzoglou, J.; Urban, F.; Arp, C.

    2009-01-01

    In 2007, the Anaktuvuk River Fire (ARF) became the largest recorded tundra fire on the North Slope of Alaska. The ARF burned for nearly three months, consuming more than 100,000 ha. At its peak in early September, the ARF burned at a rate of 7000 ha d-1. The conditions potentially responsible for this large tundra fire include modeled record high summer temperature and record low summer precipitation, a late-season high-pressure system located over the Beaufort Sea, extremely dry soil conditions throughout the summer, and sustained southerly winds during the period of vegetation senescence. Burn severity mapping revealed that more than 80% of the ARF burned at moderate to extreme severity, while the nearby Kuparuk River Fire remained small and burned at predominantly (80%) low severity. While this study provides information that may aid in the prediction of future large tundra fires in northern Alaska, the fact that three other tundra fires that occurred in 2007 combined to burn less than 1000 ha suggests site specific complexities associated with tundra fires on the North Slope, which may hamper the development of tundra fire forecasting models.

  7. Use of a cable-based system for observing the heterogeneity of vegetation communities in arctic tundra

    NASA Astrophysics Data System (ADS)

    Ahrends, H. E.; Oberbauer, S. F.; Tweedie, C.; Hollister, R. D.

    2010-12-01

    Knowledge of changing tundra vegetation and its response to climate variability is critical for understanding the land-atmosphere-interactions for the Arctic and the global system. However, vegetation characteristics, such as phenology, structure and species composition, are characterized by an extreme heterogeneity at a small scale. Manual observations of these variables are highly time-consuming, labor intensive, subjective, and disturbing to the vegetation. In contrast, recently developed robotic systems (networked infomechanical systems, NIMS) allow for performing non-intrusive spatially integrated measurements of vegetation communities. Within the ITEX (International Tundra Experiment) AON (Arctic Observation Network) project we installed a cable-based sensor system, running over a transect of approximately 50 m length and 2 m width, at two long-term arctic research sites in Alaska. The trolley was initially equipped with instruments recording the distance to vegetation canopy, up- and downwelling short- and longwave radiation, air and surface temperature and spectral reflection. We aim to study the thermal and spectral response of the vegetation communities over a wide range of ecosystem types. We expect that automated observations, covering the spatial heterogeneity of vegetation and surface characteristics, can give a deeper insight in ecosystem functioning and vegetation response to climate. The data can be used for scaling up vegetation characteristics derived from manual measurements and for linking them to aircraft and satellite data and to carbon, water and surface energy budgets measured at the ecosystem scale. Sampling errors due to cable sag are correctable and effects of wind-driven movements can be offset by repeat measurements. First hand-pulled test measurements during summer 2010 show strong heterogeneity of the observation parameters and a variable spectral and thermal response of the plants within the transects. Differences support the

  8. Isotopic identification of soil and permafrost nitrate sources in an Arctic tundra ecosystem

    SciTech Connect

    Heikoop, Jeffrey M.; Throckmorton, Heather M.; Newman, Brent D.; Perkins, George B.; Iversen, Colleen M.; Chowdhury, Taniya Roy; Romanovsky, Vladimir; Graham, David E.; Norby, Richard J.; Wilson, Cathy J.; Wullschleger, Stan D.

    2015-05-13

    The nitrate (NO3) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, to distinguish between NO3 derived from atmospheric deposition versus that derived from microbial nitrification.

  9. Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Liu, L.; Schaefer, K.; Gusmeroli, A.; Grosse, G.; Jones, B. M.; Zhang, T.; Parsekian, A. D.; Zebker, H. A.

    2013-12-01

    Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on arctic tundra lowlands, but their present-day dynamic states are seldom investigated. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located near Prudhoe Bay, Alaska where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area analyzed exhibited seasonal thaw settlement of 3-4 cm. However, four of the DTLBs analyzed exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10-35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on arctic coastal lowlands.

  10. Range Expansion of Moose in Arctic Alaska Linked to Warming and Increased Shrub Habitat

    PubMed Central

    Tape, Ken D.

    2016-01-01

    Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators. PMID:27074023

  11. Range Expansion of Moose in Arctic Alaska Linked to Warming and Increased Shrub Habitat.

    PubMed

    Tape, Ken D; Gustine, David D; Ruess, Roger W; Adams, Layne G; Clark, Jason A

    2016-01-01

    Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators. PMID:27074023

  12. Importance of Marine-Derived Nutrients Supplied by Planktivorous Seabirds to High Arctic Tundra Plant Communities

    PubMed Central

    Zwolicki, Adrian; Zmudczyńska-Skarbek, Katarzyna; Richard, Pierre; Stempniewicz, Lech

    2016-01-01

    We studied the relative importance of several environmental factors for tundra plant communities in five locations across Svalbard (High Arctic) that differed in geographical location, oceanographic and climatic influence, and soil characteristics. The amount of marine-derived nitrogen in the soil supplied by seabirds was locally the most important of the studied environmental factors influencing the tundra plant community. We found a strong positive correlation between δ15N isotopic values and total N content in the soil, confirming the fundamental role of marine-derived matter to the generally nutrient-poor Arctic tundra ecosystem. We also recorded a strong correlation between the δ15N values of soil and of the tissues of vascular plants and mosses, but not of lichens. The relationship between soil δ15N values and vascular plant cover was linear. In the case of mosses, the percentage ground cover reached maximum around a soil δ 15N value of 8‰, as did plant community diversity. This soil δ15N value clearly separated the occurrence of plants with low nitrogen tolerance (e.g. Salix polaris) from those predominating on high N content soils (e.g. Cerastium arcticum, Poa alpina). Large colonies of planktivorous little auks have a great influence on Arctic tundra vegetation, either through enhancing plant abundance or in shaping plant community composition at a local scale. PMID:27149113

  13. Importance of Marine-Derived Nutrients Supplied by Planktivorous Seabirds to High Arctic Tundra Plant Communities.

    PubMed

    Zwolicki, Adrian; Zmudczyńska-Skarbek, Katarzyna; Richard, Pierre; Stempniewicz, Lech

    2016-01-01

    We studied the relative importance of several environmental factors for tundra plant communities in five locations across Svalbard (High Arctic) that differed in geographical location, oceanographic and climatic influence, and soil characteristics. The amount of marine-derived nitrogen in the soil supplied by seabirds was locally the most important of the studied environmental factors influencing the tundra plant community. We found a strong positive correlation between δ15N isotopic values and total N content in the soil, confirming the fundamental role of marine-derived matter to the generally nutrient-poor Arctic tundra ecosystem. We also recorded a strong correlation between the δ15N values of soil and of the tissues of vascular plants and mosses, but not of lichens. The relationship between soil δ15N values and vascular plant cover was linear. In the case of mosses, the percentage ground cover reached maximum around a soil δ 15N value of 8‰, as did plant community diversity. This soil δ15N value clearly separated the occurrence of plants with low nitrogen tolerance (e.g. Salix polaris) from those predominating on high N content soils (e.g. Cerastium arcticum, Poa alpina). Large colonies of planktivorous little auks have a great influence on Arctic tundra vegetation, either through enhancing plant abundance or in shaping plant community composition at a local scale. PMID:27149113

  14. USE OF GREENHOUSE CHAMBERS FOR ENHANCING GROWTH OF TUNDRA TRANSPLANTS ON THIN GRAVEL FILL IN PRUDHOE BAY, ALASKA

    EPA Science Inventory

    An approach is presented that could facilitate disturbed tundra revegetation and monitoring in Alaska North Slope Oil Fields. xperiments were conducted on an abandoned drilling pad where the gravel was removed to a thin layer (Ca. 20 am) above tundra grade and mixed with underlyi...

  15. Paleoindians in beringia: evidence from arctic alaska.

    PubMed

    Kunz, M L; Reanier, R E

    1994-02-01

    Excavations at the Mesa site in arctic Alaska provide evidence for a Paleoindian occupation of Beringia, the region adjacent to the Bering Strait. Eleven carbon-14 dates on hearths associated with Paleoindian projectile points place humans at the site between 9,730 and 11,660 radiocarbon years before present (years B.P.). The presence of Paleoindians in Beringia at these times challenges the notion that Paleoindian cultures arose exclusively in mid-continental North America. The age span of Paleoindians at the Mesa site overlaps with dates from two other cultural complexes in interior Alaska. A hiatus in the record of human occupation occurs between 10,300 and 11,000 years B.P. Late Glacial climatic fluctuations may have made northern Alaska temporarily unfavorable for humans and spurred their southward dispersal. PMID:17747660

  16. 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.

  17. Carbon Fluxes in a sub-arctic tundra undergoing permafrost degradation

    NASA Astrophysics Data System (ADS)

    Bracho, R. G.; Webb, E.; Mauritz, M.; Schuur, E. A. G.

    2014-12-01

    As an effect of climate change, temperatures in high latitude regions are increasing faster than in the rest of the world and future projections indicate it will increase between 7°C and 8°C by the end of the 21st century. Permafrost soils store around 1700 Pg of Carbon (C), which is approximately the amount of C stored in terrestrial vegetation and in the atmosphere combined. Sustained warming induces permafrost thaw, leads to a thicker seasonal active layer, and creates subsided patches in the landscape. Carbon that was previously inaccessible to decomposition is thus exposed, increasing the likelihood of positive feedback of CO2 to the atmosphere. We measured C fluxes (Net ecosystem carbon flux, NEE, and Ecosystem respiration, Re) using the eddy covariance approach in a tundra landscape (Eight Mile Lake Watershed, Alaska) undergoing permafrost degradation from the beginning of the growing season in 2008 and throughout most winters until May 2014. This interval encompassed a range of climatic variability that included a deviation of ± 50% from the long term average in growing season precipitation. Active layer depth (thaw depth at the end of the growing season) and subsidence in the footprint were used as indicators of permafrost degradation. Results indicate that annual NEE ranged from a sink of 0.76 MgC ha-1 yr-1 to a source of 0.55 MgC ha-1 yr-1. NEE during the growing seasons fluctuated from 1.1 to 1.8 MgC ha-1 season-1 in net C uptake. Annual NEE was strongly affected by winter Re, which represented between 33% and 45% of the annual value regardless of of the large drop in both air and soil temperature. Parameters from the light response curve (optimum NEE, NEEopt and quantum yield, α) showed a seasonal and interannual variability and were different between the most and least degraded sites in the footprint, which affected the magnitude of the carbon cycle and may have implications for landscape C balance in sub-arctic tundra.

  18. Isotopic Identification of Nitrate Sources and Cycling in Arctic Tundra Active Layer Soils and Permafrost

    NASA Astrophysics Data System (ADS)

    Heikoop, J. M.; Throckmorton, H.; Newman, B. D.; Perkins, G.; Gard, M.; Iversen, C. M.; Wilson, C. J.; Wullschleger, S. D.

    2014-12-01

    The effect of nitrogen cycling on release of carbon from tundra ecosystems is being studied as part of the US Department of Energy Next Generation Ecosystem Experiment - Arctic project. Sampling and analysis of active layer soil water at the Barrow Environmental Observatory (Alaska, USA) was performed in ancient drained thaw lake basins (DTLBs), drainages, and in polygonal terrain associated with inter-DTLB tundra. Within active layer soils, nitrate was most commonly found above analytical limits of detection in pore water from the unsaturated centers of high-centered polygons. Nitrate has also been detected, though less frequently, in soil water immediately above the frost table of an ancient (14C age of 2000 - 5500 BP) DTLB and in a small drainage adjacent to high-centered polygonal terrain. Nitrate from high-centered polygons had δ15N ranging from -9.2 to +8.5 ‰ and δ18O ranging from -8.4 to +1.4 ‰. The δ15N isotopic range is consistent with microbial mineralization and nitrification of reduced nitrogen sources including ammonium, dissolved organic nitrogen, and soil organic nitrogen. The range in δ18O of nitrate is also consistent with nitrification based on the δ18O of site waters. No evidence for an atmospheric nitrate signal, as defined by δ15N and δ18O of nitrate in snow and snowmelt, is seen. In contrast, nitrate in permafrost appears to be a mixture of pre-industrial atmospheric nitrate (with higher δ15N than modern atmospheric nitrate) and nitrate that is microbial in origin. Massive ice wedges appear to contain larger proportions of snowmelt (based on δ18O of ice) and atmospheric nitrate, whereas textural ice appears to contain a greater proportion of summer precipitation and microbially-derived nitrate. Nitrate from the ancient DTLB and drainage samples also has isotopic signatures that appear to represent a mixture of pre-industrial atmospheric nitrate and nitrate from microbial nitrification, and may, at least in part, be derived from

  19. Circumpolar Dynamics of Arctic Tundra Vegetation in Relation to Temperature Trends

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Bhatt, U. S.; Raynolds, M. K.; Walker, D. A.; Reichle, L.

    2015-12-01

    Arctic tundra vegetation has generally exhibited a "greening" trend for at least the past three decades. However, these temporal trends in tundra vegetation are highly heterogeneous in space across different arctic regions, as well as showing variability over time. The factors controlling this variability are likely numerous with complex interactions, however, a first approach is to examine how vegetation dynamics relate to trends in temperature. We used a 32-year record (1982-2013) of the Normalized Difference Vegetation Index (NDVI) and Land Surface Temperatures from Advanced Very High Resolution Radiometer (AVHRR) sensors onboard NOAA satellites (GIMMS 3g dataset) to analyze observed changes in both aboveground tundra vegetation and surface temperatures. We divided the circumpolar dataset into two continental regions (North America and Eurasia), as well as by tundra subzone (A-E) sensu the Circumpolar Arctic Vegetation Map (CAVM). We 1) compared temporal trends in both MaxNDVI (peak values) and TI-NDVI (seasonally integrated values) with those of the Summer Warmth Index (SWI - sum of mean monthly temperatures > 0 °C); 2) assessed how the detrended interannual variabilities in NDVI compared to those of SWI; and 3) analyzed current and prior year SWI, as well as prior year NDVI, as controls on current year NDVI. Interannual coefficients of variation for SWI were 2.0 - 2.5 times greater than those for NDVI, and the temporal trendlines for NDVI were much "tighter" with greater r² values than those for SWI. Interannual variability in NDVI was greatest in the "Mid-Low" Arctic, whereas interannual variability in SWI was greatest in the most southern Arctic. Surprisingly, the observed relative rates of change in NDVI were greater than those of SWI for the warmer subzones for both North America and Eurasia. Finally, the change in NDVI from one year to the next was only weakly correlated with current year SWI. These results suggest that 1) there are clearly factors

  20. Estimated storage of amorphous silica in soils of the circum-Arctic tundra region

    NASA Astrophysics Data System (ADS)

    Alfredsson, H.; Clymans, W.; Hugelius, G.; Kuhry, P.; Conley, D. J.

    2016-03-01

    We investigated the vertical distribution, storage, landscape partitioning, and spatial variability of soil amorphous silica (ASi) at four different sites underlain by continuous permafrost and representative of mountainous and lowland tundra, in the circum-Arctic region. Based on a larger set of data, we present the first estimate of the ASi soil reservoir (0-1 m depth) in circum-Arctic tundra terrain. At all sites, the vertical distribution of ASi concentrations followed the pattern of either (1) declining concentrations with depth (most common) or (2) increasing/maximum concentrations with depth. Our results suggest that a set of processes, including biological control, solifluction and other slope processes, cryoturbation, and formation of inorganic precipitates influence vertical distributions of ASi in permafrost terrain, with the capacity to retain stored ASi on millennial timescales. At the four study sites, areal ASi storage (0-1 m) is generally higher in graminoid tundra compared to wetlands. Our circum-Arctic upscaling estimates, based on both vegetation and soil classification separately, suggest a storage amounting to 219 ± 28 and 274 ± 33 Tmol Si, respectively, of which at least 30% is stored in permafrost. This estimate would account for about 3% of the global soil ASi storage while occupying an equal portion of the global land area. This result does not support the hypothesis that the circum-Arctic tundra soil ASi reservoir contains relatively higher amounts of ASi than other biomes globally as demonstrated for carbon. Nevertheless, climate warming has the potential to significantly alter ASi storage and terrestrial Si cycling in the Arctic.

  1. Geologic Map of the Arctic Quadrangle, Alaska

    USGS Publications Warehouse

    Brosge, W.P.; Reiser, H.N.; Dutro, J.T., Jr.; Detterman, R.L.; Tailleur, I.L.

    2001-01-01

    Introduction The Arctic quadrangle is well located to shed light on the basic geologic relations of northern Alaska. The rocks represent all of the stratigraphic systems from Cambrian to Cretaceous and all but one of the tectono-stratigraphic subterranes of the Brooks Range, from the autochthonous subterrane in the north to the allochthonous subterranes farther south. Among the distinctive geologic features displayed in the Arctic quadrangle are voluminous volcanic rocks of probable Devonian age, a wide array of Carboniferous carbonate facies in the Lisburne Group (which here extends up into the Middle Pennsylvanian), the southward transition of Upper Devonian (Famennian) clastic facies from fluvial conglomerate to marine sandstone, a full display of Upper Devonian (Frasnian) reef-related strata, and fossiliferous Ordovician rocks in both carbonate and chert terranes. Most of the quadrangle is in the Arctic National Wildlife Refuge (ANWR) and Arctic Wildlife Refuge Wilderness. The quadrangle also includes Arctic Village, the only village in the region and a potential destination or transfer point for visitors to the wildlife refuge.

  2. Boundary layer O3 dynamics and deposition to tundra during a summer in the Alaskan Arctic

    NASA Astrophysics Data System (ADS)

    Van Dam, B. A.; Helmig, D.; Doskey, P. V.; Oltmans, S. J.; Boylan, P.

    2014-12-01

    Atmospheric turbulence quantities, boundary layer O3 levels and deposition to the tundra surface were investigated at Toolik Lake, AK during the 2011 summer season. Beginning immediately after snowmelt a diurnal cycle in ambient O3 developed, and O3 values measured over tundra throughout the summer varied significantly between nighttime minima of 5 ppbv and daytime maxima of 50 ppbv. The mean amplitude of the diurnal cycle in surface O3 following snowmelt was 13 ppbv, far larger than observed at other high Arctic locations. The diurnal cycle is attributed to a combination of surface deposition to the tundra and stable boundary layer conditions at night, and the entrainment of O3 from higher in the atmosphere during increased daytime mixing. The mean O3 deposition velocity during the month of June was 0.11 cm s-1. O3 deposition to tundra exhibited a diurnal cycle, with daytime mean of 0.2 cm s-1 and nighttime mean of 0.08 cm s-1. These values are slightly lower than previously reported summertime deposition velocities in the northern latitudes over tundra or fen, although measurements for comparison were limited.

  3. [The processes of methane formation and oxidation in the soils of the Russian arctic tundra].

    PubMed

    Berestovskaia, Iu Iu; Rusanov, I I; Vasil'eva, L V; Pimenov, N V

    2005-01-01

    Methane emission from the following types of tundra soils was studied: coarse humic gleyey loamy cryo soil, peaty gley soil, and peaty gleyey midloamy cryo soil of the arctic tundra. All the soils studied were found to be potential sources of atmospheric methane. The highest values of methane emission were recorded in August at a soil temperature of 8-10 degrees C. Flooded parcels were the sources of atmospheric methane throughout the observation period. The rates of methane production and oxidation in tundra soils of various types at 5 and 15 degrees C were studied by the radioisotope method. Methane oxidation was found to occur in bog water, in the green part of peat moss, and in all the soil horizons studied. Methane formation was recorded in the horizons of peat, in clay with plant roots, and in peaty moss dust of the bogey parcels. At both temperatures, the methane oxidation rate exceeded the rate of methane formation in all the horizons of the mossy-lichen tundra and of the bumpy sinkhole complex. Methanogenesis prevailed only in a sedge-peat moss bog at 15 degrees C. Enrichment bacterial cultures oxidizing methane at 5 and 15 degrees C were obtained. Different types of methanotrophic bacteria were shown to be responsible for methane oxidation under these conditions. A representative of type I methylotrophs oxidized methane at 5 degrees C, and Methylocella tundrae, a psychroactive representative of an acidophilic methanotrophic genus Methylocella, at 15 degrees C. PMID:15938404

  4. NGEE Arctic Webcam Photographs, Barrow Environmental Observatory, Barrow, Alaska

    DOE Data Explorer

    Bob Busey; Larry Hinzman

    2012-04-01

    The NGEE Arctic Webcam (PTZ Camera) captures two views of seasonal transitions from its generally south-facing position on a tower located at the Barrow Environmental Observatory near Barrow, Alaska. Images are captured every 30 minutes. Historical images are available for download. The camera is operated by the U.S. DOE sponsored Next Generation Ecosystem Experiments - Arctic (NGEE Arctic) project.

  5. 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.

  6. Greater shrub dominance alters breeding habitat and food resources for migratory songbirds in Alaskan arctic tundra.

    PubMed

    Boelman, Natalie T; Gough, Laura; Wingfield, John; Goetz, Scott; Asmus, Ashley; Chmura, Helen E; Krause, Jesse S; Perez, Jonathan H; Sweet, Shannan K; Guay, Kevin C

    2015-04-01

    Climate warming is affecting the Arctic in multiple ways, including via increased dominance of deciduous shrubs. Although many studies have focused on how this vegetation shift is altering nutrient cycling and energy balance, few have explicitly considered effects on tundra fauna, such as the millions of migratory songbirds that breed in northern regions every year. To understand how increasing deciduous shrub dominance may alter breeding songbird habitat, we quantified vegetation and arthropod community characteristics in both graminoid and shrub dominated tundra. We combined measurements of preferred nest site characteristics for Lapland longspurs (Calcarius lapponicus) and Gambel's White-crowned sparrows (Zonotrichia leucophrys gambelii) with modeled predictions for the distribution of plant community types in the Alaskan arctic foothills region for the year 2050. Lapland longspur nests were found in sedge-dominated tussock tundra where shrub height does not exceed 20 cm, whereas White-crowned sparrows nested only under shrubs between 20 cm and 1 m in height, with no preference for shrub species. Shrub canopies had higher canopy-dwelling arthropod availability (i.e. small flies and spiders) but lower ground-dwelling arthropod availability (i.e. large spiders and beetles). Since flies are the birds' preferred prey, increasing shrubs may result in a net enhancement in preferred prey availability. Acknowledging the coarse resolution of existing tundra vegetation models, we predict that by 2050 there will be a northward shift in current White-crowned sparrow habitat range and a 20-60% increase in their preferred habitat extent, while Lapland longspur habitat extent will be equivalently reduced. Our findings can be used to make first approximations of future habitat change for species with similar nesting requirements. However, we contend that as exemplified by this study's findings, existing tundra modeling tools cannot yet simulate the fine-scale habitat

  7. A Comparison of Satellite and Aircraft-Mounted Thermal Observations of Freeze/Thaw Cycling of the Alaska Tundra and Boreal Forests during the Carbon in the Arctic Vulnerability Experiment (CARVE)

    NASA Astrophysics Data System (ADS)

    Steiner, N.; McDonald, K. C.; Miller, C. E.; Dinardo, S. J.

    2014-12-01

    Freeze/thaw (F/T) related surface processes in the Arctic are important as they bracket negative and positive modes in the flux of CO2 and CH4 between the surface and atmosphere. The Carbon in the Arctic Vulnerability Experiment (CARVE) monitors carbon gas cycling in Alaskan using aircraft-deployed gas sampling instruments along with remote sensing observations of the land surface condition. A nadir-pointed, forward looking infrared (FLIR) imager mounted on the CARVE aircraft is used to measure upwelling mid-infrared spectral radiance at 3-5 microns. The FLIR instrument was operated during the spring, summer and fall seasons of 2013 and 2014 during clear sky conditions and targeting ecosystem components affecting the carbon cycle. The instantaneous field of view (IFOV) of the FLIR instrument allows for a resolution of ~36 cm from a height of 500 m. This high resolution data allow for the discrimination of individual landscape components such as soil, vegetation and surface water features in the image footprint. We assess the effectiveness of the FLIR thermal images in monitoring thawing and inundation processes of individual ecosystem components of importance in biogeochemical cycling. We also observe how these individual components scale using coarse resolution satellite observations of land surface temperature (LST) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Freeze/thaw state determined from the Advanced Microwave Scanning Radiometer (AMSR2) on JAXA's Shizuku (GCOM-W1) satellite. Portions of the work were carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautic and Space Administration.

  8. Seasonal thaw settlement at drained thermokarst lake basins, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Liu, L.; Schaefer, K.; Gusmeroli, A.; Grosse, G.; Jones, B. M.; Zhang, T.; Parsekian, A. D.; Zebker, H. A.

    2014-05-01

    Drained thermokarst lake basins (DTLBs) are ubiquitous landforms on Arctic tundra lowland. Their dynamic states are seldom investigated, despite their importance for landscape stability, hydrology, nutrient fluxes, and carbon cycling. Here we report results based on high-resolution Interferometric Synthetic Aperture Radar (InSAR) measurements using space-borne data for a study area located on the North Slope of Alaska near Prudhoe Bay, where we focus on the seasonal thaw settlement within DTLBs, averaged between 2006 and 2010. The majority (14) of the 18 DTLBs in the study area exhibited seasonal thaw settlement of 3-4 cm. However, four of the DTLBs examined exceeded 4 cm of thaw settlement, with one basin experiencing up to 12 cm. Combining the InSAR observations with the in situ active layer thickness measured using ground penetrating radar and mechanical probing, we calculated thaw strain, an index of thaw settlement strength along a transect across the basin that underwent large thaw settlement. We found thaw strains of 10-35% at the basin center, suggesting the seasonal melting of ground ice as a possible mechanism for the large settlement. These findings emphasize the dynamic nature of permafrost landforms, demonstrate the capability of the InSAR technique to remotely monitor surface deformation of individual DTLBs, and illustrate the combination of ground-based and remote sensing observations to estimate thaw strain. Our study highlights the need for better description of the spatial heterogeneity of landscape-scale processes for regional assessment of surface dynamics on Arctic coastal lowlands.

  9. 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.

  10. 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.

  11. Soil bacterial community composition altered by increased nutrient availability in Arctic tundra soils

    PubMed Central

    Koyama, Akihiro; Wallenstein, Matthew D.; Simpson, Rodney T.; Moore, John C.

    2014-01-01

    The pool of soil organic carbon (SOC) in the Arctic is disproportionally large compared to those in other biomes. This large quantity of SOC accumulated over millennia due to slow rates of decomposition relative to net primary productivity. Decomposition is constrained by low temperatures and nutrient concentrations, which limit soil microbial activity. We investigated how nutrients limit bacterial and fungal biomass and community composition in organic and mineral soils within moist acidic tussock tundra ecosystems. We sampled two experimental arrays of moist acidic tussock tundra that included fertilized and non-fertilized control plots. One array included plots that had been fertilized annually since 1989 and the other since 2006. Fertilization significantly altered overall bacterial community composition and reduced evenness, to a greater degree in organic than mineral soils, and in the 1989 compared to the 2006 site. The relative abundance of copiotrophic α-Proteobacteria and β-Proteobacteria was higher in fertilized than control soils, and oligotrophic Acidobacteria were less abundant in fertilized than control soils at the 1989 site. Fungal community composition was less sensitive to increased nutrient availability, and fungal responses to fertilization were not consistent between soil horizons and sites. We detected two ectomycorrhizal genera, Russula and Cortinarius spp., associated with shrubs. Their relative abundance was not affected by fertilization despite increased dominance of their host plants in the fertilized plots. Our results indicate that fertilization, which has been commonly used to simulate warming in Arctic tundra, has limited applicability for investigating fungal dynamics under warming. PMID:25324836

  12. Variation in bird's originating nitrogen availability limits High Arctic tundra development over last 2000 year (Hornsund, Svalbard)

    NASA Astrophysics Data System (ADS)

    Skrzypek, Grzegorz; Wojtuń, Bronisław; Hua, Quan; Richter, Dorota; Jakubas, Dariusz; Wojczulanis-Jakubas, Katarzyna; Samecka-Cymerman, Aleksandra

    2016-04-01

    Arctic and subarctic regions play important roles in the global carbon balance. However, nitrogen (N) deficiency is a major constraint for organic carbon sequestration in the High Arctic. Hence, the identification of the relative contributions from different N-sources is critical for understanding the constraints that limit tundra growth. The stable nitrogen composition of the three main N-sources and numerous plants were analyzed in ten tundra types (including those influenced by seabirds) in the Fuglebekken catchment (Hornsund, Svalbard, 77°N 15°E). The percentage of the total tundra N-pool provided by seabirds' feces (from planktivorous colonially breeding little auks Alle alle), ranged from 0-21% in Patterned-ground tundra to 100% in Ornithocoprophilous tundra. The total N-pool utilized by tundra plants in the studied catchment originated from birds (36%), atmospheric deposition (38%), and N2-fixation (26%). The results clearly show that N-pool in the tundra is significantly supplemented by nesting seabirds. Thus, if they experienced climate change induced substantial negative environmental pressure, it would adversely influence the tundra N-budget (Skrzypek et al. 2015). The growth rates and the sediment thickness (<15cm) in different tundra types varied considerably but the tundra age was similar in the whole area, <450 cal BP. The only exception was Ornithocoprophilous bird-N rich tundra with very diverse ages ranging from 235 to 2300 cal BP and thickness up to 110 cm. The growth rates for this tundra (62 cm core, 18 AMS 14C dates) were high (1.5-3.0 mm/yr) between 1568 and 1804 AD and then substantially declined for the period between 1804 and 1929 AD (0.2 mm/yr). These findings deliver an additional argument, that the organic matter accumulation is driven not only directly by climatic conditions but also by birds' contribution to the tundra N-pool. Skrzypek G, Wojtuń B, Richter D, Jakubas D, Wojczulanis-Jakubas K, Samecka-Cymerman A, 2015

  13. 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

  14. 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

  15. Metagenomics Reveals Pervasive Bacterial Populations and Reduced Community Diversity across the Alaska Tundra Ecosystem.

    PubMed

    Johnston, Eric R; Rodriguez-R, Luis M; Luo, Chengwei; Yuan, Mengting M; Wu, Liyou; He, Zhili; Schuur, Edward A G; Luo, Yiqi; Tiedje, James M; Zhou, Jizhong; Konstantinidis, Konstantinos T

    2016-01-01

    Alaska tundra microbial communities are less diverse and more homogenous across spatial scales than previously anticipated, and provided DNA sequences of abundant populations and genes that would be relevant for future studies of the effects of environmental change on tundra ecosystems. PMID:27199914

  16. Metagenomics Reveals Pervasive Bacterial Populations and Reduced Community Diversity across the Alaska Tundra Ecosystem

    PubMed Central

    Johnston, Eric R.; Rodriguez-R, Luis M.; Luo, Chengwei; Yuan, Mengting M.; Wu, Liyou; He, Zhili; Schuur, Edward A. G.; Luo, Yiqi; Tiedje, James M.; Zhou, Jizhong; Konstantinidis, Konstantinos T.

    2016-01-01

    that Alaska tundra microbial communities are less diverse and more homogenous across spatial scales than previously anticipated, and provided DNA sequences of abundant populations and genes that would be relevant for future studies of the effects of environmental change on tundra ecosystems. PMID:27199914

  17. Nitrogen Accumulation and Partitioning in High Arctic Tundra from Extreme Atmospheric N Deposition Events

    NASA Astrophysics Data System (ADS)

    Phoenix, G. K.; Osborn, A.; Blaud, A.; Press, M. C.; Choudhary, S.

    2013-12-01

    Arctic ecosystems are threatened by pollution from extreme atmospheric nitrogen (N) deposition events. These events occur from the long-range transport of reactive N from pollution sources at lower latitudes and can deposit up to 80% of the annual N deposition in just a few days. To date, the fate and impacts of these extreme pollutant events has remained unknown. Using a field simulation study, we undertook the first assessment of the fate of acutely deposited N on arctic tundra. Extreme N deposition events were simulated on field plots at Ny-Ålesund, Svalbard (79oN) at rates of 0, 0.04, 0.4 and 1.2 g N m-2 yr-1 applied as NH4NO3 solution over 4 days, with 15N tracers used in the second year to quantify the fate of the deposited N in the plant, soil, microbial and leachate pools. Separate applications of 15NO3- and 15NH4+ were also made to determine the importance of N form in the fate of N. Recovery of the 15N tracer at the end of the first growing season approached 100% of the 15N applied irrespective of treatment level, demonstrating the considerable capacity of High Arctic tundra to capture pollutant N from extreme deposition events. Most incorporation of the 15N was found in bryophytes, followed by the dominant vascular plant (Salix polaris) and the microbial biomass of the soil organic layer. Total recovery remained high in the second growing season (average of 90%), indicating highly conservative N retention. Between the two N forms, recovery of 15NO3- and 15NH4+ were equal in the non-vascular plants, whereas in the vascular plants (particularly Salix polaris) recovery of 15NO3- was four times higher than of 15NH4+. Overall, these findings show that High Arctic tundra has considerable capacity to capture and retain the pollutant N deposited in acute extreme deposition events. Given they can represent much of the annual N deposition, extreme deposition events may be more important than increased chronic N deposition as a pollution source. Furthermore

  18. Understanding Pan-Arctic Tundra Vegetation Change Through Long-term Remotely Sensed Data

    NASA Astrophysics Data System (ADS)

    Bhatt, U.; Walker, D. A.; Bieniek, P.; Raynolds, M. K.; Epstein, H. E.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2012-12-01

    The goal of this paper is to present an analysis of the seasonality of tundra vegetation variability and change using long-term remotely sensed data as well as ground based measurements and reanalyses. An increase of Pan-Arctic tundra vegetation greenness has been documented using the remotely sensed Normalized Difference Vegetation Index (NDVI). Coherent variability between NDVI, springtime coastal sea ice (passive microwave) and land surface temperatures (AVHRR) has also been established. Satellite based snow and cloud cover data sets are being incorporated into this analysis. The Arctic tundra is divided into domains based on Treshnikov divisions that are modified based on floristic provinces. There is notable heterogeneity in Pan-Arctic vegetation and climate trends, which necessitates a regional analysis. This study uses remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2010. The GIMMS NDVI3g data has been corrected for biases during the spring and fall, with special focus on the Arctic. Trends of Maximum NDVI (MaxNDVI), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), and open water area are calculated for the Pan Arctic. Remotely sensed snow data trends suggest varying patterns throughout the Arctic and may in part explain the heterogeneous MaxNDVI trends. Standard climate data (station, reanalysis, and model data) and ground observations are used in the analysis to provide additional support for hypothesized mechanisms. Overall, we find that trends over the 30-year record are changing as evidenced by the following examples from recent years. The sea ice decline has increased in Eurasia and slowed in North America. The weekly AVHRR landsurface temperatures reveal that there has been summer cooling over Eurasia and that the warming over North America has slowed. The MaxNDVI rates of change have diverged between N. America and Eurasia

  19. The effects of climate changes on soil methane oxidation in a dry Arctic tundra

    NASA Astrophysics Data System (ADS)

    D'Imperio, Ludovica

    2014-05-01

    The effects of climate changes on soil methane oxidation in a dry Arctic tundra. Ludovica D'Imperio1, Anders Michelsen1, Christian J. Jørgensen1, Bo Elberling1 1Center for Permafrost (CENPERM), Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark At Northern latitudes climatic changes are predicted to be most pronounced resulting in increasing active layer depth and changes in growing season length, vegetation cover and nutrient cycling. As a consequence of increased temperature, large stocks of carbon stored in the permafrost-affected soils could become available for microbial transformations and under anoxic conditions result in increasing methane production affecting net methane (CH4) budget. Arctic tundra soils also serves as an important sink of atmospheric CH4 by microbial oxidation under aerobic conditions. While several process studies have documented the mechanisms behind both production and emissions of CH4 in arctic ecosystems, an important knowledge gap exists with respect to the in situ dynamics of microbial-driven uptake of CH4 in arctic dry lands which may be enhanced as a consequence of global warming and thereby counterbalancing CH4 emissions from Arctic wetlands. In-situ methane measurements were made in a dry Arctic tundra in Disko Island, Western Greenland, during the summer 2013 to assess the role of seasonal and inter-annual variations in temperatures and snow cover. The experimental set-up included snow fences installed in 2012, allowed investigations of the emissions of GHGs from soil under increased winter snow deposition and ambient field conditions. The soil fluxes of CH4 and CO2 were measured using closed chambers in manipulated plots with increased summer temperatures and shrub removal with or without increased winter precipitation. At the control plots, the averaged seasonal CH4 oxidation rates ranged between -0.05 mg CH4 m-2 hr-1 (end of August) and -0.32 mg CH4 m-2 hr-1 (end of June). In the

  20. Post-fire Thermokarst Development Along a Planned Road Corridor in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Jones, B. M.; Grosse, G.; Larsen, C. F.; Hayes, D. J.; Arp, C. D.; Liu, L.; Miller, E.

    2015-12-01

    Wildfire disturbance in northern high latitude regions is an important factor contributing to ecosystem and landscape change. In permafrost influenced terrain, fire may initiate thermokarst development which impacts hydrology, vegetation, wildlife, carbon storage and infrastructure. In this study we differenced two airborne LiDAR datasets that were acquired in the aftermath of the large and severe Anaktuvuk River tundra fire, which in 2007 burned across a proposed road corridor in Arctic Alaska. The 2009 LiDAR dataset was acquired by the Alaska Department of Transportation in preparation for construction of a gravel road that would connect the Dalton Highway with the logistical camp of Umiat. The 2014 LiDAR dataset was acquired by the USGS to quantify potential post-fire thermokarst development over the first seven years following the tundra fire event. By differencing the two 1 m resolution digital terrain models, we measured permafrost thaw subsidence across 34% of the burned tundra area studied, and observed less than 1% in similar, undisturbed tundra terrain units. Ice-rich, yedoma upland terrain was most susceptible to thermokarst development following the disturbance, accounting for 50% of the areal and volumetric change detected, with some locations subsiding more than six meters over the study period. Calculation of rugosity, or surface roughness, in the two datasets showed a doubling in microtopography on average across the burned portion of the study area, with a 340% increase in yedoma upland terrain. An additional LiDAR dataset was acquired in April 2015 to document the role of thermokarst development on enhanced snow accumulation and subsequent snowmelt runoff within the burn area. Our findings will enable future vulnerability assessments of ice-rich permafrost terrain as a result of shifting disturbance regimes. Such assessments are needed to address questions focused on the impact of permafrost degradation on physical, ecological, and socio

  1. Russian Arctic warming and ‘greening’ are closely tracked by tundra shrub willows

    NASA Astrophysics Data System (ADS)

    Forbes, B. C.; Macias Fauria, M.; Zetterberg, P.

    2009-12-01

    Growth in arctic vegetation is generally expected to increase under a warming climate, particularly among deciduous shrubs. We analyzed annual ring growth for an abundant and nearly circumpolar erect willow (Salix lanata L.) from the coastal zone of the northwest Russian Arctic (Nenets Autonomous Okrug). The resulting chronology is strongly related to summer temperature for the period 1942-2005. Remarkably high correlations occur at long distances (>1600 km) across the tundra and taiga zones of West Siberia and Eastern Europe. We also found a clear relationship with photosynthetic activity for upland vegetation at a regional scale for the period 1981-2005, confirming a parallel ‘greening’ trend reported for similarly warming North American portions of the tundra biome. The standardized growth curve suggests a significant increase in shrub willow growth over the last six decades. These findings are in line with field and remote sensing studies that have assigned a strong shrub component to the reported greening signal since the early 1980s. Furthermore, the growth trend agrees with qualitative observations by nomadic Nenets reindeer herders of recent increases in willow size in the region. The quality of the chronology as a climate proxy is exceptional. Given its wide geographic distribution and the ready preservation of wood in permafrost, S. lanata L. has great potential for extended temperature reconstructions in remote areas across the Arctic.

  2. Pan-Arctic ice-wedge degradation in warming permafrost and its influence on tundra hydrology

    NASA Astrophysics Data System (ADS)

    Liljedahl, Anna K.; Boike, Julia; Daanen, Ronald P.; Fedorov, Alexander N.; Frost, Gerald V.; Grosse, Guido; Hinzman, Larry D.; Iijma, Yoshihiro; Jorgenson, Janet C.; Matveyeva, Nadya; Necsoiu, Marius; Raynolds, Martha K.; Romanovsky, Vladimir E.; Schulla, Jörg; Tape, Ken D.; Walker, Donald A.; Wilson, Cathy J.; Yabuki, Hironori; Zona, Donatella

    2016-04-01

    Ice wedges are common features of the subsurface in permafrost regions. They develop by repeated frost cracking and ice vein growth over hundreds to thousands of years. Ice-wedge formation causes the archetypal polygonal patterns seen in tundra across the Arctic landscape. Here we use field and remote sensing observations to document polygon succession due to ice-wedge degradation and trough development in ten Arctic localities over sub-decadal timescales. Initial thaw drains polygon centres and forms disconnected troughs that hold isolated ponds. Continued ice-wedge melting leads to increased trough connectivity and an overall draining of the landscape. We find that melting at the tops of ice wedges over recent decades and subsequent decimetre-scale ground subsidence is a widespread Arctic phenomenon. Although permafrost temperatures have been increasing gradually, we find that ice-wedge degradation is occurring on sub-decadal timescales. Our hydrological model simulations show that advanced ice-wedge degradation can significantly alter the water balance of lowland tundra by reducing inundation and increasing runoff, in particular due to changes in snow distribution as troughs form. We predict that ice-wedge degradation and the hydrological changes associated with the resulting differential ground subsidence will expand and amplify in rapidly warming permafrost regions.

  3. Range expansion of moose in arctic Alaska linked to warming and increased shrub habitat

    USGS Publications Warehouse

    Tape, Ken D.; Gustine, David D.; Reuss, Roger W.; Adams, Layne G.; Clark, Jason A.

    2016-01-01

    Twentieth century warming has increased vegetation productivity and shrub cover across northern tundra and treeline regions, but effects on terrestrial wildlife have not been demonstrated on a comparable scale. During this period, Alaskan moose (Alces alces gigas) extended their range from the boreal forest into tundra riparian shrub habitat; similar extensions have been observed in Canada (A. a. andersoni) and Eurasia (A. a. alces). Northern moose distribution is thought to be limited by forage availability above the snow in late winter, so the observed increase in shrub habitat could be causing the northward moose establishment, but a previous hypothesis suggested that hunting cessation triggered moose establishment. Here, we use recent changes in shrub cover and empirical relationships between shrub height and growing season temperature to estimate available moose habitat in Arctic Alaska c. 1860. We estimate that riparian shrubs were approximately 1.1 m tall c. 1860, greatly reducing the available forage above the snowpack, compared to 2 m tall in 2009. We believe that increases in riparian shrub habitat after 1860 allowed moose to colonize tundra regions of Alaska hundreds of kilometers north and west of previous distribution limits. The northern shift in the distribution of moose, like that of snowshoe hares, has been in response to the spread of their shrub habitat in the Arctic, but at the same time, herbivores have likely had pronounced impacts on the structure and function of these shrub communities. These northward range shifts are a bellwether for other boreal species and their associated predators.

  4. Terrimonas arctica sp. nov., isolated from Arctic tundra soil.

    PubMed

    Jiang, Fan; Qiu, Xia; Chang, Xulu; Qu, Zhihao; Ren, Lvzhi; Kan, Wenjing; Guo, Youhao; Fang, Chengxiang; Peng, Fang

    2014-11-01

    A novel, Gram-stain-negative, aerobic, non-motile and rod-shaped bacterium, designated R9-86(T), was isolated from tundra soil collected near Ny-Ålesund, Svalbard Archipelago, Norway (78° N). Growth occurred at 4-28 °C (optimum, 22-25 °C) and at pH 6.0-9.0 (optimum, pH 7.0). Flexirubin-type pigments were absent. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain R9-86(T) belonged to the genus Terrimonas in the family Chitinophagaceae. 16S rRNA gene sequence similarities between strain R9-86(T) and the type strains of species of the genus Terrimonas with validly published names ranged from 93.7 to 95.0%. Strain R9-86(T) contained iso-C(15:1)-G (25.7%), iso-C(15:0) (24.5%), iso-C(17:0)-3OH (18.3%) and summed feature 3 (C(16:1)ω7c and/or C(16:1)ω6c, 8.7%) as its major cellular fatty acids; phosphatidylethanolamine and an unknown polar lipid as its main polar lipids, and MK-7 as its predominant respiratory quinone. The DNA G+C content was 48.4 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain R9-86(T) is considered to represent a novel species of the genus Terrimonas, for which the name Terrimonas arctica sp. nov. is proposed. The type strain is R9-86(T) ( =CCTCC AB 2011004(T) =NRRL B-59114(T)). PMID:25142212

  5. Variations in evapotranspiration fluxes across geomorphological units and plant functional types in a polygonal-structure Tundra in Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Raz Yaseef, N.; Young, J. M.; Rahn, T. A.; Newman, B. D.; Torn, M. S.

    2014-12-01

    Although the landscape in tundra ecosystems is relatively flat, and the vegetation is typically shorter than 10 cm, micro-topographical changes within the polygonal structure produce spatial heterogeneity in the form of permafrost depth, soil temperature, soil moisture, and wind speed. Plants react to these conditions and form linkages with the landscape. For example, mosses occupy the wet troughs and lichens are more abundant in the drier high-centred polygons. We conducted measurements in a polygonal-structure tundra site at Barrow, Alaska, to investigate the interconnections between evapotranspiration fluxes, geomorphology and plant cover, during two consecutive years. Fluxes were measured at three spatial and temporal scales: (1) Eddy covariance flux tower, (2) Continuous, fixed, surface clear chamber, and (3) Discontinuous measurements with mobile chambers in approximately 60 locations across the landscape. Our results indicate that different environmental conditions (soil moisture, soil temperature, wind speed, and thaw depth) and plant community composition, driven by microtopographical features, have significant influences on soil greenhouse gas and energy fluxes. Among plant types, evapotranspiration fluxes from moss-covered and inundated areas were more than twice those from other plant types. Continuous chamber measurements were similar in trend and values to eddy-covariance measurements, implying on the high contribution of surface fluxes to atmospheric concentrations. However, wind direction influenced the upscaling of fluxes from chamber to tower, because maritime winds had different moisture content and temperature than terrestrial winds. Microclimate was also affected by microtopography, and wind speed was higher on polygon ridges, and lower in the more protected trough areas, affecting evapotranspiration fluxes. In addition, we observed a strong seasonal trend in fluxes. During peak summer, although 24-hour daylight occurs, our results indicated

  6. 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

  7. Alaska Arctic marine fish ecology catalog

    USGS Publications Warehouse

    2016-01-01

    The marine fishes in waters of the United States north of the Bering Strait have received new and increased scientific attention over the past decade (2005–15) in conjunction with frontier qualities of the region and societal concerns about the effects of Arctic climate change. Commercial fisheries are negligible in the Chukchi and Beaufort Seas, but many marine species have important traditional and cultural values to Alaska Native residents. Although baseline conditions are rapidly changing, effective decisions about research and monitoring investments must be based on reliable information and plausible future scenarios. For the first time, this synthesis presents a comprehensive evaluation of the marine fish fauna from both seas in a single reference. Although many unknowns and uncertainties remain in the scientific understanding, information presented here is foundational with respect to understanding marine ecosystems and addressing dual missions of the U.S. Department of the Interior for energy development and resource conservation. 

  8. Organic Carbon Transformation and Mercury Methylation in Tundra Soils from Barrow Alaska

    DOE Data Explorer

    Liang, L.; Wullschleger, Stan; Graham, David; Gu, B.; Yang, Ziming

    2016-04-20

    This dataset includes information on soil labile organic carbon transformation and mercury methylation for tundra soils from Barrow, Alaska. The soil cores were collected from high-centered polygon (trough) at BEO and were incubated under anaerobic laboratory conditions at both freezing and warming temperatures for up to 8 months. Soil organic carbon including reducing sugars, alcohols, and organic acids were analyzed, and CH4 and CO2 emissions were quantified. Net production of methylmercury and Fe(II)/Fe(total) ratio were also measured and provided in this dataset.

  9. 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

  10. Temporal and Spatial Trends in Soil Moisture in Arctic Alaska 1992-2010

    NASA Astrophysics Data System (ADS)

    Jenkins, L. K.; Bourgeau-Chavez, L. L.; French, N. H. F.; Chavez, M. C.

    2014-12-01

    Previous research in the Arctic has demonstrated changes associated with a warming climate including shrub expansion northward, drying of lakes, increasing active layer depths, and decreasing ice and snow cover. With a warming climate, potential for permafrost thaw, increased evapotranspiration from shrubs, and drying lakes, there have likely been widespread changes in patterns of surface soil moisture across the Arctic landscape over the past 20 to 30 years. We investigated trends in soil moisture in Arctic Alaska using the two-decade long data record of ERS-1 and -2 synthetic aperture radar (SAR) satellite data and ground based measurements of precipitation and soil moisture. SAR data have long been known to be highly sensitive to changes in soil moisture condition, and the C-band SAR (~5.6 cm wavelength) of ERS-1 and 2 are particularly useful for monitoring moisture in the low biomass, open ecosystems of the tundra. Eight sites in Alaska, spanning low to high Arctic and coastal to interior tundra, have been used to develop methodologies and relationships between SAR backscatter and soil moisture in tundra ecosystems. Given the dearth of long-term, in-situ soil moisture data, methods have been investigated using surrogate soil moisture information derived from weather station data and the use of the Fire Weather Index (FWI) subsystem of the Canadian Forest Fire Danger Rating System. Previous SAR work in boreal regions has demonstrated high correlations between SAR backscatter at C-band and the drought code (DC) component of the FWI subsystem. DC is a measure of moisture in the deep organic soil layers of 10-20 cm. This paper will present temporal and spatial trends in soil moisture over the two-decade long observation period among the eight study sites. Differences in soil moisture mapping using SAR data between Arctic and boreal systems will be discussed. Recommendations for the use of ERS-1 and -2 data in longitudinal studies will also be highlighted given

  11. Modeling dynamics of circum-arctic tundra plant communities in response to climate warming and grazing pressure

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Epstein, H. E.; Walker, D. A.; Forbes, B. C.; Vors, L. S.

    2011-12-01

    The Arctic is a complex system with strong interconnectedness among system components. Understanding the responses of the arctic tundra biome to a changing climate requires knowledge of the complex interactions among climate, soils, and the biological system. In this study, we investigate the individual and interactive effects of projected climate change and reindeer/caribou grazing across a variety of climate zones and soil nutrient levels on tundra plant community dynamics using an arctic vegetation model - ArcVeg. Our research questions include: 1) How does soil nutrient availability affect tundra vegetation responses to projected climate warming? 2) How does grazing affect tundra vegetation responses? 3) How do interactions of soil nutrients, climate warming and grazing affect tundra vegetation? We based our simulations on A1B scenario temperature data from the Intergovernmental Panel on Climate Change (IPCC), soil organic nitrogen data from Terrestrial Ecosystem Model (TEM) simulations and grazing pressure derived from reindeer/caribou population data from the CircumArctic Rangifer Monitoring and Assessment Network (CARMA). We found that in general tundra communities responded to warming with increased plant biomass, but the magnitude of the response is affected by the bioclimate zones, warming magnitude, available soil nutrients and grazing pressures. Regions with greater soil organic nitrogen responded to warming with greater biomass increase, Low Arctic tundra tended to have greater biomass increase than High Arctic tundra due to greater shrub abundance. However, such responses are mitigated by grazing. Regions with greater reindeer population and thus greater grazing intensity tended to have stronger negative effects on plant responses to warming than regions with less grazing. For example, in Subzone D, total biomass and NPP increases due to warming were about 71% and 43% in an Alaskan low grazing-intensity region, but 63% and 36% in a northwestern Canada

  12. Calibration, Compositing, and Classification of Landsat Datasets and High-Resolution Imagery in Arctic Alaska

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Providing calibrated, cloud-free, and phenologically consistent satellite basemaps at moderate (~30 m) and high resolution (≤2 m) is critical to the mapping of arctic tundra vegetation and landscape attributes across large study areas. We obtained ground cover (n = 107) and field spectra (n = 28) data for tundra vegetation across a network of field plots in a ~100,000 km2 study area spanning the foothills and coastal plain ecoregions of Alaska's North Slope. Calibration and atmospheric correction of Landsat TM, ETM+ and OLI, WorldView-2, and GeoEye-1 imagery were performed and we compared results across sensors and with ground spectra. For the Landsat imagery, we produced consistent basemaps using compositing approaches that focused on capturing central tendencies from multiple years of imagery within narrow phenological windows (e.g., green-up, peak growth, fall senescence). We leveraged information from the full 1985-2014 time series to optimize compositing year ranges to prevent bias due to directional changes (e.g., shrubification), and "step-changes" (e.g., tundra fire, lake drainage, ice-wedge degradation) in vegetation and landscape characteristics over the Landsat era. Finally, we explored automated classification of the calibrated Landsat and high-resolution imagery using the spectral rule-based classifier Satellite Image Automatic Mapper (SIAM).

  13. Summertime surface O3 behavior and deposition to tundra in the Alaskan Arctic

    NASA Astrophysics Data System (ADS)

    Van Dam, Brie; Helmig, Detlev; Doskey, Paul V.; Oltmans, Samuel J.

    2016-07-01

    Atmospheric turbulence quantities, boundary layer ozone (O3) levels, and O3 deposition to the tundra surface were investigated at Toolik Lake, AK, during the 2011 summer season. Beginning immediately after snowmelt, a diurnal cycle of O3 in the atmospheric surface layer developed with daytime O3 maxima, and minima during low-light hours, resulting in a mean amplitude of 13 ppbv. This diurnal O3 cycle is far larger than observed at other high Arctic locations during the snow-free season. During the snow-free months of June, July, and August, O3 deposition velocities were ˜3 to 5 times faster than during May, when snow covered the ground most of the month. The overall mean O3 deposition velocity between June and August was 0.10 cm s-1. The month of June had the highest diurnal variation, with a median O3 deposition velocity of 0.2 cm s-1 during the daytime and 0.08 cm s-1 during low-light conditions. These values are slightly lower than previously reported summertime deposition velocities in northern latitudes over tundra or fen. O3 loss during low-light periods was attributed to a combination of surface deposition to the tundra and stable boundary layer conditions. We also hypothesize that emissions of reactive biogenic volatile organic compounds into the shallow boundary layer may contribute to nighttime O3 loss.

  14. CO2 dynamics of tundra ponds in the low-Arctic, Northwest Territories, Canada

    NASA Astrophysics Data System (ADS)

    Buell, Mary-Claire

    Extensive research has gone into measuring changes to the carbon storage capacity of Arctic terrestrial environments as well as large water bodies in order to determine a carbon budget for many regions across the Arctic. Inland Arctic waters such as small lakes and ponds are often excluded from these carbon budgets, however a handful of studies have demonstrated that they can often be significant sources of carbon to the atmosphere. This study investigated the CO2 cycling of tundra ponds in the Daring Lake area, Northwest Territories, Canada (64°52'N, 111°35'W), to determine the role ponds have in the local carbon cycle. Floating chambers, nondispersive infrared (NDIR) sensors and headspace samples were used to estimate carbon fluxes from four selected local ponds. Multiple environmental, chemical and meteorological parameters were also monitored for the duration of the study, which took place during the snow free season of 2013. Average CO2 emissions for the two-month growing season ranged from approximately -0.0035 g CO2-C m-2 d -1 to 0.12 g CO2-C m-2 d-1. The losses of CO2 from the water bodies in the Daring Lake area were approximately 2-7% of the CO2 uptake over vegetated terrestrial tundra during the same two-month period. Results from this study indicated that the production of CO2 in tundra ponds was positively influenced by both increases in air temperature, and the delivery of carbon from their catchments. The relationship found between temperature and carbon emissions suggests that warming Arctic temperatures have the potential to increase carbon emissions from ponds in the future. The findings in this study did not include ebullition gas emissions nor plant mediated transport, therefore these findings are likely underestimates of the total carbon emissions from water bodies in the Daring Lake area. This study emphasizes the need for more research on inland waters in order to improve our understanding of the total impact these waters may have on the

  15. Seasonal Variability of Major Ions and δ13CDIC in Permafrost Watersheds of Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Lehn, G. O.; Jacobson, A. D.; Douglas, T. A.; McClelland, J. W.; Khosh, M. S.; Barker, A. J.

    2011-12-01

    Models and observations predict that climate change will have more severe effects at higher latitudes. Many effects may already be underway. Increasing temperatures are expected to thaw permafrost soils, changing the hydrology and biogeochemistry of Arctic watersheds. These changes are particularly important because permafrost thaw could destabilize a large carbon reservoir, potentially leading to sizable greenhouse gas emissions. Tracking soil thaw and concomitant changes in carbon export are therefore critical to predicting feedbacks between Arctic climate change and global warming. As the climate warms, the seasonally thawed active layer will extend into deeper, previously frozen, mineral-rich soils, increasing the signal of chemical weathering in streams. Historical methods of monitoring active layer thaw depth are labor intensive and may not capture the heterogeneity of Arctic soils, whereas stream geochemistry provides a unique opportunity to integrate signals across vast spatial distances. We present major ion geochemistry and δ13C of dissolved inorganic carbon (DIC) variations that relate to seasonal changes in permafrost thaw depths. Samples were collected from six watersheds on the North Slope of Alaska. All rivers drain continuous permafrost but three drain tussock tundra-dominated watersheds and three drain bare bedrock catchments with minor tundra influences. Water samples were collected from April until October in 2009 and 2010. The major ion and δ13CDIC trends of tundra streams suggest that silicate weathering dominates during the spring melt while carbonate weathering dominates as the active layer deepens in the summer. In tundra streams, early season δ13CDIC values indicate carbonic acid-silicate weathering. Summer δ13CDIC values indicate carbonic acid-carbonate weathering. In both cases, carbonic acid forms from CO2 produced by the microbial decomposition of C3 organic matter. Bedrock streams have nearly constant δ13CDIC values and high

  16. Arctic biodiversity: Increasing richness accompanies shrinking refugia for a cold-associated tundra fauna

    USGS Publications Warehouse

    Hope, Andrew; Waltari, Eric; Malaney, Jason L.; Payer, David C.; Cook, J.A.; Talbot, Sandra

    2015-01-01

    As ancestral biodiversity responded dynamically to late-Quaternary climate changes, so are extant organisms responding to the warming trajectory of the Anthropocene. Ecological predictive modeling, statistical hypothesis tests, and genetic signatures of demographic change can provide a powerful integrated toolset for investigating these biodiversity responses to climate change, and relative resiliency across different communities. Within the biotic province of Beringia, we analyzed specimen localities and DNA sequences from 28 mammal species associated with boreal forest and Arctic tundra biomes to assess both historical distributional and evolutionary responses and then forecasted future changes based on statistical assessments of past and present trajectories, and quantified distributional and demographic changes in relation to major management regions within the study area. We addressed three sets of hypotheses associated with aspects of methodological, biological, and socio-political importance by asking (1) what is the consistency among implications of predicted changes based on the results of both ecological and evolutionary analyses; (2) what are the ecological and evolutionary implications of climate change considering either total regional diversity or distinct communities associated with major biomes; and (3) are there differences in management implications across regions? Our results indicate increasing Arctic richness through time that highlights a potential state shift across the Arctic landscape. However, within distinct ecological communities, we found a predicted decline in the range and effective population size of tundra species into several discrete refugial areas. Consistency in results based on a combination of both ecological and evolutionary approaches demonstrates increased statistical confidence by applying cross-discipline comparative analyses to conservation of biodiversity, particularly considering variable management regimes that seek

  17. Vegetation-associated impacts on arctic tundra bacterial and microeukaryotic communities.

    PubMed

    Shi, Yu; Xiang, Xingjia; Shen, Congcong; Chu, Haiyan; Neufeld, Josh D; Walker, Virginia K; Grogan, Paul

    2015-01-01

    The Arctic is experiencing rapid vegetation changes, such as shrub and tree line expansion, due to climate warming, as well as increased wetland variability due to hydrological changes associated with permafrost thawing. These changes are of global concern because changes in vegetation may increase tundra soil biogeochemical processes that would significantly enhance atmospheric CO2 concentrations. Predicting the latter will at least partly depend on knowing the structure, functional activities, and distributions of soil microbes among the vegetation types across Arctic landscapes. Here we investigated the bacterial and microeukaryotic community structures in soils from the four principal low Arctic tundra vegetation types: wet sedge, birch hummock, tall birch, and dry heath. Sequencing of rRNA gene fragments indicated that the wet sedge and tall birch communities differed significantly from each other and from those associated with the other two dominant vegetation types. Distinct microbial communities were associated with soil pH, ammonium concentration, carbon/nitrogen (C/N) ratio, and moisture content. In soils with similar moisture contents and pHs (excluding wet sedge), bacterial, fungal, and total eukaryotic communities were correlated with the ammonium concentration, dissolved organic nitrogen (DON) content, and C/N ratio. Operational taxonomic unit (OTU) richness, Faith's phylogenetic diversity, and the Shannon species-level index (H') were generally lower in the tall birch soil than in soil from the other vegetation types, with pH being strongly correlated with bacterial richness and Faith's phylogenetic diversity. Together, these results suggest that Arctic soil feedback responses to climate change will be vegetation specific not just because of distinctive substrates and environmental characteristics but also, potentially, because of inherent differences in microbial community structure. PMID:25362064

  18. Vegetation-Associated Impacts on Arctic Tundra Bacterial and Microeukaryotic Communities

    PubMed Central

    Shi, Yu; Xiang, Xingjia; Shen, Congcong; Neufeld, Josh D.; Walker, Virginia K.

    2014-01-01

    The Arctic is experiencing rapid vegetation changes, such as shrub and tree line expansion, due to climate warming, as well as increased wetland variability due to hydrological changes associated with permafrost thawing. These changes are of global concern because changes in vegetation may increase tundra soil biogeochemical processes that would significantly enhance atmospheric CO2 concentrations. Predicting the latter will at least partly depend on knowing the structure, functional activities, and distributions of soil microbes among the vegetation types across Arctic landscapes. Here we investigated the bacterial and microeukaryotic community structures in soils from the four principal low Arctic tundra vegetation types: wet sedge, birch hummock, tall birch, and dry heath. Sequencing of rRNA gene fragments indicated that the wet sedge and tall birch communities differed significantly from each other and from those associated with the other two dominant vegetation types. Distinct microbial communities were associated with soil pH, ammonium concentration, carbon/nitrogen (C/N) ratio, and moisture content. In soils with similar moisture contents and pHs (excluding wet sedge), bacterial, fungal, and total eukaryotic communities were correlated with the ammonium concentration, dissolved organic nitrogen (DON) content, and C/N ratio. Operational taxonomic unit (OTU) richness, Faith's phylogenetic diversity, and the Shannon species-level index (H′) were generally lower in the tall birch soil than in soil from the other vegetation types, with pH being strongly correlated with bacterial richness and Faith's phylogenetic diversity. Together, these results suggest that Arctic soil feedback responses to climate change will be vegetation specific not just because of distinctive substrates and environmental characteristics but also, potentially, because of inherent differences in microbial community structure. PMID:25362064

  19. Phenological dynamics of arctic tundra vegetation and its implications on satellite imagery interpretation

    NASA Astrophysics Data System (ADS)

    Juutinen, Sari; Aurela, Mika; Mikola, Juha; Räsänen, Aleksi; Virtanen, Tarmo

    2016-04-01

    Remote sensing is a key methodology when monitoring the responses of arctic ecosystems to climatic warming. The short growing season and rapid vegetation development, however, set demands to the timing of image acquisition in the arctic. We used multispectral very high spatial resolution satellite images to study the effect of vegetation phenology on the spectral reflectance and image interpretation in the low arctic tundra in coastal Siberia (Tiksi, 71°35'39"N, 128°53'17"E). The study site mainly consists of peatlands, tussock, dwarf shrub, and grass tundra, and stony areas with some lichen and shrub patches. We tested the hypotheses that (1) plant phenology is responsive to the interannual weather variation and (2) the phenological state of vegetation has an impact on satellite image interpretation and the ability to distinguish between the plant communities. We used an empirical transfer function with temperature sums as drivers to reconstruct daily leaf area index (LAI) for the different plant communities for years 2005, and 2010-2014 based on measured LAI development in summer 2014. Satellite images, taken during growing seasons, were acquired for two years having late and early spring, and short and long growing season, respectively. LAI dynamics showed considerable interannual variation due to weather variation, and particularly the relative contribution of graminoid dominated communities was sensitive to these phenology shifts. We have also analyzed the differences in the reflectance values between the two satellite images taking account the LAI dynamics. These results will increase our understanding of the pitfalls that may arise from the timing of image acquisition when interpreting the vegetation structure in a heterogeneous tundra landscape. Very high spatial resolution multispectral images are available at reasonable cost, but not in high temporal resolution, which may lead to compromises when matching ground truth and the imagery. On the other hand

  20. Tundra fire alters stream water chemistry and benthic invertebrate communities, North Slope, Alaska

    NASA Astrophysics Data System (ADS)

    Allen, A. R.; Bowden, W. B.; Kling, G. W.; Schuett, E.; Kostrzewski, J. M.; Kolden Abatzoglou, C.; Findlay, R. H.

    2010-12-01

    Increased fire frequency and severity are potentially important consequences of climate change in high latitude ecosystems. The 2007 Anaktuvuk River fire, which burned from July until October, is the largest recorded tundra fire from Alaska's north slope (≈1,000 km2). The immediate effects of wildfire on water chemistry and biotic assemblages in tundra streams are heretofore unknown. We hypothesized that a tundra fire would increase inorganic nutrient inputs to P-limited tundra streams, increasing primary production and altering benthic macroinvertebrate community structure. We examined linkages among: 1) percentage of riparian zone and overall watershed vegetation burned, 2) physical, chemical and biological stream characteristics, and 3) macroinvertebrate communities in streams draining burned and unburned watersheds during the summers of 2008 and 2009. Streams in burned watersheds contained higher mean concentrations of soluble reactive phosphorus (SRP), ammonium (NH4+), and dissolved organic carbon (DOC). In contrast, stream nitrate (NO3-) concentrations were lower in burned watersheds. The net result was that the tundra fire did not affect concentrations of dissolved inorganic nitrogen (NH4+ + NO3-). In spite of increased SRP, benthic chlorophyll-a biomass was not elevated. Macroinvertebrate abundances were 1.5 times higher in streams draining burned watersheds; Chironomidae midges, Nematodes, and Nemoura stoneflies showed the greatest increases in abundance. Multivariate multiple regression identified environmental parameters associated with the observed changes in the macroinvertebrate communities. Since we identified stream latitude as a significant predictor variable, latitude was included in the model as a covariate. After removing the variation associated with latitude, 67.3 % of the variance in macroinvertebrate community structure was explained by a subset of 7 predictor variables; DOC, conductivity, mean temperature, NO3-, mean discharge, SRP and NH

  1. CO2 flux from tundra lichen, moss, and tussock, Council, Alaska: Assessment of spatial representativeness

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Chae, N.

    2012-12-01

    CO2 flux-measurement in dominant tundra vegetation on the Seward Peninsula of Alaska was examined for spatial representativeness, using a manual chamber system. In order to assess the representativeness of CO2 flux, a 40 m × 40 m (5-m interval; 81 total points) plot was used in June, August, and September of 2011. Average CO2 fluxes in lichen, moss, and tussock tundra were 3.4 ± 2.7, 4.5 ± 2.9, and 7.2 ± 5.7 mgCO2/m2/m during growing season, respectively, suggesting that tussock tundra is a significant CO2 source, especially considering the wide distribution of tussock tundra in the circumpolar region. Further, soil temperature, rather than soil moisture, held the key role in regulating CO2 flux at the study site: CO2 flux from tussock increased linearly as soil temperature increased, while the flux from lichen and moss followed soil temperature nearly exponentially, reflecting differences in surface area covered by the chamber system. Regarding sample size, the 81 total sampling points over June, August, and September satisfy an experimental average that falls within ±10% of full sample average, with a 95% confidence level. However, the number of sampling points for each variety of vegetation during each month must provide at least ±20%, with an 80% confidence level. In order to overcome the logistical constraints, we were required to identify the site's characteristics with a manual chamber system over a 40 m × 40 m plot and to subsequently employ an automated chamber for spatiotemporal representativeness.

  2. Radiation budget and soil heat fluxes in different Arctic tundra vegetation types

    NASA Astrophysics Data System (ADS)

    Juszak, Inge; Iturrate Garcia, Maitane; Gastellu-Etchegorry, Jean-Philippe; Schaepman, Michael E.; Schaepman-Strub, Gabriela

    2016-04-01

    While solar radiation is one of the primary energy sources for warming and thawing permafrost soil, the amount of shortwave radiation reaching the soil is reduced by vegetation shading. Climate change has led to greening, shrub expansion and encroachment in many Arctic tundra regions and further changes are anticipated. These vegetation changes feed back to the atmosphere and permafrost as they modify the surface energy budget. However, canopy transmittance of solar radiation has rarely been measured or modelled for a variety of tundra vegetation types. We assessed the radiation budget of the most common vegetation types at the Kytalyk field site in North-East Siberia (70.8°N, 147.5°E) with field measurements and 3D radiative transfer modelling and linked it to soil heat fluxes. Our results show that Arctic tundra vegetation types differ in canopy albedo and transmittance as well as in soil heat flux and active layer thickness. Tussock sedges transmitted on average 56% of the incoming light and dwarf shrubs 27%. For wet sedges we found that the litter layer was very important as it reduced the average transmittance to only 6%. Model output indicated that both, albedo and transmittance, also depend on the spatial aggregation of vegetation types. We found that permafrost thaw was more strongly related to soil properties than to canopy shading. The presented radiative transfer model allows quantifying effects of the vegetation layer on the surface radiation budget in permafrost areas. The parametrised model can account for diverse vegetation types and variation of properties within types. Our results highlight small scale radiation budget and permafrost thaw variability which are indicated and partly caused by vegetation. As changes in species composition and biomass increase can influence thaw rates, small scale patterns should be considered in assessments of climate-vegetation-permafrost feedbacks.

  3. Bacterial community structure and soil properties of a subarctic tundra soil in Council, Alaska

    PubMed Central

    Kim, Hye Min; Jung, Ji Young; Yergeau, Etienne; Hwang, Chung Yeon; Hinzman, Larry; Nam, Sungjin; Hong, Soon Gyu; Kim, Ok-Sun; Chun, Jongsik; Lee, Yoo Kyung

    2014-01-01

    The subarctic region is highly responsive and vulnerable to climate change. Understanding the structure of subarctic soil microbial communities is essential for predicting the response of the subarctic soil environment to climate change. To determine the composition of the bacterial community and its relationship with soil properties, we investigated the bacterial community structure and properties of surface soil from the moist acidic tussock tundra in Council, Alaska. We collected 70 soil samples with 25-m intervals between sampling points from 0–10 cm to 10–20 cm depths. The bacterial community was analyzed by pyrosequencing of 16S rRNA genes, and the following soil properties were analyzed: soil moisture content (MC), pH, total carbon (TC), total nitrogen (TN), and inorganic nitrogen ( and ). The community compositions of the two different depths showed that Alphaproteobacteria decreased with soil depth. Among the soil properties measured, soil pH was the most significant factor correlating with bacterial community in both upper and lower-layer soils. Bacterial community similarity based on jackknifed unweighted unifrac distance showed greater similarity across horizontal layers than through the vertical depth. This study showed that soil depth and pH were the most important soil properties determining bacterial community structure of the subarctic tundra soil in Council, Alaska. PMID:24893754

  4. Structural complexity and land-surface energy exchange along a gradient from arctic tundra to boreal forest

    USGS Publications Warehouse

    Thompson, C.; Beringer, J.; Chapin, F. S., III; McGuire, A.D.

    2004-01-01

    Question: Current climate changes in the Alaskan Arctic, which are characterized by increases in temperature and length of growing season, could alter vegetation structure, especially through increases in shrub cover or the movement of treeline. These changes in vegetation structure have consequences for the climate system. What is the relationship between structural complexity and partitioning of surface energy along a gradient from tundra through shrub tundra to closed canopy forest? Location: Arctic tundra-boreal forest transition in the Alaskan Arctic. Methods: Along this gradient of increasing canopy complexity, we measured key vegetation characteristics, including community composition, biomass, cover, height, leaf area index and stem area index. We relate these vegetation characteristics to albedo and the partitioning of net radiation into ground, latent, and sensible heating fluxes. Results: Canopy complexity increased along the sequence from tundra to forest due to the addition of new plant functional types. This led to non-linear changes in biomass, cover, and height in the understory. The increased canopy complexity resulted in reduced ground heat fluxes, relatively conserved latent heat fluxes and increased sensible heat fluxes. The localized warming associated with increased sensible heating over more complex canopies may amplify regional warming, causing further vegetation change in the Alaskan Arctic.

  5. An assessment of the carbon balance of arctic tundra: comparisons among observations, process models, and atmospheric inversions

    USGS Publications Warehouse

    McGuire, A.D.; Christensen, T.R.; Hayes, D.; Heroult, A.; Euskirchen, E.; Yi, Y.; Kimball, J.S.; Koven, C.; Lafleur, P.; Miller, P.A.; Oechel, W.; Peylin, P.; Williams, M.

    2012-01-01

    Although arctic tundra has been estimated to cover only 8% of the global land surface, the large and potentially labile carbon pools currently stored in tundra soils have the potential for large emissions of carbon (C) under a warming climate. These emissions as radiatively active greenhouse gases in the form of both CO2 and CH4 could amplify global warming. Given the potential sensitivity of these ecosystems to climate change and the expectation that the Arctic will experience appreciable warming over the next century, it is important to assess whether responses of C exchange in tundra regions are likely to enhance or mitigate warming. In this study we compared analyses of C exchange of Arctic tundra between 1990–1999 and 2000–2006 among observations, regional and global applications of process-based terrestrial biosphere models, and atmospheric inversion models. Syntheses of the compilation of flux observations and of inversion model results indicate that the annual exchange of CO2 between arctic tundra and the atmosphere has large uncertainties that cannot be distinguished from neutral balance. The mean estimate from an ensemble of process-based model simulations suggests that arctic tundra acted as a sink for atmospheric CO2 in recent decades, but based on the uncertainty estimates it cannot be determined with confidence whether these ecosystems represent a weak or a strong sink. Tundra was 0.6 °C warmer in the 2000s compared to the 1990s. The central estimates of the observations, process-based models, and inversion models each identify stronger sinks in the 2000s compared with the 1990s. Similarly, the observations and the applications of regional process-based models suggest that CH4 emissions from arctic tundra have increased from the 1990s to 2000s. Based on our analyses of the estimates from observations, process-based models, and inversion models, we estimate that arctic tundra was a sink for atmospheric CO2 of 110 Tg C yr-1 (uncertainty between a

  6. Seasonal Change Of CO2 Flux At Tundra Vegetation In Interior Alaska

    NASA Astrophysics Data System (ADS)

    Nojiri, A.; Harazono, Y.; Ohtaki, E.; Iwata, T.

    2003-12-01

    CO2 flux and micrometeorology have been measured to reveal the responses of forest at permafrost to climate change since October in 2002. The vegetation was black spruce and tussock tundra located in the campus (147° 51'W, 64° 51N) of the University of Alaska Fairbanks, Alaska. There have been significant gaps of flux measurements in the interior Alaska where it is generally warmer in summer and has different climate conditions. CO2 uptake started in March when the tussock tundra was still under snow cover. CO2 uptake increased after spring thaw in mid April that ranged -0.3mg/m2/s and increased gradually until early May (DOY135). After that, daily maximum CO2 uptake kept almost upper-limit level of -1mg/m2/s during summer (June and July). Day-length was longer at the site so the nighttime CO2 respiration was defined as CO2 efflux when PAR was less than 10 mol/m2/s. Averages of CO2 respiration were 0.042mg/m2/s in mid April (DOY100-109), 0.021mg/m2/s in mid May (DOY130-139), 0.15mg/m2/s in mid June (DOY160-169), and 0.15mg/m2/s in mid July (DOY190-199), respectively. Air temperature in mid summer did not changed remarkably and daily average temperature in June and July were almost the same as between 10 and 20. These were caused by lower solar radiation and higher level of precipitation in 2003 summer than the normal year. Observed CO2 flux was limited period and the CO2 budget over tussock tundra in interior Alaska was a source from spring to summer in 2003. Long term CO2 budget study is demanded to reveal whether anthropogenic or natural variation is major effect on climate change, thus it is important to continue the flux measurements and to reveal the relationships between the atmosphere and the vegetation.

  7. Soil Carbon Vulnerability in Arctic Coastal Tundra: Seasonal and Spatial Variations in 14C-CO2

    NASA Astrophysics Data System (ADS)

    Smith, L. J.; Torn, M. S.; Conrad, M. E.; Curtis, J. B.; Hahn, M. S.

    2013-12-01

    One reason permafrost soils contain large, old soil organic carbon stores is slow decomposition rates due to cold and waterlogged conditions. If climate change causes high latitude soils to warm and dry, carbon emissions from permafrost soils could be an important atmospheric greenhouse gas source. The vulnerability of global Arctic soil carbon stocks to increased decomposition due to thaw is hard to assess, due to environmental heterogeneity, complex controls on microbial processes, uncertain carbon stocks and flux rates, and poorly understood soil carbon stabilization mechanisms. To address these knowledge gaps, we are using radiocarbon measurements to estimate carbon turnover times in polygonal tundra in Barrow, Alaska. Specifically, we ask: (1) how do old versus recently fixed soil carbon pools contribute to total decomposition, (2) how does this vary seasonally, and (3) how does it vary across a permafrost degradation gradient? Old radiocarbon ages of soil organic matter in perennially frozen soils and deep portions of the seasonally thawed active layer reflect slow historic decomposition rates, and changes in the radiocarbon content of respired CO2 indicate relative mineralization rates of this old, stored carbon. At four time points from June-October 2013, we sample soil organic matter and respired CO2 from low-centered, transitional, and high-centered polygons characteristic of a permafrost degradation cycle. We measure the radiocarbon content of CO2 in surface fluxes and soil pore space from 3 depths in the soil profile, and concurrently incubate active layer soils to resolve the 14C-CO2 signatures of individual soil layers. Preliminary data from 2012 suggest that old soil carbon stores are vulnerable to decomposition. CO2 ages increase with depth in the profile from modern radiocarbon ages to as old as 3115 BP, and high incubation flux rates indicate availability to microbes. As part of the Next Generation Ecosystem Experiment (NGEE-Arctic), we now study

  8. Alaska Native cancer epidemiology in the Arctic.

    PubMed

    Bowerman, R J

    1998-01-01

    Cancer incidence and its possible relation to environmental contaminants, including radiation, continues to be a perceived health threat for the arctic-dwelling Alaska Native (Inupiat Eskimo) people despite the lack of a direct link to high-dose exposure. To better understand this concern, all known malignancies diagnosed in this population (n = 177) in three consecutive eight-year periods (1971-1994) were evaluated. The most recent average incidence rate (age-adjusted to world standard population) of 315 per 100,000 (95% confidence interval, CI = 248-382) represents a 33% surge (albeit non-significant) in Alaska Native cancer incidence over the initial period studied. The male rate 366 (95% CI = 266-466) for the same period exceeds the female rate 258 (95% CI = 169-347) by 42%. Two patterns of cancer incidence are seen at the village level. One, a 24 y upward trend found in the villages of Barrow, Point Hope and Kaktovik (combined rate of increase significant [P = 0.047]) associated with lung cancer; and the other, a stable trend over the past 16 y, associated with colon and rectal cancer. Lung cancer is the predominant cancer by site and is primarily a male disease. The recent male lung cancer incidence rate of 137 (95% CI = 73-201) exceeds the female rate by greater than five times. Total lung cancer cases are primarily confined to four villages where the incidence significantly (P = 0.0043) exceeds the remaining population. The major female cancers are colon/rectal and breast with cancer of the cervix virtually eliminated. Breast cancer is found primarily in two villages where its excess is significant (P = 0.025). Inupiat Eskimo cancer epidemiology is unique, differing from both the Alaska Native and other Circumpolar populations. At present, this uniqueness cannot be explained by an overt environmental contaminant exposure. Although tobacco very likely plays a central role, it by itself cannot fully explain the extremely high male lung cancer rate and why

  9. Shrub line advance in Arctic and alpine tundra of the Yukon Territory

    NASA Astrophysics Data System (ADS)

    Myers-Smith, I. H.; Hik, D.

    2010-12-01

    Growing evidence indicates an expansion of canopy-forming woody shrubs up mountain slopes and northward into Arctic tundra. The correlation between warming and greening has been used to link climate change with shrub expansion; however, the exact mechanisms driving observed increases in canopy-forming shrubs are probably more complex. Shrub expansion that results in a change in canopy cover may modify the ecology of tundra ecosystems by changing understory plant composition, soil thermal dynamics, surface albedo, nutrient turnover times and carbon storage. We surveyed the abundance of all tundra willow species (Salix spp.) growing at three sites in the Yukon Territory: the mountains of the Kluane Region, the Richardson Mountains, and on Qikiqtaruk - Herschel Island in the Beaufort Sea. At the two mountainous sites, we collected sections from the largest stem of willow shrubs at shrub line (the maximum elevation at which canopy-forming shrubs grow) and below shrub line (at approximately 50% shrub cover) in a total of 16 valleys. At the coastal site we collected samples from each of the 4 vegetation types: the alluvial fan, ridges, tussock tundra and disturbed terrain. Shrub stems were thin-sectioned using a microtome, photographed with a microscope and ring widths were measured from the digital images. We compared age distributions of willow individuals at and below shrub line and found younger populations at higher elevations, particularly on warm, south-facing aspects. Younger willows at shrub line and a lack of significant mortality in the field surveys indicate that shrubs have advanced up slope at the mountainous sites. Photographic and long-term plot data indicate increases in cover and height of willow shrub patches at the coastal site. We compared growth rings to regional weather data, and found positive correlations between annual growth and summer temperatures. Our results indicate that willows grew most in years with a warm June and July. This evidence of

  10. 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.

  11. 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).

  12. Constraint of soil moisture on CO2 efflux from tundra lichen, moss, and tussock in Council, Alaska using a hierarchical Bayesian model

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Nishina, K.; Chae, N.; Park, S.; Yoon, Y.; Lee, B.

    2014-04-01

    The tundra ecosystem is quite vulnerable to drastic climate change in the Arctic, and the quantification of carbon dynamics is of significant importance in response to thawing permafrost, changes in the snow-covered period and snow and shrub community extent, and the decline of sea ice in the Arctic. Here, CO2 efflux measurements using a manual chamber system within a 40 m × 40 m (5 m interval; 81 total points) plot were conducted in dominant tundra vegetation on the Seward Peninsula of Alaska, during the growing seasons of 2011 and 2012, for the assessment of the driving parameters of CO2 efflux. We applied a hierarchical Bayesian (HB) model - which is a function of soil temperature, soil moisture, vegetation type and thaw depth - to quantify the effect of environmental parameters on CO2 efflux, and to estimate growing season CO2 emission. Our results showed that average CO2 efflux in 2011 is 1.4-fold higher than in 2012, resulting from the distinct difference in soil moisture between the two years. Tussock-dominated CO2 efflux is 1.4 to 2.3 times higher than those measured in lichen and moss communities, reflecting tussock as a significant CO2 source in the Arctic, with wide area distribution on a circumpolar scale. CO2 efflux followed soil temperature nearly exponentially from both the observed data and the posterior medians of the HB model. This reveals soil temperature as the most important parameter in regulating CO2 efflux, rather than soil moisture and thaw depth. Obvious changes in soil moisture during the growing seasons of 2011 and 2012 resulted in an explicit difference in CO2 efflux - 742 and 539 g CO2 m-2 period-1 in 2011 and 2012, respectively, suggesting that the 2012 CO2 emission rate was constrained by 27% (95% credible interval: 17-36%) compared to 2011, due to higher soil moisture from severe rain. Estimated growing season CO2 emission rate ranged from 0.86 Mg CO2 period-1 in 2012 to 1.2 Mg CO2 period-1 in 2011 within a 40 m × 40 m plot

  13. Constraint of soil moisture on CO2 efflux from tundra lichen, moss, and tussock in Council, Alaska, using a hierarchical Bayesian model

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Nishina, K.; Chae, N.; Park, S. J.; Yoon, Y. J.; Lee, B. Y.

    2014-10-01

    The tundra ecosystem is quite vulnerable to drastic climate change in the Arctic, and the quantification of carbon dynamics is of significant importance regarding thawing permafrost, changes to the snow-covered period and snow and shrub community extent, and the decline of sea ice in the Arctic. Here, CO2 efflux measurements using a manual chamber system within a 40 m × 40 m (5 m interval; 81 total points) plot were conducted within dominant tundra vegetation on the Seward Peninsula of Alaska, during the growing seasons of 2011 and 2012, for the assessment of driving parameters of CO2 efflux. We applied a hierarchical Bayesian (HB) model - a function of soil temperature, soil moisture, vegetation type, and thaw depth - to quantify the effects of environmental factors on CO2 efflux and to estimate growing season CO2 emissions. Our results showed that average CO2 efflux in 2011 was 1.4 times higher than in 2012, resulting from the distinct difference in soil moisture between the 2 years. Tussock-dominated CO2 efflux is 1.4 to 2.3 times higher than those measured in lichen and moss communities, revealing tussock as a significant CO2 source in the Arctic, with a wide area distribution on the circumpolar scale. CO2 efflux followed soil temperature nearly exponentially from both the observed data and the posterior medians of the HB model. This reveals that soil temperature regulates the seasonal variation of CO2 efflux and that soil moisture contributes to the interannual variation of CO2 efflux for the two growing seasons in question. Obvious changes in soil moisture during the growing seasons of 2011 and 2012 resulted in an explicit difference between CO2 effluxes - 742 and 539 g CO2 m-2 period-1 for 2011 and 2012, respectively, suggesting the 2012 CO2 emission rate was reduced to 27% (95% credible interval: 17-36%) of the 2011 emission, due to higher soil moisture from severe rain. The estimated growing season CO2 emission rate ranged from 0.86 Mg CO2 in 2012 to 1

  14. Winter precipitation and snow accumulation drive the methane sink or source strength of Arctic tussock tundra.

    PubMed

    Blanc-Betes, Elena; Welker, Jeffrey M; Sturchio, Neil C; Chanton, Jeffrey P; Gonzalez-Meler, Miquel A

    2016-08-01

    Arctic winter precipitation is projected to increase with global warming, but some areas will experience decreases in snow accumulation. Although Arctic CH4 emissions may represent a significant climate forcing feedback, long-term impacts of changes in snow accumulation on CH4 fluxes remain uncertain. We measured ecosystem CH4 fluxes and soil CH4 and CO2 concentrations and (13) C composition to investigate the metabolic pathways and transport mechanisms driving moist acidic tundra CH4 flux over the growing season (Jun-Aug) after 18 years of experimental snow depth increases and decreases. Deeper snow increased soil wetness and warming, reducing soil %O2 levels and increasing thaw depth. Soil moisture, through changes in soil %O2 saturation, determined predominance of methanotrophy or methanogenesis, with soil temperature regulating the ecosystem CH4 sink or source strength. Reduced snow (RS) increased the fraction of oxidized CH4 (Fox) by 75-120% compared to Ambient, switching the system from a small source to a net CH4 sink (21 ± 2 and -31 ± 1 mg CH4  m(-2)  season(-1) at Ambient and RS). Deeper snow reduced Fox by 35-40% and 90-100% in medium- (MS) and high- (HS) snow additions relative to Ambient, contributing to increasing the CH4 source strength of moist acidic tundra (464 ± 15 and 3561 ± 97 mg CH4  m(-2)  season(-1) at MS and HS). Decreases in Fox with deeper snow were partly due to increases in plant-mediated CH4 transport associated with the expansion of tall graminoids. Deeper snow enhanced CH4 production within newly thawed soils, responding mainly to soil warming rather than to increases in acetate fermentation expected from thaw-induced increases in SOC availability. Our results suggest that increased winter precipitation will increase the CH4 source strength of Arctic tundra, but the resulting positive feedback on climate change will depend on the balance between areas with more or less snow accumulation than they are currently

  15. 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

  16. Labile carbon concentrations are strongly linked to plant production in Arctic tussock tundra soils

    NASA Astrophysics Data System (ADS)

    Darrouzet-Nardi, A.; Weintraub, M. N.; Euskirchen, E. S.; Steltzer, H.; Sullivan, P.

    2013-12-01

    The exchange of carbon and nutrients between plants and microbes is a key determinant of carbon balance in Arctic soils. Microbes rely on labile plant carbon for the energy they need to produce enzymes that can release nutrients and less energetically favorable carbon from soil organic matter. One of the main mechanisms of carbon transfer is rhizodeposition, the exudation of labile plant carbon such as sugars from roots into the rhizosphere. Despite the importance of this flow of energy and materials from plants to microbes, there have been few attempts to quantify labile carbon pools or fluxes in Arctic soils. To improve our knowledge of labile carbon dynamics in Arctic soils, we address two basic questions: (1) What are the seasonal patterns of labile carbon concentrations? and (2) How do seasonal patterns in labile carbon correlate with plant production, microbial biomass, and soil nutrients? We measured concentrations of total reducing sugars (TRS) in the soil solution of moist acidic tussock tundra on 28 dates during the 2012 growing season in 20 plots of an early snowmelt × warming experiment. We evaluated these total reducing sugar concentrations in the context of eddy flux carbon exchange data, plant NDVI, total dissolved carbon in soils, microbial biomass, and soil nutrients. Though we did not see treatment effects of the snowmelt × warming experiment, we did observe a clear seasonal pattern in TRS concentrations in which they started low at the time of thaw, then built to a maximum value around the time of peak plant physiology in July, followed by a decline as plants senesced. We observed a clear correlation between TRS and gross primary production (GPP). NDVI values also increased with TRS concentrations during the first half of the season and then leveled off as TRS began its decline. These relationships were in contrast to labile N concentrations, which remained at low concentrations all season. Our data suggest that rhizodeposition of labile carbon

  17. Long-term experimental manipulation of winter snow regime and summer temperature in arctic and alpine tundra

    USGS Publications Warehouse

    Walker, M.D.; Walker, D. A.; Welker, J.M.; Arft, A.M.; Bardsley, T.; Brooks, P.D.; Fahnestock, J.T.; Jones, M.H.; Losleben, M.; Parsons, A.N.; Seastedt, T.R.; Turner, P.L.

    1999-01-01

    Three 60 m long, 2.8 m high snowfences have been erected to study long-term effects of changing winter snow conditions on arctic and alpine tundra. This paper describes the experimental design and short-term effects. Open-top fiberglass warming chambers are placed along the experimental snow gradients and in controls areas outside the fences; each warming plot is paired with an unwarmed plot. The purpose of the experiment is to examine short- and long-term changes to the integrated physical-biological systems under simultaneous changes of winter snow regime and summer temperature, as part of the Long-Term Ecological Research network and the International Tundra Experiment. The sites were at Niwot Ridge, Colorado, a temperate high altitude site in the Colorado Rockies, and Toolik Lake, Alaska, a high-latitude site. Initial results indicate that although experimental designs are essentially identical at the arctic and alpine sites, experimental effects are different. The drift at Niwot Ridge lasts much longer than do the Toolik Lake drifts, so that the Niwot Ridge fence affects both summer and winter conditions, whereas the Toolik Lake fence affects primarily winter conditions. The temperature experiment also differs in effect between the sites. Although the average temperature increase at the two sites is similar (daily increase 1.5??C at Toolik and 1.9??C at Niwot Ridge), at Toolik Lake there is only minor diurnal variation, whereas at Niwot Ridge the daytime increases are extreme on sunny days (as much as 7-10??C), and minimum nighttime temperatures in the chambers are often slightly cooler than ambient (by about 1??C). The experimental drifts resulted in wintertime increases in temperature and CO2 flux. Temperatures under the deep drifts were much more consistent and warmer than in control areas, and at Niwot Ridge remained very close to 0??C all winter. These increased temperatures were likely responsible for observed increases in system carbon loss. Initial

  18. Long-term experimental warming alters community composition of ascomycetes in Alaskan moist and dry arctic tundra.

    PubMed

    Semenova, Tatiana A; Morgado, Luis N; Welker, Jeffrey M; Walker, Marilyn D; Smets, Erik; Geml, József

    2015-01-01

    Arctic tundra regions have been responding to global warming with visible changes in plant community composition, including expansion of shrubs and declines in lichens and bryophytes. Even though it is well known that the majority of arctic plants are associated with their symbiotic fungi, how fungal community composition will be different with climate warming remains largely unknown. In this study, we addressed the effects of long-term (18 years) experimental warming on the community composition and taxonomic richness of soil ascomycetes in dry and moist tundra types. Using deep Ion Torrent sequencing, we quantified how OTU assemblage and richness of different orders of Ascomycota changed in response to summer warming. Experimental warming significantly altered ascomycete communities with stronger responses observed in the moist tundra compared with dry tundra. The proportion of several lichenized and moss-associated fungi decreased with warming, while the proportion of several plant and insect pathogens and saprotrophic species was higher in the warming treatment. The observed alterations in both taxonomic and ecological groups of ascomycetes are discussed in relation to previously reported warming-induced shifts in arctic plant communities, including decline in lichens and bryophytes and increase in coverage and biomass of shrubs. PMID:25522194

  19. Simulating the effects of climate change and climate variability on carbon dynamics in Arctic tundra

    NASA Astrophysics Data System (ADS)

    Stieglitz, Marc; Giblin, Anne; Hobbie, John; Williams, Matthew; Kling, George

    2000-12-01

    Through a simple modeling exercise, three mechanisms have been identified, each operating at a different timescale, that may govern carbon dynamics in Arctic tundra regions and partially explain observed CO2 flux variability. At short timescales the biosphere reacts to meteorological forcing. Drier conditions are associated with aerobic soil decomposition, a large CO2efflux, and a net ecosystem loss of carbon. Cooler and moister conditions favor slower anaerobic decomposition in soils, good growing conditions, and terrestrial carbon sequestration. At intermediate timescales, periods of terrestrial carbon loss are directly linked to periods of carbon sequestration by the ability of the ecosystem to retain labile nitrogen. Labile nitrogen released to the soil during periods when the tundra is a source of carbon (soil respiration > net primary productivity) is retained within the ecosystem and accessed during periods when carbon sequestration is favored (net primary productivity > soil respiration). Finally, the ability of vegetation to respond to long-term changes in soil nutrient status via changes in leaf nitrogen and leaf area index modulates this dynamic at intermediate to long timescales.

  20. Inundation, sedimentation, and subsidence creates goose habitat along the Arctic coast of Alaska

    USGS Publications Warehouse

    Tape, Ken D.; Flint, Paul L.; Meixell, Brandt W.; Gaglioti, Benjamin V.

    2013-01-01

    The Arctic Coastal Plain of Alaska is characterized by thermokarst lakes and drained lake basins, and the rate of coastal erosion has increased during the last half-century. Portions of the coast are <1 m above sea level for kilometers inland, and are underlain by ice-rich permafrost. Increased storm surges or terrestrial subsidence would therefore expand the area subject to marine inundation. Since 1976, the distribution of molting Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain has shifted from inland freshwater lakes to coastal marshes, such as those occupying the Smith River and Garry Creek estuaries. We hypothesized that the movement of geese from inland lakes was caused by an expansion of high quality goose forage in coastal areas. We examined the recent history of vegetation and geomorphological changes in coastal goose habitat by combining analysis of time series imagery between 1948 and 2010 with soil stratigraphy dated using bomb-curve radiocarbon. Time series of vertical imagery and in situ verification showed permafrost thaw and subsidence of polygonal tundra. Soil stratigraphy and dating within coastal estuaries showed that non-saline vegetation communities were buried by multiple sedimentation episodes between 1948 and 1995, accompanying a shift toward salt-tolerant vegetation. This sedimentation allowed high quality goose forage plants to expand, thus facilitating the shift in goose distribution. Declining sea ice and the increasing rate of terrestrial inundation, sedimentation, and subsidence in coastal estuaries of Alaska may portend a 'tipping point' whereby inland areas would be transformed into salt marshes.

  1. Mortality of arctic fox pups in northern Alaska

    SciTech Connect

    Not Available

    1982-01-01

    Reports of mortality among arctic foxes, Alopex lagopus, generally consist of isolated incidents of predation by bald eagles, Haliaeetus leucocephalus, snowy owls, Nyctea scandiaca, red foxes, Vulpes vulpes, and dogs, Canis familiaris. This is a report of observations made on mortality of arctic fox pups observed at dens in the Prudhoe Bay and Colville River Delta areas of northern Alaska during summers of 1975 to 1978 and 1976 to 1979, respectively.

  2. Carbon-Degrading Enzyme Activities Stimulated by Increased Nutrient Availability in Arctic Tundra Soils

    PubMed Central

    Koyama, Akihiro; Wallenstein, Matthew D.; Simpson, Rodney T.; Moore, John C.

    2013-01-01

    Climate-induced warming of the Arctic tundra is expected to increase nutrient availability to soil microbes, which in turn may accelerate soil organic matter (SOM) decomposition. We increased nutrient availability via fertilization to investigate the microbial response via soil enzyme activities. Specifically, we measured potential activities of seven enzymes at four temperatures in three soil profiles (organic, organic/mineral interface, and mineral) from untreated native soils and from soils which had been fertilized with nitrogen (N) and phosphorus (P) since 1989 (23 years) and 2006 (six years). Fertilized plots within the 1989 site received annual additions of 10 g N⋅m-2⋅year-1 and 5 g P⋅m-2⋅year-1. Within the 2006 site, two fertilizer regimes were established – one in which plots received 5 g N⋅m-2⋅year-1 and 2.5 g P⋅m-2⋅year-1 and one in which plots received 10 g N⋅m-2⋅year-1 and 5 g P⋅m-2⋅year-1. The fertilization treatments increased activities of enzymes hydrolyzing carbon (C)-rich compounds but decreased phosphatase activities, especially in the organic soils. Activities of two enzymes that degrade N-rich compounds were not affected by the fertilization treatments. The fertilization treatments increased ratios of enzyme activities degrading C-rich compounds to those for N-rich compounds or phosphate, which could lead to changes in SOM chemistry over the long term and to losses of soil C. Accelerated SOM decomposition caused by increased nutrient availability could significantly offset predicted increased C fixation via stimulated net primary productivity in Arctic tundra ecosystems. PMID:24204773

  3. Carbon-degrading enzyme activities stimulated by increased nutrient availability in Arctic tundra soils.

    PubMed

    Koyama, Akihiro; Wallenstein, Matthew D; Simpson, Rodney T; Moore, John C

    2013-01-01

    Climate-induced warming of the Arctic tundra is expected to increase nutrient availability to soil microbes, which in turn may accelerate soil organic matter (SOM) decomposition. We increased nutrient availability via fertilization to investigate the microbial response via soil enzyme activities. Specifically, we measured potential activities of seven enzymes at four temperatures in three soil profiles (organic, organic/mineral interface, and mineral) from untreated native soils and from soils which had been fertilized with nitrogen (N) and phosphorus (P) since 1989 (23 years) and 2006 (six years). Fertilized plots within the 1989 site received annual additions of 10 g N · m(-2) · year(-1) and 5 g P · m(-2) · year(-1). Within the 2006 site, two fertilizer regimes were established--one in which plots received 5 g N · m(-2) · year(-1) and 2.5 g P · m(-2) · year(-1) and one in which plots received 10 g N · m(-2) · year(-1) and 5 g P · m(-2) · year(-1). The fertilization treatments increased activities of enzymes hydrolyzing carbon (C)-rich compounds but decreased phosphatase activities, especially in the organic soils. Activities of two enzymes that degrade N-rich compounds were not affected by the fertilization treatments. The fertilization treatments increased ratios of enzyme activities degrading C-rich compounds to those for N-rich compounds or phosphate, which could lead to changes in SOM chemistry over the long term and to losses of soil C. Accelerated SOM decomposition caused by increased nutrient availability could significantly offset predicted increased C fixation via stimulated net primary productivity in Arctic tundra ecosystems. PMID:24204773

  4. Isotopic insights into methane production, oxidation, and emissions in Arctic polygon tundra.

    PubMed

    Vaughn, Lydia J S; Conrad, Mark E; Bill, Markus; Torn, Margaret S

    2016-10-01

    Arctic wetlands are currently net sources of atmospheric CH4 . Due to their complex biogeochemical controls and high spatial and temporal variability, current net CH4 emissions and gross CH4 processes have been difficult to quantify, and their predicted responses to climate change remain uncertain. We investigated CH4 production, oxidation, and surface emissions in Arctic polygon tundra, across a wet-to-dry permafrost degradation gradient from low-centered (intact) to flat- and high-centered (degraded) polygons. From 3 microtopographic positions (polygon centers, rims, and troughs) along the permafrost degradation gradient, we measured surface CH4 and CO2 fluxes, concentrations and stable isotope compositions of CH4 and DIC at three depths in the soil, and soil moisture and temperature. More degraded sites had lower CH4 emissions, a different primary methanogenic pathway, and greater CH4 oxidation than did intact permafrost sites, to a greater degree than soil moisture or temperature could explain. Surface CH4 flux decreased from 64 nmol m(-2)  s(-1) in intact polygons to 7 nmol m(-2)  s(-1) in degraded polygons, and stable isotope signatures of CH4 and DIC showed that acetate cleavage dominated CH4 production in low-centered polygons, while CO2 reduction was the primary pathway in degraded polygons. We see evidence that differences in water flow and vegetation between intact and degraded polygons contributed to these observations. In contrast to many previous studies, these findings document a mechanism whereby permafrost degradation can lead to local decreases in tundra CH4 emissions. PMID:26990225

  5. Age-specific survival of tundra swans on the lower Alaska Peninsula

    USGS Publications Warehouse

    Meixell, Brandt W.; Lindberg, Mark S.; Conn, Paul B.; Dau, Christian P.; Sarvis, John E.; Sowl, Kristine M.

    2013-01-01

    The population of Tundra Swans (Cygnus columbianus columbianus) breeding on the lower Alaska Peninsula represents the southern extremity of the species' range and is uniquely nonmigratory. We used data on recaptures, resightings, and recoveries of neck-collared Tundra Swans on the lower Alaska Peninsula to estimate collar loss, annual apparent survival, and other demographic parameters for the years 1978–1989. Annual collar loss was greater for adult males fitted with either the thinner collar type (0.34) or the thicker collar type (0.15) than for other age/sex classes (thinner: 0.10, thicker: 0.04). The apparent mean probability of survival of adults (0.61) was higher than that of immatures (0.41) and for both age classes varied considerably by year (adult range: 0.44–0.95, immature range: 0.25–0.90). To assess effects of permanent emigration by age and breeding class, we analyzed post hoc the encounter histories of swans known to breed in our study area. The apparent mean survival of known breeders (0.65) was generally higher than that of the entire marked sample but still varied considerably by year (range 0.26–1.00) and indicated that permanent emigration of breeding swans was likely. We suggest that reductions in apparent survival probability were influenced primarily by high and variable rates of permanent emigration and that immigration by swans from elsewhere may be important in sustaining a breeding population at and near Izembek National Wildlife Refuge.

  6. Vegetation-Soil-Active Layer Relationships Along a Low-Arctic Bioclimate Gradient, Alaska

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Jia, G. J.; Epstein, H. E.; Shiklomanov, N.; Nelson, F.; Hinzman, L. D.; Romanovsky, V. E.

    2002-12-01

    Northern Alaska has three of five Arctic bioclimate subzones, which are representative of the circumpolar Low Arctic. This portion of the Arctic has more or less continuous tundra plant cover and well-developed moss canopies. We examined the biomass and remotely sensed spectral properties of the vegetation canopy, active-layer thickness, and the soil properties at 21 sites on the Arctic Slope and Seward Peninsula of Alaska. The sites were grouped into three bioclimate subzones according the summer warmth at the sites. The summer warmth index (SWI) is the sum of the mean monthly temperatures greater than 0 degrees C. Subzone C, the coldest subzone, occurs in a narrow strip along the northern coast of the Alaska. Subzone D covers most of the Arctic Coastal Plain and the northwest portion of the Seward Peninsula, and Subzone E covers most of the Foothills and most of the unforested portion of the Seward Peninsula. The SWIs in Subzones C, D, and E are generally less than 10-15 degrees C, 15-25 degrees C, and 25-35 degrees C respectively. The average active layer depths were 44, 55, and 47 cm respectively The shallow active layer in Subzone E is to a large degree a response to the denser vegetation canopies in Subzone E. Total plant biomass in Subzone C, D, and E averaged 421 g m-2, 503 g m-2, and 1178 g m-2 respectively. The much higher biomass in Subzone E was due primarily to woody shrubs (40 g m-2 in Subzone C, 51 g m-2 in Subzone D, and 730 g m-2 in Subzone E). The normalized difference vegetation index (NDVI) is one measure of greenness. Highest NDVI values were obtained from acidic tundra regions in Subzone E, and the lowest NDVI values were obtained in the nonacidic areas of Subzone C. In summary, the insulative properties of the vegetation play a very important role controlling the thickness of the active layer, and the amount of vegetation biomass differs according to summer warmth and soil properties. Acidic soils in the warmest parts of the Arctic (Subzone E

  7. Simulating the effects of soil organic nitrogen and grazing on arctic tundra vegetation dynamics on the Yamal Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Yu, Qin; Epstein, Howard; Walker, Donald

    2009-10-01

    Sustainability of tundra vegetation under changing climate on the Yamal Peninsula, northwestern Siberia, home to the world's largest area of reindeer husbandry, is of crucial importance to the local native community. An integrated investigation is needed for better understanding of the effects of soils, climate change and grazing on tundra vegetation in the Yamal region. In this study we applied a nutrient-based plant community model—ArcVeg—to evaluate how two factors (soil organic nitrogen (SON) levels and grazing) interact to affect tundra responses to climate warming across a latitudinal climatic gradient on the Yamal Peninsula. Model simulations were driven by field-collected soil data and expected grazing patterns along the Yamal Arctic Transect (YAT), within bioclimate subzones C (high arctic), D (northern low arctic) and E (southern low arctic). Plant biomass and NPP (net primary productivity) were significantly increased with warmer bioclimate subzones, greater soil nutrient levels and temporal climate warming, while they declined with higher grazing frequency. Temporal climate warming of 2 °C caused an increase of 665 g m-2 in total biomass at the high SON site in subzone E, but only 298 g m-2 at the low SON site. When grazing frequency was also increased, total biomass increased by only 369 g m-2 at the high SON site in contrast to 184 g m-2 at the low SON site in subzone E. Our results suggest that high SON can support greater plant biomass and plant responses to climate warming, while low SON and grazing may limit plant response to climate change. In addition to the first order factors (SON, bioclimate subzones, grazing and temporal climate warming), interactions among these significantly affect plant biomass and productivity in the arctic tundra and should not be ignored in regional scale studies.

  8. 100% Retention of Snowpack Derived Nitrogen Over 10 Years in High Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Choudhary, S.; Tye, A. M.; Young, S. D.; West, H. M.; Phoenix, G. K.

    2013-12-01

    ecosystem sinks for the 15N tracer in the long-term were organic humus soil, followed by bryophytes and then vascular plants, it is concluded that greater N deposition resulting in greater released of N from melting snowpack could significantly enrich the plant N pool and possibly enhance plant growth (with a potential to increase C storage) in the future. Overall, this study shows that high arctic tundra has considerable short- and long term- capacity for retention of snow-melt deposited N, with very tight internal recycling that allows 100% of the initially sequestered N to be retained over 10 years. Such capacity for pollutant N retention may exacerbate the impact that increased N deposition has on high arctic tundra.

  9. Sea Ice, Hydrocarbon Extraction, Rain-on-Snow and Tundra Reindeer Nomadism in Arctic Russia

    NASA Astrophysics Data System (ADS)

    Forbes, B. C.; Kumpula, T.; Meschtyb, N.; Laptander, R.; Macias-Fauria, M.; Zetterberg, P.; Verdonen, M.

    2015-12-01

    It is assumed that retreating sea ice in the Eurasian Arctic will accelerate hydrocarbon development and associated tanker traffic along Russia's Northern Sea Route. However, oil and gas extraction along the Kara and Barents Sea coasts will likely keep developing rapidly regardless of whether the Northwest Eurasian climate continues to warm. Less certain are the real and potential linkages to regional biota and social-ecological systems. Reindeer nomadism continues to be a vitally important livelihood for indigenous tundra Nenets and their large herds of semi-domestic reindeer. Warming summer air temperatures over the NW Russian Arctic have been linked to increases in tundra productivity, longer growing seasons, and accelerated growth of tall deciduous shrubs. These temperature increases have, in turn, been linked to more frequent and sustained summer high-pressure systems over West Siberia, but not to sea ice retreat. At the same time, winters have been warming and rain-on-snow (ROS) events have become more frequent and intense, leading to record-breaking winter and spring mortality of reindeer. What is driving this increase in ROS frequency and intensity is not clear. Recent modelling and simulation have found statistically significant near-surface atmospheric warming and precipitation increases during autumn and winter over Arctic coastal lands in proximity to regions of sea-ice loss. During the winter of 2013-14 an extensive and lasting ROS event led to the starvation of 61,000 reindeer out of a population of ca. 300,000 animals on Yamal Peninsula, West Siberia. Historically, this is the region's largest recorded mortality episode. More than a year later, participatory fieldwork with nomadic herders during spring-summer 2015 revealed that the ecological and socio-economic impacts from this extreme event will unfold for years to come. There is an urgent need to understand whether and how ongoing Barents and Kara Sea ice retreat may affect the region's ancient

  10. Increasing shrub abundance and N addition in Arctic tundra affect leaf and root litter decomposition differently

    NASA Astrophysics Data System (ADS)

    McLaren, J.; van de Weg, M. J.; Shaver, G. R.; Gough, L.

    2013-12-01

    Changes in global climate have resulted in a ';greening' of the Arctic as the abundance of deciduous shrub species increases. Consequently, not only the living plant community, but also the litter composition changes, which in turn can affect carbon turnover patterns in the Arctic. We examined effects of changing litter composition (both root and leaf litter) on decomposition rates with a litter bag study, and specifically focused on the impact of deciduous shrub Betula nana litter on litter decomposition from two evergreen shrubs (Ledum palustre, and Vaccinium vitis-idaea) and one graminoid (Eriophorum vaginatum) species. Additionally, we investigated how decomposition was affected by nutrient availability by placing the litterbags in an ambient and a fertilized moist acidic tundra environment. Measurements were carried out seasonally over 2 years (after snow melt, mid-growing season, end growing season). We measured litter mass loss over time, as well as the respiration rates (standardized for temperature and moisture) and temperature sensitivity of litter respiration at the time of harvesting the litter bags. For leaves, Betula litter decomposed faster than the other three species, with Eriophorum leaves decomposing the slowest. This pattern was observed for both mass loss and litter respiration rates, although the differences in respiration became smaller over time. Surprisingly, combining Betula with any other species resulted in slower overall weight loss rates than would be predicted based on monoculture weight loss rates. This contrasted with litter respiration at the time of sampling, which showed a positive mixing effect of adding Betula leaf liter to the other species. Apparently, during the first winter months (September - May) Betula litter decomposition is negatively affected by mixing the species and this legacy can still be observed in the total mass loss results later in the year. For root litter there were fewer effects of species identity on root

  11. Feedbacks between tall shrubland development and active layer temperatures in northwest Siberian arctic tundra

    NASA Astrophysics Data System (ADS)

    Epstein, H. E.; Frost, G. V.; Walker, D. A.; Matyshak, G.

    2013-12-01

    Permafrost soils are a globally significant carbon store, but changes in permafrost thermal regime observed in recent decades across much of the Arctic suggest that permafrost carbon balance is likely to change with continued climate warming. Critical to changes in permafrost carbon balance in a warmer world, however, are feedbacks between changes in the composition and density of surface vegetation, and the thermal state of permafrost. Shrub expansion has been widely observed in the northwest Siberian Low Arctic, but the magnitude and direction of shrub-induced impacts to permafrost temperature and stability remain poorly understood. Here we evaluate changes to active layer properties and thermal regime that occur during tall shrubland development (shrubs > 1.5 m height) within a northwest Siberian landscape dominated by well-developed, small-scale patterned ground features (e.g., non-sorted circles). We measured the annual time-series of soil temperature at 5 cm and 20 cm depth, and the structural attributes of vegetation at patterned-ground microsites across four stages of tall shrubland development: low-growing tundra lacking erect shrubs, newly-developed shrublands, mature shrublands, and paludified shrublands. Mean summer soil temperatures declined with increasing shrub cover and moss thickness, but winter soil temperatures increased with shrub development. Shrubland development strongly attenuated cryoturbation, promoting the establishment of complete vegetation cover and the development of a continuous organic mat. Increased vegetation cover, in turn, led to further reduced cryoturbation and an aggrading permafrost table. These observations indicate that tall shrub expansion that is now occurring in patterned-ground landscapes of the northwest Siberian Arctic may buffer permafrost from atmospheric warming, and increase carbon storage in these systems at least in the short term.

  12. Twelve Years of Interviews with the Inupiat people of Arctic Alaska: Report from a Community Workshop

    NASA Astrophysics Data System (ADS)

    Eisner, W. R.; Hinkel, K. M.; Cuomo, C.

    2015-12-01

    On 20 August 2015, a workshop was held in Barrow, Alaska, which presented the highlights of 12 years of research connecting local indigenous knowledge of landscape processes with scientific research on arctic lakes, tundra changes, and permafrost stability. Seventy-six Iñupiat elders, hunters, and other knowledge-holders from the North Slope villages of Barrow, Atqasuk, Wainwright, Nuiqsut, and Anaktuvuk Pass were interviewed, and over 75 hours of videotaped interviews were produced. The interviews provided information and observations on landforms, lakes, erosion, permafrost degradation and thermokarst, changes in the environment and in animal behavior, human modification of lakes, tundra damage from 4-wheel off-road vehicles, tundra trail expansion, and other phenomena. Community concerns regarding the impact of environmental change on food procurement, animal migration, human travel routes, and the future of subsistence practices were also prominent themes. Following an interview, each videotaped session was logged. Each time an elder pointed to a location on a map and explained a landscape event/observation or told a story, the time-stamp in the video was recorded. Each logged event consisted of a code and a short account of the observation. From these reference sheets, a Geographic Information System (GIS) dataset was created. A logged account for each videotape, with geographic coordinates, event code, and event description is available for each videotape. The goal of the workshop was to report on our findings, thank the community for their support, and collaboratively develop plans for archiving and disseminating this data. A complete video library and searchable, printed and digital issues of the logging dataset for archiving in the communities were also produced. Discussions with administrative personnel at the Tuzzy Library in Barrow and the Inupiat Heritage Center have enabled us to set standards and develop a timeline for turning over the library of

  13. Drivers of post-fire successional trajectories in arctic tundra: the importance of physical and biophysical interactions

    NASA Astrophysics Data System (ADS)

    Rocha, A. V.; Jiang, Y.; Rastetter, E. B.; Drysdale, J.; Kremers, K.; Shaver, G. R.

    2013-12-01

    Fires in arctic tundra are rare with return intervals in the hundreds to thousands of years, but these events have large implications for carbon and energy fluxes in an environmentally changing and sensitive ecosystem. Permafrost degradation, species composition shifts, and ecosystem function alterations are just a few of the potential consequences of fire that could feedback on future climate change. Here we describe remote sensing, eddy covariance, thaw depth, and biomass measurements along an arctic tundra chronosequence to understand long-term post-fire carbon and energy budgets. Historical remote sensing and fire perimeter data were used to choose sites that were representative of a 0-6, 18, and 36 year old fire scar, which were paired with a representative nearby unburned control. Fires caused successional changes to carbon and energy budgets through changes to the soil thermal regime, caused by decreased organic layer from combustion, and shifts from tussock to grass and shrub dominated systems. Measurements and modeling with the Multiple Element Limitation (MEL) model indicate that nutrients played a key role in these shifts and that these dynamics change are controlled by biophysical conditions immediately after fire (i.e. residual organic layer depth) and climate during early succession. Results highlight the importance of initial conditions in determining the successional trajectory of arctic tundra and yield important insights on how these systems will respond to future climate change.

  14. Index of streamflow and water quality records to September 30, 1978, Arctic Slope, Alaska

    USGS Publications Warehouse

    Still, Patsy J.

    1980-01-01

    This report, which is one of a series of reports for Alaska, lists stations in Arctic Slope, Alaska, at which streamflow and water quality data have been collected by the U.S. Geological Survey. Included are a hydrologic subregion map of Arctic Slope, Alaska, and a table listing the types of data collected and periods of record. (USGS)

  15. Identifying the main drivers of soil carbon response to climate change in arctic and boreal Alaska.

    NASA Astrophysics Data System (ADS)

    Genet, H.; McGuire, A. D.; He, Y.; Johnson, K.; Wylie, B. K.; Pastick, N. J.; Zhuang, Q.; Zhu, Z.

    2015-12-01

    Boreal and arctic regions represent the largest reservoir of carbon among terrestrial biomes. Most of this carbon is stored deep in the soil in permafrost where frozen organic matter is protected from decomposition. The vulnerability of soil carbon stocks to a changing climate in high latitudes depends on a number of physical and ecological processes. The importance of these processes in controlling the dynamics of soil carbon stocks vary across regions because of variability in vegetation composition, drainage condition, and permafrost characteristics. To better understand the main drivers of the vulnerability of soil carbon stocks to climate change in Alaska, we ran a process-based ecosystem model, the Terrestrial Ecosystem Model. This model explicitly simulates interactions between the carbon cycle and permafrost dynamics and was coupled with a disturbance model and a model of biogenic methane dynamics to assess historical and projected soil carbon dynamics in Alaska, from 1950 to 2100. The uncertainties related to climate, fire regime and atmospheric CO2projections on soil carbon dynamics were quantified by running simulations using climate projections from 2 global circulation models, 3 fossil fuel emission scenarios and 3 alternative fire management scenarios. During the historical period [1950-2009], soil carbon stocks increased by 4.7 TgC/yr in Alaska. Soil carbon stocks decreased in boreal Alaska due to substantial fire activity in the early 2000's. This loss was offset by carbon accumulation in the arctic. Changes in soil carbon stocks from 2010 to 2099 ranged from 8.9 to 25.6 TgC/yr, depending on the climate projections. Soil carbon accumulation was slower in lowlands than in uplands and slower in the boreal than in the arctic regions because of the negative effect of fire activity on soil carbon stocks. Tundra ecosystems were more vulnerable to carbon loss from fire than forest ecosystems because of a lower productivity. As a result, the increase in

  16. Continuous monitoring of soil gas efflux with Forced Diffusion (FD) chamber technique in a tundra ecosystem, Alaska

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Park, S. J.; Lee, B. Y.

    2015-12-01

    Continuous measurements of soil carbon dioxide (CO2) efflux provide essential information about the soil carbon budget in response to an abruptly changing climate at Arctic and Subarctic scales. The Forced Diffusion (FD) chamber technique has a gas permeable membrane, which passively regulates the mixing of atmosphere and soil air in the chamber, in place of the active pumping system inside a regular dynamics efflux chamber system (Risk et al., 2011). Here the system has been modified the sampling routine to eliminate the problem of sensor drift. After that, we deployed the FD chamber system in a tundra ecosystem over the discontinuous permafrost regime of Council, Alaska. The representative understory plants are tussock (17 %), lichen (32 %), and moss (51 %), within a 40 נ40 m plot at an interval of five meters (81 points total) for efflux-measurement by dynamic chamber. The FD chamber monitored soil CO2 efflux from moss, lichen, and tussock regimes at an interval of 30 min during the growing season of 2015. As the results, mean soil CO2 effluxes in sphagnum moss, lichen, and tussock were 1.98 ± 1.10 (coefficient of variance: 55.8 %), 3.34 ± 0.84 (CV: 25.0 %), and 5.32 ± 1.48 (CV: 27.8 %) gCO2/m2/d, respectively. The difference between the 30-min efflux interval and the average efflux of three 10-min intervals is not significant for sphagnum (n = 196), lichen (n = 918), and tussock (n = 918) under a 95 % confidence level. The deploying interval was then set to 30 min and synchronized with eddy covariance tower data. During the deployment period of 2015, soil CO2 efflux over moss, lichen, and tussock using the FD chamber system were 44 ± 24, 73 ± 18, and 117 ± 33 gCO2/m2/period, respectively. Using the dynamic chamber, mean ecosystem respiration (Re) ranges for moss, lichen, and tussock were 2.2-2.6, 1.8-2.0, and 3.3-3.6 gCO2/m2/d, respectively, during June and July of 2015. These techniques provide the representativeness of spatiotemporal variation of soil

  17. 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.

  18. 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)

  19. Nitrogen dynamics in arctic tundra soils of varying age: differential responses to fertilization and warming.

    PubMed

    Yano, Yuriko; Shaver, Gaius R; Rastetter, Edward B; Giblin, Anne E; Laundre, James A

    2013-12-01

    In the foothills of the Brooks Range, Alaska, different glaciation histories have created landscapes with varying soil age. Productivity of most of these landscapes is generally N limited, but varies widely, as do plant species composition and soil properties (e.g., pH). We hypothesized that the projected changes in productivity and vegetation composition under a warmer climate might be mediated through differential changes in N availability across soil age. We compared readily available [water-soluble NH4 (+), NO3 (-), and amino acids (AA)], moderately available (soluble proteins), hydrolyzable, and total N pools across three tussock-tundra landscapes with soil ages ranging from 11.5k to 300k years. The effects of fertilization and warming on these N pools were also compared for the two younger sites. Readily available N was highest at the oldest site, and AA accounted for 80-89 % of this N. At the youngest site, inorganic N constituted the majority (80-97 %) of total readily available N. This variation reflected the large differences in plant functional group composition and soil chemical properties. Long-term (8-16 years) fertilization increased the soluble inorganic N by 20- to 100-fold at the intermediate-age site, but only by twofold to threefold at the youngest site. Warming caused small and inconsistent changes in the soil C:N ratio and AA, but only in soils beneath Eriophorum vaginatum, the dominant tussock-forming sedge. These differential responses suggest that the ecological consequences of warmer climates on these tundra ecosystems are more complex than simply elevated N-mineralization rates, and that the responses of landscapes might be impacted by soil age, or time since deglaciation. PMID:23928888

  20. Isotopic identification of soil and permafrost nitrate sources in an Arctic tundra ecosystem

    NASA Astrophysics Data System (ADS)

    Heikoop, Jeffrey M.; Throckmorton, Heather M.; Newman, Brent D.; Perkins, George B.; Iversen, Colleen M.; Roy Chowdhury, Taniya; Romanovsky, Vladimir; Graham, David E.; Norby, Richard J.; Wilson, Cathy J.; Wullschleger, Stan D.

    2015-06-01

    The nitrate (NO3-) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, to distinguish between NO3- derived from atmospheric deposition versus that derived from microbial nitrification. Snowmelt had an atmospheric NO3- signal with δ15N averaging -4.8 ± 1.0‰ (standard error of the mean) and δ18O averaging 70.2 ± 1.7‰. In active layer pore waters, NO3- primarily occurred at concentrations suitable for isotopic analysis in the relatively dry and oxic centers of high-centered polygons. The average δ15N and δ18O of NO3- from high-centered polygons were 0.5 ± 1.1‰ and -4.1 ± 0.6‰, respectively. When compared to the δ15N of reduced nitrogen (N) sources, and the δ18O of soil pore waters, it was evident that NO3- in high-centered polygons was primarily from microbial nitrification. Permafrost NO3- had δ15N ranging from approximately -6‰ to 10‰, similar to atmospheric and microbial NO3-, and highly variable δ18O ranging from approximately -2‰ to 38‰. Permafrost ice wedges contained a significant atmospheric component of NO3-, while permafrost textural ice contained a greater proportion of microbially derived NO3-. Large-scale permafrost thaw in this environment would release NO3- with a δ18O signature intermediate to that of atmospheric and microbial NO3. Consequently, while atmospheric and microbial sources can be readily distinguished by the NO3- dual isotope technique in tundra environments, attribution of NO3- from thawing permafrost will not be straightforward. The NO3- isotopic signature, however, appears useful in identifying NO3- sources in extant permafrost ice.

  1. Fire, temperature and nutrient responses on the C balance of arctic tundra soils from surface, mineral horizons and permafrost

    NASA Astrophysics Data System (ADS)

    De Baets, S. L.; Lewis, R.; van de Weg, M. J.; Quine, T. A.; Shaver, G. R.; Hartley, I. P.

    2013-12-01

    Models predict substantial release of carbon (C) from thawing permafrost as the climate warms. Therefore, determining how the decomposition of the organic matter stored in near surface permafrost is controlled represents a key research priority. Important questions remain regarding how readily decomposable the organic matter may be, as well as the extent to which microbial activity is limited by the low temperatures, the rate of new labile C inputs, and/or nitrogen (N) availability. Accurate model predictions require that these questions are addressed.Disturbances, including fire, which is becoming increasingly common in the tundra biome, may promote rates of permafrost thaw. In 2007, the Anaktuvuk River fire burned over 1,000 km2 of tundra on the North Slope of the Brooks Range, Alaska, USA, doubling the cumulative area burned in this region over the past 50 years. This fire enhanced active layer thickness by removing insulating plant biomass and exposing surfaces with low albedo. In this study we investigated how temperature, N and labile C additions affected rates of CO2 production over a one-year incubation of samples collected from different depths (topsoil, mineral horizons and near-surface permafrost) in burnt and unburnt sites within the Anaktuvik river catchment. The results show that respiration rates did not decline substantially during the 1-year incubation, indicating there were relatively large amounts of readily decomposable C present. However, decomposition rates per gram of C did decline with depth, especially in the burnt sites where some of the surface soil may have been lost. This indicates that the C present in the near surface permafrost may be less labile than C nearer the soil surface. In addition, respiration rates in the deeper horizons were more temperature sensitive, potentially reflecting the lower lability of the C present. Against expectations, N addition inhibited respiration in the deeper layers, especially at low temperatures

  2. The impact of vegetation type on the shortwave radiation balance of the Arctic tundra

    NASA Astrophysics Data System (ADS)

    Juszak, Inge; Schaepman-Strub, Gabriela

    2015-04-01

    Profound changes in vegetation composition in the Arctic tundra have been observed and are predicted in a warmer future climate. Shrub expansion may positively feed back to climate warming by decreasing the shortwave albedo. On the other hand, permafrost protection through soil shading by shrubs has been discussed in literature. Several studies compared the average radiation balance across vegetation zones. However, variation within vegetation zones may be as important as differences between vegetation zones. The lowland tundra ecosystem at the Kytalyk research site (NE Siberia) is dominated by two vegetation types (dwarf shrub (Betula nana) and wet sedge (Eriophorum angustifolium)) organised in patches at a scale of about 10m. We investigated the shortwave radiation balance of both types separately and related it to the 11 year data set of the fluxtower with a mixed footprint. In addition to canopy albedo, we measured canopy transmittance below dwarf shrubs and wet sedges to quantify the often discussed effect of soil shading. Our results show that at our field site, wet sedge vegetation is shading the soil more efficiently than dwarf shrubs due to multi-year standing litter. While we measured an average transmission of 36% of the incoming shortwave radiation below dwarf shrubs, the transmission of wet sedge was 28%. Wet sedge summer albedo was on average 16% higher than dwarf shrub albedo. Additionally, the snow melted 10 days later in the sedge patches, leading to large albedo differences in the second half of May 2014. Our analysis shows, that cloud cover is the second most important control on albedo and transmittance of both vegetation types. Clouds reduced the summer albedo of both vegetation types across all zenith angles. On average, the growing season albedo was about 11% higher on clear sky days as compared to overcast days whereas the transmittance was about 23% lower. As cloud cover is expected to change with climate change, field studies of the cloud

  3. Spectral determination of concentrations of functionally diverse pigments in increasingly complex arctic tundra canopies.

    PubMed

    Boelman, Natalie T; Magney, Troy S; Logan, Barry A; Griffin, Kevin L; Eitel, Jan U H; Greaves, Heather; Prager, Case M; Vierling, Lee A

    2016-09-01

    As the Arctic warms, tundra vegetation is becoming taller and more structurally complex, as tall deciduous shrubs become increasingly dominant. Emerging studies reveal that shrubs exhibit photosynthetic resource partitioning, akin to forests, that may need accounting for in the "big leaf" net ecosystem exchange models. We conducted a lab experiment on sun and shade leaves from S. pulchra shrubs to determine the influence of both constitutive (slowly changing bulk carotenoid and chlorophyll pools) and facultative (rapidly changing xanthophyll cycle) pigment pools on a suite of spectral vegetation indices, to devise a rapid means of estimating within canopy resource partitioning. We found that: (1) the PRI of dark-adapted shade leaves (PRIo) was double that of sun leaves, and that PRIo was sensitive to variation among sun and shade leaves in both xanthophyll cycle pool size (V + A + Z) (r (2) = 0.59) and Chla/b (r (2) = 0.64); (2) A corrected PRI (difference between dark and illuminated leaves, ΔPRI) was more sensitive to variation among sun and shade leaves in changes to the epoxidation state of their xanthophyll cycle pigments (dEPS) (r (2) = 0.78, RMSE = 0.007) compared to the uncorrected PRI of illuminated leaves (PRI) (r (2) = 0.34, RMSE = 0.02); and (3) the SR680 index was correlated with each of (V + A + Z), lutein, bulk carotenoids, (V + A + Z)/(Chla + b), and Chla/b (r (2) range = 0.52-0.69). We suggest that ΔPRI be employed as a proxy for facultative pigment dynamics, and the SR680 for the estimation of constitutive pigment pools. We contribute the first Arctic-specific information on disentangling PRI-pigment relationships, and offer insight into how spectral indices can assess resource partitioning within shrub tundra canopies. PMID:27193900

  4. Contrasting radiation and soil heat fluxes in Arctic shrub and wet sedge tundra

    NASA Astrophysics Data System (ADS)

    Juszak, Inge; Eugster, Werner; Heijmans, Monique M. P. D.; Schaepman-Strub, Gabriela

    2016-07-01

    Vegetation changes, such as shrub encroachment and wetland expansion, have been observed in many Arctic tundra regions. These changes feed back to permafrost and climate. Permafrost can be protected by soil shading through vegetation as it reduces the amount of solar energy available for thawing. Regional climate can be affected by a reduction in surface albedo as more energy is available for atmospheric and soil heating. Here, we compared the shortwave radiation budget of two common Arctic tundra vegetation types dominated by dwarf shrubs (Betula nana) and wet sedges (Eriophorum angustifolium) in North-East Siberia. We measured time series of the shortwave and longwave radiation budget above the canopy and transmitted radiation below the canopy. Additionally, we quantified soil temperature and heat flux as well as active layer thickness. The mean growing season albedo of dwarf shrubs was 0.15 ± 0.01, for sedges it was higher (0.17 ± 0.02). Dwarf shrub transmittance was 0.36 ± 0.07 on average, and sedge transmittance was 0.28 ± 0.08. The standing dead leaves contributed strongly to the soil shading of wet sedges. Despite a lower albedo and less soil shading, the soil below dwarf shrubs conducted less heat resulting in a 17 cm shallower active layer as compared to sedges. This result was supported by additional, spatially distributed measurements of both vegetation types. Clouds were a major influencing factor for albedo and transmittance, particularly in sedge vegetation. Cloud cover reduced the albedo by 0.01 in dwarf shrubs and by 0.03 in sedges, while transmittance was increased by 0.08 and 0.10 in dwarf shrubs and sedges, respectively. Our results suggest that the observed deeper active layer below wet sedges is not primarily a result of the summer canopy radiation budget. Soil properties, such as soil albedo, moisture, and thermal conductivity, may be more influential, at least in our comparison between dwarf shrub vegetation on relatively dry patches and

  5. How Spatial Variation in Areal Extent and Configuration of Labile Vegetation States Affect the Riparian Bird Community in Arctic Tundra

    PubMed Central

    Henden, John-André; Yoccoz, Nigel G.; Ims, Rolf A.; Langeland, Knut

    2013-01-01

    The Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by large herbivores and growing human activity. Thickets of tall shrubs represent a conspicuous vegetation state in northern and temperate ecosystems, where it serves important ecological functions, including habitat for wildlife. Thickets are however labile, as tall shrubs respond rapidly to both abiotic and biotic environmental drivers. Our aim was to assess how large-scale spatial variation in willow thicket areal extent, configuration and habitat structure affected bird abundance, occupancy rates and species richness so as to provide an empirical basis for predicting the outcome of environmental change for riparian tundra bird communities. Based on a 4-year count data series, obtained through a large-scale study design in low arctic tundra in northern Norway, statistical hierarchical community models were deployed to assess relations between habitat configuration and bird species occupancy and community richness. We found that species abundance, occupancy and richness were greatly affected by willow areal extent and configuration, habitat features likely to be affected by intense ungulate browsing as well as climate warming. In sum, total species richness was maximized in large and tall willow patches of small to intermediate degree of fragmentation. These community effects were mainly driven by responses in the occupancy rates of species depending on tall willows for foraging and breeding, while species favouring other vegetation states were not affected. In light of the predicted climate driven willow shrub encroachment in riparian tundra habitats, our study predicts that many bird species would increase in abundance, and that the bird community as a whole could become enriched. Conversely, in tundra regions where overabundance of large herbivores leads to decreased areal extent, reduced height and increased fragmentation of willow thickets

  6. A hermaphroditic Arctic flounder, Liopsetta glacialis (Pleuronectidae), from Alaska

    USGS Publications Warehouse

    Goldberg, S.R.; Yasutake, W.T.; West, R.L.

    1986-01-01

    We discovered a hermaphrodite Liopsetta glacialis while examining tissues from a sample of 30 representatives of this species for a histopathological survey of fishes from the Beaufort Sea, Alaska. L. glacialis occurs in the Arctic Ocean from Queen Maude Gulf in arctic Canada, along the North American and Siberian coasts to the White Sea and Barents Sea (Morrow, 1980). The specimen was collected from Beaufort Lagoon on July 29, 1984, weighed 15, measured 100 mm (total length) and was between 3 and 4 years old.

  7. Automatic monitoring of the effective thermal conductivity of snow in a low Arctic shrub tundra

    NASA Astrophysics Data System (ADS)

    Domine, F.; Barrere, M.; Sarrazin, D.; Morin, S.

    2015-03-01

    The effective thermal conductivity of snow, keff, is a critical variable which determines the temperature gradient in the snowpack and heat exchanges between the ground and the atmosphere through the snow. Its accurate knowledge is therefore required to simulate snow metamorphism, the ground thermal regime, permafrost stability, nutrient recycling and vegetation growth. Yet, few data are available on the seasonal evolution of snow thermal conductivity in the Arctic. We have deployed heated needle probes on low Arctic shrub tundra near Umiujaq, Quebec, (56°34´ N; 76°29´ W) and monitored automatically the evolution of keff for two consecutive winters, 2012-2013 and 2013-2014, at 4 heights in the snowpack. Shrubs are 20 cm high dwarf birch. Here, we develop an algorithm for the automatic determination of keff from the heating curves and obtain 404 keff values. We evaluate possible errors and biases associated with the use of the heated needles. The time-evolution of keff is very different for both winters. This is explained by comparing the meteorological conditions in both winters, which induced different conditions for snow metamorphism. In particular, important melting events the second year increased snow hardness, impeding subsequent densification and increase in thermal conductivity. Shrubs are observed to have very important impacts on snow physical evolution: (1) shrubs absorb light and facilitate snow melt under intense radiation; (2) the dense twig network of dwarf birch prevents snow compaction and therefore keff increase; (3) the low density depth hoar that forms within shrubs collapsed in late winter, leaving a void that was not filled by snow.

  8. Automatic monitoring of the effective thermal conductivity of snow in a low-Arctic shrub tundra

    NASA Astrophysics Data System (ADS)

    Domine, F.; Barrere, M.; Sarrazin, D.; Morin, S.; Arnaud, L.

    2015-06-01

    The effective thermal conductivity of snow, keff, is a critical variable which determines the temperature gradient in the snowpack and heat exchanges between the ground and the atmosphere through the snow. Its accurate knowledge is therefore required to simulate snow metamorphism, the ground thermal regime, permafrost stability, nutrient recycling and vegetation growth. Yet, few data are available on the seasonal evolution of snow thermal conductivity in the Arctic. We have deployed heated needle probes on low-Arctic shrub tundra near Umiujaq, Quebec, (N56°34'; W76°29') and monitored automatically the evolution of keff for two consecutive winters, 2012-2013 and 2013-2014, at four heights in the snowpack. Shrubs are 20 cm high dwarf birch. Here, we develop an algorithm for the automatic determination of keff from the heating curves and obtain 404 keff values. We evaluate possible errors and biases associated with the use of the heated needles. The time evolution of keff is very different for both winters. This is explained by comparing the meteorological conditions in both winters, which induced different conditions for snow metamorphism. In particular, important melting events in the second year increased snow hardness, impeding subsequent densification and increase in thermal conductivity. We conclude that shrubs have very important impacts on snow physical evolution: (1) shrubs absorb light and facilitate snow melt under intense radiation; (2) the dense twig network of dwarf birch prevent snow compaction, and therefore keff increase; (3) the low density depth hoar that forms within shrubs collapsed in late winter, leaving a void that was not filled by snow.

  9. Seasonal and Intra-annual Controls on CO2 Flux in Arctic Alaska

    SciTech Connect

    Oechel, Walter; Kalhori, Aram

    2015-12-01

    In order to advance the understanding of the patterns and controls on the carbon budget in the Arctic region, San Diego State University has maintained eddy covariance flux towers at three sites in Arctic Alaska, starting in 1997.

  10. The Effect of Silver Nanoparticles on Seasonal Change in Arctic Tundra Bacterial and Fungal Assemblages

    PubMed Central

    Kumar, Niraj; Palmer, Gerald R.; Shah, Vishal; Walker, Virginia K.

    2014-01-01

    The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages. PMID:24926877

  11. The effect of silver nanoparticles on seasonal change in arctic tundra bacterial and fungal assemblages.

    PubMed

    Kumar, Niraj; Palmer, Gerald R; Shah, Vishal; Walker, Virginia K

    2014-01-01

    The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages. PMID:24926877

  12. Hydrocarbon contamination of arctic tundra soils of the Bol'shoi Lyakhovskii Island (the Novosibirskie Islands)

    NASA Astrophysics Data System (ADS)

    Kachinskii, V. L.; Zavgorodnyaya, Yu. A.; Gennadiev, A. N.

    2014-02-01

    Data on the distribution of the components of oil products that have accumulated in the arctic tundra soils of the Bol'shoi Lyakhovskii Island (the Novosibirskie Islands) under the impact of technogenic loads are analyzed. The examined soils differ in the vertical and lateral distribution patterns of the methanenaphthenic and naphthenic hydrocarbons and in the degree of their transformation. This is determined by the position of particular soils in the catenas and by the sorption of particular hydrocarbon compounds in the soils. The portion of light molecular-weight hydrocarbons in the upper horizons decreases by two-ten times in comparison with the deeper soil layers. In the lateral direction, the twofold difference in the contents of the methane-naphthenic and naphthenic hydrocarbons in the upper horizons is seen. The degree of transformation of the hydrocarbons under the impact of microbiological processes depends on the aeration conditions, the depth of permafrost table, the composition of oil products, and the soil organic matter content.

  13. Long-term warming restructures Arctic tundra without changing net soil carbon storage.

    PubMed

    Sistla, Seeta A; Moore, John C; Simpson, Rodney T; Gough, Laura; Shaver, Gaius R; Schimel, Joshua P

    2013-05-30

    High latitudes contain nearly half of global soil carbon, prompting interest in understanding how the Arctic terrestrial carbon balance will respond to rising temperatures. Low temperatures suppress the activity of soil biota, retarding decomposition and nitrogen release, which limits plant and microbial growth. Warming initially accelerates decomposition, increasing nitrogen availability, productivity and woody-plant dominance. However, these responses may be transitory, because coupled abiotic-biotic feedback loops that alter soil-temperature dynamics and change the structure and activity of soil communities, can develop. Here we report the results of a two-decade summer warming experiment in an Alaskan tundra ecosystem. Warming increased plant biomass and woody dominance, indirectly increased winter soil temperature, homogenized the soil trophic structure across horizons and suppressed surface-soil-decomposer activity, but did not change total soil carbon or nitrogen stocks, thereby increasing net ecosystem carbon storage. Notably, the strongest effects were in the mineral horizon, where warming increased decomposer activity and carbon stock: a 'biotic awakening' at depth. PMID:23676669

  14. Diurnal patterns of gas-exchange and metabolic pools in tundra plants during three phases of the arctic growing season

    PubMed Central

    Patankar, Rajit; Mortazavi, Behzad; Oberbauer, Steven F; Starr, Gregory

    2013-01-01

    Arctic tundra plant communities are subject to a short growing season that is the primary period in which carbon is sequestered for growth and survival. This period is often characterized by 24-h photoperiods for several months a year. To compensate for the short growing season tundra plants may extend their carbon uptake capacity on a diurnal basis, but whether this is true remains unknown. Here, we examined in situ diurnal patterns of physiological activity and foliar metabolites during the early, mid, and late growing season in seven arctic species under light-saturated conditions. We found clear diurnal patterns in photosynthesis and respiration, with midday peaks and midnight lulls indicative of circadian regulation. Diurnal patterns in foliar metabolite concentrations were less distinct between the species and across seasons, suggesting that metabolic pools are likely governed by proximate external factors. This understanding of diurnal physiology will also enhance the parameterization of process-based models, which will aid in better predicting future carbon dynamics for the tundra. This becomes even more critical considering the rapid changes that are occurring circumpolarly that are altering plant community structure, function, and ultimately regional and global carbon budgets. PMID:23467719

  15. Dynamics of the recovery of damaged tundra vegetation: preliminary results of revegetation experiments of maritime tundra with Elymus mollis on Adak Island, Alaska. Progress report

    SciTech Connect

    Amundsen, C C; McCord, R A

    1982-08-01

    The vegetation of the central Aleutian Islands, Alaska is maritime tundra (Amundsen, 1977). While maritime tundra is not characterized by the presence of permafrost, the soil temperatures remain low (5 to 7/sup 0/C) year-round (Williams, 1980). The low soil temperature, a high level of soil moisture, and a low level of incident solar radiation are thought to delay the development of the vegetation. Natural revegetation of natural or man made open areas is relatively slow. Disturbed areas from World War II military activity are not completely revegetated after almost 40 years. Because of the windy and wet climate of the region, exposed soil is unstable and subject to extensive freeze-thaw action and erosion. Insults to the vegetation, both marine and aeolian, are common. Successful reproduction by seed is uncommon among species of this flora. The primary means of reproduction appears to be by vegetative propagules which are usually fragments of the shoot and rhizome. While the transport of the fragments by wind and water aids in the dispersal of the propagules, the same action often removes these fragments from open areas. This later activity further delays the revegetation of open and disturbed areas. Elymus mollis Trin. is the most successful major native species found to date as it fragments due to wind and water action and transplants easily. Transplanting experiments with sprigs of Elymus mollis Trin. have been conducted on Adak Island, Alaska since 1977. Preliminary results indicate that Elymus mollis may be transplanted for revegetation with a survival rate of at least 90 percent. Experiments were set up in 1979 to determine appropriate planting density, sprig rhizome length, and best time of year for transplanting. Preliminary results for these experiments are reported here.

  16. Simulating the effects of soil organic nitrogen and grazing on arctic tundra vegetation dynamics on the Yamal Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Yu, Q.; Epstein, H. E.; Walker, D. A.

    2009-12-01

    Sustainability of tundra vegetation under changing climate on the Yamal Peninsula, northwestern Siberia, home to the world’s largest area of reindeer husbandry, is of crucial importance to the local native community. An integrated investigation is needed for better understanding of the effects of soils, climate change and grazing on tundra vegetation in the Yamal region. In this study we applied a nutrient-based plant community model (ArcVeg) to evaluate how two factors (soil organic nitrogen [SON] levels and grazing) interact to affect tundra responses to climate warming across a latitudinal climatic gradient on the Yamal Peninsula. Model simulations were driven by field-collected soil data and expected grazing patterns along the Yamal Arctic Transect (YAT), within bioclimate subzones C (High Arctic), D (northern Low Arctic) and E (southern Low Arctic). Plant biomass and NPP (net primary productivity) were significantly increased with warmer bioclimate subzones, greater soil nutrient levels and temporal climate warming, while they declined with higher grazing frequency. Temporal climate warming of 2 °C caused an increase of 665 g/m2 in total biomass at the high SON site in subzone E, while only 298 g/m2 in the low SON site. When grazing frequency was also increased, total biomass increased by only 369 g/m2 in the high SON site in contrast to 184 g/m2 in the low SON site in subzone E. When comparing low grazing to high grazing effects on soil organic nitrogen pools over time (Figure 1), higher grazing frequency led to either slower SON accumulation rates or more rapid SON depletion rates. Warming accentuated these differences caused by grazing, suggesting the interaction between grazing and warming may yield greater differences in SON levels across sites. Our results suggest that low SON and grazing may limit plant response to climate change. Interactions among bioclimate subzones, soils, grazing and warming significantly affect plant biomass and productivity in

  17. Long-Term Hydrological Changes of Coastal Arctic Tundra Ponds in Drained Thaw Lake Basins

    NASA Astrophysics Data System (ADS)

    Andresen, C. G.; Lougheed, V.

    2013-12-01

    Given the dominance of these ponds in the tundra landscape, documenting long-term changes in these aquatic systems is essential to understand carbon and energy balance, trophic energy flow, and biodiversity for the Arctic. The combination of remote sensing using historical imagery, as well as rare historical data from the International Biological Program, provides a unique opportunity for understanding long-term changes in hydrology, chemistry and biology of these significant freshwater environments. To assess the changes in pond area and abundance in 22 drained thaw-lake basins (DTLB) across the Barrow Peninsula over the past 60 years, we utilized historic aerial imagery from USGS archives (1948) and modern high-resolution Quickbird (2002, 2008, 2010). Age classification of DTLB was based on Hinkel et al 2003. We compared water temperature, active layer thickness, and aboveground biomass of these systems to historical datasets compiled in the Limnology of Tundra Ponds' by Hobbie et al 1975. We observed an overall decrease of 28% in pond area and 19% decrease in pond number, where smaller ponds (<100m2) had the highest change. These losses were coincident with significantly higher air and water temperature and reduced annual rainfall, which has decreased by 2.5 cm over the past 62 years (-0.4mm/yr). Active layer in ponds increased on average by 15cm. Aquatic grasses increased in density and cover in ponds over the past 40 years. Area and number of ponds loss was independent of DTLB age; however, medium-age DTLBs had significantly higher number of new ponds over old and ancient-age basins. While we observe new ponds due to thaw lake processes, climate seems to be having a stronger effect on these systems by reducing the overall inundated area and pond number in these basins. Increased evaporation due to warmer and longer summers, permafrost degradation, transpiration from encroaching aquatic grasses and changes in precipitation patterns are likely the current major

  18. Isotopic identification of soil and permafrost nitrate sources in an Arctic tundra ecosystem

    SciTech Connect

    Heikoop, Jeffrey M.; Throckmorton, Heather M.; Newman, Brent D.; Perkins, George B.; Iversen, Colleen M.; Chowdhury, Taniya Roy; Romanovsky, Vladimir E.; Graham, David E.; Norby, Richard J.; Wilson, Cathy J.; Wullschleger, Stan D.

    2015-06-08

    The nitrate (NO₃⁻) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, to distinguish between NO₃⁻ derived from at NO₃⁻ signal with δ¹⁵N averaging –4.8 ± 1.0‰ (standard error of the mean) and δ¹⁸O averaging 70.2 ±1.7‰. In active layer pore waters, NO₃⁻ primarily occurred at concentrations suitable for isotopic analysis in the relatively dry and oxic centers of high-centered polygons. The average δ¹⁵N and δ¹⁸O of NO₃⁻ from high-centered polygons were 0.5 ± 1.1‰ and –4.1 ± 0.6‰, respectively. When compared to the δ¹⁵N of reduced nitrogen (N) sources, and the δ¹⁸O of soil pore waters, it was evident that NO₃⁻ in high-centered polygons was primarily from microbial nitrification. Permafrost NO₃⁻ had δ¹⁵N ranging from approximately –6‰ to 10‰, similar to atmospheric and microbial NO₃⁻, and highly variable δ¹⁸O ranging from approximately –2‰ to 38‰. Permafrost ice wedges contained a significant atmospheric component of NO₃⁻, while permafrost textural ice contained a greater proportion of microbially derived NO₃⁻. Large-scale permafrost thaw in this environment would release NO₃⁻ with a δ¹⁸O signature intermediate to that of atmospheric and microbial NO₃. Consequently, while atmospheric and microbial sources can be readily distinguished by the NO₃⁻ dual isotope technique in tundra environments, attribution of NO₃⁻ from thawing permafrost will not be straightforward. The NO₃⁻ isotopic signature, however, appears useful in identifying NO₃⁻ sources in extant permafrost ice.

  19. Isotopic identification of soil and permafrost nitrate sources in an Arctic tundra ecosystem

    DOE PAGESBeta

    Heikoop, Jeffrey M.; Throckmorton, Heather M.; Newman, Brent D.; Perkins, George B.; Iversen, Colleen M.; Chowdhury, Taniya Roy; Romanovsky, Vladimir E.; Graham, David E.; Norby, Richard J.; Wilson, Cathy J.; et al

    2015-06-08

    The nitrate (NO₃⁻) dual isotope approach was applied to snowmelt, tundra active layer pore waters, and underlying permafrost in Barrow, Alaska, USA, to distinguish between NO₃⁻ derived from at NO₃⁻ signal with δ¹⁵N averaging –4.8 ± 1.0‰ (standard error of the mean) and δ¹⁸O averaging 70.2 ±1.7‰. In active layer pore waters, NO₃⁻ primarily occurred at concentrations suitable for isotopic analysis in the relatively dry and oxic centers of high-centered polygons. The average δ¹⁵N and δ¹⁸O of NO₃⁻ from high-centered polygons were 0.5 ± 1.1‰ and –4.1 ± 0.6‰, respectively. When compared to the δ¹⁵N of reduced nitrogen (N) sources,more » and the δ¹⁸O of soil pore waters, it was evident that NO₃⁻ in high-centered polygons was primarily from microbial nitrification. Permafrost NO₃⁻ had δ¹⁵N ranging from approximately –6‰ to 10‰, similar to atmospheric and microbial NO₃⁻, and highly variable δ¹⁸O ranging from approximately –2‰ to 38‰. Permafrost ice wedges contained a significant atmospheric component of NO₃⁻, while permafrost textural ice contained a greater proportion of microbially derived NO₃⁻. Large-scale permafrost thaw in this environment would release NO₃⁻ with a δ¹⁸O signature intermediate to that of atmospheric and microbial NO₃. Consequently, while atmospheric and microbial sources can be readily distinguished by the NO₃⁻ dual isotope technique in tundra environments, attribution of NO₃⁻ from thawing permafrost will not be straightforward. The NO₃⁻ isotopic signature, however, appears useful in identifying NO₃⁻ sources in extant permafrost ice.« less

  20. Inundation, sedimentation, and subsidence creates goose habitat along the Arctic coast of Alaska

    NASA Astrophysics Data System (ADS)

    Tape, Ken D.; Flint, Paul L.; Meixell, Brandt W.; Gaglioti, Benjamin V.

    2013-12-01

    The Arctic Coastal Plain of Alaska is characterized by thermokarst lakes and drained lake basins, and the rate of coastal erosion has increased during the last half-century. Portions of the coast are <1 m above sea level for kilometers inland, and are underlain by ice-rich permafrost. Increased storm surges or terrestrial subsidence would therefore expand the area subject to marine inundation. Since 1976, the distribution of molting Black Brant (Branta bernicla nigricans) on the Arctic Coastal Plain has shifted from inland freshwater lakes to coastal marshes, such as those occupying the Smith River and Garry Creek estuaries. We hypothesized that the movement of geese from inland lakes was caused by an expansion of high quality goose forage in coastal areas. We examined the recent history of vegetation and geomorphological changes in coastal goose habitat by combining analysis of time series imagery between 1948 and 2010 with soil stratigraphy dated using bomb-curve radiocarbon. Time series of vertical imagery and in situ verification showed permafrost thaw and subsidence of polygonal tundra. Soil stratigraphy and dating within coastal estuaries showed that non-saline vegetation communities were buried by multiple sedimentation episodes between 1948 and 1995, accompanying a shift toward salt-tolerant vegetation. This sedimentation allowed high quality goose forage plants to expand, thus facilitating the shift in goose distribution. Declining sea ice and the increasing rate of terrestrial inundation, sedimentation, and subsidence in coastal estuaries of Alaska may portend a ‘tipping point’ whereby inland areas would be transformed into salt marshes.

  1. Regional biomass and leaf-area estimates derived from satellite imagery as inputs to spatial trace-gas flux models for arctic tundra

    SciTech Connect

    Shippert, M.M.; Walker, D.A.; Auerbach, N.A.; Lewis, B.E. )

    1994-06-01

    Reflectance spectra, leaf area index (LAI), and live biomass measurements were collected for 60 plots near Toolik Lake and Imnavait Creek, Alaska during July and August, 1993. Normalized difference vegetation indices (NDVI) were calculated from the reflectance spectra. NDVI was found to be highly correlated to both LAI and biomass. These relationships have been seen in temperate ecosystems, but have never been tested in Arctic tundra previous to this study. In addition, a clear relationship is seen between NDVI values and pH and moisture. Acidic plots have much higher NDVI values than non-acidic plots, while moist plots have high NDVI values relative to dry and wet plots. The average field NDVI measurements for major physiognomic categories were compared to average NDVI values for the same categories derived from a SPOT multispectral satellite image of the area. These values were also found to be highly correlated. However, field NDVI values were consistently about 40% higher than SPOT NDVI values. Possible explanations for this consistent trend include effects of low sun angle in the Arctic in combination with relatively high view angle of the SPOT sensor. Using the regression equations for the above relationships, biomass and LAI images were calculated from the SPOT image. The resulting images show expected trends in the LAI and biomass across the landscape. The image of biomass will be used as an input to a spatial model of methane emissions for the Alaskan Arctic. Another key input variable to the methane model will be soil moisture. Alternative image processing methods and/or radar images will be used to derive this important variable.

  2. Soil bacterial community shifts in response to vegetation and soil temperature change in moist acidic tundra of Northern Alaska

    NASA Astrophysics Data System (ADS)

    Ricketts, M. P.; Gonzalez-Meler, M. A.

    2013-12-01

    The effects of rising temperatures on Earth's ecosystems remain largely unknown and are an active area of research. In temperate systems, plant species often respond directly to climate forcing factors causing complex cascading effects in ecosystem C and nutrient cycling. Similarly, in the Arctic tundra, shifts in aboveground species composition and distribution have been observed in response to warming and other climate change factors, following increases in active layer depth and soil temperature. These abiotic changes provide soil microorganisms access to previously unavailable soil organic matter via thawing soils and increases soil microbial mineralization rates, suggesting that soil microorganisms may be eliciting the plant response. It is hypothesized that this release of nutrients may be providing a competitive advantage to N rich woody species, such as dwarf birch and diamond-leaf willow, over grassy species such as cottongrass tussock. Here we examine how microbial communities respond to increases in soil thermal insulation and vegetative change caused by the accumulation of winter precipitation at a snowfence installed in 1998 at Toolik Field Station, Alaska. In addition to soil temperature, increased snow depth also results in increased surface moisture, soil temperature, and active layer depth. Bacterial phylogenies and relative abundances from soils collected in August of 2012 were determined by sequencing 16S rRNA genes and analyzed using the QIIME software package. We found many significant relative abundance shifts between snow depth treatments (deep, intermediate, low) and soil depths (organic, transition, mineral), most notable of which include in an increase in Deltaproteobacteria in the deep treatment zones, a decrease in Alphaproteobacteria with increased soil depth, and a marked increase in Chloroflexi Anaerolineae (a green non-sulfur bacteria found in a wide range of habitats) in the deep treatment and mineral layers. Other interesting

  3. Impact of seabird activity on nitrous oxide and methane fluxes from High Arctic tundra in Svalbard, Norway

    NASA Astrophysics Data System (ADS)

    Zhu, Renbin; Chen, Qingqing; Ding, Wei; Xu, Hua

    2012-12-01

    In this study, tundra N2O and CH4 fluxes were measured from one seabird sanctuary (SBT) and two non-seabird colonies (NST-I and NST-II) in Ny-Ålesund (79°55'N, 11°56'E), Svalbard during the summers of 2008 and 2009. N2O and CH4 fluxes from SBT showed large temporal and spatial variations depending on the intensity of seabird activity. High seabird activity sites showed large N2O and CH4 emissions while low N2O and CH4 emissions, even CH4 uptake occurred at medium and low seabird activity sites. Overall the mean fluxes were 18.3 ± 3.6 μg N2O m-2 h-1 and 53.5 ± 20.3 μg CH4 m-2 h-1 from tundra SBT whereas tundra NST-I and NST-II represented a relatively weak N2O source (8.3 ± 13.2 μg N2O m-2 h-1) and strong CH4 sink (-82.8 ± 22.3 μg CH4 m-2 h-1). Seabird activity was the strongest control of N2O and CH4 fluxes compared with soil temperature and moisture, and high N2O and CH4 emissions were created by soil physical and chemical processes (the sufficient supply of nutrients NH4+-N, NO3--N, total nitrogen, total phosphorus and total carbon from seabird guano, seabird tramp and appropriate water content) related to the seabird activity. Our work suggests that tundra ecosystems impacted by seabird activity are the potential "hotspots" for N2O and CH4 emissions although these sources have been largely neglected at present. Furthermore the combination of seabird activity and warming climate will likely further enhance N2O and CH4 emissions from the High Arctic tundra.

  4. Soil carbon content and CO2 flux along a hydrologic gradient in a High-Arctic tundra lake basin, Northwest Greenland

    NASA Astrophysics Data System (ADS)

    McKnight, J.; Klein, E. S.; Welker, J. M.; Schaeffer, S. M.; Franklin, M.

    2015-12-01

    High Arctic landscapes are composed of watershed basins that vary in size and ecohydrology, but typically have a plant community complex that ranges from dry tundra to moist tundra to wet sedge systems along water body shorelines. The spatial extent of these plant communities reflects mean annual soil moisture and temperature, and is vulnerable to changes in climate conditions. Soil moisture and temperature significantly influence organic matter microbial activity and decomposition, and can affect the fate of soil carbon in tundra soils. Consequently, due to the unique soil carbon differences between tundra plant communities, shifts in their spatial extent may drive future High Arctic biosphere-atmosphere interactions. Understanding this terrestrial-atmosphere trace gas feedback, however, requires quantification of the rates and patterns of CO2 exchange along soil moisture gradients and the associated soil properties. In summer of 2015, soil CO2 flux rate, soil moisture and temperature were measured along a soil moisture gradient spanning three vegetation zones (dry tundra, wet tundra, and wet grassland) in a snow melt-fed lake basin near Thule Greenland. Mean soil temperature during the 2015 growing season was greater in dry tundra than in wet tundra and wet grassland (13.0 ± 1.2, 7.8 ± 0.8, and 5.5 ± 0.9°C, respectively). Mean volumetric soil moisture differed among all three vegetation zones where the soil moisture gradient ranged from 9 % (dry tundra) to 34 % (wet tundra) to 51 % (wet grassland). Mean soil CO2 flux was significantly greater in the wet grassland (1.7 ± 0.1 μmol m-2 s-1) compared to wet tundra (0.9 ± 0.2 μmol m-2 s-1) and dry tundra (1.2 ± 0.2 μmol m-2 s-1). Soil CO2 flux increased and decreased with seasonal warming and cooling of soil temperature. Although soil temperature was an important seasonal driver of soil CO2 flux rates, differences in mean seasonal soil CO2 flux rates among vegetation zones appeared to be a function of the

  5. Spatial variation in landscape-level CO2 and CH4 fluxes from arctic coastal tundra: influence from vegetation, wetness, and the thaw lake cycle.

    PubMed

    Sturtevant, Cove S; Oechel, Walter C

    2013-09-01

    Regional quantification of arctic CO2 and CH4 fluxes remains difficult due to high landscape heterogeneity coupled with a sparse measurement network. Most of the arctic coastal tundra near Barrow, Alaska is part of the thaw lake cycle, which includes current thaw lakes and a 5500-year chronosequence of vegetated thaw lake basins. However, spatial variability in carbon fluxes from these features remains grossly understudied. Here, we present an analysis of whole-ecosystem CO2 and CH4 fluxes from 20 thaw lake cycle features during the 2011 growing season. We found that the thaw lake cycle was largely responsible for spatial variation in CO2 flux, mostly due to its control on gross primary productivity (GPP). Current lakes were significant CO2 sources that varied little. Vegetated basins showed declining GPP and CO2 sink with age (R(2) = 67% and 57%, respectively). CH4 fluxes measured from a subset of 12 vegetated basins showed no relationship with age or CO2 flux components. Instead, higher CH4 fluxes were related to greater landscape wetness (R(2) = 57%) and thaw depth (additional R(2) = 28%). Spatial variation in CO2 and CH4 fluxes had good satellite remote sensing indicators, and we estimated the region to be a small CO2 sink of -4.9 ± 2.4 (SE) g C m(-2) between 11 June and 25 August, which was countered by a CH4 source of 2.1 ± 0.2 (SE) g C m(-2) . Results from our scaling exercise showed that developing or validating regional estimates based on single tower sites can result in significant bias, on average by a factor 4 for CO2 flux and 30% for CH4 flux. Although our results are specific to the Arctic Coastal Plain of Alaska, the degree of landscape-scale variability, large-scale controls on carbon exchange, and implications for regional estimation seen here likely have wide relevance to other arctic landscapes. PMID:23649775

  6. Plant phenological responses to a long-term experimental extension of growing season and soil warming in the tussock tundra of Alaska.

    PubMed

    Khorsand Rosa, Roxaneh; Oberbauer, Steven F; Starr, Gregory; Parker La Puma, Inga; Pop, Eric; Ahlquist, Lorraine; Baldwin, Tracey

    2015-12-01

    Climate warming is strongly altering the timing of season initiation and season length in the Arctic. Phenological activities are among the most sensitive plant responses to climate change and have important effects at all levels within the ecosystem. We tested the effects of two experimental treatments, extended growing season via snow removal and extended growing season combined with soil warming, on plant phenology in tussock tundra in Alaska from 1995 through 2003. We specifically monitored the responses of eight species, representing four growth forms: (i) graminoids (Carex bigellowii and Eriophorum vaginatum); (ii) evergreen shrubs (Ledum palustre, Cassiope tetragona, and Vaccinium vitis-idaea); (iii) deciduous shrubs (Betula nana and Salix pulchra); and (iv) forbs (Polygonum bistorta). Our study answered three questions: (i) Do experimental treatments affect the timing of leaf bud break, flowering, and leaf senescence? (ii) Are responses to treatments species-specific and growth form-specific? and (iii) Which environmental factors best predict timing of phenophases? Treatment significantly affected the timing of all three phenophases, although the two experimental treatments did not differ from each other. While phenological events began earlier in the experimental plots relative to the controls, duration of phenophases did not increase. The evergreen shrub, Cassiope tetragona, did not respond to either experimental treatment. While the other species did respond to experimental treatments, the total active period for these species did not increase relative to the control. Air temperature was consistently the best predictor of phenology. Our results imply that some evergreen shrubs (i.e., C. tetragona) will not capitalize on earlier favorable growing conditions, putting them at a competitive disadvantage relative to phenotypically plastic deciduous shrubs. Our findings also suggest that an early onset of the growing season as a result of decreased snow cover

  7. Diurnal and seasonal patterns of ecosystem CO{sub 2} efflux from upland tundra in the foothills of the Brooks Range, Alaska, U.S.A.

    SciTech Connect

    Oberbauer, S.F.; Gillespie, C.T.; Cheng, Weixin

    1996-08-01

    Carbon dioxide efflux and soil microenvironment were measured in three upland tundra communities in the foothills of the Brooks Range in arctic Alaska to determine the magnitude of CO{sub 2} efflux rates and the relative importance of the belowground factors that influence them. Gas exchange and soil microenvironment measurements were made weekly between 14 June and 31 July 1990. The study communities included lichen-heath, a sparse community vegetated by lichens and dwarf ericaceous shrubs on rocky soils, moist Cassiope dwarf-shrub heath tundra, dominated by Carex and evergreen and deciduous shrubs on relatively deep organic soils, and dry Cassiope dwarf-shrub heath of stone-stripe areas, which was of intermediate character. Rates of CO{sub 2} efflux were similar for the three communities until mid-season when they peaked at rates between 4.9 and 5.9 g m{sup {minus}2} d{sup {minus}1}. Following the mid-season peak, the rates in all three communities declined, particularly in the lichen-heath. Seasonal patterns of CO{sub 2} efflux, soil temperature, and soil moisture suggest changing limitations to CO{sub 2} efflux, soil temperature, and soil moisture suggest changing limitations to CO{sub 2} efflux over the course of the season. Rates of carbon dioxide efflux followed changes in soil temperature early in the season when soil moisture was highest. Mid-season efflux appeared to be limited by soil, moss, and lichen hydration until the end of July, when temperature again limited efflux. Differences between the communities were related to microenvironmental differences and probable differences in carbon quality. The presence of peat-forming mosses is suggested to play an important role in differences in efflux and micro-environment among the communities. 32 refs., 3 figs., 4 tab.

  8. Assessing the spatial variability in peak season CO2 exchange characteristics across the Arctic tundra using a~light response curve parameterization

    NASA Astrophysics Data System (ADS)

    Mbufong, H. N.; Lund, M.; Aurela, M.; Christensen, T. R.; Eugster, W.; Friborg, T.; Hansen, B. U.; Humphreys, E. R.; Jackowicz-Korczynski, M.; Kutzbach, L.; Lafleur, P. M.; Oechel, W. C.; Parmentier, F. J. W.; Rasse, D. P.; Rocha, A. V.; Sachs, T.; van der Molen, M. M.; Tamstorf, M. P.

    2014-05-01

    This paper aims to assess the functional and spatial variability in the response of CO2 exchange to irradiance across the Arctic tundra during peak season using light response curve (LRC) parameters. This investigation allows us to better understand the future response of Arctic tundra under climatic change. Data was collected using the micrometeorological eddy covariance technique from 12 circumpolar Arctic tundra sites, in the range of 64-74° N. The LRCs were generated for 14 days with peak net ecosystem exchange (NEE) using an NEE -irradiance model. Parameters from LRCs represent site specific traits and characteristics describing: (a) NEE at light saturation (Fcsat), (b) dark respiration (Rd), (c) light use efficiency (α), (d) NEE when light is at 1000 μmol m-2 s-1 (Fc1000), (e) potential photosynthesis at light saturation (Psat) and (f) the light compensation point (LCP). Parameterization of LRCs was successful in predicting CO2 flux dynamics across the Arctic tundra. Yet we did not find any trends in LRC parameters across the whole Arctic tundra but there were indications for temperature and latitudinal differences within sub-regions like Russia and Greenland. Together, LAI and July temperature had a high explanatory power of the variance in assimilation parameters (Fcsat, Fc1000 and Psat), thus illustrating the potential for upscaling CO2 exchange for the whole Arctic tundra. Dark respiration was more variable and less correlated to environmental drivers than was assimilation parameters. Thus, indicating the inherent need to include other parameters such as nutrient availability, substrate quantity and quality in flux monitoring activities.

  9. Assessing the spatial variability in peak season CO2 exchange characteristics across the Arctic tundra using a light response curve parameterization

    NASA Astrophysics Data System (ADS)

    Mbufong, H. N.; Lund, M.; Aurela, M.; Christensen, T. R.; Eugster, W.; Friborg, T.; Hansen, B. U.; Humphreys, E. R.; Jackowicz-Korczynski, M.; Kutzbach, L.; Lafleur, P. M.; Oechel, W. C.; Parmentier, F. J. W.; Rasse, D. P.; Rocha, A. V.; Sachs, T.; van der Molen, M. K.; Tamstorf, M. P.

    2014-09-01

    This paper aims to assess the spatial variability in the response of CO2 exchange to irradiance across the Arctic tundra during peak season using light response curve (LRC) parameters. This investigation allows us to better understand the future response of Arctic tundra under climatic change. Peak season data were collected during different years (between 1998 and 2010) using the micrometeorological eddy covariance technique from 12 circumpolar Arctic tundra sites, in the range of 64-74° N. The LRCs were generated for 14 days with peak net ecosystem exchange (NEE) using an NEE-irradiance model. Parameters from LRCs represent site-specific traits and characteristics describing the following: (a) NEE at light saturation (Fcsat), (b) dark respiration (Rd), (c) light use efficiency (α), (d) NEE when light is at 1000 μmol m-2 s-1 (Fc1000), (e) potential photosynthesis at light saturation (Psat) and (f) the light compensation point (LCP). Parameterization of LRCs was successful in predicting CO2 flux dynamics across the Arctic tundra. We did not find any trends in LRC parameters across the whole Arctic tundra but there were indications for temperature and latitudinal differences within sub-regions like Russia and Greenland. Together, leaf area index (LAI) and July temperature had a high explanatory power of the variance in assimilation parameters (Fcsat, Fc1000 and Psat, thus illustrating the potential for upscaling CO2 exchange for the whole Arctic tundra. Dark respiration was more variable and less correlated to environmental drivers than were assimilation parameters. This indicates the inherent need to include other parameters such as nutrient availability, substrate quantity and quality in flux monitoring activities.

  10. Biomarkers as Indicators of Respiration During Laboratory Incubations of Alaskan Arctic Tundra Permafrost Soils

    NASA Astrophysics Data System (ADS)

    Hutchings, J.; Schuur, E.; Bianchi, T. S.; Bracho, R. G.

    2015-12-01

    High latitude permafrost soils are estimated to store 1,330 - 1,580 Pg C, which account for ca. 40% of global soil C and nearly twice that of atmospheric C. Disproportionate heating of high latitude regions during climate warming potentially results in permafrost thaw and degradation of surficial and previously-frozen soil C. Understanding how newly-thawed soils respond to microbial degradation is essential to predicting C emissions from this region. Laboratory incubations have been a key tool in understanding potential respiration rates from high latitude soils. A recent study found that among the common soil measurements, C:N was the best predictor of C losses. Here, we analyzed Alaskan Arctic tundra soils from before and after a nearly 3-year laboratory incubation. Bulk geochemical values as well as the following biomarkers were measured: lignin, amino acids, n-alkanes, and glycerol dialkyl glycerol tetraethers (GDGT). We found that initial C:N did not predict C losses and no significant change in C:N between initial and final samples. The lignin acid to aldehyde (Ad:Al) degradation index showed the same results with a lack of C loss prediction and no significant change during the experiment. However, we did find that C:N and Ad:Al had a significant negative correlation suggesting behavior consistent with expectations. The failure to predict C losses was likely influenced by a number of factors, including the possibility that biomarkers were tracking a smaller fraction of slower cycling components of soil C. To better interpret these results, we also used a hydroxyproline-based amino acid degradation index and n-alkanes to estimate the contribution Sphagnum mosses to soil samples - known to have slower turnover times than vascular plants. Finally, we applied a GDGT soil temperature proxy to estimate the growing season soil temperatures before each incubation, as well as investigating the effects of incubation temperature on the index's temperature estimate.

  11. 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

  12. Spatial distribution of thermokarst landforms across Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Farquharson, L. M.; Grosse, G.; Romanovsky, V. E.; Jones, B. M.; Arp, C. D.; McGuire, A. D.

    2013-12-01

    Arctic Alaska is characterized by widespread past and present thaw of ice rich permafrost and subsequent thermokarst development. Variations in ice content and distribution, and topography across Arctic Alaska result in thermokarst landform diversity. Thermokarst causes a number of biogeochemical and ecological shifts that include changes in soil carbon dynamics, nutrient cycling, vegetation composition, wildlife habitat, and fresh water availability. Ongoing climate change may lead to an increase in thermokarst landscape features. Thus, a better understanding of the current temporal and spatial dynamics of thermokarst is needed in order to project its future dynamics. Understanding how vulnerable Arctic Alaska is to future thermokarst development is critical for resource management, industry development, and subsistence hunting. We focused on the distribution of thermokarst landforms among ten study sites aligned with the NSF CALON (Towards a Circum-Arctic Lakes Observation Network) project in Arctic Alaska. Sites represent diverse substrates including eolian silt, eolian sand, marine sand, deltaic, and marine silt. We conducted thermokarst landform mapping and spatial and morphometric analyses using high-resolution aerial photography, an interferometric synthetic aperture radar derived digital elevation model (IfSAR DEM), and hydrographic layers from the National Land Cover Database derived from Landsat-7. Non-lake thermokarst landforms were visually mapped and hand digitized using aerial photographs and the IfSAR DEM. Initial results show thermokarst forms are most prevalent in marine silt areas with up to 99% of study areas affected by thermokarst activity. Eolian sand areas are the least thermokarst affected (mean of 57%). Drained thermokarst lake basins, thermokarst lakes, and areas affected by thermokarst pit formation were the dominant thermokarst landforms, covering up to 70%, 54%, and 8% of the landscape. The number of overlapping lake and basin

  13. EnMAP Specific BRDF Measurements and Vegetation Indices for Low-Growing Biomes in the Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Buchhorn, M.; Heim, B.; van der Linden, S.

    2011-12-01

    Global warming is highest in the Arctic where the tundra regions are expected to undergo pronounced changes. Remote sensing can provide spatial and temporal data on variables linked to vegetation and ecosystem processes on global scale. Specifically, hyperspectral remote sensing data can relate to Vegetation Indices (VIs), Leaf Area Index (LAI) and the fraction of Photosynthetically active Radiation (fPAR). Currently, spaceborne hyperspectral imaging data is provided by the CHRIS/PROBA and the Hyperion programs. The Environmental Mapping and Analysis Program (EnMAP), a German hyperspectral mission, is the next step in this line and will provide high spectral resolution observations with a ground sampling distance of 30 meter. The continuous spectral sampling provided by imaging spectroscopy offers the possibility to develop robust algorithms for vegetation indices in low-growing tundra biomes. Since the EnMAP sensor has pointing capabilities, both spectral and directional reflection characteristics need to be taken into account. In order to examine the influence of the bidirectional reflectance distribution function (BRDF) on spectral variables such as the Vegetation Indices, LAI and fPAR, we developed the EnMAP specific field goniospectrometer, EyeSight. We took part at the summer field campaign of the Earth Cryosphere Institute (RU) in 2011 on the Yamal Peninsula, Western Siberia, Russia. Field spectroscopy, vegetation and biomass analysis, and field goniometer measurements under varying sun zenith angles and moisture conditions have been conducted. The spectral measurements and BRDF measurements of the low-growing tundra are presented and discussed.

  14. CO2 and CH4 Production from Arctic Tundra Polygons: A Comparative Assessment of Temperature Sensitivity and Geochemical Controls

    NASA Astrophysics Data System (ADS)

    Roy Chowdhury, T.; Tang, G.; Herndon, E.; Elias, D. A.; Phelps, T. J.; Gu, B.; Liang, L.; Wullschleger, S. D.; Graham, D. E.

    2013-12-01

    Emissions of carbon dioxide (CO2) and methane (CH4) from Arctic and sub-Arctic tundra are highly variable and challenging to examine for geochemical and microbial controls. The large scale variability in in situ emission observations between high-centered and low-centered polygons and between microtopographic sites of a polygon (center, ridge and trough) underscores the difficulty of estimating precise regional to global-scale CO2 and CH4 emissions. This in turn poses a challenge to the extrapolation approaches used in predictive climate models for such complex high-latitude ecosystems. This study addresses the quantification and a comparative assessment of temperature sensitivity of CO2 and CH4 production rates between high-centered and low-centered polygons from the Barrow Environmental Observatory (Barrow, Alaska) under ecologically relevant experimental conditions. In addition, we elucidate the role of geochemical parameters including depth of organic matter, water content and pH in controlling the microbial pathways by which soil organic carbon are mineralized and CO2 and CH4 released. Intact frozen soil cores were collected from the center, ridge and trough areas of a low-centered polygon (LCP) and the center and trough of a high-centered polygon (HCP) using a SIPRE auger. A typical soil core consisted of a 0-20 cm deep organic (O) horizon, 20-50 cm deep mineral (B) horizon and 50-90 cm deep permafrost. The presence of significant amounts of iron(II) in O and B horizons constituting the active layer indicated predominantly anoxic soil biochemistry in the LCP and in the trough of the HCP. Therefore, soils were incubated in microcosms in anoxic or oxic conditions based on the redox conditions at three ecologically relevant temperatures of -2, +4 or +8 °C for up to 45 days. Production rates for both CH4 and CO2 were substantially higher in microcosms of O horizon at all temperatures, compared to B horizon samples at all sites of the LCP and the center of the

  15. An eddy covariance network to investigate post-fire carbon and energy dynamics in remote regions of Alaskan arctic tundra

    NASA Astrophysics Data System (ADS)

    Rocha, A. V.; Shaver, G. R.; Rastetter, E.; Jiang, Y.

    2012-12-01

    The Alaskan arctic is experiencing pronounced changes such as fires, increased shrub cover, and permafrost thaw that are the result of increased air temperatures. Quantifying the effect of these changes on arctic carbon and energy fluxes is difficult because the Arctic is remote and difficult to access throughout the year. Here we report on an experimental design that uses a roving eddy covariance network, remote sensing, and model data fusion to determine post-fire effects on carbon and energy exchange over hours to decadal timescales in Alaskan arctic tundra. We describe the approach, challenges and goals of this project, and present some preliminary data. Our approach incorporated a number of sites along an Alaskan tundra fire chronosequence, and paired fire scars of different age with an unburned control. Challenges included; limited site access and power, communication and data acquisition, spatial variability, and missing data. We approached these challenges in a variety of ways, including; assessing spatial variability with MODIS data and roving towers, comparing burned to nearby unburned sites, harvesting biomass to understand decadal carbon recovery, and developing models that incorporate remotely sensed, eddy covariance, and biomass data. Our experimental design provides a test-bed for assessing large-scale variability across time and space, which is critical for understanding the role of disturbance on regional carbon and energy fluxes. Conceptual framework for our study. Field measurements will encompass both fast [top of hatched line] to slow [bottom of hatched line] ecosystem processes and states along a fire chronosequence [1] that will be assimilated into a fast and slow response model framework through model-data fusion [2], and used to scale up to the North Slope with MODIS data [3].

  16. Evidence and Implications of Frequent Fires in Ancient Shrub Tundra

    SciTech Connect

    Higuera, P E; Brubaker, L B; Anderson, P M; Brown, T A; Kennedy, A T; Hu, F S

    2008-03-06

    Understanding feedbacks between terrestrial and atmospheric systems is vital for predicting the consequences of global change, particularly in the rapidly changing Arctic. Fire is a key process in this context, but the consequences of altered fire regimes in tundra ecosystems are rarely considered, largely because tundra fires occur infrequently on the modern landscape. We present paleoecological data that indicate frequent tundra fires in northcentral Alaska between 14,000 and 10,000 years ago. Charcoal and pollen from lake sediments reveal that ancient birchdominated shrub tundra burned as often as modern boreal forests in the region, every 144 years on average (+/- 90 s.d.; n = 44). Although paleoclimate interpretations and data from modern tundra fires suggest that increased burning was aided by low effective moisture, vegetation cover clearly played a critical role in facilitating the paleo-fires by creating an abundance of fine fuels. These records suggest that greater fire activity will likely accompany temperature-related increases in shrub-dominated tundra predicted for the 21st century and beyond. Increased tundra burning will have broad impacts on physical and biological systems as well as land-atmosphere interactions in the Arctic, including the potential to release stored organic carbon to the atmosphere.

  17. 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

  18. 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.

  19. Climate Change and Thawing Permafrost in Two Iñupiaq Communities of Alaska's Arctic: Observations, Implications, and Resilience

    NASA Astrophysics Data System (ADS)

    Woodward, A.; Kofinas, G.

    2013-12-01

    For thousands of years the Iñupiat of northern Alaska have relied on ecosystems underlain by permafrost for material and cultural resources. As permafrost thaws across the Arctic, these social-ecological systems are changing rapidly. Community-based research and extensive local knowledge of Iñupiaq villagers offer unique and valuable contributions to understanding permafrost change and its implications for humans. We partnered with two Iñupiaq communities in Alaska's Arctic to investigate current and potential effects of thawing permafrost on social-ecological systems. Anaktuvuk Pass is situated on thaw-stable consolidated gravel in the Brooks Range, while Selawik rests on ice-rich permafrost in Beringia lowland tundra. Using the transdisciplinary approach of resilience theory and mixed geophysical and ethnographic methods, we measured active layer thaw depths and documented local knowledge about climate and permafrost change. Thaw depths were greater overall in Selawik. Residents of both communities reported a variety of changes in surface features, hydrology, weather, flora, and fauna that they attribute to thawing permafrost and / or climate change. Overall, Selawik residents described more numerous and extreme examples of such changes, expressed higher degrees of certainty that change is occurring, and anticipated more significant and negative implications for their way of life than did residents of Anaktuvuk Pass. Of the two villages, Selawik faces greater and more immediate challenges to the resilience of its social-ecological system as permafrost thaws.

  20. Mortality of arctic fox pups in northern Alaska

    SciTech Connect

    Garrott, R.A.; Eberhardt, L.E.

    1982-01-01

    Reports of mortality among arctic foxes, Alopex lagopus, generally consist of isolated incidents of predation by bald eagles, Haliaeetus leucocephalus, snowy owls, Nyctea scandiaca, red foxes, Vulpes vulpes, and dogs, Canis familiaris. This is a report of observations made on mortality of arctic fox pups observed at dens in the Prudhoe Bay and Colville River Delta areas of northern Alaska during summers of 1975 to 1978 and 1976 to 1979, respectively. Pup mortality was noted amng 15 (19%) of 79 families whose dens we visited. Evidence of at least 20 dead pups was found with remains ranging from intact carcasses to a few bone fragments and tufts of hair. Undoubtedly, researchers failed to detect some dead pups, as predators sometimes carry small pups away from the den before consuming them and adult foxes were observed to dispose of bodies of dead pups within den burrows.

  1. Foods of arctic foxes (Alopex lagopus) during winter and spring in western Alaska

    USGS Publications Warehouse

    Anthony, M.; Barten, N.K.; Seiser, P.E.

    2000-01-01

    During 1986-1991, carcasses of 619 arctic fares (Alopex lagopus) collected from local trappers and at biological field camps on the Yukon-Kuskokwim Delta in western Alaska from November through May were analyzed to determine gastrointestinal contents, age, sex, and body condition. Prey in declining order of importance were small mammals (95% tundra voles, Microtus oeconomus), birds, marine mammals, and fishes. Foxes with small mammal remains in their stomachs were captured farther from the Bering Sea coast ((X) over bar = 5.2 km) than those without small-mammal remains (2.8 km); foxes consuming remains of marine mammals were closer to the coast (1.9 km) than others (4.9 km). Although eggshells had a poor likelihood of occurrence in stomachs, they were found in all months and years. In 1986 and 1987, foxes consumed fewer small mammals than in other years. Mean ages of foxes captured in 1986 (3.7 years) and 1987 (3.2) were greater than in all ether years (1.5). Capture of adults was more common as winter progressed. Indexes of subcutaneous fat decreased annually in April-May and were highest in 1991, when occurrence of carrion of marine mammals was highest.

  2. Disappearing Arctic tundra ponds: Fine-scale analysis of surface hydrology in drained thaw lake basins over a 65 year period (1948-2013)

    NASA Astrophysics Data System (ADS)

    Andresen, Christian G.; Lougheed, Vanessa L.

    2015-03-01

    Long-term fine-scale dynamics of surface hydrology in Arctic tundra ponds (less than 1 ha) are largely unknown; however, these small water bodies may contribute substantially to carbon fluxes, energy balance, and biodiversity in the Arctic system. Change in pond area and abundance across the upper Barrow Peninsula, Alaska, was assessed by comparing historic aerial imagery (1948) and modern submeter resolution satellite imagery (2002, 2008, and 2010). This was complemented by photogrammetric analysis of low-altitude kite-borne imagery in combination with field observations (2010-2013) of pond water and thaw depth transects in seven ponds of the International Biological Program historic research site. Over 2800 ponds in 22 drained thaw lake basins (DTLB) with different geological ages were analyzed. We observed a net decrease of 30.3% in area and 17.1% in number of ponds over the 62 year period. The inclusion of field observations of pond areas in 1972 from a historic research site confirms the linear downward trend in area. Pond area and number were dependent on the age of DTLB; however, changes through time were independent of DTLB age, with potential long-term implications for the hypothesized geomorphologic landscape succession of the thaw lake cycle. These losses were coincident with increases in air temperature, active layer, and density and cover of aquatic emergent plants in ponds. Increased evaporation due to warmer and longer summers, permafrost degradation, and transpiration from encroaching aquatic emergent macrophytes are likely the factors contributing to the decline in surface area and number of ponds.

  3. Effect of warming on the degradation and production of low-molecular-weight labile organic carbon in an Arctic tundra soil

    DOE PAGESBeta

    Yang, Ziming; Wullschleger, Stan D.; Liang, Liyuan; Graham, David E.; Gu, Baohua

    2016-01-16

    The fate of soil organic carbon (SOC) stored in the Arctic permafrost is a key concern as temperatures continue to rise in the northern hemisphere. Studies and conceptual models suggest that SOC degradation is affected by the composition of SOC, but it is unclear exactly what portions of SOC are vulnerable to rapid breakdown and what mechanisms may be controlling SOC degradation upon permafrost thaw. Here, we examine the dynamic consumption and production of labile SOC in an anoxic incubation experiment using soil samples from the active layer at the Barrow Environmental Observatory, Barrow, Alaska, USA. Free-reducing sugars, alcohols, andmore » low-molecular-weight (LMW) organic acids were analyzed during incubation at either –2 or 8 °C for up to 240 days. Results show that simple sugar and alcohol SOC largely account for the initial rapid release of CO2 and CH4 through anaerobic fermentation, whereas the fermentation products, acetate and formate, are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important role as an electron acceptor in tundra SOC respiration. These observations are further supported in a glucose addition experiment, in which rapid CO2 and CH4 production occurred concurrently with rapid production and consumption of labile organics such as acetate. However, addition of tannic acid, as a more complex organic substrate, showed little influence on the overall production of CO2 and CH4 and organic acids. Together our study shows that LMW labile organics in SOC control the initial rapid release of green-house gases upon warming. We thus present a conceptual framework for the labile SOC transformations and their relations to fermentation, iron reduction and methanogenesis, thereby providing the basis for improved model prediction of climate feedbacks in the Arctic.« less

  4. Spatial Variation in Carbon Release From Arctic Tundra Resulting From Microtopography Created by Permafrost Thawing

    NASA Astrophysics Data System (ADS)

    Lee, H.; Schuur, E. A.; Vogel, J. G.

    2007-12-01

    One of the biggest potential feedbacks to global climate change from high latitude ecosystems may come from thawing of permafrost, which stores 30% of the total global terrestrial soil organic carbon (SOC). Thawing of permafrost may accelerate decomposition of soil organic matter (SOM) and increase carbon dioxide (CO2) emissions and such emissions from soil can lead to further warming in global scale. When permafrost thaws in ice-rich areas, it creates localized topographical surface subsidence called thermokarst, which can induce variations in soil abiotic properties. By altering multiple resources in soil, thermokarst can change C cycling in high latitude ecosystems beyond simple increases in temperature alone. The objective was to determine how thermokarst affects ecosystem C exchange. We hypothesized that there would be a positive relationship between the degree of ground subsidence and CO2 emissions from decomposition of SOM. This study was conducted in a tundra site near Denali National Park, Alaska. Three study sites were established according to the degree of surface depressions: Severe Thaw, Moderate Thaw, and Minimal Thaw. We established 50 equally spaced grid points each site and they were surveyed using GPS to measure the micro-elevation. Clear static chamber measurements were used to measure ecosystem C exchange, while soil properties such as temperature and volumetric water content (VWC) were measured simultaneously. Normalized Difference Vegetation Index (NDVI) was measured as an indicator of primary productivity. We used forward stepwise regression analysis to quantify how much microtopography explained ecosystem C exchange. There was a negative correlation between ecosystem respiration and relative elevation at the Severe and Minimal site. The best predictor variable for ecosystem C exchange was VWC alone, which was better than temperature alone, or mixed effects of temperature and VWC. There was no relationship between NDVI and microtopography

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. A new hepadnavirus endemic in arctic ground squirrels in Alaska.

    PubMed Central

    Testut, P; Renard, C A; Terradillos, O; Vitvitski-Trepo, L; Tekaia, F; Degott, C; Blake, J; Boyer, B; Buendia, M A

    1996-01-01

    We present evidence for a novel member of the hepadnavirus family that is endemic in wild arctic ground squirrels (Spermophylus parryi kennicotti) in Alaska. This virus, designated arctic squirrel hepatitis virus (ASHV), was initially detected in the livers of animals bearing large hepatic nodules by nucleic acid hybridization with hepadnavirus probes and in plasma by cross-reactivity with antibodies to hepadnavirus surface and core antigens. The complete nucleotide sequence of the 3,302-bp-long ASHV genome was determined and compared with those of ground squirrel hepatitis virus (GSHV) and woodchuck hepatitis virus (WHV); all sequences were organized into four open reading frames, designated pre-C/C, pre-S/S, pol, and X. Despite roughly equivalent variability among the three rodent hepadnaviruses (around 16% base and 19% amino acid exchanges), ASHV appeared to be more closely related to GSHV than to WHV in phylogenetic analysis. Accordingly, preliminary studies of the pathology of ASHV infection suggested that ASHV may be a less efficient oncogenic agent than WHV. About one-third of aged animals maintained in captivity, including virus-infected as well as uninfected squirrels, developed large liver nodules, consisting of hepatocellular adenomas or carcinomas or nonmalignant lesions characterized by drastic microvesicular steatosis. ASHV-infected arctic ground squirrels may serve as a new model with which to analyze the contribution of hepadnavirus- and host-specific determinants to liver pathology and tumorigenesis. PMID:8676441

  10. Seasonality of Air-sea-ice-land Variables for Arctic Tundra in Northern Eurasia and North America

    NASA Astrophysics Data System (ADS)

    Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Steele, M.; Epstein, H.; Jia, G.; Comiso, J. C.; Pinzon, J. E.; Tucker, C. J.

    2009-12-01

    The strength of tundra productivity trends as measured by the annual maximum Normalized Difference Vegetation Index (MaxNDVI) and time integrated NDVI (TI-NDVI) vary around the Arctic over the 1982-2008 period. Our analysis suggests that the timing of terrestrial vegetation growth is connected to seasonal patterns of sea-ice concentrations, ocean temperatures and land surface temperatures. This study used SSMI estimates of sea ice concentration, based on a bootstrap algorithm and AVHRR radiometric surface temperature. Summer Warmth Index (SWI) was calculated as the sum from May to August of the degree months above freezing of surface temperature at each pixel and is an accepted measure of plant growth potential. The Normalized Difference Vegetation Index (NDVI) represents vegetation greenness and has been used extensively to monitor changes in the Arctic. The albedo of green plants varies with solar radiation wavelength, which is the basis for the NDVI index. The analysis was conducted within 50 km of the Arctic coastline to focus on the region of maximum maritime influence. Time series of regional sea-ice concentration, SWI and NDVI were constructed for the 50-km width domains for the Pan-Arctic, North America, Eurasia and Arctic subregions. Standard climate analysis techniques were applied to the regional time series to investigate the seasonality of sea ice, NDVI and SWI. MaxNDVI has increased in the 50-km land domain contiguous to the Beaufort Sea by 17% since 1982, whereas it has only increased by 3% in the coastal Kara Sea region. Analysis of semimonthly MaxNDVI indicates that the vegetation greens up more rapidly in the spring in the Beaufort than the W. Kara and the Kara has slightly higher NDVI in the fall. The climatological weekly sea ice concentrations in 50-km coastal domain displays an earlier breakup in the Beaufort and a later freeze-up in the Kara Sea area. Regional differences in the seasonal cycle can in part explain the spatially varied trends

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

    SciTech Connect

    Chapin, F.S. III

    1995-01-01

    We successfully developed a series of models to explore the importance of species differences in phenologies of growth and nitrogen uptake to competitive interactions in upland tussock tundra. We developed growth models for 4 major tussock tundra species, based on observed growth rates and phenologies. We found that differences in phenology and nutrient use strategy could permit coexistence of some, but not all of the tundra plants modeled. The plant that was the best competitor, because of its rapid growth rate and superior ability to retranslocate nitrogen, may be naturally limited in its competitive ability by its tussock growth form. The mechanisms behind this limitation, and the contributions of patterns of mortality to observed production, will be explored in future modeling and experimental studies. In addition, our models point out that our understanding of the dynamics of nitrogen supply is still inadequate.

  12. Changes in Landscape-level Carbon Balance of an Arctic Coastal Plain Tundra Ecosystem Between 1970-2100, in Response to Projected Climate Change

    NASA Astrophysics Data System (ADS)

    Lara, M. J.; McGuire, A. D.; Euskirchen, E. S.; Genet, H.; Sloan, V. L.; Iversen, C. M.; Norby, R. J.; Zhang, Y.; Yuan, F.

    2014-12-01

    Northern permafrost regions are estimated to cover 16% of the global soil area and account for approximately 50% of the global belowground organic carbon pool. However, there are considerable uncertainties regarding the fate of this soil carbon pool with projected climate warming over the next century. In northern Alaska, nearly 65% of the terrestrial surface is composed of polygonal tundra, where geomorphic land cover types such as high-, flat-, and low-center polygons influence local surface hydrology, plant community composition, nutrient and biogeochemical cycling, over small spatial scales. Due to the lack of representation of these fine-scale geomorphic types and ecosystem processes, in large-scale terrestrial ecosystem models, future uncertainties are large for this tundra region. In this study, we use a new version of the terrestrial ecosystem model (TEM), that couples a dynamic vegetation model (in which plant functional types compete for water, nitrogen, and light) with a dynamic soil organic model (in which temperature, moisture, and associated organic/inorganic carbon and nitrogen pools/fluxes vary together in vertically resolved layers) to simulate ecosystem carbon balance. We parameterized and calibrated this model using data specific to the local climate, vegetation, and soil associated with tundra geomorphic types. We extrapolate model results at a 1km2 resolution across the ~1800 km2 Barrow Peninsula using a tundra geomorphology map, describing ten dominant geomorphic tundra types (Lara et al. submitted), to estimate the likely change in landscape-level carbon balance between 1970 and 2100 in response to projected climate change. Preliminary model runs for this region indicated temporal variability in carbon and active layer dynamics, specific to tundra geomorphic type over time. Overall, results suggest that it is important to consider small-scale discrete polygonal tundra geomorphic types that control local structure and function in regional

  13. Flux Of Carbon from an Airborne Laboratory (FOCAL): Synergy of airborne and surface measures of carbon emission and isotopologue content from tundra landscape in Alaska

    NASA Astrophysics Data System (ADS)

    Dobosy, R.; Dumas, E.; Sayres, D. S.; Kochendorfer, J.

    2013-12-01

    Arctic tundra, recognized as a potential major source of new atmospheric carbon, is characterized by low topographic relief and small-scale heterogeneity consisting of small lakes and intervening tundra vegetation. This fits well the flux-fragment method (FFM) of analysis of data from low-flying aircraft. The FFM draws on 1)airborne eddy-covariance flux measurements, 2)a classified surface-characteristics map (e.g. open water vs tundra), 3)a footprint model, and 4)companion surface-based eddy-covariance flux measurements. The FOCAL, a collaboration among Harvard University's Anderson Group, NOAA's Atmospheric Turbulence and Diffusion Division (ATDD), and Aurora Flight Sciences, Inc., made coordinated flights in 2013 August with a collaborating surface site. The FOCAL gathers not only flux data for CH4 and CO2 but also the corresponding carbon-isotopologue content of these gases. The surface site provides a continuous sample of carbon flux from interstitial tundra over time throughout the period of the campaign. The FFM draws samples from the aircraft data over many instances of tundra and also open water. From this we will determine how representative the surface site is of the larger area (100 km linear scale), and how much the open water differs from the tundra as a source of carbon.

  14. 50 CFR Appendix I to Part 37 - Legal Description of the Coastal Plain, Arctic National Wildlife Refuge, Alaska

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Refuge approximately 57 miles along the line of extreme low water of the Arctic Ocean, including all..., Arctic National Wildlife Refuge, Alaska I Appendix I to Part 37 Wildlife and Fisheries UNITED STATES FISH... GEOLOGICAL AND GEOPHYSICAL EXPLORATION OF THE COASTAL PLAIN, ARCTIC NATIONAL WILDLIFE REFUGE, ALASKA Pt....

  15. 50 CFR Appendix I to Part 37 - Legal Description of the Coastal Plain, Arctic National Wildlife Refuge, Alaska

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Refuge approximately 57 miles along the line of extreme low water of the Arctic Ocean, including all..., Arctic National Wildlife Refuge, Alaska I Appendix I to Part 37 Wildlife and Fisheries UNITED STATES FISH... GEOLOGICAL AND GEOPHYSICAL EXPLORATION OF THE COASTAL PLAIN, ARCTIC NATIONAL WILDLIFE REFUGE, ALASKA Pt....

  16. Characterizing the Drivers of Intermittent Flow in Arctic Alaska Streams

    NASA Astrophysics Data System (ADS)

    Betts, E.; Kane, D. L.; Stephan, N.

    2012-12-01

    Fish and wildlife species in the Arctic have developed life history strategies to deal with the extreme climate of the North. In the case of Arctic grayling, these strategies include long life, yearly spawning and migration.. In order to understand how such a species will be affected by a changing climate, we must first determine how these adaptive strategies may be at odds with the changing Arctic landscape. Arctic grayling migrate to spawning grounds just after spring break-up; then they migrate to feeding sites in early summer and finally in the fall migrate back to their overwintering sites. Low precipitation and high evapotranspiration rates during the summer can lead to low water levels and a fragmentation of the hydrologic landscape. This fragmentation creates a barrier to fish migration. The Kuparuk River is a perennial stream originating in the foothills of the Brooks Range on the North Slope of Alaska. The basin is underlain by continuous permafrost which essentially blocks the surface system from interacting with the subpermafrost groundwater system. Shallow subsurface flow occurs in the active layer, that area above permafrost which undergoes seasonal thawing in the summer. Sections of the Kuparuk are intermittent in that during low flows in the system these reaches appear dry (no flow in channel). Water reappears in the channel, downstream of these dry reaches, and it is believed that water continues to flow below the surface through the unfrozen thaw bulb beneath these reaches. These dry reaches act as summer barriers to fish migration within the Kuparuk River system. Previous research of this phenomenon sought to understand the location and timing of these dry events. The current research to be presented here attempts to determine the drivers of these dry channel events. Dye tracers and discharge measurements are used to determine the amount of hyporheic flow along these dry reaches and a statistical model incorporating soil moisture, precipitation

  17. Landscape- and decadal-scale changes in the composition and structure of plant communities in the northern foothills of the Brooks Range of Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Mercado-Díaz, J. A.; Gould, W. A.

    2010-12-01

    Scientists have predicted an increase in vascular plant cover in some tundra ecosystems as a result of global climate change. In Arctic Alaska, observational studies have documented increases in shrub cover for some regions; however, only a few studies have provided detailed quantitative evidence supporting the existence such changes. To address these shortcomings, we analyzed plant community data from 156 1m2 vegetation plots located at two 1km2 grids in Toolik Lake, Alaska. This data covered the time period from 1989-2008. After 18 years, we found that the relative abundance of vascular vegetation have increased by 16%, while the relative abundance of nonvascular vegetation decreased by 19%. Mean plant canopy height has experienced an increase from 4.4 cm in 1990 to 6.5 cm in 2008 and the extent and complexity of the canopy have increased over time from about 60% to 80%. Species diversity was also significantly reduced. While major vegetation changes in other tundra regions have been attributed to gradual increases in surface air temperature, changes documented in this study were apparently promoted by increasing soil moisture conditions that resulted from increased summer rainfall in our region. These results support the idea that tundra ecosystems in this region of the Alaskan Arctic are experiencing significant increases in aboveground standing crop and a shift in carbon allocation to vascular plants vs. bryophytes. These changes will likely affect important ecosystem processes like snow re-deposition, winter biological activities, nutrient cycling and could ultimately result in significant feedbacks to climate.

  18. Effects of permafrost on stream channel behavior in Arctic Alaska

    USGS Publications Warehouse

    Scott, Kevin M.

    1978-01-01

    Sites with drainage areas ranging from 88 to 12,200 sq km were monitored on five streams in northern Alaska during the breakup in 1976 to determine (1) the effects of frozen bed and bank material on channel behavior, and (2) the importance of the annual breakup flood in forming the channels of arctic streams. The thawing and concomitant erosion of channels varied with changes in bed-material size, channel pattern, drainage area, and climate. The response of channels to breakup flooding ranged from total permafrost control of channel processes, including both bed scour and lateral erosion, to only brief restriction of channel behavior early in the rise of the flooding. The watershed characteristic that appears to explain much of this variation is size of drainage area. (Woodard-USGS)

  19. Ice-age megafauna in Arctic Alaska: extinction, invasion, survival

    USGS Publications Warehouse

    Mann, Daniel H.; Groves, Pamela; Kunz, Michael L.; Reanier, Richard E.; Gaglioti, Benjamin V.

    2013-01-01

    Radical restructuring of the terrestrial, large mammal fauna living in arctic Alaska occurred between 14,000 and 10,000 years ago at the end of the last ice age. Steppe bison, horse, and woolly mammoth became extinct, moose and humans invaded, while muskox and caribou persisted. The ice age megafauna was more diverse in species and possibly contained 6× more individual animals than live in the region today. Megafaunal biomass during the last ice age may have been 30× greater than present. Horse was the dominant species in terms of number of individuals. Lions, short-faced bears, wolves, and possibly grizzly bears comprised the predator/scavenger guild. The youngest mammoth so far discovered lived ca 13,800 years ago, while horses and bison persisted on the North Slope until at least 12,500 years ago during the Younger Dryas cold interval. The first people arrived on the North Slope ca 13,500 years ago. Bone-isotope measurements and foot-loading characteristics suggest megafaunal niches were segregated along a moisture gradient, with the surviving species (muskox and caribou) utilizing the warmer and moister portions of the vegetation mosaic. As the ice age ended, the moisture gradient shifted and eliminated habitats utilized by the dryland, grazing species (bison, horse, mammoth). The proximate cause for this change was regional paludification, the spread of organic soil horizons and peat. End-Pleistocene extinctions in arctic Alaska represent local, not global extinctions since the megafaunal species lost there persisted to later times elsewhere. Hunting seems unlikely as the cause of these extinctions, but it cannot be ruled out as the final blow to megafaunal populations that were already functionally extinct by the time humans arrived in the region.

  20. Ice-age megafauna in Arctic Alaska: extinction, invasion, survival

    NASA Astrophysics Data System (ADS)

    Mann, Daniel H.; Groves, Pamela; Kunz, Michael L.; Reanier, Richard E.; Gaglioti, Benjamin V.

    2013-06-01

    Radical restructuring of the terrestrial, large mammal fauna living in arctic Alaska occurred between 14,000 and 10,000 years ago at the end of the last ice age. Steppe bison, horse, and woolly mammoth became extinct, moose and humans invaded, while muskox and caribou persisted. The ice age megafauna was more diverse in species and possibly contained 6× more individual animals than live in the region today. Megafaunal biomass during the last ice age may have been 30× greater than present. Horse was the dominant species in terms of number of individuals. Lions, short-faced bears, wolves, and possibly grizzly bears comprised the predator/scavenger guild. The youngest mammoth so far discovered lived ca 13,800 years ago, while horses and bison persisted on the North Slope until at least 12,500 years ago during the Younger Dryas cold interval. The first people arrived on the North Slope ca 13,500 years ago. Bone-isotope measurements and foot-loading characteristics suggest megafaunal niches were segregated along a moisture gradient, with the surviving species (muskox and caribou) utilizing the warmer and moister portions of the vegetation mosaic. As the ice age ended, the moisture gradient shifted and eliminated habitats utilized by the dryland, grazing species (bison, horse, mammoth). The proximate cause for this change was regional paludification, the spread of organic soil horizons and peat. End-Pleistocene extinctions in arctic Alaska represent local, not global extinctions since the megafaunal species lost there persisted to later times elsewhere. Hunting seems unlikely as the cause of these extinctions, but it cannot be ruled out as the final blow to megafaunal populations that were already functionally extinct by the time humans arrived in the region.

  1. Decadal Time Scale change in terrestrial plant communities in North American arctic and alpine tundra: A contribution to the International Polar Year Back to the Future Project (Invited)

    NASA Astrophysics Data System (ADS)

    Tweedie, C. E.; Ebert-May, D.; Hollister, R. D.; Johnson, D. R.; Lara, M. J.; Villarreal, S.; Spasojevic, M.; Webber, P.

    2010-12-01

    The International Polar Year-Back to the Future (IPY-BTF) is an endorsed International Polar Year project (IPY project #214). The overarching goal of this program is to determine how key structural and functional characteristics of high latitude/altitude terrestrial ecosystems have changed over the past 25 or more years and assess if such trajectories of change are likely to continue in the future. By rescuing data, revisiting, re-sampling historic research sites and assessing environmental change over time, we aim to provide greater understanding of how tundra is changing and what the possible drivers of these changes are. Resampling of sites established by Patrick J. Webber between 1964 and 1975 in northern Baffin Island, Northern Alaska and in the Rocky Mountains form a key contribution to the BTF project. Here we report on resampling efforts at each of these locations and initial results of a synthesis effort that finds similarities and differences in change between sites. Results suggest that although shifts in plant community composition are detectable at each location, the magnitude and direction of change differ among locations. Vegetation shifts along soil moisture gradients is apparent at most of the sites resampled. Interestingly, however, wet communities seem to have changed more than dry communities in the Arctic locations, while plant communities at the alpine site appear to be becoming more distinct regardless of soil moisture status. Ecosystem function studies performed in conjunction with plant community change suggest that there has been an increase in plant productivity at most sites resampled, especially in wet and mesic land cover types.

  2. Reservoir quality studies, Arctic National Wildlife Refuge, Alaska

    SciTech Connect

    Mowatt, T.C.; Banet, A. )

    1991-03-01

    Reservoir quality studies are part of the reservoir management and resource assessment programs of the U.S. Bureau of Land Management in Alaska. Petrographic analyses have been carried out of samples collected from surface exposures in the Arctic National Wildlife Refuge (ANWR), Alaska, to evaluate surface materials as to their potential reservoir rock qualities in the subsurface. This entails characterization of relevant petrologic-petrophysical properties, integration with regional geological-geophysical relationships, and synthesis in terms of likely diagenetic, structural, and stratigraphic conditions in the subsurface. There is a paucity of relevant data in this region. Inferences must be predicated largely on general principles and known relationships elsewhere. A spectrum of lithologies were studied, representing a substantial portion of the regional stratigraphic column. In a number of cases, particularly among the pre-Brookian samples, the rocks appear to have low reservoir potential, based on their present high degree of diagenetic maturity. There is always the possibility - deemed somewhat unlikely here - of subsurface equivalents with more favorable characteristics, due to different original compositions, textures, and/or geologic histories. Brookian sandstones and conglomerates feature samples with fair-good reservoir characteristics, with prospects of being equally good or better in the subsurface. The samples studied suggest the likelihood of horizons with viable reservoir qualities in the subsurface within the ANWR region.

  3. Pollen analysis of a late pliocene and early pleistocene section from the Gubik Formation of Arctic Alaska

    USGS Publications Warehouse

    Nelson, R.E.; Carter, L.D.

    1985-01-01

    A 14-m-thick section of marine and nonmarine sediments of the Gubik Formation of northern Alaska, exposed in bluffs near Ocean Point on the Colville River, has been studied by means of pollen analysis. Pollen from the marine sediments, of probable late Pliocene age, records a boreal forest of spruce and birch with minor amounts of alder in the adjacent terrestrial vegetation. Pine and perhaps true fir were probably at or near their northern limit here, but hemlocks and hardwoods were absent. The suggested environment for the Arctic Slope during the time represented by the marine sediments is similar to that of present-day Anchorage. Pollen floras from the overlying fluvial strata, of early or middle Pleistocene age, record predominantly herbaceous taxa indicating tundra conditions probably more severe than those of the present day. These deposits were most likely contemporaneous with glacial conditions in the Brooks Range to the south. Pollen of woody taxa (spruce, alder, birch, heaths) is rare through most of the section, although birch and alder percentages similar to those found in modern river sediments indicate an interstadial or interglacial warming in midsection. Inland climates during glacial episodes may have been similar to those of the present Arctic coast. ?? 1985.

  4. Stemming the Revolving Door: Teacher Retention and Attrition in Arctic Alaska Schools

    ERIC Educational Resources Information Center

    Kaden, Ute; Patterson, Philip P.; Healy, Joanne; Adams, Barbara L.

    2016-01-01

    Limited research is available concerning teacher retention and teacher attrition in Arctic Alaska. This paper reports survey research findings, which identify factors related to teacher retention and attrition in Alaskan Arctic Native communities. Teacher retention rates (2009-2013) vary widely over time showing no significant trends. Results…

  5. Intense, natural pollution affects Arctic tundra vegetation at the Smoking Hills, Canada

    SciTech Connect

    Freedman, B. ); Zobens, V.; Hutchinson, T.C.; Gizyn, W.I. )

    1990-04-01

    Long-term, natural emissions of sulfur dioxide and acidic aerosols have had an impact on remote tundra at the Smoking Hills. The emissions have caused plant damage by SO{sub 2} toxicity, and have severely acidified soil and freshwater. At the most intensively fumigated locations closest to the sources of emission, pollution stresses have devegetated the terrestrial ecosystem. The first plants that are encountered along a spatial gradient of decreasing pollution stress are Artemisia tilesii and Arctagrostis latifolia, which dominate a characteristic, pollution-tolerant community. Farther away at moderately polluted sites there are mixed communities with floristic elements of both fumigated and reference, unfumigated tundra. This pattern of ecosystem response to a concatenation of stresses caused by natural air and soil pollution is qualitatively similar to the damage that occurs in the vicinity of anthropogenic point sources of air pollution, such as smelters.

  6. Mercury Concentrations in Coastal and Inland Snow In Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Douglas, T. A.; Sturm, M.; Simpson, W. R.; Brooks, S. B.; Lindberg, S. E.; Perovich, D. K.

    2004-12-01

    Elevated mercury concentrations in arctic coastal and inland snow have been reported at remote locations. This mercury is attributed to mercury depletion events (MDEs) where gas-phase mercury is depleted due to photochemical conversion to reactive gaseous mercury that is subsequently deposited to snow and ice surfaces. The high mercury concentrations are generally observed near the coast, suggesting that sea ice or leads play a role in MDEs. We sampled the snow pack during 250-km over snow traverses from the central Brooks Range north to the sea ice off of Barrow, Alaska in the spring of 2002 and in the spring of 2004. Our goal was to gain a better understanding of the spatial pattern of mercury concentrations in surface snow. Mercury concentrations in surface snow more than 200 km inland from the Arctic Ocean coast ranged from 5 to 25 ng/L. Samples of a layer of recently deposited snow between 75 km inland from Barrow and Barrow yielded mercury concentrations that ranged from 25 to 147 ng/L and were not correlated with distance from the coast. Snow samples obtained from locations on the sea ice yielded far greater mercury concentrations than terrestrial snow. Mercury concentrations of as high as 820 ng/L were measured in surface hoar snow forming at the edge of a 200 meter wide open lead. Recently formed frost flowers on nilas ice at the edge of a refreezing lead contained mercury in concentrations ranging from 150 to 185 ng/L. Our work yields two important results. First, the relationship between mercury concentrations in snow and distance from the coast is complex and non-monotonic. Second, large leads, those with convective plumes that drive vapor transport, most likely play an important but unresolved role in lower tropospheric MDE chemistry near the Arctic Ocean coast. The existence of highly elevated mercury concentrations near leads suggests the need for a more detailed investigation of the chemical and physical regime near leads.

  7. RECONSTRUCTION AND ANALYSIS OF HISTORICAL CHANGES IN CARBON STORAGE IN ARCTIC TUNDRA

    EPA Science Inventory

    Surface air temperature in arctic regions has increased since pre-industrial times, raising concerns that warmer and possibly drier conditions have increased soil decomposition rates, thereby stimulating the release to the atmosphere of the large stores of carbon (C) in arctic so...

  8. Connecting Indigenous Knowledge to Thaw Lake Cycle Research on the Arctic Coastal Plain of Alaska

    NASA Astrophysics Data System (ADS)

    Eisner, W. R.; Cuomo, C. J.; Hinkel, K. M.; Jones, B. M.; Hurd, J.

    2005-12-01

    Thaw lakes cover about 20% of the Arctic Coastal Plain of Alaska. Another 26% is scarred by basins that form when lakes drain, and these drained thaw-lake basins are sites for preferential carbon accumulation as plant biomass. Recent studies in the continuous permafrost zone of Western Siberia suggest that lakes have been expanding in the past several decades in response to regional warming. Anticipated regional warming would likely mobilize sequestered soil organic carbon, resulting in the emission of CO2 and CH4. Our understanding of the processes leading to thaw lake formation, expansion, and drainage in northern Alaska has been limited because models are specific to the flat, young Outer (seaward) Coastal Plain comprising 1/3 of the region. Furthermore, spatial and temporal analysis of lake dynamics is largely restricted to the period since 1948, when aerial photographs first became available across large regions of the Coastal Plain. In order to fill these gaps, we have been interviewing Iñupiaq elders, hunters, and berry pickers from the villages of Atqasuk and Barrow. The objective of these interviews is to obtain accounts of lake formation, expansion and drainage that have occurred within living or oral memory, and extend the record back several generations. To date, we have interviewed fifteen Iñupiat; most of these are people who travel the tundra frequently and have done so for decades. They have first-hand experience of lake drainage, sea cliff and river bank erosion, permafrost degradation, and other landscape changes. Many informants expressed concern that landscape changes are occurring at an increasingly rapid rate. They have identified lakes that have drained, areas where the permafrost is thawing, and places where the sea and river coastline is eroding. We have been able to corroborate reports of lake drainage from our informants with a series of aerial photographs, satellite images, and radiocarbon dates. In many instances, the elders have

  9. Modeled changes in terrestrial C storage on the Arctic coastal plain of Alaska suggest a mid-century 21st shift from C sink to source.

    NASA Astrophysics Data System (ADS)

    Tucker, C.; Euskirchen, E. S.; Genet, H.; McGuire, A. D.; Rupp, S. T.; Breen, A. L.; Kurkowski, T. A.; Bennett, A.; Kofinas, G.

    2014-12-01

    Arctic tundra contains significant carbon (C) stocks, which are likely to change in response to climate change, depending on the balance of plant production and decomposition responses to warming and thawing permafrost. We modeled terrestrial C over the period 1901-2100 in a 67,000 km2 region of the eastern Arctic Coastal Plain of Alaska with four dominant vegetation types: wet sedge, tussock, shrub and heath tundra. The Terrestrial Ecosystem Model (TEM) is a biogeochemical model that simulates the C and N dynamics of vegetation and soils in response to climatic drivers. The version of TEM used here includes a dynamic organic soil module that allows the size of the organic soil layer to change through time. We model historical (1900-2010) and future (2010-2100) dynamics for low, intermediate and high CO2 emissions scenarios. During the period 2000-2010, modeled net primary productivity and vegetation C were significantly positively correlated with the MODIS derived normalized difference vegetation index, as were the start and end of the growing season, and the duration of the snow-covered season. Between 1900 and 2100, C storage in vegetation increased most in shrub and tussock tundra (52 % and 43 %, respectively) and somewhat less in wet sedge and heath tundra (15 % and 21 %, respectively), consistent with observed expansion of shrubby biomass across the region. Simulated terrestrial C storage for the study region changed from 40.5 kg C m-2 (soil=39.6, vegetation=1.0) in 1901 to 42.2 kg C m-2 (soil=40.9, vegetation=1.2) in 2010. In the intermediate warming scenario, by 2050, the total terrestrial C storage in the study region increased by 0.5 kg C m-2 but by 2100, 60% of this new C storage was lost, indicating a shift from net C uptake to net C loss in the study region toward the end of the century, driven by a shift in the relative magnitudes of C inputs from litter and losses from heterotrophic respiration. These changes were correlated with a 21 day increase in

  10. Paleoenvironmental analyses of an organic deposit from an erosional landscape remnant, Arctic Coastal Plain of Alaska

    SciTech Connect

    Eisner, W R; Bockheim, J G; Hinkel, K M; Brown, T A; Nelson, F E; Peterson, K M; Jones, B M

    2005-01-02

    The dominant landscape process on the Arctic Coastal Plain of northern Alaska is the formation and drainage of thaw lakes. Lakes and drained thaw lake basins account for approximately 75% of the modern surface expression of the Barrow Peninsula. The thaw lake cycle usually obliterates lacustrine or peat sediments from previous cycles which could otherwise be used for paleoecological reconstruction of long-term landscape and vegetation changes. Several possible erosional remnants of a former topographic surface that predates the formation of the thaw lakes have been tentatively identified. These remnants are characterized by a higher elevation, a thick organic layer with very high ground ice content in the upper permafrost, and a plant community somewhat atypical of the region. Ten soil cores were collected from one site, and one core was intensively sampled for soil organic carbon content, pollen analysis, and {sup 14}C dating. The lowest level of the organic sediments represents the earliest phase of plant growth and dates to ca. 9000 cal BP. Palynological evidence indicates the presence of mesic shrub tundra (including sedge, birch, willow, and heath vegetation); and microfossil indicators point to wetter eutrophic conditions during this period. Carbon accumulation was rapid due to high net primary productivity in a relatively nutrient-rich environment. These results are interpreted as the local response to ameliorating climate during the early Holocene. The middle Holocene portion of the record contains an unconformity, indicating that between 8200 and 4200 cal BP sediments were eroded from the site, presumably in response to wind activity during a drier period centered around 4500 cal BP. The modern vegetation community of the erosional remnant was established after 4200 cal BP, and peat growth resumed. During the late Holocene, carbon accumulation rates were greatly reduced in response to the combined effects of declining productivity associated with climatic

  11. The role of seasonality and large-scale climate drivers in recent Pan-Arctic tundra vegetation variability and change

    NASA Astrophysics Data System (ADS)

    Bhatt, U. S.; Walker, D. A.; Bieniek, P. A.; Raynolds, M. K.; Comiso, J. C.; Pinzon, J.; Tucker, C. J.

    2011-12-01

    An increase of Pan-Arctic tundra vegetation greenness has been documented using the remotely sensed Normalized Difference Vegetation Index (NDVI) and a coherent variability between NDVI, springtime coastal sea ice and land surface temperatures has been shown. The goal of this paper is to understand the forcing factors of this change and variability better through an analysis of the seasonality of these remotely sensed variables as well as long-term climate data sets. This study uses remotely sensed submonthly 25-km sea ice concentration, surface temperature, and NDVI from 1982 to 2010. The NDVI3g data has been corrected for biases in the spring and fall. Standard climate data (station, reanalysis, and model data) and ground observations are also examined. For overall trends, we find that summer time open water area has increased most in the Beaufort, and Siberian Seas. The seasonality of SWI trends display distinct heterogeneity across the Arctic, with maximum warming in August for most regions (Figure 1). The monthly time integrated NDVI trends display the largest positive values for most of the Arctic in July, with the exception of the E. Bering and Kara regions, which show declines during most months (Figure 2). The largest magnitude increases in Max-NDVI tend to be in subzones that are inland, particularly in the Beaufort and Chukchi regions. NDVI has increased more during spring in Eurasia and more during peak vegetation activity (July) over North America. The analysis suggests that local atmospheric circulation as well as other local factors likely plays an important role in vegetation productivity.

  12. Estimating Arctic Tundra Soil Water Content Variability and Relationship to Landscape Properties Using Above- and Below-Ground Imaging

    NASA Astrophysics Data System (ADS)

    Dafflon, B.; Hubbard, S. S.; Peterson, J.; Ulrich, C.; Oktem, R.; Curtis, J. B.; Tran, A. P.; Wu, Y.; Cable, W.; Romanovsky, V. E.

    2014-12-01

    Estimating the spatiotemporal distribution of soil water content is crucial for ecosystem understanding because of its strong influence on vegetation dynamics, surface-subsurface energy exchange, water and heat flux, microbial activity and biogeochemical mechanisms. In particular, quantifying Arctic ecosystem feedbacks to climate requires advances in monitoring soil moisture in sufficiently high resolution over modeling-relevant scales, and in understanding its coupling with landscape and soil characteristics. As part of the DOE Next-Generation Ecosystem Experiments (NGEE-Arctic) we investigated diverse strategies to estimate the soil water content spatial distribution in Arctic tundra using various proxies including electrical conductivity from electrical resistivity tomography (ERT) and from electromagnetic induction imaging, dielectric permittivity from time-domain reflectometery (TDR), and vegetation index from low-altitude multi-spectral imaging. In addition to occasional campaigns along a 500x40 m corridor, high temporal resolution is achieved through continuous monitoring of surface and subsurface dynamics along a 35 m transect using ERT, temperature loggers, TDR, and visible and NIR imaging from pole-based cameras. This was conducted at the NGEE Barrow, AK site. The results of this study inform on the complementary nature of and trade-offs between various approaches with regard to accuracy, resolution and coverage. In short, while point-scale measurements are relatively hard data, ERT data improves spatiotemporal monitoring of soil water content and state, and low-altitude aerial imaging can be used to extend predictions at larger scale using field-dependent relationships. Importantly, this study enables the identification of spatiotemporal links between soil and landscape properties (such as water inundation, vegetation, topography, thaw layer thickness, water content, temperature, and snow thickness). While some of these properties show strong co

  13. Greening of the Arctic: Spatial and temporal (1982-2009) variation of circumpolar tundra NDVI and aboveground biomass

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Epstein, H. E.; Bhatt, U. S.; Raynolds, M. K.; Jia, G.; Comiso, J. C.; Pinzon, J.; Tucker, C. J.

    2010-12-01

    The Greening of the Arctic project examined the spatial and temporal variability of tundra productivity during field studies along two transects in North America and Russia and in circumpolar remote-sensing studies. Aboveground biomass of zonal vegetation was strongly correlated with summer air temperature along the North America transect (r2 > 0.8), but on the Yamal Peninsula, Russia, there was a nearly flat relationship with air temperature in the central part of the climate gradient. The more homogeneous nature of the Russian transect is caused by more consistent soil conditions, warmer than expected temperatures along the central part of the Russian transect, and the homogenizing effect of various landscape-scale disturbances including reindeer grazing and disturbances related to permafrost thawing. We examined the circumpolar spatial variability of the NDVI with respect to land temperatures and a suite of vegetation/terrain variables in a circumpolar geographic information system (GIS). Tests of sensitivity of NDVI to increases in summer temperature showed the largest percentage increases in NDVI will likely occur in northern partially-vegetated areas. A temporal analysis of maximum summer NDVI from 1982-2008 also indicated the ongoing changes have been strongest in the Far North. The percentage changes in the annual maximum NDVI were highest in the Baffin Bay, Beaufort Sea, Canadian Archipelago and Davis Strait areas (10-15% changes). The NDVI trends for most Arctic regions were highly positively correlated with the changes in summer land temperatures and negatively correlated with temporal changes in the near-shore early-summer sea-ice concentrations. Trends from these and several other lines of evidence point to a general increase in biomass across the Arctic during the period of satellite observations. The most rapid changes are occurring in the Far North. The impact of shrubification on these trends is probably greatest in the southern parts of the Arctic

  14. Domibacillus tundrae sp. nov., isolated from active layer soil of tussock tundra in Alaska, and emended description of the genus Domibacillus.

    PubMed

    Gyeong, Hye Ryeon; Baek, Kiwoon; Hwang, Chung Yeon; Park, Key Hun; Kim, Hye Min; Lee, Hong Kum; Lee, Yoo Kyung

    2015-10-01

    A novel Gram-stain-positive, spore-forming, aerobic, motile and rod-shaped bacterium designated strain PAMC 80007T was isolated from an active layer soil sample of Council, Alaska. Optimal growth of strain PAMC 80007T was observed at 30 °C, pH 7.0 and in the presence of 2 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain PAMC 80007T belonged to the genus Domibacillus. This strain was closely related to Domibacillus enclensis (98.3 %), Domibacillus robiginosus (98.3 %) and Domibacillus indicus (97.2 %). Genomic DNA G+C content was 43.5 mol% and genomic relatedness analyses based on the average nucleotide identity and the genome-to-genome distance showed that strain PAMC 80007T is clearly distinguished from the closely related species of the genus Domibacillus. The major fatty acids (>5 %) were iso-C15 : 0 (24.7 %), C16 : 1ω11c (16.8 %), anteiso-C15 : 0 (16.5 %), C16 : 0 (15.6 %) and anteiso-C17 : 0 (8.7 %). The major respiratory isoprenoid quinones were menaquinone-6 (MK-6) and menaquinone-7 (MK-7), and the polar lipid profile contained diphosphatidylglycerol, phosphatidylglycerol, phosphoglycolipid, phospholipid and two unidentified lipids. meso-Diaminopimelic acid (type A1γ) was present in the cell-wall peptidoglycan, and the major whole-cell sugar was ribose with a minor quantity of glucose. Results from a polyphasic study suggested that strain PAMC 80007T represents a novel species of the genus Domibacillus for which the name Domibacillus tundrae sp. nov. is proposed. The type strain is PAMC 80007T ( = JCM 30371T = KCTC 33549T = DSM 29572T). An emended description of the genus Domibacillus is also provided. PMID:26296675

  15. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl F.; Gamon, John; Tweedie, Craig; Campbell, Petya P. K.; Landis, David; Middleton, Elizabeth

    2012-01-01

    Climate change in tundra regions may alter vegetation species composition and ecosystem carbon balance. Remote sensing provides critical tools for monitoring these changes as optical signals provide a way to scale from plot measurements to regional patterns. Gas exchange measurements of pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow AK, show three significantly different values of light use efficiency (LUE) with values of 0.013+/-0.001, 0.0018+/-0.0002, and 0.0012 0.0001 mol C/mol absorbed quanta for vascular plants, mosses and lichens, respectively. Further, discriminant analysis of patch reflectance identifies five spectral bands that can separate each vegetation functional type as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. Patch-level statistical discriminant functions applied to in situ hyperspectral reflectance successfully unmixed cover fractions of the vegetation functional types. These functions, developed from the tram data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine regional variability in distribution of the vegetation functional types and from those distributions, the variability of LUE. Across the landscape, there was a fivefold variation in tundra LUE that was correlated to a spectral vegetation index developed to detect vegetation chlorophyll content.

  16. Isotope Hydrology of Arctic Tundra Lakes in a Region Impacted by Permafrost Disturbance

    NASA Astrophysics Data System (ADS)

    Peters, D. L.

    2009-05-01

    A projected "hot spot" of climate warming and development is the Mackenzie River Delta region, Northwest Territories, Canada. The upland tundra areas within the Mackenzie Gas Project development area north of Inuvik contain thousands of small lakes and ponds with poorly defined ephemeral drainage that are underlain by thick permafrost and ice-rich sediments for which the basic water balance controls are not fully understood. Natural retrogressive thaw slumps are common along lakeshores and the rapid drainage of ice-rich permafrost-dammed lakes has been occurring. Ongoing oil/gas exploration activities and infrastructure construction may result in terrain disturbance and localized degradation of permafrost, while climate change may increase the magnitude and frequency of thermokarst processes. These disturbed lakes are believed to act as historical analogues for the future effects of climate change on the hydrology, geochemistry, and aquatic ecology of small tundra lake catchments in the continuous permafrost zone of northwestern Canada. Environment Canada initiated an integrated research program in 2005 with the overall goal of improving our understanding of hydro-ecological processes in freshwater aquatic ecosystems affected by shoreline slumping vs. pristine lakes. Limited catchment studies have examined water-balance parameters (e.g., precipitation, evaporation, and surface flows) for tundra lakes in the development area. Enrichment of oxygen-18 (18O) and deuterium (2H) stable isotopes in surface waters have been shown to be useful indicators of water balance variations in remote permafrost regions of Canada where hydroclimatic information is very limited. In particular, information on evaporation: inflow (E/I) ratios and residence times would provide useful information for estimating appropriate water withdrawals from lakes within the proposed development area. A key question is "does permafrost slumping impact the hydrology of tundra lakes via catchment area

  17. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl Fred; Gamon, John A.; Tweedie, Craig E.; Campbell, Petya K. Entcheva; Landis, David R.; Middleton, Elizabeth M.

    2013-01-01

    Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow, AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013 plus or minus 0.0002, 0.0018 plus or minus 0.0002, and 0.0012 plus or minus 0.0001 mol C mol (exp -1) absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals. Along the transect, area-averaged canopy LUE estimated from coverage fractions of the three functional types varied widely, even over short distances. The patch-level statistical discriminant functions applied to in situ hyperspectral reflectance data collected along the transect successfully unmixed cover fractions of the vegetation functional types. The unmixing functions, developed from the transect data, were applied to 30 m spatial resolution Earth Observing-1 Hyperion imaging spectrometer data to examine variability in distribution of the vegetation functional types for an area near Barrow, AK. Spatial variability of LUE was derived from the observed functional type distributions. Across this landscape, a

  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. Remote Sensing of the Arctic Coast of Alaska Using Airborne Lidar Data

    NASA Astrophysics Data System (ADS)

    Gibbs, A.; Richmond, B. M.; Palaseanu, M.; Erikson, L. H.; Jones, B. M.; Brock, J. C.

    2013-12-01

    As part of a U.S. Geological Survey assessment of coastal change hazards, over 11,000 km2 of airborne lidar elevation data were collected along the Arctic coast of Alaska between 2009 and 2012. Data coverage includes the barrier islands and mainland coast between Icy Cape and the U.S.-Canadian border, from the shoreline to ~1.5 km inland. Data coverage extends further inland to around 3 km on the Barrow Peninsula and along the coast of the Teshekpuk Lake Special Area (TLSA) where coastal erosion rates are among the highest in the world (> 18 m/yr). Nominal point density is 1.5 m and vertical accuracy is better than 30 cm. Data were not collected over most river deltas or large embayments, with the exception of Admiralty Bay, Smith Bay (Ikpikpik Delta), Kogru River, and the Fish Creek portion of Colville River Delta. The primary use of the lidar data is to establish a modern shoreline position to be used for change analyses with historical shoreline positions. However, the lidar DEM provides a wealth of topographic and intensity data that can be used for morphological mapping of the remote arctic coast. This is one of the first comprehensive lidar datasets collected in a continuous permafrost environment. Many periglacial landscape features, such as patterned ground, ice-wedge polygons, and thermokarst lakes and former lake basins (recent and relict) are discernible in the dataset. Traditional coastal landscape features including shoreline position, beach width, slope, and bluff height and morphology are also distinct. Here we present an overview of the dataset and an assessment of methodologies developed for characterizing and classifying a variety of landscape features including overall complexity, geometry and morphology of polygonal tundra (polygon spacing, high center vs. low center), coastal bluff morphology (vertical or overhanging, convex vs. concave), drainage patterns and hydrologic connectivity. We also investigate the dataset to estimate offsets between

  20. Arctic Tundra Vegetation Functional Types Based on Photosynthetic Physiology and Optical Properties

    NASA Technical Reports Server (NTRS)

    Huemmrich, Karl F.; Gamon, John; Tweedie, Craig; Campbell, Petya K.; Landis, David R.; Middleton, Elizabeth M.

    2013-01-01

    Non-vascular plants (lichens and mosses) are significant components of tundra landscapes and may respond to climate change differently from vascular plants affecting ecosystem carbon balance. Remote sensing provides critical tools for monitoring plant cover types, as optical signals provide a way to scale from plot measurements to regional estimates of biophysical properties, for which spatial-temporal patterns may be analyzed. Gas exchange measurements were collected for pure patches of key vegetation functional types (lichens, mosses, and vascular plants) in sedge tundra at Barrow AK. These functional types were found to have three significantly different values of light use efficiency (LUE) with values of 0.013+/-0.001, 0.0018+/-0.0002, and 0.0012+/-0.0001 mol C/mol absorbed quanta for vascular plants, mosses and lichens, respectively. Discriminant analysis of the spectra reflectance of these patches identified five spectral bands that separated each of these vegetation functional types as well as nongreen material (bare soil, standing water, and dead leaves). These results were tested along a 100 m transect where midsummer spectral reflectance and vegetation coverage were measured at one meter intervals.

  1. Evaluating CO2 and CH4 fluxes in Arctic peatland and tundra using a satellite remote sensing driven biophysical model

    NASA Astrophysics Data System (ADS)

    Watts, J.; Kimball, J. S.; Parmentier, F. W.; Sachs, T.; Rinne, J.; Zona, D.; Oechel, W. C.; Tagesson, T.

    2013-12-01

    The Arctic terrestrial carbon sink is contingent on the balance between vegetation gross primary productivity (GPP) and emissions of carbon dioxide (CO2) and methane (CH4). With climate change, warming temperatures could increase GPP within high latitude systems but may also accelerate soil decomposition and CO2 loss. Regional wetting may also shift carbon emissions towards greater CH4 release, a greenhouse gas at least 25 times more potent than CO2. However, an effective framework for monitoring changes in the Arctic net ecosystem carbon balance (NECB) is lacking. Here we introduce an integrated terrestrial carbon flux (TCF) model approach to estimate CO2 and CH4 fluxes from northern peatland and tundra ecosystems at a daily time step. The TCF model framework uses a light-use efficiency (LUE) algorithm to estimate GPP according to satellite NDVI inputs and estimated moisture and temperature constraints. Ecosystem respiration is derived using a three-pool soil organic carbon decomposition model regulated by surface (< 10 cm depth) soil temperature and volumetric moisture inputs. A TCF-CH4 component simulates gas production according to near-surface temperature, anaerobic soil fractions and labile soil carbon inputs derived during model spin-up. Plant transport, soil diffusion and ebullition pathways are used to regulate CH4 emissions into the atmosphere. The combined TCF CO2 and CH4 model was evaluated against tower eddy covariance (EC) flux datasets from six peatland and tundra sites in North America, Eurasia and Greenland. TCF model simulations driven with site information explained on average > 70% (r^2; p < 0.05) of the respective EC record 8-day cumulative CO2 and CH4 fluxes. The TCF results from model simulations using coarser satellite (MODIS 250-m resolution) and reanalysis (MERRA; 1/2 x 2/3° resolution) inputs were more variable, but captured the overall seasonality and magnitude of ecosystem carbon exchange. Model simulations of annual carbon fluxes

  2. Changing Seasonality in the Arctic and its Influences on Biogeochemical Processing in Tundra River Networks

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    One of the primary expressions of climate change in the arctic is a change in "seasonality"; i.e., changes in the timing, duration, and characteristics of the traditional arctic seasons. These changes are most likely to affect temperature and precipitation patterns but will have relatively little effect on the annual light regime. Temperature, precipitation, and light are crucial drivers in any ecosystem and so the potential that the relationships between these three master environmental variables will change in the future has important consequences. Our research addresses how river networks process critical nutrients (C, N, and P) delivered from land as they are transported to coastal zones. We are currently focusing on land-water interactions in headwater streams. As in any ecosystem, temperature strongly influences microbial processing in soils and thus net mineralization of organic nutrients. Nutrients made available by microbial processing in the soil will be used by vegetation as long as the vegetation actively grows. However, active growth by vegetation is highly dependent on the annual light regime, which is not changing substantially. Thus, as arctic seasonality changes there is a growing asynchrony developing between production of nutrients by soil microbes and the demand for nutrients by vegetation, with greater production of nutrients by temperature-dependent microbes than demand by light-dependent vegetation. It is reasonable to expect that the "excess" nutrients produced in this way will migrate to streams and we hypothesize that this seasonal subsidy may strongly influence the structure and function of arctic stream ecosystems. Previous stream research in the arctic largely ignored the spring and fall tail seasons. Preliminary findings indicate that the seasonal asynchrony has profound influences on nutrient concentrations and autotrophic biomass in arctic streams. We expect this to have important influences on key processes such as primary

  3. 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.

  4. Scaling Issues Between Plot and Satellite Radiobrightness Observations of Arctic Tundra

    NASA Technical Reports Server (NTRS)

    Kim, Edward J.; England, Anthony W.; Judge, Jasmeet; Zukor, Dorothy J. (Technical Monitor)

    2000-01-01

    Data from generation of satellite microwave radiometer will allow the detection of seasonal to decadal changes in the arctic hydrology cycle as expressed in temporal and spatial patterns of moisture stored in soil and snow This nw capability will require calibrated Land Surface Process/Radiobrightness (LSP/R) model for the principal terrains found in the circumpolar Arctic. These LSP/R models can than be used in weak constraint. Dimensional Data Assimilation (DDA)of the daily satellite observation to estimate temperature and moisture profiles within the permafrost in active layer.

  5. Circumpolar Arctic vegetation: a hierarchic review and roadmap toward an internationally consistent approach to survey, archive and classify tundra plot data

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Daniëls, F. J. A.; Alsos, I.; Bhatt, U. S.; Breen, A. L.; Buchhorn, M.; Bültmann, H.; Druckenmiller, L. A.; Edwards, M. E.; Ehrich, D.; Epstein, H. E.; Gould, W. A.; Ims, R. A.; Meltofte, H.; Raynolds, M. K.; Sibik, J.; Talbot, S. S.; Webber, P. J.

    2016-05-01

    Satellite-derived remote-sensing products are providing a modern circumpolar perspective of Arctic vegetation and its changes, but this new view is dependent on a long heritage of ground-based observations in the Arctic. Several products of the Conservation of Arctic Flora and Fauna are key to our current understanding. We review aspects of the PanArctic Flora, the Circumpolar Arctic Vegetation Map, the Arctic Biodiversity Assessment, and the Arctic Vegetation Archive (AVA) as they relate to efforts to describe and map the vegetation, plant biomass, and biodiversity of the Arctic at circumpolar, regional, landscape and plot scales. Cornerstones for all these tools are ground-based plant-species and plant-community surveys. The AVA is in progress and will store plot-based vegetation observations in a public-accessible database for vegetation classification, modeling, diversity studies, and other applications. We present the current status of the Alaska Arctic Vegetation Archive (AVA-AK), as a regional example for the panarctic archive, and with a roadmap for a coordinated international approach to survey, archive and classify Arctic vegetation. We note the need for more consistent standards of plot-based observations, and make several recommendations to improve the linkage between plot-based observations biodiversity studies and satellite-based observations of Arctic vegetation.

  6. Influence of grounding ice on the Arctic shelf of Alaska

    USGS Publications Warehouse

    Reimnitz, E.; Barnes, P.; Forgatsch, T.; Rodeick, C.

    1972-01-01

    Alaska's Beaufort Sea shelf is characterized by small-scale relief with an average amplitude of 1-2 m and wavelength of 50-100 m. Diving observations confirm that much of the bottom roughness reflects the action of grounded ice. Except for areas in the shadow of islands, bars, and offshore bathymetric highs, the entire shelf surface from the beach to at least the 75-m contour is now or has been modified by ice gouging. Ice contact with the bottom is more common, and rates of sedimentation higher on the inner shelf than on the outer shelf; the density of gouge features is about equal in both areas. Therefore, the chances are that an area of gouging on the inner shelf contains younger gouges than a similar area on the outer shelf. When ice grounds, it becomes an important agent in the sedimentary and morphologic environment of the Arctic shelf, directly by deforming bottom deposits and secondarily by affecting the current regime near the sediment/ice contact. While bulldozing action and rafting do not seem to contribute significantly to the direct transport of sediment, re-suspension of bottom material during bulldozing, which makes sediment available for transport, may be significant. ?? 1972.

  7. The footprint of Alaskan tundra fires during the past half-century: implications for surface properties and radiative forcing

    USGS Publications Warehouse

    Rocha, Adrian V.; Loranty, Michael M.; Higuera, Phil E.; Mack, Michelle C.; Hu, Feng Sheng; Jones, Benjamin M.; Breen, Amy L.; Rastetter, Edward B.; Goetz, Scott J.; Shaver, Gus R.

    2012-01-01

    Recent large and frequent fires above the Alaskan arctic circle have forced a reassessment of the ecological and climatological importance of fire in arctic tundra ecosystems. Here we provide a general overview of the occurrence, distribution, and ecological and climate implications of Alaskan tundra fires over the past half-century using spatially explicit climate, fire, vegetation and remote sensing datasets for Alaska. Our analyses highlight the importance of vegetation biomass and environmental conditions in regulating tundra burning, and demonstrate that most tundra ecosystems are susceptible to burn, providing the environmental conditions are right. Over the past two decades, fire perimeters above the arctic circle have increased in size and importance, especially on the North Slope, indicating that future wildfire projections should account for fire regime changes in these regions. Remote sensing data and a literature review of thaw depths indicate that tundra fires have both positive and negative implications for climatic feedbacks including a decadal increase in albedo radiative forcing immediately after a fire, a stimulation of surface greenness and a persistent long-term (>10 year) increase in thaw depth. In order to address the future impact of tundra fires on climate, a better understanding of the control of tundra fire occurrence as well as the long-term impacts on ecosystem carbon cycling will be required.

  8. 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.

  9. 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.

  10. Environmental Controls over Peat Accumulation in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Baughman, C. A.; Mann, D. H.; Heiser, P. A.; Kunz, M. L.

    2012-12-01

    Wide spread accumulation of peat (paludification) began on Alaska's North Slope during the Pleistocene/Holocene transition starting ca. 12,000 14C years ago and established this region as a carbon sink. Its status as a C sink is in question today because of rapid climate change. Our project's focus is on the relationship between peat, microclimate, and topography in a portion of the Arctic Foothills 300-350 km south of Point Barrow on the northern flank of the Brooks Range. Our objectives are 1) Quantify how varying microclimate factors found along a climosequence determine the thickness of the thin surface peats (<50 cm) that have developed during the Holocene; 2) Estimate peat accumulation rates on level, initially well-drained geomorphic surfaces using a 3,000 year old chronosequence on river point bars; 3) Quantify how peat accumulation affects soil temperature regimes; 4) Develop a GIS-based peat-prediction model for a 50 km2 study area and estimate this area's pool of standing carbon. We used a combination of remotely sensed data, field measurements, and a GIS to gather data regarding slope, aspect, elevation, near-ground temperature, soil moisture, temperature at the organic/mineral horizon interface, solar radiation, upslope drainage area, and lastly, peat thickness. Peat is defined here as any near-surface soil horizon containing >25% organic carbon by volume. We employ statistical analyses to examine how each factor independently influences peat thickness and what suite of factors best explains peat distribution and thickness across the landscape. Results show a significant inverse relationship (R2 = 0.27, p-value <<.001) between slope and peat thickness, with an increase in steepness accompanying a decrease in peat thickness. There is a less significant relationship (R2 = 0.03, p-value = .02) between aspect and peat thickness. There is a significant positive relationship (R2 = 0.81, P-value <<.001) between peat thickness and July active layer thickness

  11. Environmental Limits of Tall Shrubs in Alaska's Arctic National Parks.

    PubMed

    Swanson, David K

    2015-01-01

    We sampled shrub canopy volume (height times area) and environmental factors (soil wetness, soil depth of thaw, soil pH, mean July air temperature, and typical date of spring snow loss) on 471 plots across five National Park Service units in northern Alaska. Our goal was to determine the environments where tall shrubs thrive and use this information to predict the location of future shrub expansion. The study area covers over 80,000 km2 and has mostly tundra vegetation. Large canopy volumes were uncommon, with volumes over 0.5 m3/m2 present on just 8% of plots. Shrub canopy volumes were highest where mean July temperatures were above 10.5°C and on weakly acid to neutral soils (pH of 6 to 7) with deep summer thaw (>80 cm) and good drainage. On many sites, flooding helped maintain favorable soil conditions for shrub growth. Canopy volumes were highest where the typical snow loss date was near 20 May; these represent sites that are neither strongly wind-scoured in the winter nor late to melt from deep snowdrifts. Individual species varied widely in the canopy volumes they attained and their response to the environmental factors. Betula sp. shrubs were the most common and quite tolerant of soil acidity, cold July temperatures, and shallow thaw depths, but they did not form high-volume canopies under these conditions. Alnus viridis formed the largest canopies and was tolerant of soil acidity down to about pH 5, but required more summer warmth (over 12°C) than the other species. The Salix species varied widely from S. pulchra, tolerant of wet and moderately acid soils, to S. alaxensis, requiring well-drained soils with near neutral pH. Nearly half of the land area in ARCN has mean July temperatures of 10.5 to 12.5°C, where 2°C of warming would bring temperatures into the range needed for all of the potential tall shrub species to form large canopies. However, limitations in the other environmental factors would probably prevent the formation of large shrub canopies

  12. Airborne trace metals and organochlorine compounds in arctic Alaska and Siberia: How important?

    SciTech Connect

    Landers, D.H.; Allen-Gil, S.; Gubala, C.P.; Ford, J.

    1995-12-31

    Metal contaminants of anthropogenic origin identified in the arctic atmosphere and the presence of organochlorines in arctic marine mammal tissues has raised the question of the importance of long-range transport of contaminants to the Arctic. Research focused on arctic regions in Alaska and the Taimyr peninsula of north central Russia. Inland watersheds were examined for evidence of increases in trace metal flux during the past 150 years and the presence of organochlorine compounds. Fish and ground squirrels were examined for body burdens of organic contaminants and plasma biomarkers were examined to evaluate biological effects. Sediment data from several lakes suggest that over broad regions, trace metal fluxes have increased only slightly (< 10%), if at all, since the pre-industrial era. The highest metal concentrations in lake sediments are associated with known elevated geologic sources of metals within the respective watersheds. Organochlorines are present in remote inland arctic ecosystems and are most concentrated in the tissues (e.g. liver) of organisms representing higher trophic levels. Arctic Siberia and Alaska (Taimyr peninsula) are similar with regard to contaminant concentrations. However, lichen and moss data suggest that Pb from Eurasian sources does not reach arctic Alaska. The results indicate that long range, transpolar transport and deposition of trace metals is not a large scale current phenomena in the two study regions. The transport and deposition of organochlorine compounds, however, is occurring but at relatively low levels.

  13. What are the patterns of carbon allocation in Arctic shrub tundra: do species differ?

    NASA Astrophysics Data System (ADS)

    Street, Lorna; Subke, Jens-Arne; Baxter, Robert; Billett, Mike; Dinsmore, Kerry; Lessels, Jason; Wookey, Philip

    2014-05-01

    Arctic "greening" is now a well-accepted phenomenon; multiple lines of evidence suggest that plant productivity has increased, driven by increases in shrub abundance. There is very little understanding, however, of how this "shrubification" will impact biogeochemical cycling, including the allocation and turnover of carbon. Recent research has shown, for example, that greater plant productivity is not necessary associated with greater ecosystem C storage. Proliferation of a number of shrub species has been observed in different regions; for example increased willow growth in Arctic Russia, as opposed to primarily alder expansion in NW Canada, where stem density increased 68 % between 1968 and 2004. The degree to which shrub type will determine the impacts of shrub expansion on the carbon cycle is unknown. We use 13C pulse-labelling to trace the fate of recently photosynthesised carbon in vegetation dominated by two common Arctic shrubs, Betula nana (dwarf birch) and Alnus viridis (green alder) just above the Arctic treeline in NW Canada. We quantify the amount of 13C assimilated, and the proportion of assimilate returned to the atmosphere via respiration versus that allocated to plant tissues. This enables an analysis of the contrasting carbon-use-efficiencies and aboveground versus belowground allocation patterns in the two vegetation types. We use these novel field data to address the hypothesis that belowground C allocation in A. viridis (a symbiotic nitrogen fixing species) is a smaller proportion of total C assimilation, as this species supports less extensive ectomycorrhizal networks compared to B. nana. This is the first tracer study of carbon allocation in N-fixing and non-N-fixing vegetation types in a natural system and provides crucial data for predictive modelling of the Arctic carbon cycle.

  14. 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

  15. Impact of elevated CO2, water table, and temperature changes on CO2 and CH4 fluxes from arctic tundra soils

    NASA Astrophysics Data System (ADS)

    Zona, Donatella; Haynes, Katherine; Deutschman, Douglas; Bryant, Emma; McEwing, Katherine; Davidson, Scott; Oechel, Walter

    2015-04-01

    Large uncertainties still exist on the response of tundra C emissions to future climate due, in part, to the lack of understanding of the interactive effects of potentially controlling variables on C emissions from Arctic ecosystems. In this study we subjected 48 soil cores (without active vegetation) from dominant arctic wetland vegetation types, to a laboratory manipulation of elevated atmospheric CO2, elevated temperature, and altered water table, representing current and future conditions in the Arctic for two growing seasons. To our knowledge this experiment comprised the most extensively replicated manipulation of intact soil cores in the Arctic. The hydrological status of the soil was the most dominant control on both soil CO2 and CH4 emissions. Despite higher soil CO2 emission occurring in the drier plots, substantial CO2 respiration occurred under flooded conditions, suggesting significant anaerobic respirations in these arctic tundra ecosystems. Importantly, a critical control on soil CO2 and CH4 fluxes was the original vascular plant cover. The dissolved organic carbon (DOC) concentration was correlated with cumulative CH4 emissions but not with cumulative CO2 suggesting C quality influenced CH4 production but not soil CO2 emissions. An interactive effect between increased temperature and elevated CO2 on soil CO2 emissions suggested a potential shift of the soils microbial community towards more efficient soil organic matter degraders with warming and elevated CO2. Methane emissions did not decrease over the course of the experiment, even with no input from vegetation. This result indicated that CH4 emissions are not carbon limited in these C rich soils. Overall CH4 emissions represented about 49% of the sum of total C (C-CO2 + C-CH4) emission in the wet treatments, and 15% in the dry treatments, representing a dominant component of the overall C balance from arctic soils.

  16. Polar Gateways Arctic Circle Sunrise Conference 2008, Barrow, Alaska: IHY-IPY Outreach on Exploration of Polar and Icy Worlds in The Solar System

    NASA Astrophysics Data System (ADS)

    Cooper, John F.; Kauristie, K.; Weatherwax, A. T.; Sheehan, G. W.; Smith, R. W.; Sandahl, I.; Østgaard, N.; Chernouss, S.; Moore, M. H.; Peticolas, L. M.; Senske, D. A.; Thompson, B. J.; Tamppari, L. K.; Lewis, E. M.

    2008-09-01

    Polar, heliophysical, and planetary science topics related to the International Heliophysical and Polar Years 2007-2009 were addressed during this circumpolar video conference hosted January 23-29, 2008 at the new Barrow Arctic Research Center of the Barrow Arctic Science Consortium in Barrow, Alaska. This conference was planned as an IHY-IPY event science outreach event bringing together scientists and educational specialists for the first week of sunrise at subzero Arctic temperatures in Barrow. Science presentations spanned the solar system from the polar Sun to Earth, Moon, Mars, Jupiter, Saturn, and the Kuiper Belt. On-site participants experienced look and feel of icy worlds like Europa and Titan by being in the Barrow tundra and sea ice environment and by going "on the ice" during snowmobile expeditions to the near-shore sea ice environment and to Point Barrow, closest geographic point in the U.S. to the North Pole. Many science presentations were made remotely via video conference or teleconference from Sweden, Norway, Russia, Canada, Antarctica, and the United States, spanning up to thirteen time zones (Alaska to Russia) at various times. Extensive educational outreach activities were conducted with the local Barrow and Alaska North Slope communities and through the NASA Digital Learning Network live from the "top of the world" at Barrow. The Sun-Earth Day team from Goddard, and a videographer from the Passport to Knowledge project, carried out extensive educational interviews with many participants and native Inupiaq Eskimo residents of Barrow. Video and podcast recordings of selected interviews are available at http://sunearthday.nasa.gov/2008/multimedia/podcasts.php. Excerpts from these and other interviews will be included in a new high definition video documentary called "From the Sun to the Stars: The New Science of Heliophysics" from Passport to Knowledge that will later broadcast on NASA TV and other educational networks. Full conference

  17. Polar Gateways Arctic Circle Sunrise Conference 2008, Barrow, Alaska: IHY-IPY Outreach on Exploration of Polar and Icy Worlds in the Solar System

    NASA Technical Reports Server (NTRS)

    Cooper, John F.; Kauristie, Kirsti; Weatherwax, Allan T.; Sheehan, Glenn W.; Smith, Roger W.; Sandahl, Ingrid; Ostgaard, Nikolai; Chernouss, Sergey; Thompson, Barbara J.; Peticolas, Laura; Moore, Marla H.; Senske, David A.; Tamppari, Leslie K.; Lewis, Elaine M.

    2008-01-01

    Polar, heliophysical, and planetary science topics related to the International Heliophysical and Polar Years 2007-2009 were addressed during this circumpolar video conference hosted January 23-29, 2808 at the new Barrow Arctic Research Center of the Barrow Arctic Science Consortium in Barrow, Alaska. This conference was planned as an IHY-IPY event science outreach event bringing together scientists and educational specialists for the first week of sunrise at subzero Arctic temperatures in Barrow. Science presentations spanned the solar system from the polar Sun to Earth, Moon, Mars, Jupiter, Saturn, and the Kuiper Belt. On-site participants experienced look and feel of icy worlds like Europa and Titan by being in the Barrow tundra and sea ice environment and by going "on the ice" during snowmobile expeditions to the near-shore sea ice environment and to Point Barrow, closest geographic point in the U.S. to the North Pole. Many science presentations were made remotely via video conference or teleconference from Sweden, Norway, Russia, Canada, Antarctica, and the United States, spanning up to thirteen time zones (Alaska to Russia) at various times. Extensive educational outreach activities were conducted with the local Barrow and Alaska North Slope communities and through the NASA Digital Learning Network live from the "top of the world" at Barrow. The Sun- Earth Day team from Goddard, and a videographer from the Passport to Knowledge project, carried out extensive educational interviews with many participants and native Inupiaq Eskimo residents of Barrow. Video and podcast recordings of selected interviews are available at http://sunearthday.nasa.gov/2008/multimedidpodcasts.php. Excerpts from these and other interviews will be included in a new high definition video documentary called "From the Sun to the Stars: The New Science of Heliophysics" from Passport to Knowledge that will later broadcast on NASA TV and other educational networks. Full conference

  18. Siberian Origins of Neoproterozoic to Upper Triassic Rocks of Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Clough, J. G.; Blodgett, R. B.

    2007-12-01

    Evidence for a connection of the Arctic Alaska plate (including Chukotka) with Siberia from Cambrian until Late Triassic time can be made on the basis of paleobiogeography. Arctic Alaska contains a number of biogeographically distinctive megafossils for select time intervals, notably the Middle Cambrian, Early and Late Ordovician, Early and Middle Devonian, Mississippian, and Late Triassic. Middle Cambrian trilobites are strictly Siberian in affinity, but also show close affinities with coeval trilobites from the Farewell terrane of SW Alaska. Late Ordovician brachiopods, gastropods, trilobites, and ostracodes are known from the Shublik Mountains, NE Brooks Range and York Mountains of the Seward Peninsula. Affinities are likewise primarily with Siberia (sharing the primarily Siberian pentameroid brachiopod genera Tcherskidium and Eoconchidium and the strictly Siberian trilobite genus Monorakos), but also with the Farewell terrane. Late Early Devonian and Middle Devonian brachiopods and calcareous green algae from Arctic Alaska are similarly allied with Siberia and the Farewell and Alexander terranes of southern Alaska. Early Mississippian faunas from the lower part of the Lisburne Group and underlying Endicott Group contain relatively widespread fauna, including taxa recognized both in North America and Eurasia, consistent with the relatively cosmopolitan paleobiogeographic conditions of this interval. However, Late Mississippian brachiopod fauna from the upper part of the Lisburne Group contain many brachiopods of strictly Eurasian affinities, notably the gigantoproductids, which are unknown in cratonic North America, but widespread across Eurasia and even North Africa. Late Mississippian lycopods from this terrane have previously been noted as demonstrating strong Angaran affinities. Permian faunas of Arctic Alaska show strong affinities as well with the Siberian Arctic, virtually lacking any fusilinids and reefal buildups, which in contradistinction are commonly

  19. 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

  20. Carbon balance of Arctic tundra under increased snow cover mediated by a plant pathogen

    NASA Astrophysics Data System (ADS)

    Olofsson, Johan; Ericson, Lars; Torp, Mikaela; Stark, Sari; Baxter, Robert

    2011-07-01

    Climate change is affecting plant community composition and ecosystem structure, with consequences for ecosystem processes such as carbon storage. Climate can affect plants directly by altering growth rates, and indirectly by affecting predators and herbivores, which in turn influence plants. Diseases are also known to be important for the structure and function of food webs. However, the role of plant diseases in modulating ecosystem responses to a changing climate is poorly understood. This is partly because disease outbreaks are relatively rare and spatially variable, such that that their effects can only be captured in long-term experiments. Here we show that, although plant growth was favoured by the insulating effects of increased snow cover in experimental plots in Sweden, plant biomass decreased over the seven-year study. The decline in biomass was caused by an outbreak of a host-specific parasitic fungus, Arwidssonia empetri, which killed the majority of the shoots of the dominant plant species, Empetrum hermaphroditum, after six years of increased snow cover. After the outbreak of the disease, instantaneous measurements of gross photosynthesis and net ecosystem carbon exchange were significantly reduced at midday during the growing season. Our results show that plant diseases can alter and even reverse the effects of a changing climate on tundra carbon balance by altering plant composition.

  1. Den use by arctic foxes (Alopex lagopus) in a subarctic region of western Alaska

    USGS Publications Warehouse

    Anthony, R.M.

    1996-01-01

    Distribution, abundance, and use of arctic fox dens located in coastal tundra communities of the Yukon-Kuskokwim delta were determined in studies from 1985 to 1990. Dens were denser and less complex than those described in studies conducted above the Arctic Circle. Eighty-three dens of varying complexity were found in the 52-km2 study area. Nineteen dens were used by arctic foxes for whelping or rearing pups. Three females relocated litters to multiple dens; a maximum of four dens were used concurrently by pups from one litter. Although red foxes were common in the region, their use of dens in the study area was minimal. Differences in vegetation at den sites and nearby unoccupied sites were minimal. Furthermore, den sites could not be distinguished from non-den sites during aerial surveys.

  2. The Arctic National Wildlife Refuge: An Interdisciplinary Unit.

    ERIC Educational Resources Information Center

    Thieman, Gayle; Geil, Mike

    This paper presents a set of interdisciplinary lessons for teaching about the Arctic National Wildlife Refuge (Alaska). Lessons include a petroleum product treasure hunt, an examination of life without petroleum, the development of a wildlife poster, an exploration of the tundra ecosystem and the plants and animals that live there, identification…

  3. Phytomass, LAI, and NDVI in northern Alaska: Relationships to summer warmth, soil pH, plant functional types, and extrapolation to the circumpolar Arctic

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Epstein, H. E.; Jia, G. J.; Balser, A.; Copass, C.; Edwards, E. J.; Gould, W. A.; Hollingsworth, J.; Knudson, J.; Maier, H. A.; Moody, A.; Raynolds, M. K.

    2003-01-01

    We examined the effects of summer warmth on leaf area index (LAI), total aboveground phytomass (TAP), and normalized difference vegetation index (NDVI) across the Arctic bioclimate zone in Alaska and extrapolated our results to the circumpolar Arctic. Phytomass, LAI, and within homogeneous areas of vegetation on acidic and nonacidic soils were regressed against the total summer warmth index (SWI) at 12 climate stations in northern Alaska (SWI = sum of mean monthly temperatures greater than 0°C). SWI varies from 9°C at Barrow to 37°C at Happy Valley. A 5°C increase in the SWI is correlated with about a 120 g m-2 increase in the aboveground phytomass for zonal vegetation on acidic sites and about 60 g m-2 on nonacidic sites. Shrubs account for most of the increase on acidic substrates, whereas mosses account for most of the increase on nonacidic soils. LAI is positively correlated with SWI on acidic sites but not on nonacidic sites. The NDVI is positively correlated with SWI on both acidic and nonacidic soils, but the NDVI on nonacidic parent material is consistently lower than the NDVI on acidic substrates. Extrapolation to the whole Arctic using a five-subzone zonation approach to stratify the circumpolar NDVI and phytomass data showed that 60% of the aboveground phytomass is concentrated in the low-shrub tundra (subzone 5), whereas the high Arctic (subzones 1-3) has only 9% of the total. Estimated phytomass densities in subzones 1-5 are 47, 256, 102, 454, and 791 g m-2, respectively. Climate warming will likely result in increased phytomass, LAI, and NDVI on zonal sites. These changes will be most noticeable in acidic areas with abundant shrub phytomass.

  4. Facies patterns and conodont biogeography in Arctic Alaska and the Canadian Arctic Islands: Evidence against juxtaposition of these areas during early Paleozoic time

    USGS Publications Warehouse

    Dumoulin, J.A.; Harris, A.G.; Bradley, D.C.; De Freitas, T. A.

    2000-01-01

    Differences in lithofacies and biofacies suggest that lower Paleozoic rocks now exposed in Arctic Alaska and the Canadian Arctic Islands did not form as part of a single depositional system. Lithologic contrasts are noted in shallow- and deep-water strata and are especially marked in Ordovician and Silurian rocks. A widespread intraplatform basin of Early and Middle Ordovician age in northern Alaska has no counterpart in the Canadian Arctic, and the regional drowning and backstepping of the Silurian shelf margin in Canada has no known parallel in northern Alaska. Lower Paleozoic basinal facies in northern Alaska are chiefly siliciclastic, whereas resedimented carbonates are volumetrically important in Canada. Micro- and macrofossil assemblages from northern Alaska contain elements typical of both Siberian and Laurentian biotic provinces; coeval Canadian Arctic assemblages contain Laurentian forms but lack Siberian species. Siberian affinities in northern Alaskan biotas persist from at least Middle Cambrian through Mississippian time and appear to decrease in intensity from present-day west to east. Our lithologic and biogeographic data are most compatible with the hypothesis that northern Alaska-Chukotka formed a discrete tectonic block situated between Siberia and Laurentia in early Paleozoic time. If Arctic Alaska was juxtaposed with the Canadian Arctic prior to opening of the Canada basin, biotic constraints suggest that such juxtaposition took place no earlier than late Paleozoic time.

  5. 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.

  6. Contrasting denitrifier communities relate to contrasting N2O emission patterns from acidic peat soils in arctic tundra

    PubMed Central

    Palmer, Katharina; Biasi, Christina; Horn, Marcus A

    2012-01-01

    Cryoturbated peat circles (that is, bare surface soil mixed by frost action; pH 3–4) in the Russian discontinuous permafrost tundra are nitrate-rich ‘hotspots' of nitrous oxide (N2O) emissions in arctic ecosystems, whereas adjacent unturbated peat areas are not. N2O was produced and subsequently consumed at pH 4 in unsupplemented anoxic microcosms with cryoturbated but not in those with unturbated peat soil. Nitrate, nitrite and acetylene stimulated net N2O production of both soils in anoxic microcosms, indicating denitrification as the source of N2O. Up to 500 and 10 μ nitrate stimulated denitrification in cryoturbated and unturbated peat soils, respectively. Apparent maximal reaction velocities of nitrite-dependent denitrification were 28 and 18 nmol N2O gDW−1 h−1, for cryoturbated and unturbated peat soils, respectively. Barcoded amplicon pyrosequencing of narG, nirK/nirS and nosZ (encoding nitrate, nitrite and N2O reductases, respectively) yielded ≈49 000 quality-filtered sequences with an average sequence length of 444 bp. Up to 19 species-level operational taxonomic units were detected per soil and gene, many of which were distantly related to cultured denitrifiers or environmental sequences. Denitrification-associated gene diversity in cryoturbated and in unturbated peat soils differed. Quantitative PCR (inhibition-corrected per DNA extract) revealed higher copy numbers of narG in cryoturbated than in unturbated peat soil. Copy numbers of nirS were up to 1000 × higher than those of nirK in both soils, and nirS nirK−1 copy number ratios in cryoturbated and unturbated peat soils differed. The collective data indicate that the contrasting N2O emission patterns of cryoturbated and unturbated peat soils are associated with contrasting denitrifier communities. PMID:22134649

  7. Multi-annual Turbulent Energy Fluxes in the Lena River Delta: Eddy Covariance and Remote Sensing in Siberian Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Runkle, B.; Wille, C.; Langer, M.; Boike, J.; Sachs, T.; Pfeiffer, E. M.; Kutzbach, L.

    2015-12-01

    Evapotranspiration (ET) is a key component of the energy and water balances in permafrost tundra, establishing hydrological conditions for the next year and controlling several aspects of the carbon cycle. Both the energy balance and hydrological conditions of the landscape surface are important drivers of how Arctic climate change will impact landscape processes, including the carbon feedback. The accurate measurement of evapotranspiration within an energy balance context therefore provides crucial information on ecosystem functioning and raises our predictive capacity for estimating the impact of climate change. In this study we report field measurements from 13 summers (2002-14) using the eddy covariance method in a lowland ice-wedge polygon landscape within Russia's Lena River Delta. These time-series are gap-filled and extrapolated with both statistical and process-based models to generate estimates of growing season ET. We find that interannual differences - including two August periods with high ET and two with low ET - are locally driven more by changes in air temperature and vapor pressure deficit (VPD) than in land surface characteristics or radiation. Except for periods of high VPD, aerodynamic resistance was greater than canopy surface resistance. We explore predictive relationships between various land surface indicators (e.g., NDVI, LAI, LST, Growing season length) derived from remote sensing products (MODIS) to quantify local mechanisms necessary for upscaling to the Delta region. Nighttime land surface temperature (MODIS) is found to be a strong predictor of evaporative flux at weekly to monthly time scales. Contrary to expectations resulting from climate change studies, we do not see evidence of a sustained interannual trend in ET or sensible heat flux. We conclude with implications for the local energy balance and responses to changes in sea ice extent and a warming climate.

  8. Coupled Monitoring and Inverse Modeling to Investigate Surface - Subsurface Hydrological and Thermal Dynamics in the Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Tran, A. P.; Dafflon, B.; Hubbard, S. S.; Bisht, G.; Peterson, J.; Ulrich, C.; Romanovsky, V. E.; Kneafsey, T. J.; Wu, Y.

    2015-12-01

    Quantitative characterization of the soil surface-subsurface hydrological and thermal processes is essential as they are primary factors that control the biogeochemical processes, ecological landscapes and greenhouse gas fluxes. In the Artic region, the surface-subsurface hydrological and thermal regimes co-interact and are both largely influenced by soil texture and soil organic content. In this study, we present a coupled inversion scheme that jointly inverts hydrological, thermal and geophysical data to estimate the vertical profiles of clay, sand and organic contents. Within this inversion scheme, the Community Land Model (CLM4.5) serves as a forward model to simulate the land-surface energy balance and subsurface hydrological-thermal processes. Soil electrical conductivity (from electrical resistivity tomography), temperature and water content are linked together via petrophysical and geophysical models. Particularly, the inversion scheme accounts for the influences of the soil organic and mineral content on both of the hydrological-thermal dynamics and the petrophysical relationship. We applied the inversion scheme to the Next Generation Ecosystem Experiments (NGEE) intensive site in Barrow, AK, which is characterized by polygonal-shaped arctic tundra. The monitoring system autonomously provides a suite of above-ground measurements (e.g., precipitation, air temperature, wind speed, short-long wave radiation, canopy greenness and eddy covariance) as well as below-ground measurements (soil moisture, soil temperature, thaw layer thickness, snow thickness and soil electrical conductivity), which complement other periodic, manually collected measurements. The preliminary results indicate that the model can well reproduce the spatiotemporal dynamics of the soil temperature, and therefore, accurately predict the active layer thickness. The hydrological and thermal dynamics are closely linked to the polygon types and polygon features. The results also enable the

  9. Evaluation of a Thermodynamically Based Soil Microbial Decomposition Model Based on a 13c Tracer Study in Arctic Tundra Soils

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Tang, J.; Riley, W. J.; Wallenstein, M. D.; Cotrufo, M. F.; Machmuller, M. B.; Lynch, L.

    2014-12-01

    The incorporation of explicit representation of biological complexity in soil carbon decomposition models may improve our ability to accurately predict terrestrial carbon-climate feedbacks. A new generation of microbe-explicit soil decomposition models (MEMs) are being developed that represent soil biological complexity, but only a few take into account detailed biotic and abiotic components and competitive interactions in the complex soil system. In view of this, we have developed a thermodynamically based MEM with a detailed component network (polymeric organic carbon, dissolved organic carbon, microbes, extracellular enzymes, and mineral surfaces), in which competitive interactions and microbial metabolism are modeled using Equilibrium Chemistry Approximation kinetics and Dynamic Energy Budget theory, respectively. The model behavior has been tested and is qualitatively consistent with many empirical studies, but further evaluation of the model with field or lab experimental data in specific ecosystems is needed. Stable carbon isotope (13C) tracer experiments provide a means to directly evaluate soil carbon dynamics simulated by MEMs. In this study, we further develop the model to explicitly account for different carbon isotopes, including 13C and 14C. Isotopic fractionations in soil decomposition processes, including soil organic matter transformations and microbial metabolism, are considered. The 13C signals of different soil components derived from a 13C tracer experiment in Arctic tundra soils are used to test the model behavior and identify needed parametric and structural improvements. Our modeling and data comparison identify several key mechanisms that need to be included in MEMs. Finally, we present an analysis of the relative benefits and costs of additional complexity in MEMs compared to traditional pool-based modeling structures.

  10. Effects of 45 Years of Heavy Road Traffic and Infrastructure on Permafrost and Tundra at Prudhoe Bay, Alaska

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Buchhorn, M.; Raynolds, M. K.; Kanevskiy, M. Z.; Matyshak, G. V.; Shur, Y.; Peirce, J.

    2015-12-01

    The upper permafrost of the Prudhoe Bay Oilfield, the largest oil field in both the United States and in North America, contains significant amounts of excess ground ice, mainly in ice wedges. An increase in infrastructure development and road traffic since the initial development of the Prudhoe Bay Oilfield in 1968 has resulted in extensive flooding, accumulation of road dust, and roadside snowbanks, all of which affect the vegetation and alter the thermal properties of the ground surface. As part of the NSF's Arctic Science, Engineering, and Education for Sustainability (ArcSEES) project, we established four transects in 2014 and 2015 to document the effects of infrastructure and heavy road traffic on adjacent tundra. Two transects were established perpendicular to the Prudhoe Bay Spine Road north of Lake Colleen and two perpendicular to the Dalton Highway next to the Deadhorse airstrip. Prior to infrastructure development in 1949, rather homogeneous networks of low-centered polygons with less than 30 cm of trough-rim elevation contrast covered both locations. We present the detailed results of vegetation analysis, ice-core drilling, and extensive topographic surveys along the transects. A time series of aerial photographs from 1949 to 2014 (yearly since 1969) documents the changing landscapes in relationship to the record of air-temperature, active layer depths, and permafrost temperatures at Deadhorse. Flooding, road dust, and snow drifts have all contributed to creating warmer soil temperatures and deeper active layers near the road. These factors have all contributed in different ways to alteration of the plant canopy. The altered plant canopies in turn further altered the surface albedo and the ground temperatures. Historical photos indicate that between 1989 and 2012 a regional thawing of the ice-wedges occurred, increasing the extent of thermokarst. Our analysis demonstrates the cumulative effects of infrastructure-related and climate-related factors to

  11. A methane flux transect along the trans-Alaska pipeline haul road

    NASA Technical Reports Server (NTRS)

    Whalen, S. C.; Reeburgh, W. S.

    1990-01-01

    This paper reports and analyzes methane flux measurements made during the summer of 1987 at 10 km intervals along a north-south direction from Prudhoe Bay to the Arctic Circle in Alaska. Mean CH4 flux from the arctic tundra was 52 mg/sq m/d while that from high-latitude taiga was 11 mg/sq m/d. Fluxes in mg/sq m/d for various plant communities were: wet tundra, 90; low brush-muskeg bog, 45; moist tundra, 31; freshwater ponds, 21; spruce forest, 4.6; and alpine tundra, 0.6. Annual CH4 emission from global tundra and taiga environments is estimated at 38 Tg and 15 Tg, respectively. This is about 46 percent of the wetland emission term of 10 percent of the global atmospheric input.

  12. Isotopic and Geochemical signatures of different aged drained thaw lake basins (DTLBs) and drainage channels in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Throckmorton, H.; Perkins, G.; Rearick, M.; Altmann, G. L.; Cohen, L. R.; Hudak, M.; Gard, M.; Newman, B. D.; Heikoop, J. M.; Wilson, C. J.

    2013-12-01

    The Arctic tundra contains a vast amount of C stored in permafrost soils, which are highly susceptible to thawing with climate change. Permafrost degradation has implications for land-atmosphere feedbacks through the release of stored C as greenhouse gases (CO2, methane), and runoff of dissolved C. Coastal Arctic topography and geomorphology in particular is highly complex, consisting of irregular polygonal ground features, drainage channel networks, and different aged drained thaw lake basins (DTLBs). Such substantial spatial variability complicates predictions of permafrost degradation with regard to land-atmosphere feedbacks affecting climate and regional ecosystem responses. The DOE Office of Science Biological and Environmental Research Program has funded the Next Generation Ecosystem Experiment (NGEE) Arctic project to assess the release of greenhouse gases from melting Arctic permafrost, with emphasis on regional geomorphology; and to establish a coordinated effort among several research institutions to link field observations with process-based Land models. Results will focus on geochemical and isotopic signatures of waters collected at different depths (surface; from the shallow organic layer; and from the deeper frost table) in Barrow, Alaska in July and September of 2013. Sampling sites were stationed across distinct microtopographic features, including polygonal terrain, different aged DTLBs, and larger drainage channels. The aims of these field campaigns were to assess geochemical and biogeochemical trends and isotopic variability in waters across unique micro-topographic features and with depth, and infer vertical and lateral flows of water and C by collecting field data to validate large-scale regional models. Preliminary results showed some differences with depth and across unique micro-topographic features. Redox indicators (Fe2+ and dissolved oxygen) showed greater reducing conditions with depth, as was expected. In particular, subsurface waters

  13. Changing arctic ecosystems—What is causing the rapid increase of snow geese in northern Alaska?

    USGS Publications Warehouse

    Hupp, Jerry W.; Ward, David H.; Whalen, Mary E.; Pearce, John M.

    2015-01-01

    Through the Changing Arctic Ecosystems (CAE) initiative, the U.S. Geological Survey (USGS) informs key resource management decisions for Arctic Alaska by providing scientific information on current and future ecosystem response to a warming climate. The Arctic Coastal Plain (ACP) of northern Alaska is a key study area within the USGS CAE initiative. This region has experienced a warming trend over the past decades, leading to decreased sea ice, permafrost thaw, and an advancement of spring phenology. The number of birds on the ACP also is changing, marked by increased populations of the four species of geese that nest in the region. The Snow Goose (Chen caerulescens) is the most rapidly increasing of these species. USGS CAE research is quantifying these changes and their implications for management agencies.

  14. The Infuence of Physical Variables on Whole-Stream Metabolism in an Arctic Tundra River

    NASA Astrophysics Data System (ADS)

    Cappelletti, C. K.; Bowden, W.

    2005-05-01

    We examined the influence of light, temperature, nutrients, and discharge on whole-stream metabolism (WSM) in three experimental reaches of the Kuparuk River, Alaska, using the open-system, single-station method. Ambient PO4 levels in the reference reach were ~0.05μM, while addition of phosphoric acid since 1983 in the fertilized reach and since 2004 in the ultra-fertilized reach increased PO4 levels to ~0.30μM and ~0.90μM, respectively. Among all reaches, gross primary production (GPP) was positively correlated with light, temperature, and PO4 and negatively correlated with discharge. Temperature explained most of the variance in GPP. Among all reaches, community respiration (CR) was weakly correlated with light, temperature, PO4, and discharge. However, CR showed a greater response to temperature in the fertilized reaches. Benthic respiration by mosses in the fertilized reaches responds to temperature while heterotrophic respiration in the hyporheic zone is similar in all reaches and does not respond to temperature due to thermal buffering. Light, temperature, and discharge were moderately intercorrelated. An Information-Theoretic approach using Akaike's Information Criterion (AIC) was used to examine the relative importance of each physical variable on WSM and to develop a photosynthesis model.

  15. Pathways and transformations of dissolved methane and dissolved inorganic carbon in Arctic tundra soils: Evidence from analysis of stable isotopes

    NASA Astrophysics Data System (ADS)

    Throckmorton, H.; Perkins, G.; Muss, J. D.; Smith, L. J.; Conrad, M. E.; Torn, M. S.; Heikoop, J. M.; Newman, B. D.; Wilson, C. J.; Wullschleger, S. D.

    2014-12-01

    Arctic soils contain a large pool of terrestrial C and are of great interest because of their potential for releasing significant amounts of carbon dioxide (CO2) and methane (CH4) to the atmosphere. Few attempts have been made, however, to derive quantitative budgets of CO2 and CH4 budgets for high-latitude ecosystems. Therefore, this study used naturally occurring geochemical and isotopic tracers to estimate production pathways and transformations of dissolved inorganic carbon (DIC = Σ (total) dissolved CO2) and dissolved CH4 in soil pore waters from 17 locations (drainages) in Barrow, Alaska (USA) in July and September, 2013; and to approximate a complete balance of belowground C cycling at our sampling locations. Results suggest that CH4 was primarily derived from biogenic acetate fermentation, with a shift at 4 locations from July to September towards CO2 reduction as the dominant methanogenic pathway. A large majority of CH4 produced at the frost table methane was transferred directly to the atmosphere via plant roots and ebullition (94.0 ± 1.4% and 96.6 ± 5.0% in July and September). A considerable fraction of the remaining CH4 was oxidized to CO2 during upward diffusion in July and September, respectively. Methane oxidization produced <1% of CO2 relative to alternative production mechanisms in deep subsurface pore waters. The majority of subsurface CO2 was produced from anaerobic respiration, likely due to reduction of Fe oxides and humics (52 ± 6 to 100 ± 13%, on average) while CO2 produced from methanogenesis accounted for the remainder (0 ± 13% to 47 ± 6%, on average) for July and September, respectively. Dissolved CH4 and dissolved CO2 concentrations correlated with thaw depth, suggesting that Arctic ecosystems will likely produce and release a greater amount of greenhouse gasses under projected warming and deepening of active layer thaw depth under future climate change scenarios.

  16. Pathways and transformations of dissolved methane and dissolved inorganic carbon in Arctic tundra watersheds: Evidence from analysis of stable isotopes

    DOE PAGESBeta

    Throckmorton, Heather M.; Heikoop, Jeffrey M.; Newman, Brent D.; Altmann, Garrett L.; Conrad, Mark S.; Muss, Jordan D.; Perkins, George B.; Smith, Lydia J.; Torn, Margaret S.; Wullschleger, Stan D.; et al

    2015-11-08

    Arctic soils contain a large pool of terrestrial C and are of interest due to their potential for releasing significant carbon dioxide (CO2) and methane (CH4) to the atmosphere. Due to substantial landscape heterogeneity, predicting ecosystem-scale CH4 and CO2 production is challenging. This study assessed dissolved inorganic carbon (DIC = Σ (total) dissolved CO2) and CH4 in watershed drainages in Barrow, Alaska as critical convergent zones of regional geochemistry, substrates, and nutrients. In July and September of 2013, surface waters and saturated subsurface pore waters were collected from 17 drainages. Based on simultaneous DIC and CH4 cycling, we synthesized isotopicmore » and geochemical methods to develop a subsurface CH4 and DIC balance by estimating mechanisms of CH4 and DIC production and transport pathways and oxidation of subsurface CH4. We observed a shift from acetoclastic (July) toward hydrogenotropic (September) methanogenesis at sites located toward the end of major freshwater drainages, adjacent to salty estuarine waters, suggesting an interesting landscape-scale effect on CH4 production mechanism. The majority of subsurface CH4 was transported upward by plant-mediated transport and ebullition, predominantly bypassing the potential for CH4 oxidation. Thus, surprisingly, CH4 oxidation only consumed approximately 2.51± 0.82% (July) and 0.79 ± 0.79% (September) of CH4 produced at the frost table, contributing to <0.1% of DIC production. DIC was primarily produced from respiration, with iron and organic matter serving as likely e- acceptors. Furthermore, this work highlights the importance of spatial and temporal variability of CH4 production at the watershed scale and suggests broad scale investigations are required to build better regional or pan-Arctic representations of CH4 and CO2 production.« less

  17. Pathways and transformations of dissolved methane and dissolved inorganic carbon in Arctic tundra watersheds: Evidence from analysis of stable isotopes

    NASA Astrophysics Data System (ADS)

    Throckmorton, Heather M.; Heikoop, Jeffrey M.; Newman, Brent D.; Altmann, Garrett L.; Conrad, Mark S.; Muss, Jordan D.; Perkins, George B.; Smith, Lydia J.; Torn, Margaret S.; Wullschleger, Stan D.; Wilson, Cathy J.

    2015-11-01

    Arctic soils contain a large pool of terrestrial C and are of interest due to their potential for releasing significant carbon dioxide (CO2) and methane (CH4) to the atmosphere. Due to substantial landscape heterogeneity, predicting ecosystem-scale CH4 and CO2 production is challenging. This study assessed dissolved inorganic carbon (DIC = Σ (total) dissolved CO2) and CH4 in watershed drainages in Barrow, Alaska as critical convergent zones of regional geochemistry, substrates, and nutrients. In July and September of 2013, surface waters and saturated subsurface pore waters were collected from 17 drainages. Based on simultaneous DIC and CH4 cycling, we synthesized isotopic and geochemical methods to develop a subsurface CH4 and DIC balance by estimating mechanisms of CH4 and DIC production and transport pathways and oxidation of subsurface CH4. We observed a shift from acetoclastic (July) toward hydrogenotropic (September) methanogenesis at sites located toward the end of major freshwater drainages, adjacent to salty estuarine waters, suggesting an interesting landscape-scale effect on CH4 production mechanism. The majority of subsurface CH4 was transported upward by plant-mediated transport and ebullition, predominantly bypassing the potential for CH4 oxidation. Thus, surprisingly, CH4 oxidation only consumed approximately 2.51 ± 0.82% (July) and 0.79 ± 0.79% (September) of CH4 produced at the frost table, contributing to <0.1% of DIC production. DIC was primarily produced from respiration, with iron and organic matter serving as likely e- acceptors. This work highlights the importance of spatial and temporal variability of CH4 production at the watershed scale and suggests broad scale investigations are required to build better regional or pan-Arctic representations of CH4 and CO2 production.

  18. 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

  19. Spatial and Temporal Variability of Methane Mole Fractions and Exchanges in and Between Soil, Snow, and the Atmosphere in a Tundra System in Northern Alaska

    NASA Astrophysics Data System (ADS)

    Agnan, Y.; Obrist, D.; Edwards, G. C.; Moore, C.; Hedge, C.; Helmig, D.; Paxton, D.; Jacques, H.

    2015-12-01

    An important global source of atmospheric methane (CH4) is production in tundra soils (an important global source). To place constraints on the potential role that tundra soils play in global CH4 cycling, we have been continuously measuring mole the air space in soils, snow, and the atmosphere as gradient-based surface-atmosphere fluxes for arctic tundra at Toolik Field Station (68° 38' N) starting in October 2014. We have found that atmospheric CH4 mole fractions were, on average, relatively constant during the first 9 months of sampling (averaging 1.93 µmol mol-1), with pronounced diel patterns starting in May and nighttime exceeding daytime mole fractions. However, gradients measured within the soil profile showed high variability in air withdrawn from different locations of these tundra soils (Typic Aquiturbels), with one soil profile indicating a CH4 sink during fall until January; mole fractions were similar to the atmospheric measurements during winter indicating no source or sink (average 1.89 µmol mol-1). A second soil profile 5 m away showed production of CH4 (average 2.48 µmol mol-1, two-times higher than atmospheric levels), even during mid-winter when soil temperatures were below -10 °C. Measurements of CH4 in interstitial snowpack air also exhibited a similar combination of sources and sinks. We used micrometeorological gradient surface flux measurements to confirm that the area was a net source of CH4 in fall, winter, and spring, with emissions averaging 26.6, 25.2, and 16.8 mg m-2 d-1, respectively. In the summer months, we saw strong diel flux patterns with deposition during day and emission at night, corresponding with observed diel variability in CH4 snowpack mole fractions. Our results indicated a high variability of tundra landscape CH4 fluxes, which locally shift from sources to sinks with high temporal variability. CH4 oxidation by methanotrophic bacteria probably occurs in tundra soils, confirming observations in one soil, snowpack, and

  20. CO2, CH4, and DOC Flux During Long Term Thaw of High Arctic Tundra

    NASA Astrophysics Data System (ADS)

    Stackhouse, B. T.; Vishnivetskaya, T. A.; Layton, A.; Bennett, P.; Mykytczuk, N.; Lau, C. M.; Whyte, L.; Onstott, T. C.

    2013-12-01

    Arctic regions are expected to experience temperature increases of >4° C by the end of this century. This warming is projected to cause a drastic reduction in the extent of permafrost at high northern latitudes, affecting an estimated 1000 Pg of SOC in the top 3 m. Determining the effects of this temperature change on CO2 and CH4 emissions is critical for defining source constraints to global climate models. To investigate this problem, 18 cores of 1 m length were collected in late spring 2011 before the thawing of the seasonal active layer from an ice-wedge polygon near the McGill Arctic Research Station (MARS) on Axel Heiberg Island, Nunavut, Canada (N79°24, W90°45). Cores were collected from acidic soil (pH 5.5) with low SOC (~1%), summertime active layer depth between 40-70 cm (2010-2013), and sparse vegetation consisting primarily of small shrubs and sedges. Cores were progressively thawed from the surface over the course of 14 weeks to a final temperature of 4.5° C and held at that temperature for 15 months under the following conditions: in situ water saturation conditions versus fully water saturated conditions using artificial rain fall, surface light versus no surface light, cores from the polygon edge, and control cores with a permafrost table maintained at 70 cm depth. Core headspaces were measured weekly for CO2, CH4, H2, CO, and O2 flux during the 18 month thaw experiment. After ~20 weeks of thawing maximum, CO2 flux for the polygon edge and dark treatment cores were 3.0×0.7 and 1.7×0.4 mmol CO2 m-2 hr-1, respectively. The CO2 flux for the control, saturated, and in situ saturation cores reached maximums of 0.6×0.2, 0.9×0.5, and 0.9×0.1 mmol CO2 m-2 hr-1, respectively. Field measurements of CO2 flux from an adjacent polygon during the mid-summer of 2011 to 2013 ranged from 0.3 to 3.7 mmol CO2 m-2 hr-1. Cores from all treatments except water saturated were found to consistently oxidize CH4 at ~atmospheric concentrations (2 ppmv) with a maximum

  1. HEAVY METAL, ORGANOCHLORINE PESTICIDE AND POLYCHLORINATED BIPHENYL CONTAMINATION IN ARCTIC GROUND SQUIRRELS (SPERMOPHILUS PARRYI) IN NORTHERN ALASKA

    EPA Science Inventory

    Heavy metal and organochlorine (OC)concentrations, including organochlorine pesticides and polychlorinated biphenyl congeners (PCBs), were determined in arctic ground squirrels (Spermophilus parryi) from three sites in the Brooks Range of northern Alaska in 1991-93. Heavy metals ...

  2. New York's TUNDRA.

    ERIC Educational Resources Information Center

    Kalinowski, Thomas

    1983-01-01

    Found at the summit of some of the highest peaks of New York State's Adirondack Mountains are low-growing plants similar, and in many cases, identical to plants growing in the Arctic. Describes these plants and the environment in which they are found. Includes a color plate of alpine tundra plants. (Author/JN)

  3. Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska.

    PubMed

    Carey, Michael P; Zimmerman, Christian E

    2014-05-01

    Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to

  4. Laurentian origin for the North Slope of Alaska: Implications for the tectonic evolution of the Arctic

    USGS Publications Warehouse

    Strauss, J. V.; Macdonald, F. A.; Taylor, J. F.; Repetski, John E.; McClelland, W. C.

    2013-01-01

    The composite Arctic Alaska–Chukotka terrane plays a central role in tectonic reconstructions of the Arctic. An exotic, non-Laurentian origin of Arctic Alaska–Chukotka has been proposed based on paleobiogeographic faunal affinities and various geochronological constraints from the southwestern portions of the terrane. Here, we report early Paleozoic trilobite and conodont taxa that support a Laurentian origin for the North Slope subterrane of Arctic Alaska, as well as new Neoproterozoic–Cambrian detrital zircon geochronological data, which are both consistent with a Laurentian origin and profoundly different from those derived from similar-aged strata in the southwestern subterranes of Arctic Alaska–Chukotka. The North Slope subterrane is accordingly interpreted as allochthonous with respect to northwestern Laurentia, but it most likely originated farther east along the Canadian Arctic or Atlantic margins. These data demonstrate that construction of the composite Arctic Alaska–Chukotka terrane resulted from juxtaposition of the exotic southwestern fragments of the terrane against the northern margin of Laurentia during protracted Devonian(?)–Carboniferous tectonism.

  5. Arctic Shrub Growth Response to Climate Variation and Infrastructure Development on the North Slope of Alaska

    NASA Astrophysics Data System (ADS)

    Ackerman, D.; Finlay, J. C.; Griffin, D.

    2015-12-01

    Woody shrub growth in the arctic tundra is increasing on a circumpolar scale. Shrub expansion alters land-atmosphere carbon fluxes, nutrient cycling, and habitat structure. Despite these ecosystem effects, the drivers of shrub expansion have not been precisely established at the landscape scale. This project examined two proposed anthropogenic drivers: global climate change and local infrastructure development, a press disturbance that generates high levels of dust deposition. Effects of global change were studied using dendrochronology to establish a relationship between climate and annual growth in Betula and Salix shrubs growing in the Alaskan low Arctic. To understand the spatial heterogeneity of shrub expansion, this analysis was replicated in shrub populations across levels of landscape properties including soil moisture and substrate age. Effects of dust deposition on normalized difference vegetation index (NDVI) and photosynthetic rate were measured on transects up to 625 meters from the Dalton Highway. Dust deposition rates decreased exponentially with distance from road, matching previous models of road dust deposition. NDVI tracked deposition rates closely, but photosynthetic rates were not strongly affected by deposition. These results suggest that dust deposition may locally bias remote sensing measurements such as NDVI, without altering internal physiological processes such as photosynthesis in arctic shrubs. Distinguishing between the effects of landscape properties, climate, and disturbance will improve our predictions of the biogeochemical feedbacks of arctic shrub expansion, with potential application in climate change modeling.

  6. Changing Seasonality of Tundra Vegetation and Associated Climatic Variables

    NASA Astrophysics Data System (ADS)

    Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Bieniek, P.; Epstein, H. E.; Comiso, J. C.; Pinzon, J.; Tucker, C. J.; Steele, M.; Ermold, W. S.; Zhang, J.

    2014-12-01

    This study documents changes in the seasonality of tundra vegetation productivity and its associated climate variables using long-term data sets. An overall increase of Pan-Arctic tundra greenness potential corresponds to increased land surface temperatures and declining sea ice concentrations. While sea ice has continued to decline, summer land surface temperature and vegetation productivity increases have stalled during the last decade in parts of the Arctic. To understand the processes behind these features we investigate additional climate parameters. This study employs remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2013. Maximum NDVI (MaxNDVI, Maximum Normalized Difference Vegetation Index), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), ocean heat content (PIOMAS, model incorporating ocean data assimilation), and snow water equivalent (GlobSnow, assimilated snow data set) are explored. We analyzed the data for the full period (1982-2013) and for two sub-periods (1982-1998 and 1999-2013), which were chosen based on the declining Pan-Arctic SWI since 1998. MaxNDVI has increased from 1982-2013 over most of the Arctic but has declined from 1999 to 2013 over western Eurasia, northern Canada, and southwest Alaska. TI-NDVI has trends that are similar to those for MaxNDVI for the full period but displays widespread declines over the 1999-2013 period. Therefore, as the MaxNDVI has continued to increase overall for the Arctic, TI-NDVI has been declining since 1999. SWI has large relative increases over the 1982-2013 period in eastern Canada and Greenland and strong declines in western Eurasia and southern Canadian tundra. Weekly Pan-Arctic tundra land surface temperatures warmed throughout the summer during the 1982-1998 period but display midsummer declines from 1999-2013. Weekly snow water equivalent over Arctic tundra has declined over

  7. Geographic Information Network of Alaska: Real-Time Synoptic Satellite Data for Alaska and the High Arctic, Best Available DEMs, and Highest Available Resolution Imagery for Alaska

    NASA Astrophysics Data System (ADS)

    Heinrichs, T. A.; Sharpton, V. L.; Engle, K. E.; Ledlow, L. L.; Seman, L. E.

    2006-12-01

    In support of the International Polar Year, the Geographic Information Network of Alaska (GINA) intends to make available to researchers three important Arctic data sets. The first is near-real-time synoptic scale data from GINA and NOAA/NESDIS satellite ground stations. GINA operates ground stations that receive direct readout from the AVHRR (1.1-km per pixel resolution) and MODIS (250- to 1000-meter) sensors carried on NOAA and NASA satellites. GINA works in partnership with NOAA/NESDIS's Fairbanks Command and Data Acquisition Station (FCDAS) to distribute real-time data captured by FCDAS facilities in Fairbanks and Barrow, Alaska. AVHRR and Feng Yun 1D (1.1-km) sensors are captured in Fairbanks by FCDAS and distributed by GINA. AVHRR data is captured by FCDAS in Barrow and distributed by GINA. Due to its high latitude, the station mask of the Barrow station extends well beyond the Pole, showing the status in real-time of Arctic basin cloud and sea ice conditions. Second, digital elevation models (DEM) for Alaska vary greatly in quality and availability. The best available DEMs for Alaska will be combined and served through a GINA gateway. Third, the best available imagery for more than three quarters of Alaska is 15-meter pan-sharpened Landsat data. Less than a quarter of the state is covered by 5-meter or better data. The best available imagery for Alaska will be combined and served through a GINA gateway. In accordance with the IPY Subcommittee on Data Policy and Management recommendations, all data will be made available via Open Geospatial Consortium protocols, including Web Mapping, Feature, and Coverage Services. Data will also be made available for download in georeferenced formats such as GeoTIFF, MrSID, or GRID. Metadata will be available though the National Spatial Data Infrastructure via Z39.50 GEO protocols and through evolving web-based metadata standards.

  8. Pathways and transformations of dissolved methane and dissolved inorganic carbon in Arctic tundra watersheds: Evidence from analysis of stable isotopes

    SciTech Connect

    Throckmorton, Heather M.; Heikoop, Jeffrey M.; Newman, Brent D.; Altmann, Garrett L.; Conrad, Mark S.; Muss, Jordan D.; Perkins, George B.; Smith, Lydia J.; Torn, Margaret S.; Wullschleger, Stan D.; Wilson, Cathy J.

    2015-11-08

    Arctic soils contain a large pool of terrestrial C and are of interest due to their potential for releasing significant carbon dioxide (CO2) and methane (CH4) to the atmosphere. Due to substantial landscape heterogeneity, predicting ecosystem-scale CH4 and CO2 production is challenging. This study assessed dissolved inorganic carbon (DIC = Σ (total) dissolved CO2) and CH4 in watershed drainages in Barrow, Alaska as critical convergent zones of regional geochemistry, substrates, and nutrients. In July and September of 2013, surface waters and saturated subsurface pore waters were collected from 17 drainages. Based on simultaneous DIC and CH4 cycling, we synthesized isotopic and geochemical methods to develop a subsurface CH4 and DIC balance by estimating mechanisms of CH4 and DIC production and transport pathways and oxidation of subsurface CH4. We observed a shift from acetoclastic (July) toward hydrogenotropic (September) methanogenesis at sites located toward the end of major freshwater drainages, adjacent to salty estuarine waters, suggesting an interesting landscape-scale effect on CH4 production mechanism. The majority of subsurface CH4 was transported upward by plant-mediated transport and ebullition, predominantly bypassing the potential for CH4 oxidation. Thus, surprisingly, CH4 oxidation only consumed approximately 2.51± 0.82% (July) and 0.79 ± 0.79% (September) of CH4 produced at the frost table, contributing to <0.1% of DIC production. DIC was primarily produced from respiration, with iron and organic matter serving as likely e- acceptors. Furthermore, this work highlights the importance of spatial and temporal variability of CH4 production at the watershed scale and suggests broad scale investigations are required to build better regional or pan-Arctic representations of CH

  9. Forage site selection by lesser snow geese during autumn staging on the Arctic National Wildlife Refuge, Alaska

    USGS Publications Warehouse

    Hupp, J.W.; Robertson, Donna G.

    1998-01-01

    Lesser snow geese (Chen caerulescens caerulescens) of the Western Canadian Arctic Population feed intensively for 2-4 weeks on the coastal plain of the Beaufort Sea in Canada and Alaska at the beginning of their autumn migration. Petroleum leasing proposed for the Alaskan portion of the staging area on the Arctic National Wildlife Refuge (ANWR) could affect staging habitats and their use by geese. Therefore we studied availability, distribution, and use by snow geese of tall and russett cotton-grass (Eriophorum angustifolium and E. russeolum, respectively) feeding habitats on the ANWR. We studied selection of feeding habitats at 3 spatial scales (feeding sites [0.06 m2], feeding patches [ca. 100 m2], and feeding areas [>1 ha]) during 1990-93. We used logistic regression analysis to discriminate differences in soil moisture and vegetation between 1,548 feeding sites where snow geese exploited individual cotton-grass plants and 1,143 unexploited sites at 61 feeding patches in 1990. Feeding likelihood increased with greater soil moisture and decreased where nonforage species were present. We tested the logistic regression model in 1991 by releasing human-imprinted snow geese into 4 10 ?? 20-m enclosed plots where plant communities had been mapped, habitats sampled, and feeding probabilities calculated. Geese selected more feeding sites per square meter in areas of predicted high quality feeding habitat (feeding probability ??? 0.6) than in medium (feeding probability = 0.3-0.59) or poor (feeding probability < 0.3) quality habitat (P < 0.0001). Geese increasingly used medium quality areas and spent more time feeding as trials progressed and forage was presumably reduced in high quality habitats. We examined relationships between underground biomass of plants, feeding probability, and surface microrelief at 474 0.06-m2 sites in 20 thermokarst pits in 1992. Feeding probability was correlated with the percentage of underground biomass composed of cotton-grass (r = 0

  10. The Tundra Is the Text: Using Alaska Native Contexts To Promote Cultural Relevancy in Teacher Professional Development.

    ERIC Educational Resources Information Center

    Fickel, Letitia Hochstrasser; Jones, Ken

    In summer 2000, the University of Alaska Anchorage and cooperating professional development schools organized four summer institutes to enhance teachers' cultural and subject matter knowledge. This dual focus was prompted by the new Alaska Content Standards and by guidelines for preparing culturally responsive teachers, developed by Alaska Native…

  11. Atmospheric Deposition and Critical Loads for Nitrogen and Metals in Arctic Alaska: Review and Current Status

    USGS Publications Warehouse

    Linder, Greg L.; Brumbaugh, William G.; Neitlich, Peter; Little, Edward

    2013-01-01

    To protect important resources under their bureau’s purview, the United States National Park Service’s (NPS) Arctic Network (ARCN) has developed a series of “vital signs” that are to be periodically monitored. One of these vital signs focuses on wet and dry deposition of atmospheric chemicals and further, the establishment of critical load (CL) values (thresholds for ecological effects based on cumulative depositional loadings) for nitrogen (N), sulfur, and metals. As part of the ARCN terrestrial monitoring programs, samples of the feather moss Hylocomium splendens are being col- lected and analyzed as a cost-effective means to monitor atmospheric pollutant deposition in this region. Ultimately, moss data combined with refined CL values might be used to help guide future regulation of atmospheric contaminant sources potentially impacting Arctic Alaska. But first, additional long-term studies are needed to determine patterns of contaminant deposition as measured by moss biomonitors and to quantify ecosystem responses at particular loadings/ ranges of contaminants within Arctic Alaska. Herein we briefly summarize 1) current regulatory guidance related to CL values 2) derivation of CL models for N and metals, 3) use of mosses as biomonitors of atmospheric deposition and loadings, 4) preliminary analysis of vulnerabilities and risks associated with CL estimates for N, 5) preliminary analysis of existing data for characterization of CL values for N for interior Alaska and 6) implications for managers and future research needs.

  12. Atmospheric methane sources - Alaskan tundra bogs, an alpine fen, and a subarctic boreal marsh

    NASA Technical Reports Server (NTRS)

    Sebacher, D. I.; Harriss, R. C.; Grice, S. S.; Bartlett, K. B.; Sebacher, S. M.

    1986-01-01

    Methane (CH4) flux measurements from Alaska tundra bogs, an alpine fen, and a subarctic boreal marsh were obtained at field sites ranging from Prudhoe Bay on the coast of the Arctic Ocean to the Alaskan Range south of Fairbanks during August 1984. In the tundra, average CH4 emission rates varied from 4.9 mg CH4 per sq m per day (moist tundra) to 119 mg CH4 per sq m per day (waterlogged tundra). Fluxes averaged 40 mg CH4 per sq m per day from wet tussock meadows in the Brooks Range and 289 mg Ch4 per sq m per day from an alpine fen in the Alaskan Range. The boreal marsh had an average CH4 emission rate of 106 mg CH4 per sq m per day. Significant emissions were detected in tundra areas where peat temperatures were as low as 4 C, and permafrost was only 25 cm below the ground surface. Emission rates from the 17 sites sampled were found to be logarithmically related to water levels at the sites. Extrapolation of the data to an estimate of the total annual CH4 emission from all arctic and boreal wetlands suggests that these ecosystems are a major source of atmospheric CH4 and could account for up to 23 percent of global CH4 emissions from wetlands.

  13. 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.

  14. Polar bear maternal den habitat in the Arctic National Wildlife Refuge, Alaska

    USGS Publications Warehouse

    Durner, G.M.; Amstrup, Steven C.; Ambrosius, K.J.

    2006-01-01

    Polar bears (Ursus maritimus) give birth during mid-winter in dens of ice and snow. Denning polar bears subjected to human disturbances may abandon dens before their altricial young can survive the rigors of the Arctic winter. Because the Arctic coastal plain of Alaska is an area of high petroleum potential and contains existing and planned oil field developments, the distribution of polar bear dens on the plain is of interest to land managers. Therefore, as part of a study of denning habitats along the entire Arctic coast of Alaska, we examined high-resolution aerial photographs (n = 1655) of the 7994 km2 coastal plain included in the Arctic National Wildlife Refuge (ANWR) and mapped 3621 km of bank habitat suitable for denning by polar bears. Such habitats were distributed uniformly and comprised 0.29% (23.2 km2) of the coastal plain between the Canning River and the Canadian border. Ground-truth sampling suggested that we had correctly identified 91.5% of bank denning habitats on the ANWR coastal plain. Knowledge of the distribution of these habitats will help facilitate informed management of human activities and minimize disruption of polar bears in maternal dens.

  15. Relationships among depth to frozen soil, soil wetness, and vegetation type and biomass in Tundra near Bethel, Alaska, U. S. A

    SciTech Connect

    Gross, M.F. ); Hardisky, M.A. ); Doolittle, J.A. ); Klemas, V. )

    1990-08-01

    Vegetation was sampled in three types of tundra habitat (upland, wet meadow, and lake) in southwestern Alaska. Aboveground and belowground biomass were measured by harvesting, and the depth to frozen soil was measured using ground-penetrating radar. Live and dead aboveground biomass increased, and dead belowground biomass decreased, as habitat wetness and depth to frozen soil increased. The proportion of live aerial biomass that was graminoid increased as habitat wetness and depth to frozen soil increased, whereas the proportion that was woody shrub biomass decreased with increases in habitat wetness and depth to frozen soil. The results indicate that information pertaining to either vegetation type/biomass, habitat wetness, or depth to frozen soil, could be used to infer information about the other two variables. Vegetation and frozen soil depth could be monitored remotely for large areas using tools such as satellite images and radar. Since the cycling of carbon is related to carbon storage (biomass) and depth of the biologically active (thawed) layer, it should be possible to study carbon cycles in tundra remotely, based on the relationships stated above.

  16. ``What comes up … must come down'': Peat carbon and mineral-interactions in Arctic Coastal tundra

    NASA Astrophysics Data System (ADS)

    Raab, T. K.; Lipson, D.; Crook, N. P.; Miller, K.; Bozzolo, F.

    2010-12-01

    Coastal arctic tundra is a significant landscape unit above 65o N, and in the absence of significant nitrate, sulfate or manganese, these wet, permafrost-influenced soils have few electron acceptors readily available to support microbial anaerobiosis. Based on morphological criteria and satellite photos, we selected 4 drained, thaw-lake basins (DTLBs) of vastly differing ages - 50 to 5500 years, based on 14C-dating efforts near Barrow AK. Replicate 100m transects for each thawed-lake basin were collected using a towable 500 MHz ground-penetrating radar system. Inspection of the raw profiles in the field further suggested points along which 20m-length common-midpoint gathers were also obtained to discriminate contrasting propagation speeds within the top 0.5 m of the surface. At later visits, several SIPRE cores were taken to 0.5 m-depth, and the cores stored frozen until analysis. The cores were measured, and physical/color and mineral data collected to correlate with the CMP velocity-profiles. The point of these measurements was to ascertain the minimum-depth to mineral material below the surficial peats, and to build-up a profile of basin age versus mineral-depth. Availability of inorganic reducing agents may provide a significant constraint on soil microbial C-processing. Minimum-tension microlysimeters (PTFE and iron-free) were deployed along replicate transects in each of 5 basins, and filtered soil-pore water was collected from 0-10 cm, as was filtered, acidified standing water from early June-Sept of both 2009 and 2010. Results of inorganic analyses are presented in a separate poster. Fluorescence spectroscopy was used to monitor seasonal patterns in DOC composition, and fluorescence emission intensity of soil pore-water was inversely proportional to basin age - humic signature emission spectra peaked sharply at 445 nm, and a broader secondary maximum occurred at 500 nm. Fluorescence emission varied 5-fold among basins, and decreased at all sites as soil

  17. Migration potential of tundra plant species in a warming Arctic: Responses of southern ecotypes of three species to experimental warming in the High Arctic

    NASA Astrophysics Data System (ADS)

    Bjorkman, Anne; Henry, Greg; Vellend, Mark

    2013-04-01

    Climatic changes due to anthropogenic activity are predicted to have a profound effect on the world's biodiversity and ecosystem functioning. The response of natural communities to climate change will depend primarily on two factors: 1) the ability of species to adapt quickly to changing temperatures and precipitation trends, and 2) the ability of species and populations from southern latitudes to migrate northward and establish in new environments. The assumption is often made that species and populations will track their optimal climate northward as the earth warms, but this assumption ignores a host of other potentially important factors, including the lack of adaptation to photoperiod, soil moisture, and biotic interactions at higher latitudes. In this study, we aim to better understand the ability of southern populations to establish and grow at northern latitudes under warmer temperatures. We collected seeds or ramets of three Arctic plant species (Papaver radicatum, Oxyria digyna, and Arctagrostis latifolia) from Alexandra Fiord on Ellesmere Island, Canada and from southern populations at Cornwallis Island, Canada, Barrow, Alaska, and Latnjajaure, Sweden. These seeds were planted into experimentally warmed and control plots at Alexandra Fiord in 2011. We have tracked their survival, phenology, and growth over two growing seasons. Here, we will present the preliminary results of these experiments. In particular, we will discuss whether individuals originating from southern latitudes exhibit higher growth rates in warm plots than control plots, and whether southern populations survive and grow as well as or better than individuals from Alexandra Fiord in the warmed plots. In both cases, a positive response would indicate that a warming climate may facilitate a migration northward of more southerly species or populations, and that the lack of adaptation to local conditions (soil chemistry, microhabitat, etc.) will not limit this migration. Alternately, a

  18. C-N-P interactions control climate driven changes in regional patterns of C storage on the North Slope of Alaska

    SciTech Connect

    Jiang, Yueyang; Rocha, Adrian; Rastetter, Edward; Shaver, Gaius; Mishra, U.; Zhuang, Qianlai; Kwiatkowski, Bonnie

    2016-01-01

    As climate warms, changes in the carbon (C) balance of arctic tundra will play an important role in the global C balance. The C balance of tundra is tightly coupled to the nitrogen (N) and phosphorus (P) cycles because soil organic matter is the principal source of plant-available nutrients and determines the spatial variation of vegetation biomass across the North Slope of Alaska. Warming will accelerate these nutrient cycles, which should stimulate plant growth.

  19. 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.

  20. 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.

  1. Continuous measurement of soil carbon efflux with Forced Diffusion (FD) chambers in a tundra ecosystem of Alaska.

    PubMed

    Kim, Yongwon; Park, Sang-Jong; Lee, Bang-Yong; Risk, David

    2016-10-01

    Soil is a significant source of CO2 emission to the atmosphere, and this process is accelerating at high latitudes due to rapidly changing climates. To investigate the sensitivity of soil CO2 emissions to high temporal frequency variations in climate, we performed continuous monitoring of soil CO2 efflux using Forced Diffusion (FD) chambers at half-hour intervals, across three representative Alaskan soil cover types with underlying permafrost. These sites were established during the growing season of 2015, on the Seward Peninsula of western Alaska. Our chamber system is conceptually similar to a dynamic chamber, though FD is more durable and water-resistant and consumes less power, lending itself to remote deployments. We first conducted methodological tests, testing different frequencies of measurement, and did not observe a significant difference between collecting data at 30-min and 10-min measurement intervals (averaged half-hourly) (p<0.001). Temperature and thaw depth, meanwhile, are important parameters in influencing soil carbon emission. At the study sites, we observed cumulative soil CO2 emissions of 62.0, 126.3, and 133.5gCm(-2) for the growing period, in sphagnum, lichen, and tussock, respectively, corresponding to 83.8, 63.7, and 79.6% of annual carbon emissions. Growing season soil carbon emissions extrapolated over the region equated to 0.17±0.06 MgC over the measurement period. This was 47% higher than previous estimates from coarse-resolution manual chamber sampling, presumably because it better captured high efflux events. This finding demonstrates how differences in measurement method and frequency can impact interpretations of seasonal and annual soil carbon budgets. We conclude that annual CO2 efflux-measurements using FD chamber networks would be an effective means for quantifying growing and non-growing season soil carbon budgets, with optimal pairing with time-lapse imagery for tracking local and regional changes in environment and climate

  2. AmeriFlux US-ICh Imnavait Creek Watershed Heath Tundra

    DOE Data Explorer

    Bret-Harte, Syndonia [University of Alaska Fairbanks; Euskirchen, Eugenie [University of Alaska Fairbanks; Shaver, Gaius [Marine Biological Laboratory

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ICh Imnavait Creek Watershed Heath Tundra. Site Description - The Imnavait Creek Watershed Heath Tundra (Ridge Station) is located near Imnavait Creek in Alaska, north of the Brooks Range in the Kuparuk basin near Lake Toolik and the Toolik Field Station. The Kuparuk River has its headwaters in the Brooks Range and drains through northern Alaska into the Arctic Ocean. Within these headwaters lies the Imnavait basin at an average elevation of 930 m. Water tracks run down the hill in parallel zones with a spacing of approximately 10 m. The Ridge Station was deployed at the end of Summer 2007.

  3. AmeriFlux US-ICs Imnavait Creek Watershed Wet Sedge Tundra

    DOE Data Explorer

    Bret-Harte, Syndonia [University of Alaska Fairbanks; Euskirchen, Eugenie [University of Alaska Fairbanks; Shaver, Gaius [Marine Biological Laboratory

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ICs Imnavait Creek Watershed Wet Sedge Tundra. Site Description - The Imnavait Creek Watershed Wet Sedge Tundra (Fen Station) is located near Imnavait Creek in Alaska, north of the Brooks Range in the Kuparuk basin near Lake Toolik and the Toolik Field Station. The Kuparuk River has its headwaters in the Brooks Range and drains through northern Alaska into the Arctic Ocean. Within these headwaters lies the Imnavait basin at an average elevation of 930 m. Water tracks run down the hill in parallel zones with a spacing of approximately 10 m. The Fen Station was deployed at the end of Summer 2007.

  4. AmeriFlux US-ICt Imnavait Creek Watershed Tussock Tundra

    DOE Data Explorer

    Bret-Harte, Syndonia [University of Alaska Fairbanks; Euskirchen, Eugenie [University of Alaska Fairbanks; Shaver, Gaius [Marine Biological Laboratory

    2016-01-01

    This is the AmeriFlux version of the carbon flux data for the site US-ICt Imnavait Creek Watershed Tussock Tundra. Site Description - The Imnavait Creek Watershed Tussock Tundra (Biocomplexity Station) is located near Imnavait Creek in Alaska, north of the Brooks Range in the Kuparuk basin near Lake Toolik and the Toolik Field Station. The Kuparuk River has its headwaters in the Brooks Range and drains through northern Alaska into the Arctic Ocean. Within these headwaters lies the Imnavait basin at an average elevation of 930 m. Water tracks run down the hill in parallel zones with a spacing of approximately 10 m. The Biocomplexity Station was deployed in 2004, and it has been in operation during the melt seasons ever since.

  5. Soil Surface Organic Layers in Alaska's Arctic Foothills: Development, Distribution and Microclimatic Feedbacks

    NASA Astrophysics Data System (ADS)

    Baughman, C. A.; Mann, D. H.; Verbyla, D.; Valentine, D.; Kunz, M. L.; Heiser, P. A.

    2013-12-01

    Accumulated organic matter at the ground surface plays an important role in arctic ecosystems. These soil surface organic layers (SSOLs) influence temperature, moisture, and chemistry in the underlying mineral soil and, on a global basis, comprise enormous stores of labile carbon. Understanding the dynamics of SSOLs is prerequisite to modeling the responses of arctic ecosystem processes to climate changes. Here, we ask three questions regarding SSOLs in the Arctic Foothills in northern Alaska: 1) What environmental factors control their spatial distribution? 2) How long do they take to form? 3) What is the relationship between SSOL thickness and mineral soil temperature through the growing season? The best topographically-controlled predictors of SSOL thickness and spatial distribution are duration of sunlight during the growing-season, upslope drainage area, slope gradient, and elevation. SSOLs begin to form within several decades following disturbance but require 500-700 years to reach equilibrium states. Once formed, mature SSOLs lower peak growing-season temperature and mean annual temperature in the underlying mineral horizon by 8° and 3° C respectively, which reduces available growing degree days within the upper mineral soil by nearly 80%. How ongoing climate change in northern Alaska will affect the region's SSOLs is an open and potentially crucial question.

  6. Hydrologic reconnaissance of western Arctic Alaska, 1976 and 1977

    USGS Publications Warehouse

    Childers, Joseph M.; Kernodle, Donald R.; Loeffler, Robert M.

    1979-01-01

    Reconnaissance water-resource investigations were conducted on the western Alaskan Arctic Slope during April 1976 and August 1977; these months are times of winter and summer low flow. The information gathered is important for coordinated development in the area. Such development has been spurred by oil and gas discoveries on the North Slope, most notably at Prudhoe Bay. Little water resources information is currently available. The study area extended from the Colville River to the vicinity of Kotzebue. It included the western Arctic Slope and the western foothills of the Brooks Range. Nine springs, nine lakes and eleven rivers were sampled during the April 1976 reconnaissance trip. Its purpose was to locate winter flow and describe its quantity and quality. Field water-quality measurements made at these sites were: ice thickness, water depth, discharge (spring and streams), specific conductance, water temperature, dissolved oxygen, alkalinity (bicarbonate, HOC3), and pH. A followup summer trip was made in August 1977 to determine flood characteristics of twenty selected streams. Bankfull and maximum evident flood-peak discharges were determined by measuring channel geometry and estimating channel roughness. Aquatic invertebrate samples were collected at springs and flood survey sites visited during both reconnaissance trips. (Woodard-USGS)

  7. Substrate Geochemistry and Soil Development in Boreal Forest and Tundra Ecosystems in the Yukon-Tanana Upland and Seward Peninsula, Alaska

    USGS Publications Warehouse

    Gough, L.P.; Crock, J.G.; Wang, B.; Day, W.C.; Eberl, D.D.; Sanzolone, R.F.; Lamothe, P.J.

    2008-01-01

    We report on soil development as a function of bedrock type and the presence of loess in two high latitude ecosystems (boreal forest and tundra) and from two regions in Alaska?the Yukon-Tanana Upland (YTU, east-central Alaska) and the Seward Peninsula (SP, far-west coastal Alaska). This approach to the study of 'cold soils' is fundamental to the quantification of regional geochemical landscape patterns. Of the five state factors in this study, bedrock and biota (ecosystem; vegetation zone) vary whereas climate (within each area) and topography are controlled. The influence of time is assumed to be controlled, as these soils are thousands of years old (late Quaternary to Holocene). The primary minerals in soils from YTU, developed over loess and crystalline bedrock (metamorphic and intrusive), are quartz, plagioclase, and 2:1 clays; whereas in the SP, where loess and metasedimentary bedrock (schist and quartzite) predominate, they are quartz and muscovite. The A horizon of both regions is rich in peat. Examination of the ratio of mobile (K2O, CaO, and Fe2O3) to immobile (TiO2) major oxides, within each region, shows that very little difference exists in the chemical weathering of soils developed between the two ecosystems examined. Differences were observed between tundra soils developed in the two regions. These differences are most probably due to the dissimilarity in the geochemical importance of both loess and bedrock. A minimal loss of cadmium with soil depth is seen for soils developed over YTU crystalline bedrock in the boreal forest environments. This trend is related to the mobility of cadmium in these soils as well as to its biogenic cycling. Major differences were observed in the proportion of cadmium and zinc among the A, B, and C horizon material sequestered in various soil fractions as measured by sequential soil extractions. These trends followed such variables as the decrease with depth in organic matter, the change in clay minerals, and the change

  8. Regional shoreline change and coastal erosion hazards in Arctic Alaska

    USGS Publications Warehouse

    Gibbs, Ann E.; Richmond, Bruce M.; Erikson, Li H.; Harden, E. Lynne

    2011-01-01

    Historical shoreline positions along the mainland Beaufort Sea coast of Alaska were digitized and analyzed to determine the long-term rate of change. Average shoreline change rates and ranges from 1947 to the mid-2000s were determined every 50 meters between Barrow and Demarcation Point, at the U.S.-Canadian border. Results show that shoreline change rates are highly variable along the coast, with an average regional shoreline change rate of-2.0 m/yr and localized rates of up to -19 m/yr. The highest erosion rates were observed at headlands, points, and associated with breached thermokarst lakes. Areas of accretion were limited, and generally associated with spit extension and minor beach accretion. In general, erosion rates increase from east to west, with overall higher rates east of Harrison Bay.

  9. Regional shoreline change and coastal erosion hazards in Arctic Alaska

    USGS Publications Warehouse

    Gibbs, A.E.; Harden, E.L.; Richmond, B.M.; Erikson, L.H.

    2011-01-01

    Historical shoreline positions along the mainland Beaufort Sea coast of Alaska were digitized and analyzed to determine the long-term rate of change. Average shoreline change rates and ranges from 1947 to the mid-2000s were determined every 50 meters between Barrow and Demarcation Point, at the U.S.-Canadian border. Results show that shoreline change rates are highly variable along the coast, with an average regional shoreline change rate of-2.0 m/yr and localized rates of up to -19 m/yr. The highest erosion rates were observed at headlands, points, and associated with breached thermokarst lakes. Areas of accretion were limited, and generally associated with spit extension and minor beach accretion. In general, erosion rates increase from east to west, with overall higher rates east of Harrison Bay. ?? 2011 ASCE.

  10. Recovery and archiving key Arctic Alaska vegetation map and plot data for the Arctic-Boreal Vulnerability Field Experiment (ABoVE)

    NASA Astrophysics Data System (ADS)

    Walker, D. A.; Breen, A. L.; Broderson, D.; Epstein, H. E.; Fisher, W.; Grunblatt, J.; Heinrichs, T.; Raynolds, M. K.; Walker, M. D.; Wirth, L.

    2013-12-01

    Abundant ground-based information will be needed to inform remote-sensing and modeling studies of NASA's Arctic-Boreal Vulnerability Experiment (ABoVE). A large body of plot and map data collected by the Alaska Geobotany Center (AGC) and collaborators from the Arctic regions of Alaska and the circumpolar Arctic over the past several decades is being archived and made accessible to scientists and the public via the Geographic Information Network of Alaska's (GINA's) 'Catalog' display and portal system. We are building two main types of data archives: Vegetation Plot Archive: For the plot information we use a Turboveg database to construct the Alaska portion of the international Arctic Vegetation Archive (AVA) http://www.geobotany.uaf.edu/ava/. High quality plot data and non-digital legacy datasets in danger of being lost have highest priority for entry into the archive. A key aspect of the database is the PanArctic Species List (PASL-1), developed specifically for the AVA to provide a standard of species nomenclature for the entire Arctic biome. A wide variety of reports, documents, and ancillary data are linked to each plot's geographic location. Geoecological Map Archive: This database includes maps and remote sensing products and links to other relevant data associated with the maps, mainly those produced by the Alaska Geobotany Center. Map data include GIS shape files of vegetation, land-cover, soils, landforms and other categorical variables and digital raster data of elevation, multispectral satellite-derived data, and data products and metadata associated with these. The map archive will contain all the information that is currently in the hierarchical Toolik-Arctic Geobotanical Atlas (T-AGA) in Alaska http://www.arcticatlas.org, plus several additions that are in the process of development and will be combined with GINA's already substantial holdings of spatial data from northern Alaska. The Geoecological Atlas Portal uses GINA's Catalog tool to develop a

  11. A comprehensive climatology of Arctic aerosol properties on the North Slope of Alaska

    NASA Astrophysics Data System (ADS)

    Creamean, Jessie; de Boer, Gijs; Shupe, Matthew; McComiskey, Allison

    2016-04-01

    Evaluating aerosol properties has implications for the formation of Arctic clouds, resulting in impacts on cloud lifetime, precipitation processes, and radiative forcing. There are many remaining uncertainties and large discrepancies regarding modeled and observed Arctic aerosol properties, illustrating the need for more detailed observations to improve simulations of Arctic aerosol and more generally, projections of the components of the aerosol-driven processes that impact sea ice loss/gain. In particular, the sources and climatic effects of Arctic aerosol particles are severely understudied. Here, we present a comprehensive, long-term record of aerosol observations from the North Slope of Alaska baseline site at Barrow. These measurements include sub- and supermicron (up to 10 μm) total mass and number concentrations, sub- and supermicron soluble inorganic and organic ion concentrations, submicron metal concentrations, submicron particle size distributions, and sub- and supermicron absorption and scattering properties. Aerosol extinction and number concentration measurements extend back to 1976, while the remaining measurements were implemented since. Corroboration between the chemical, physical, and optical property measurements is evident during periods of overlapping observations, demonstrating the reliability of the measurements. During the Arctic Haze in the winter/spring, high concentrations of long-range transported submicron sea salt, mineral dust, industrial metals, pollution (non-sea salt sulfate, nitrate, ammonium), and biomass burning species are observed concurrent with higher concentrations of particles with sizes that span the submicron range, enhanced absorption and scattering coefficients, and largest Ångström exponents. The summer is characterized by high concentrations of small biogenic aerosols (< 100 nm) and low extinction coefficients. Fall is characterized by clean conditions, with supermicron sea salt representing the dominant aerosol

  12. 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.

  13. Wave climate and trends along the eastern Chukchi Arctic Alaska coast

    USGS Publications Warehouse

    Erikson, L.H.; Storlazzi, C.D.; Jensen, R.E.

    2011-01-01

    Due in large part to the difficulty of obtaining measurements in the Arctic, little is known about the wave climate along the coast of Arctic Alaska. In this study, numerical model simulations encompassing 40 years of wave hind-casts were used to assess mean and extreme wave conditions. Results indicate that the wave climate was strongly modulated by large-scale atmospheric circulation patterns and that mean and extreme wave heights and periods exhibited increasing trends in both the sea and swell frequency bands over the time-period studied (1954-2004). Model simulations also indicate that the upward trend was not due to a decrease in the minimum icepack extent. ?? 2011 ASCE.

  14. Early Tertiary marine fossils from northern Alaska: implications for Arctic Ocean paleogeography and faunal evolution.

    USGS Publications Warehouse

    Marincovich, L., Jr.; Brouwers, E.M.; Carter, L.D.

    1985-01-01

    Marine mollusks and ostracodes indicate a post-Danian Paleocene to early Eocene (Thanetian to Ypresian) age for a fauna from the Prince Creek Formation at Ocean Point, northern Alaska, that also contains genera characteristic of the Cretaceous and Neogene-Quaternary. The life-assocation of heterochronous taxa at Ocean Point resulted from an unusual paleogeographic setting, the nearly complete isolation of the Arctic Ocean from about the end of the Cretaceous until sometime in the Eocene, in which relict Cretaceous taxa survived into Tertiary time while endemic taxa evolved in situ; these later migrated to the northern mid- latitudes. Paleobiogeographic affinities of the Ocean Point assocation with mild temperate faunas of the London Basin (England), Denmark, and northern Germany indicate that a shallow, intermittent Paleocene seaway extended through the Norwegian-Greenland Sea to the North Sea Basin. Early Tertiary Arctic Ocean paleogeography deduced from faunal evidence agrees with that inferred from plate-tectonic reconstructions.-Authors

  15. Seismic images of the Brooks Range, Arctic Alaska, reveal crustal- scale duplexing

    USGS Publications Warehouse

    Fuis, G.S.; Levander, A.R.; Lutter, W.J.; Wissinger, E.S.; Moore, T.E.; Christensen, N.I.

    1995-01-01

    An integrated set of seismic reflection and refraction data collected across the Brooks Range, Arctic Alaska, in 1990, has yielded a composite image of this Mesozoic and Cenozoic fold-and-thrust belt that reveals duplexing to lower-crustal depths. Interpretations from this image are discussed. The position of the thickest crust may indicate that either the duplexed crust above the decollement was thrust onto and depressed the plate beneath the North Slope or the protracted tectonic history of the Brooks Range has left structures not simply explainable in terms of a single collisional event. -from Authors

  16. The lab and the land: overcoming the Arctic in Cold War Alaska.

    PubMed

    Farish, Matthew

    2013-03-01

    The militarization of Alaska during and after World War II created an extraordinary set of new facilities. But it also reshaped the imaginative role of Alaska as a hostile environment, where an antagonistic form of nature could be defeated with the appropriate combination of technology and training. One of the crucial sites for this reformulation was the Arctic Aeromedical Laboratory, based at Ladd Air Force Base in Fairbanks. In the first two decades of the Cold War, its employees conducted numerous experiments on acclimatization and survival. The laboratory is now best known for an infamous set of tests involving the application of radioactive tracers to indigenous Alaskans--experiments publicized by post-Cold War panels established to evaluate the tragic history of atomic-era human subject research. But little else has been written about the laboratory's relationship with the populations and landscapes that it targeted for study. This essay presents the laboratory as critical to Alaska's history and the history of the Cold War sciences. A consideration of the laboratory's various projects also reveals a consistent fascination with race. Alaskan Natives were enrolled in experiments because their bodies were understood to hold clues to the mysteries of northern nature. A scientific solution would aid American military campaigns not only in Alaska, but in cold climates everywhere. PMID:23789506

  17. Characterization of a storm surge exposed arctic inlet: Shaktoolik, Alaska

    NASA Astrophysics Data System (ADS)

    Ohman, K. A.; Erikson, L. H.; Kinsman, N.

    2011-12-01

    The Inupiaq community of Shaktoolik, in northwestern Alaska is constructed on a low-lying barrier spit located on Norton Sound. The inhabited portion of the spit is ~200m across and vulnerable to flooding from both the open water and lagoon sides during storm events. Previously modeled storm events estimate elevated sea surfaces reaching a maximum storm surge of 6.4m (21 feet) in the Norton Sound region. Historical storm events have been documented every few years in the region, usually occurring during the fall, but storm surge heights in Shaktoolik have never been recorded. An inlet is located at the northern terminus of the barrier spit, adjacent to the community, and provides access for fishing boats to and from the sheltered lagoon. This research focuses on the responses of Shaktoolik's inlet to storm surge and subsequent flooding of the spit. Fieldwork conducted in July 2011 focused on mapping the on land and nearshore coastal morphology of the barrier system. Prior to this, limited baseline data about the Shaktoolik coastal zone was available. The research goals for this project are to understand the morphodynamics of the inlet and surrounding coastal area and to analyze impacts on the inlet by storm surge events. This study is in support of a larger geohazard mapping project with the Alaska Department of Geological and Geophysical Surveys. Onshore, beach profiles and wrackline positions were surveyed, and grain size samples were collected north and south of the inlet. These data provide insight into the longshore sediment transport patterns, past flood levels, and the extent of possible flooding and inundation in the future. In the nearshore, bathymetric data, current velocity measurements, and suspended and bedload sediment samples were obtained seaward of the spit, in the inlet, and within the lagoon. Nearshore measurements characterize the inlet channel depths and composition, and locate areas of sediment deposition. In addition, three months of fall

  18. Crystal alignments in the fast ice of Arctic Alaska

    SciTech Connect

    Weeks, W.F.; Gow, A.J.

    1980-02-20

    Field observations at 60 sites located in the fast or near-fast ice along a 1200-km stretch of the north coast of Alaska between the Bering Strait and Barter Island have shown that the great majority of the ice samples (95%) exhibit striking c axis alignments within the horizontal plane. In all cases the degree of preferred orientation increased with depth in the ice. Representative standard deviations around a mean direction in the horizontal plane are commonly less than +- 10/sup 0/ for samples collected near the bottom of the ice. At a given site the mean c axis direction X-bar/sub 0/ may vary as much as 20/sup 0/ with vertical location in the ice sheet. The c axis allignments in the nearshore region generally parallel the coast, with strong alignments occurring in the lagoon systems between the barrier islands and the coast and seaward of the barrier islands. In passes between islands and in entrances such as the opening to Kotzebue Sound the alignment is parallel to the channel. Only limited observations are available farther seaward over the inner (10- to 50-m isobaths) and outer (50-m isobath to shelf break) shelf regions. These indicate Ne-SW and E-W alignments, respectively, in the Beaufort Sea north of Prudhoe Bay.

  19. Population structure of two rabies hosts relative to the known distribution of rabies virus variants in Alaska.

    PubMed

    Goldsmith, Elizabeth W; Renshaw, Benjamin; Clement, Christopher J; Himschoot, Elizabeth A; Hundertmark, Kris J; Hueffer, Karsten

    2016-02-01

    For pathogens that infect multiple species, the distinction between reservoir hosts and spillover hosts is often difficult. In Alaska, three variants of the arctic rabies virus exist with distinct spatial distributions. We tested the hypothesis that rabies virus variant distribution corresponds to the population structure of the primary rabies hosts in Alaska, arctic foxes (Vulpes lagopus) and red foxes (Vulpes vulpes) to possibly distinguish reservoir and spillover hosts. We used mitochondrial DNA (mtDNA) sequence and nine microsatellites to assess population structure in those two species. mtDNA structure did not correspond to rabies virus variant structure in either species. Microsatellite analyses gave varying results. Bayesian clustering found two groups of arctic foxes in the coastal tundra region, but for red foxes it identified tundra and boreal types. Spatial Bayesian clustering and spatial principal components analysis identified 3 and 4 groups of arctic foxes, respectively, closely matching the distribution of rabies virus variants in the state. Red foxes, conversely, showed eight clusters comprising two regions (boreal and tundra) with much admixture. These results run contrary to previous beliefs that arctic fox show no fine-scale spatial population structure. While we cannot rule out that the red fox is part of the maintenance host community for rabies in Alaska, the distribution of virus variants appears to be driven primarily by the arctic fox. Therefore, we show that host population genetics can be utilized to distinguish between maintenance and spillover hosts when used in conjunction with other approaches. PMID:26661691

  20. Enabling Scientific and Technological Improvements to Meet Core Partner Service Requirements in Alaska - An Arctic Test Bed

    NASA Astrophysics Data System (ADS)

    Petrescu, E. M.; Scott, C. A.

    2014-12-01

    NOAA/NWS Test beds, such as the Joint Hurricane Test Bed (Miami, FL) and the Hazardous Weather Test Bed (Norman, OK) have been highly effective in meeting unique or pressing science and service challenges for the NWS. NWS Alaska Region leadership has developed plans for a significant enhancement to our operational forecast and decision support capabilities in Alaska to address the emerging requirements of the Arctic: An Arctic Test Bed. Historically, the complexity of forecast operations and the inherent challenges in Alaska have not been addressed well by the R&D programs and projects that support the CONUS regions of the NWS. In addition, there are unique science,technology, and support challenges (e.g., sea ice forecasts and arctic drilling prospects) and opportunities (Bilateral agreements with Canada, Russia, and Norway) that would best be worked through Alaska operations. A dedicated test bed will provide a mechanism to transfer technology, research results, and observations advances into operations in a timely and effective manner in support of Weather Ready Nation goals and to enhance decision support services in Alaska. A NOAA Arctic Test Bed will provide a crucial nexus for ensuring NOAA's developers understand Alaska's needs, which are often cross disciplinary (atmosphere, ocean, cryosphere, and hydrologic), to improve NOAA's responsiveness to its Arctic-related science and service priorities among the NWS and OAR (CPO and ESRL), and enable better leveraging of other research initiatives and data sources external to NOAA, including academia, other government agencies, and the private sector, which are particular to the polar region (e.g., WWRP Polar Prediction Project). Organization, capabilities and opportunities will be presentation.

  1. Late Quaternary and future biome simulations for Alaska and Eastern Russia

    NASA Astrophysics Data System (ADS)

    Hendricks, Amy S.

    Arctic biomes across a region including Alaska and Eastern Russia were investigated using the BIOME4 biogeochemical and biogeography vegetation model. This study investigated past (the last 21,000 years), present, and future vegetation distributions in the study area, using climate forcing from five CMIP5 models (CCSM4, GISS-E2-R, MIROC-ESM, MPI-ESM, and MRI-CGCM3). The present-day BIOME4 simulations were generally consistent with current vegetation observations in the study region characterized by evergreen and deciduous taiga and shrub tundras. Paleoclimatological simulations were compared with pollen data samples collected in the study region. Pre-industrial biome simulations are generally similar to the modern reconstruction but differ by having more shrub tundra in both Russia and Alaska to the north, as well as less deciduous taiga in Alaska. Pre-industrial simulations were in good agreement with the pollen data. Mid-Holocene simulations place shrub tundras along the Arctic coast, and in some cases along the eastern coast of Russia. Simulations for the Mid-Holocene are in good agreement with pollen-based distributions of biomes. Simulations for the Last Glacial Maximum (LGM) show that the Bering Land Bridge was covered almost entirely by cushion forb, lichen and moss tundra, shrub tundra, and graminoid tundra. Three out of the five models' climate data produce evergreen and deciduous taiga in what is now southwestern Alaska, however the pollen data does not support this. The distributions of cushion forb, lichen, and moss tundra and graminoid tundra differ noticeably between models, while shrub tundra distributions are generally similar. Future simulations of BIOME4 based on the RCP8.5 climate scenario indicate a northward shift of the treeline and a significant areal decrease of shrub tundra and graminoid tundra regions in the 21st century. Intrusions of cool mixed, deciduous, and conifer forests above 60°N, especially in southwest Alaska, were notable

  2. 50 CFR Appendix I to Part 37 - Legal Description of the Coastal Plain, Arctic National Wildlife Refuge, Alaska

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 50 Wildlife and Fisheries 6 2010-10-01 2010-10-01 false Legal Description of the Coastal Plain, Arctic National Wildlife Refuge, Alaska I Appendix I to Part 37 Wildlife and Fisheries UNITED STATES FISH AND WILDLIFE SERVICE, DEPARTMENT OF THE INTERIOR (CONTINUED) THE NATIONAL WILDLIFE REFUGE SYSTEM GEOLOGICAL AND GEOPHYSICAL EXPLORATION OF...

  3. Cultural Resilience of Nenets Social-Ecological Systems in Arctic Russia: A Focus on Reindeer Nomads of the Tundra

    NASA Astrophysics Data System (ADS)

    Forbes, B. C.

    2013-12-01

    Empirical data on resilience in social-ecological systems (SESs) are reviewed from local and regional scale case studies among full-time nomads in the neighbouring Nenets and Yamal-Nenets Autonomous Okrugs, Russia. The focus is on critical cultural factors contributing to SES resilience. In particular, this work presents an integrated view of people situated in specific tundra landscapes that face significantly different prospects for adaptation depending on existing or planned infrastructure associated with oil and gas development. Factors contributing to general resilience are compared to those that are adapted to certain spatial and temporal contexts. Environmental factors include ample space and an abundance of resources, such as fish and game (e.g. geese), to augment the diet of not only the migratory herders, but also residents from coastal settlements. In contrast to other regions, such as the Nenets Okrug, Yamal Nenets households consist of intact nuclear families with high retention among youth in the nomadic tundra population. Accepting attitudes toward exogenous drivers such as climate change and industrial development appear to play a significant role in how people react to both extreme weather events and piecemeal confiscation or degradation of territory. Consciousness of their role as responsible stewards of the territories they occupy has likely been a factor in maintaining viable wildlife populations over centuries. Institutions administering reindeer herding have remained flexible, especially on Yamal, and so accommodate decision-making that is sensitive to herders' needs and timetables. This affects factors such as herd demography, mobility and energetics. Resilience is further facilitated within the existing governance regimes by herders' own agency, most recently in the post-Soviet shift to smaller, privately managed herds that can better utilize available pastures in a highly dynamic environment experiencing rapid socio-economic, climate and

  4. Modeling the influence of hydrological processes on spatial and temporal patterns of CO{sub 2} soil efflux from an arctic tundra catchment

    SciTech Connect

    Ostendorf, B.

    1996-08-01

    Spatial and temporal patterns of CO{sub 2} efflux from arctic tundra soils are examined with three, linked simulation models at a 2.2-km{sup 2} catchment. The model complex runs on a 20*20 m grid and a temporal resolution of 1 h over one growing season. TOPMODEL is used to predict the dynamics of the water balance and spatial pattern of water table. A canopy model (GAS-FLUX) is used to predict moss and vascular plant transpiration rates. Soil respiration is computed form an empirical regression model incorporating the effects of soil temperature and depth to the water table. Soil efflux in the riparian zones of 60 g C m{sup {minus}2} compares to 119 g C m{sup {minus}2} in the hillslopes indicating large spatial differences. An increase of air temperature and solar radiation or a decrease of precipitation increase soil respiration. The results indicate a tight connection between water and carbon cycles at the catchment scale. Keeping all other conditions constant, a seasonal increase of transpiration rates by 10% increases soil respiration by 5% or 4.6 g Cm{sup {minus}2}. Data deficiencies and suggestions for future modeling are discussed. 40 refs., 8 figs.

  5. 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.

  6. 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

  7. Factors in Rapid Coastal Retreat: Comparing Two New Datasets for Alaska's Arctic Coast

    NASA Astrophysics Data System (ADS)

    Higman, B. M.; Gibbs, A.; Richmond, B. M.

    2014-12-01

    Dramatic coastal change dominated by erosion and retreat is widespread on arctic coasts, and two extensive new datasets in Alaska's Arctic provide insight into the extent and character of this change. ShoreZone data provides detailed categorical descriptions of physical coastal morphology for about 6000 km of Beaufort and Chukchi Seas coast. A USGS National Assessment of Shoreline Change (NASC) study documents coastal change rates at 50 meter intervals along about 1300 km of coast distributed between the Canadian Border and Icy Cape, almost entirely within the ShoreZone study area. Descriptive ShoreZone data provides a framework for better understanding coastal environments and their importance to change rates. We are applying a new method for clustering and comparing ShoreZone units to generate subsets of NASC coastal change rates with similar coastal morphology, and mapping areas outside the NASC study that show similarity to areas with documented high rates of erosion or accretion. Joint analysis of these two datasets provides insight into the processes that control coastal change, and a starting point for understanding how climate change is transforming Arctic coasts.

  8. Shifting balance of thermokarst lake ice regimes across the Arctic Coastal Plain of northern Alaska

    NASA Astrophysics Data System (ADS)

    Arp, C. D.; Jones, B. M.; Lu, Z.; Whitman, M. S.

    2012-08-01

    The balance of thermokarst lakes with bedfast- and floating-ice regimes across Arctic lowlands regulates heat storage, permafrost thaw, winter-water supply, and over-wintering aquatic habitat. Using a time-series of late-winter synthetic aperture radar (SAR) imagery to distinguish lake ice regimes in two regions of the Arctic Coastal Plain of northern Alaska from 2003-2011, we found that 18% of the lakes had intermittent ice regimes, varying between bedfast-ice and floating-ice conditions. Comparing this dataset with a radar-based lake classification from 1980 showed that 16% of the bedfast-ice lakes had shifted to floating-ice regimes. A simulated lake ice thinning trend of 1.5 cm/yr since 1978 is believed to be the primary factor driving this form of lake change. The most profound impacts of this regime shift in Arctic lakes may be an increase in the landscape-scale thermal offset created by additional lake heat storage and its role in talik development in otherwise continuous permafrost as well as increases in over-winter aquatic habitat and winter-water supply.

  9. Analysis of the origin of Aufeis feed-water on the arctic slope of Alaska

    NASA Technical Reports Server (NTRS)

    Hall, D. K.; Roswell, C. (Principal Investigator)

    1980-01-01

    The origin of water feeding large aufeis fields (overflow river ice) on the Arctic Slope of Alaska is analyzed. Field measurements of two large aufeis fields on the eastern Arctic Slope were taken during July of 1978 and 1979. Measurements of aufeis extent and distribution were made using LANDSAT Multispectral Scanner Subsystem (MSS) satellite data from 1973 through 1979. In addition, ice cores were analyzed in the laboratory. Results of the field and laboratory studies indicate that the water derived from aufeis melt water has a chemical composition different from the adjacent upstream river water. Large aufeis fields are found in association with springs and faults thus indicating a subterranean origin of the feed water. In addition, the maximum extent of large aufeis fields was not found to follow meteorological patterns which would only be expected if the origin of the feed water were local. It is concluded that extent of large aufeis in a given river channel on the Arctic Slope is controlled by discharge from reservoirs of groundwater. It seems probable that precipitation passes into limestone aquifers in the Brooks Range, through an interconnecting system of subterranean fractures in calcareous rocks and ultimately discharges into alluvial sediments on the coastal plain to form aufeis. It is speculated that only small aufeis patches are affected by local meteorological parameters in the months just prior to aufeis formation.

  10. Assessment of undiscovered petroleum resources of the Arctic Alaska Petroleum Province

    USGS Publications Warehouse

    Houseknecht, David W.; Bird, Kenneth J.; Garrity, Christopher P.

    2012-01-01

    The Arctic Alaska Petroleum Province encompasses all lands and adjacent continental shelf areas north of the Brooks Range-Herald arch tectonic belts and south of the northern (outboard) margin of the Alaska rift shoulder. Even though only a small part is thoroughly explored, it is one of the most prolific petroleum provinces in North America, with total known resources (cumulative production plus proved reserves) of about 28 billion barrels of oil equivalent. For assessment purposes, the province is divided into a platform assessment unit, comprising the Alaska rift shoulder and its relatively undeformed flanks, and a fold-and-thrust belt assessment unit, comprising the deformed area north of the Brooks Range and Herald arch tectonic belts. Mean estimates of undiscovered, technically recoverable resources include nearly 28 billion barrels of oil and 122 trillion cubic feet of nonassociated gas in the platform assessment unit and 2 billion barrels of oil and 59 trillion cubic feet of nonassociated gas in the fold-and-thrust belt assessment unit.

  11. Early Wisconsinan (MIS 4) Arctic ground squirrel middens and a squirrel-eye-view of the mammoth-steppe

    NASA Astrophysics Data System (ADS)

    Zazula, Grant D.; Froese, Duane G.; Elias, Scott A.; Kuzmina, Svetlana; Mathewes, Rolf W.

    2011-08-01

    Fossil arctic ground squirrel ( Spermophilus parryii) middens were recovered from ice-rich loess sediments in association with Sheep Creek-Klondike and Dominion Creek tephras (ca 80 ka) exposed in west-central Yukon. These middens provide plant and insect macrofossil evidence for a steppe-tundra ecosystem during the Early Wisconsinan (MIS 4) glacial interval. Midden plant and insect macrofossil data are compared with those previously published for Late Wisconsinan middens dating to ˜25-29 14C ka BP (MIS 3/2) from the region. Although multivariate statistical comparisons suggest differences between the relative abundances of plant macrofossils, the co-occurrence of steppe-tundra plants and insects (e.g., Elymus trachycaulus, Kobresia myosuroides, Artemisia frigida, Phlox hoodii, Connatichela artemisiae) provides evidence for successive reestablishment of the zonal steppe-tundra habitats during cold stages of the Late Pleistocene. Arctic ground squirrels were well adapted to the cold, arid climates, steppe-tundra vegetation and well-drained loessal soils that characterize cold stages of Late Pleistocene Beringia. These glacial conditions enabled arctic ground squirrel populations to expand their range to the interior regions of Alaska and Yukon, including the Klondike, where they are absent today. Arctic ground squirrels have endured numerous Quaternary climate oscillations by retracting populations to disjunct "interglacial refugia" during warm interglacial periods (e.g., south-facing steppe slopes, well-drained arctic and alpine tundra areas) and expanding their distribution across the mammoth-steppe biome during cold, arid glacial intervals.

  12. Initial Conceptualization and Application of the Alaska Thermokarst Model

    NASA Astrophysics Data System (ADS)

    Bolton, W. R.; Lara, M. J.; Genet, H.; Romanovsky, V. E.; McGuire, A. D.

    2015-12-01

    Thermokarst topography forms whenever ice-rich permafrost thaws and the ground subsides due to the volume loss when ground ice transitions to water. The Alaska Thermokarst Model (ATM) is a large-scale, state-and-transition model designed to simulate transitions between landscape units affected by thermokarst disturbance. The ATM uses a frame-based methodology to track transitions and proportion of cohorts within a 1-km2 grid cell. In the arctic tundra environment, the ATM tracks thermokarst-related transitions among wetland tundra, graminoid tundra, shrub tundra, and thermokarst lakes. In the boreal forest environment, the ATM tracks transitions among forested permafrost plateau, thermokarst lakes, collapse scar fens and bogs. The transition from one cohort to another due to thermokarst processes can take place if thaw reaches ice-rich ground layers either due to pulse disturbance (i.e. large precipitation event or fires), or due to gradual active layer deepening that eventually results in penetration of the protective layer. The protective layer buffers the ice-rich soils from the land surface and is critical to determine how susceptible an area is to thermokarst degradation. The rate of terrain transition in our model is determined by a set of rules that are based upon the ice-content of the soil, the drainage efficiency (or the ability of the landscape to store or transport water), the cumulative probability of thermokarst initiation, distance from rivers, lake dynamics (increasing, decreasing, or stable), and other factors. Tundra types are allowed to transition from one type to another (for example, wetland tundra to graminoid tundra) under favorable climatic conditions. In this study, we present our conceptualization and initial simulation results from in the arctic (the Barrow Peninsula) and boreal (the Tanana Flats) regions of Alaska.

  13. 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

  14. Stock origins of Dolly Varden collected from Beaufort Sea coastal sites of Arctic Alaska and Canada

    USGS Publications Warehouse

    Krueger, C.C.; Wilmot, R.L.; Everett, R.J.

    1999-01-01

    Anadromous northern Dolly Varden Salvelinus malma support a summer subsistence fishery in Beaufort Sea coastal waters. These same waters coincide with areas of oil and gas exploration and development. The purpose of this study was to assess variation in stock origins of Dolly Varden collected from sites along 400 km of Beaufort Sea coast. Mixed-stock analyses (MSA) of allozyme data were used to compare collections from four sites (Endicolt near Prudhoe Bay, Mikkelsen Bay, and Kaktovik in Alaska and Phillips Bay in Canada) and to assess variation in stock contributions among summer months and between 1987 and 1988. The MSA estimates for individual stocks were summed into estimates for three stock groups: western stocks from the area near Sagavarnirktok River and Prudhoe Bay (SAG), Arctic National Wildlife Refuge stocks (Arctic Refuge), and Canadian stocks. The MSA of Endicott samples taken in 1987 and 1988 did not differ among months in terms of contributions from local SAG stocks (range, 71-95%). Contributions from nonlocal (>100 km distant) Canadian and Arctic Refuge stocks were not different from zero in 1987, but contributions from Canadian stocks were so in July (17%) and August (20%) but not in September of 1988. Thus, stock contributions to Endicott collections were different between 1987 and 1988. Samples from the Kaktovik area in 1988 were different between months in terms of contributions from nonlocal SAG stocks (July, 7%; August, 27%). Significant contributions to these samples were made both months by Canadian (25% and 17%) and local Arctic Refuge stocks (68% and 56%). Among the four coastal sites, local stocks typically contributed most to collections; however, every site had collections that contained significant contributions from nonlocal stocks. The MSA estimates clearly revealed the movement of Dolly Varden between U.S. and Canada coastal waters. If local stocks are affected by oil and gas development activities, distant subsistence fisheries

  15. A comparison of multi-spectral, multi-angular, and multi-temporal remote sensing datasets for fractional shrub canopy mapping in Arctic Alaska

    USGS Publications Warehouse

    Selkowitz, D.J.

    2010-01-01

    Shrub cover appears to be increasing across many areas of the Arctic tundra biome, and increasing shrub cover in the Arctic has the potential to significantly impact global carbon budgets and the global climate system. For most of the Arctic, however, there is no existing baseline inventory of shrub canopy cover, as existing maps of Arctic vegetation provide little information about the density of shrub cover at a moderate spatial resolution across the region. Remotely-sensed fractional shrub canopy maps can provide this necessary baseline inventory of shrub cover. In this study, we compare the accuracy of fractional shrub canopy (> 0.5 m tall) maps derived from multi-spectral, multi-angular, and multi-temporal datasets from Landsat imagery at 30 m spatial resolution, Moderate Resolution Imaging SpectroRadiometer (MODIS) imagery at 250 m and 500 m spatial resolution, and MultiAngle Imaging Spectroradiometer (MISR) imagery at 275 m spatial resolution for a 1067 km2 study area in Arctic Alaska. The study area is centered at 69 ??N, ranges in elevation from 130 to 770 m, is composed primarily of rolling topography with gentle slopes less than 10??, and is free of glaciers and perennial snow cover. Shrubs > 0.5 m in height cover 2.9% of the study area and are primarily confined to patches associated with specific landscape features. Reference fractional shrub canopy is determined from in situ shrub canopy measurements and a high spatial resolution IKONOS image swath. Regression tree models are constructed to estimate fractional canopy cover at 250 m using different combinations of input data from Landsat, MODIS, and MISR. Results indicate that multi-spectral data provide substantially more accurate estimates of fractional shrub canopy cover than multi-angular or multi-temporal data. Higher spatial resolution datasets also provide more accurate estimates of fractional shrub canopy cover (aggregated to moderate spatial resolutions) than lower spatial resolution datasets

  16. Influence of pre-Mississippian paleogeology on Carboniferous Lisburne Group, Arctic National Wildlife refuge, northeastern Alaska

    SciTech Connect

    Watts, K.F.; Carlson, R.; Imm, T.; Gruzlovic, P.; Hanks, C.

    1988-02-01

    The Carboniferous Lisburne Group of northern Alaska formed an extensive carbonate platform, which was later deformed as part of the Brooks Range fold and thrust belt. In the northeast, the Lisburne Group is parautochthonous and analogous to that at Prudhoe Bay. The Lisburne's paleogeography and facies relationships pertain to assessment of the petroleum potential of the Arctic National Wildlife Refuge (ANWR). The Franklinian paleogeology, unconformably underlying the Ellesmerian sequence, has influenced sedimentation patterns in the Lisburne Group. The transgressive Endicott Group (Kekiktuk Conglomerate and Kayak, Shale) and Lisburne Group thin northward over Franklinian basement highs. In the Sadlerochit Mountains, the Katakturuk Dolomite formed a paleotopographic high over which the Endicott Group inched out and the Lisburne Group thinned. Shallow-marine oolitic grainstone developed in the cyclic Pennsylvanian Wahoo Limestone.

  17. Methane turnover and environmental change from Holocene biomarker records in a thermokarst lake in Arctic Alaska

    USGS Publications Warehouse

    Elvert, Marcus; Pohlman, John; Becker, Kevin W.; Gaglioti, Benjamin V.; Hinrichs, Kai-Uwe; Wooller, Matthew J.

    2016-01-01

    Arctic lakes and wetlands contribute a substantial amount of methane to the contemporary atmosphere, yet profound knowledge gaps remain regarding the intensity and climatic control of past methane emissions from this source. In this study, we reconstruct methane turnover and environmental conditions, including estimates of mean annual and summer temperature, from a thermokarst lake (Lake Qalluuraq) on the Arctic Coastal Plain of northern Alaska for the Holocene by using source-specific lipid biomarkers preserved in a radiocarbon-dated sediment core. Our results document a more prominent role for methane in the carbon cycle when the lake basin was an emergent fen habitat between ~12,300 and ~10,000 cal yr BP, a time period closely coinciding with the Holocene Thermal Maximum (HTM) in North Alaska. Enhanced methane turnover was stimulated by relatively warm temperatures, increased moisture, nutrient supply, and primary productivity. After ~10,000 cal yr BP, a thermokarst lake with abundant submerged mosses evolved, and through the mid-Holocene temperatures were approximately 3°C cooler. Under these conditions, organic matter decomposition was attenuated, which facilitated the accumulation of submerged mosses within a shallower Lake Qalluuraq. Reduced methane assimilation into biomass during the mid-Holocene suggests that thermokarst lakes are carbon sinks during cold periods. In the late-Holocene from ~2700 cal yr BP to the most recent time, however, temperatures and carbon deposition rose and methane oxidation intensified, indicating that more rapid organic matter decomposition and enhanced methane production could amplify climate feedback via potential methane emissions in the future.

  18. 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.

  19. Seasonal to Decadal Change of Arctic Coastal Bluffs, Barter Island, Alaska

    NASA Astrophysics Data System (ADS)

    Richmond, B. M.; Gibbs, A.; Erikson, L. H.; Beitch, M. J.

    2015-12-01

    Warming air and sea temperatures in the Arctic are leading to elevated levels of permafrost thaw and longer periods of ice-free conditions during the summer months which can lead to increased coastal exposure to storm surge and wave impacts. Using recently collected time-lapse photography, historical maps and imagery, and DEM's derived from airborne lidar and aerial photography using structure from motion (SfM) algorithms, we document coastal bluff change along a 5 km stretch of coast on Barter Island in NE Alaska during a single summer and over several decades. Time-lapse cameras installed during the summers of 2014 and 2015 on the coastal bluffs are used to create an archive of hourly air temperature and pressure, bluff morphology, and sea conditions allowing us to document individual bluff failure events and conditions at the time of failure. The historical rates of bluff retreat are derived from 1947 T-sheet maps, various periods of satellite imagery, aerial orthophoto mosaics, and more recently acquired lidar and SfM DEM data. Coastal change rates at 50 m transect spacing have been calculated over a seven decade time span. We combine these results with elevation models and bluff geology to estimate overall volume change and sediment contribution to the nearshore. These combined datasets are used to better understand the timing and processes of arctic coastal retreat.

  20. Cadmium in arctic Alaska wildlife: Kidney and liver residues and potential exposure in indigenous people

    SciTech Connect

    O`Hara, T.; Fairbrother, A.; Becker, P.; Tarpley, R.

    1995-12-31

    In arctic Alaska, cadmium (Cd) levels are of concern in kidney and liver of terrestrial and marine mammals including: bowhead whale, beluga whale, walrus, caribou, and ringed seal. Cd levels in some animals exceed threshold criteria in kidney for renal dysfunction and other effects, tolerance levels for human consumption (liver = 1 ppm, kidney = 3 ppm), and WHO weekly intake limits (500 ug Cd/week). An assessment of risk to indigenous people and to wildlife populations, will be presented. Cigarette smoking is another major source of Cd to be considered. Reports from Greenland have concluded a health risk from Cd exposure from marine dietary sources and smoking exist for these residents. Bowhead whale kidney and walrus kidney and liver represent major dietary sources of Cd (blubber and meat have very little Cd). Followed by: ringed seal liver (kidney data not available), beluga whale liver and kidney, and caribou kidney. Small portions of bowhead and walrus kidney (< 10g/week) exceed weekly intake levels. Age positively correlates with Cd levels in kidney indicating that avoiding older (larger) animals would reduce exposure. Adverse effects of Cd in wildlife were not grossly evident, however, with no historic data, it is difficult to determine if tissue concentrations are elevated. Harvest of wildlife is important to many arctic people for nutritional and cultural survival. Assessing risks associated with contaminants is essential for the wellbeing of indigenous people and wildlife. The nutritional value of the local resources and the potential inadequate alternatives must be considered.

  1. Petrologic-petrophysical-engineering relationships, selected wells near the Arctic National Wildlife Refuge, Alaska

    SciTech Connect

    Mowatt, T.C.; Gibson, C.; Seidlitz, A.; Bascle, R.; Dygas, J. )

    1991-03-01

    In the context of the reservoir management and resource assessment programs of the U.S. Bureau of Land Management in Alaska, selected stratigraphic horizons were studied in a number of wells adjacent to the Arctic National Wildlife Refuge (ANWR), northeast Alaska. Petrographic analyses were integrated with petrophysical and engineering data, in order to provide a substantive knowledge base from which to infer reservoir potentials elsewhere in the region, using geological and geophysical methods. Of particular interest in the latter regard is the ANWR area. Horizons of concern with regard to reservoir characteristics include Franklinian through Brookian strata. Of particular interest are clastic Ellesmerian 'Break-up/Rift Sequence' sediments such as the Lower Cretaceous Thomson sand, and deeper-water marine clastics, as exemplified by the Brookian Colville Group 'turbidites.' Also of concern are pre-Ellesmerian 'basement' rocks, some of which are hosts to hydrocarbon accumulations in the Point Thomson field. Petrologic-mineralogic characteristics have been keyed to various wireline log responses and related to available engineering data, as feasible, for the wells considered. Synthesis of this information in terms of the regional geological framework, tied in with geophysical data, will facilitate more refined, effective resource assessment and management.

  2. Late Quaternary and Future Biome Simulations for Alaska and Eastern Russia

    NASA Astrophysics Data System (ADS)

    Hendricks, Amy; Walsh, John; Saito, Kazuyuki; Bigelow, Nancy

    2015-04-01

    We simulated Arctic biomes across a region including Alaska and Eastern Russia using the BIOME4 biogeochemical and biogeography vegetation model. BIOME4, which produces an equilibrium vegetation distribution under a given climate condition, was forced by CMIP5/PMIP3 climate data. We are exploring vegetation and permafrost distributions during the last 21,000 years and future projections (2100 C.E.) to gain an understanding of the effects of climate shifts on this complex subsystem. When forced with the baseline modern climatology, compiled from the University of Delaware temperature and precipitation climatology and ERA-40 sunshine data, our biome simulations were generally consistent with current vegetation observations in the study region. Much of the study area was simulated to have evergreen and deciduous taiga and shrub tundras. Paleoclimatological simulations were compared with pollen data samples taken through the study region. Simulations for the Last Glacial Maximum show the Bering Land Bridge covered almost entirely by cushion forb, lichen, and moss tundra, shrub tundra, and graminoid tundra. Three out of the five models' climate data produce evergreen and deciduous taiga in what is now southwestern Alaska. The distributions of cushion forb, lichen, and moss tundra and graminoid tundra differ noticeably between models, however, shrub tundra distributions are generally in agreement. Simulations for the Mid-Holocene are in better agreement on pollen-based distributions of biomes. Shrub tundra is simulated along the Arctic coast, and in some cases along the eastern coast of Russia. All models show evergreen taiga along the southern coast of Russia as well as covering the southern half of present-day Alaska. Deciduous taiga is simulated in the interior regions of eastern Russia and Alaska, though the distributions in Alaska differ between models. Pre-Industrial biome simulations were very similar to Mid-Holocene simulations. Differences include more shrub

  3. Mineral and whole-rock compositions of seawater-dominated hydrothermal alteration at the Arctic volcanogenic massive sulfide prospect, Alaska

    USGS Publications Warehouse

    Schmidt, J.M.

    1988-01-01

    The Arctic volcanogenic massive sulfide prospect, located in the Ambler mineral district of northwestern Alaska, includes three types of hydrothermally altered rocks overlying, underlying, and interlayered with semimassive sulfide mineralization. Hydrothermal alteration of wall rocks and deposition of sulfide and gangue minerals were contemporaneous with Late Devonian of Early Mississippian basalt-rhyolite volcanism. Alteration developed asymmetrically around a linear fissure, suggesting fracture control of ore fluids rather than a point source. Microprobe analyses of phyllosilicates from the Arctic area indicate two discrete mineral populations. These differences in mineral chemistry are the result of differences in protolith composition caused by hydrothermal alteration-metasomatism. -from Author

  4. Temperature data acquired from the DOI/GTN-P Deep Borehole Array on the Arctic Slope of Alaska, 1973-2013

    USGS Publications Warehouse

    Clow, Gary D.

    2014-01-01

    System (GTOS). The data will also be useful for refining our basic understanding of the physical conditions in permafrost in Arctic Alaska, as well as providing important information for validating predictive models used for climate impact assessments. The processed data are available from the Advanced Cooperative Arctic Data and Information Service (ACADIS) repository at doi:10.5065/D6N014HK.

  5. Arctic Animals of Alaska. First Grade Activity. Schools of California Online Resources for Education (SCORE): Connecting California's Classrooms to the World.

    ERIC Educational Resources Information Center

    Boe, Sandra

    The Arctic is covered with ice and snow for most of the year. Animals that live in Alaska's arctic region must be able to survive long winters and very cold temperatures. Surprisingly, many animals live in the harsh, cold climate. This first-grade activity plan helps students learn about the animals of the far north. The plan gives six steps for…

  6. Remote sensing of global snowpack energy and mass balance: In-situ measurements on the snow of interior and Arctic Alaska

    NASA Technical Reports Server (NTRS)

    Benson, Carl S.

    1994-01-01

    This project is continuing along the lines of the semiannual report dated January 1993. Four major tasks have been addressed: analysis of variability in the seasonal snow of interior and arctic Alaska, the interpretation of microwave brightness temperature across Alaska on transects from south to north, study of nonclimatic controls which affect glaciers, and the location of glacier facies boundaries.

  7. Methane sources in arctic thermokarst lake sediments on the North Slope of Alaska.

    PubMed

    Matheus Carnevali, P B; Rohrssen, M; Williams, M R; Michaud, A B; Adams, H; Berisford, D; Love, G D; Priscu, J C; Rassuchine, O; Hand, K P; Murray, A E

    2015-03-01

    The permafrost on the North Slope of Alaska is densely populated by shallow lakes that result from thermokarst erosion. These lakes release methane (CH4 ) derived from a combination of ancient thermogenic pools and contemporary biogenic production. Despite the potential importance of CH4 as a greenhouse gas, the contribution of biogenic CH4 production in arctic thermokarst lakes in Alaska is not currently well understood. To further advance our knowledge of CH4 dynamics in these lakes, we focused our study on (i) the potential for microbial CH4 production in lake sediments, (ii) the role of sediment geochemistry in controlling biogenic CH4 production, and (iii) the temperature dependence of this process. Sediment cores were collected from one site in Siqlukaq Lake and two sites in Sukok Lake in late October to early November. Analyses of pore water geochemistry, sedimentary organic matter and lipid biomarkers, stable carbon isotopes, results from CH4 production experiments, and copy number of a methanogenic pathway-specific gene (mcrA) indicated the existence of different sources of CH4 in each of the lakes chosen for the study. Analysis of this integrated data set revealed that there is biological CH4 production in Siqlukaq at moderate levels, while the very low levels of CH4 detected in Sukok had a mixed origin, with little to no biological CH4 production. Furthermore, methanogenic archaea exhibited temperature-dependent use of in situ substrates for methanogenesis, and the amount of CH4 produced was directly related to the amount of labile organic matter in the sediments. This study constitutes an important first step in better understanding the actual contribution of biogenic CH4 from thermokarst lakes on the coastal plain of Alaska to the current CH4 budgets. PMID:25612141

  8. Long-term monitoring at multiple trophic levels suggests heterogeneity in responses to climate change in the Canadian Arctic tundra

    PubMed Central

    Gauthier, Gilles; Bêty, Joël; Cadieux, Marie-Christine; Legagneux, Pierre; Doiron, Madeleine; Chevallier, Clément; Lai, Sandra; Tarroux, Arnaud; Berteaux, Dominique

    2013-01-01

    Arctic wildlife is often presented as being highly at risk in the face of current climate warming. We use the long-term (up to 24 years) monitoring records available on Bylot Island in the Canadian Arctic to examine temporal trends in population attributes of several terrestrial vertebrates and in primary production. Despite a warming trend (e.g. cumulative annual thawing degree-days increased by 37% and snow-melt date advanced by 4–7 days over a 23-year period), we found little evidence for changes in the phenology, abundance or productivity of several vertebrate species (snow goose, foxes, lemmings, avian predators and one passerine). Only primary production showed a response to warming (annual above-ground biomass of wetland graminoids increased by 123% during this period). We nonetheless found evidence for potential mismatches between herbivores and their food plants in response to warming as snow geese adjusted their laying date by only 3.8 days on average for a change in snow-melt of 10 days, half of the corresponding adjustment shown by the timing of plant growth (7.1 days). We discuss several reasons (duration of time series, large annual variability, amplitude of observed climate change, nonlinear dynamic or constraints imposed by various rate of warming with latitude in migrants) to explain the lack of response by herbivores and predators to climate warming at our study site. We also show how length and intensity of monitoring could affect our ability to detect temporal trends and provide recommendations for future monitoring. PMID:23836788

  9. Contrasting effects of warming and increased snowfall on Arctic tundra plant phenology over the past two decades.

    PubMed

    Bjorkman, Anne D; Elmendorf, Sarah C; Beamish, Alison L; Vellend, Mark; Henry, Gregory H R

    2015-12-01

    Recent changes in climate have led to significant shifts in phenology, with many studies demonstrating advanced phenology in response to warming temperatures. The rate of temperature change is especially high in the Arctic, but this is also where we have relatively little data on phenological changes and the processes driving these changes. In order to understand how Arctic plant species are likely to respond to future changes in climate, we monitored flowering phenology in response to both experimental and ambient warming for four widespread species in two habitat types over 21 years. We additionally used long-term environmental records to disentangle the effects of temperature increase and changes in snowmelt date on phenological patterns. While flowering occurred earlier in response to experimental warming, plants in unmanipulated plots showed no change or a delay in flowering over the 21-year period, despite more than 1 °C of ambient warming during that time. This counterintuitive result was likely due to significantly delayed snowmelt over the study period (0.05-0.2 days/yr) due to increased winter snowfall. The timing of snowmelt was a strong driver of flowering phenology for all species - especially for early-flowering species - while spring temperature was significantly related to flowering time only for later-flowering species. Despite significantly delayed flowering phenology, the timing of seed maturation showed no significant change over time, suggesting that warmer temperatures may promote more rapid seed development. The results of this study highlight the importance of understanding the specific environmental cues that drive species' phenological responses as well as the complex interactions between temperature and precipitation when forecasting phenology over the coming decades. As demonstrated here, the effects of altered snowmelt patterns can counter the effects of warmer temperatures, even to the point of generating phenological responses

  10. Chapter 32: Geology and petroleum potential of the Arctic Alaska petroleum province

    USGS Publications Warehouse

    Bird, K.J.; Houseknecht, D.W.

    2011-01-01

    The Arctic Alaska petroleum province encompasses all lands and adjacent continental shelf areas north of the Brooks Range-Herald Arch orogenic belt and south of the northern (outboard) margin of the Beaufort Rift shoulder. Even though only a small part is thoroughly explored, it is one of the most prolific petroleum provinces in North America with total known resources (cumulative production plus proved reserves) of c. 28 BBOE. The province constitutes a significant part of a displaced continental fragment, the Arctic Alaska microplate, that was probably rifted from the Canadian Arctic margin during formation of the Canada Basin. Petroleum prospective rocks in the province, mostly Mississippian and younger, record a sequential geological evolution through passive margin, rift and foreland basin tectonic stages. Significant petroleum source and reservoir rocks were formed during each tectonic stage but it was the foreland basin stage that provided the necessary burial heating to generate petroleum from the source rocks. The lion's share of known petroleum resources in the province occur in combination structural-stratigraphic traps formed as a consequence of rifting and located along the rift shoulder. Since the discovery of the super-giant Prudhoe Bay accumulation in one of these traps in the late 1960s, exploration activity preferentially focused on these types of traps. More recent activity, however, has emphasized the potential for stratigraphic traps and the prospect of a natural gas pipeline in this region has spurred renewed interest in structural traps. For assessment purposes, the province is divided into a Platform assessment unit (AU), comprising the Beaufort Rift shoulder and its relatively undeformed flanks, and a Fold-and-Thrust Belt AU, comprising the deformed area north of the Brooks Range and Herald Arch tectonic belt. Mean estimates of undiscovered, technically recoverable resources include nearly 28 billion barrels of oil (BBO) and 122 trillion

  11. Quantifying the historic and future distribution of fire in Alaskan tundra ecosystems

    NASA Astrophysics Data System (ADS)

    Young, A. M.; Higuera, P. E.; Duffy, P. A.

    2012-12-01

    During the past 60 years fire has been relatively rare and small in size within tundra ecosystems. However, historical observations and paleoecological evidence indicates that fire regimes vary widely across Alaskan tundra, in both space and time. These lines of evidence suggest that fire occupies a highly specified niche or ecological space in Alaskan tundra, which may change significantly with future climate warming. The objective of this research was to quantify the relationships between fire occurrence and different seasonal climate variables, and to begin to make inferences about future distributions of fire across the tundra landscape. The results of this research will ultimately contribute to the goal of summarizing the linkages that exist among climate, vegetation, and fire in the historical record, and for making predictions concerning fire disturbance in tundra ecosystems throughout the next century. Historic tundra fires occurred non-randomly across space, and a relationship exists between fire occurrence and warm, dry climates. We quantified this relationship with generalized boosting models (GBM) using datasets of downscaled temperature and precipitation (2 km, 1971-2000), and historic records of tundra area burned (1950-2010). The GBM used six seasonal climate variables, focused on growing season temperature and precipitation, to predict the probability of fire occurrence over the 1950-2010 time period. To understand implications of these historic relationships given ongoing climate warming, we constructed future climatologies of temperature and precipitation for the five GCMs which performed best in Alaska under the IPCC AR4 A1B (middle-of-the-road) emissions scenario for the time period 2021-2050. The GBM performed well predicting the observed spatial distribution of tundra area burned, capturing key regions which experienced the most fire activity from 1950-2010. The mean temperature of the warmest month (MeanMaxTemp) was the most influential

  12. Greater deciduous shrub abundance extends tundra peak season and increases modeled net CO2 uptake.

    PubMed

    Sweet, Shannan K; Griffin, Kevin L; Steltzer, Heidi; Gough, Laura; Boelman, Natalie T

    2015-06-01

    Satellite studies of the terrestrial Arctic report increased summer greening and longer overall growing and peak seasons since the 1980s, which increases productivity and the period of carbon uptake. These trends are attributed to increasing air temperatures and reduced snow cover duration in spring and fall. Concurrently, deciduous shrubs are becoming increasingly abundant in tundra landscapes, which may also impact canopy phenology and productivity. Our aim was to determine the influence of greater deciduous shrub abundance on tundra canopy phenology and subsequent impacts on net ecosystem carbon exchange (NEE) during the growing and peak seasons in the arctic foothills region of Alaska. We compared deciduous shrub-dominated and evergreen/graminoid-dominated community-level canopy phenology throughout the growing season using the normalized difference vegetation index (NDVI). We used a tundra plant-community-specific leaf area index (LAI) model to estimate LAI throughout the green season and a tundra-specific NEE model to estimate the impact of greater deciduous shrub abundance and associated shifts in both leaf area and canopy phenology on tundra carbon flux. We found that deciduous shrub canopies reached the onset of peak greenness 13 days earlier and the onset of senescence 3 days earlier compared to evergreen/graminoid canopies, resulting in a 10-day extension of the peak season. The combined effect of the longer peak season and greater leaf area of deciduous shrub canopies almost tripled the modeled net carbon uptake of deciduous shrub communities compared to evergreen/graminoid communities, while the longer peak season alone resulted in 84% greater carbon uptake in deciduous shrub communities. These results suggest that greater deciduous shrub abundance increases carbon uptake not only due to greater leaf area, but also due to an extension of the period of peak greenness, which extends the period of maximum carbon uptake. PMID:25556338

  13. 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.

  14. Ozone and aerosol distributions measured by airborne lidar during the 1988 Arctic Boundary Layer Experiment

    NASA Technical Reports Server (NTRS)

    Browell, Edward V.; Butler, Carolyn F.; Kooi, Susan A.

    1991-01-01

    Consideration is given to O3 and aerosol distributions measured from an aircraft using a DIAL system in order to study the sources and sinks of gases and aerosols over the tundra regions of Alaska during summer 1988. The tropospheric O3 budget over the Arctic was found to be strongly influenced by stratospheric intrusions. Regions of low aerosol scattering and enhanced O3 mixing ratios were usually correlated with descending air from the upper troposphere or lower stratosphere.

  15. Leucocytozoon simondi in emperor geese from the Yukon-Kuskokwim delta in Alaska

    USGS Publications Warehouse

    Hollmén, Tuula E.; Franson, J.C.; Creekmore, L.H.; Schmutz, J.A.; Fowler, A.C.

    1998-01-01

    We surveyed Emperor Geese (Chen canagica) in western Alaska for avian hematozoa. Blood smears were collected from 134 adults and goslings in late July 1996, on their breeding grounds on the Yukon-Kuskokwim Delta. One of 134 (0.7%) Emperor Geese harbored Leucocytozoon simondi, representing a new host record for this parasite. No other hematozoa were detected. This is one of few reports of avian blood parasites from the arctic tundra.

  16. Genetics, recruitment, and migration patterns of Arctic Cisco (Coregonus autumnalis) in the Colville River, Alaska and Mackenzie River, Canada

    USGS Publications Warehouse

    Zimmerman, Christian E.; Ramey, Andy M.; Turner, S.; Mueter, Franz J.; Murphy, S.; Nielsen, Jennifer L.

    2013-01-01

    Arctic cisco Coregonus autumnalis have a complex anadromous life history, many aspects of which remain poorly understood. Some life history traits of Arctic cisco from the Colville River, Alaska, and Mackenzie River basin, Canada, were investigated using molecular genetics, harvest data, and otolith microchemistry. The Mackenzie hypothesis, which suggests that Arctic cisco found in Alaskan waters originate from the Mackenzie River system, was tested using 11 microsatellite loci and a single mitochondrial DNA gene. No genetic differentiation was found among sample collections from the Colville River and the Mackenzie River system using molecular markers (P > 0.19 in all comparisons). Model-based clustering methods also supported genetic admixture between sample collections from the Colville River and Mackenzie River basin. A reanalysis of recruitment patterns to Alaska, which included data from recent warm periods and suspected changes in atmospheric circulation patterns, still finds that recruitment is correlated to wind conditions. Otolith microchemistry (Sr/Ca ratios) confirmed repeated, annual movements of Arctic cisco between low-salinity habitats in winter and marine waters in summer.

  17. Stoichiometry and temperature sensitivity of methanogenesis and CO 2 production from saturated polygonal tundra in Barrow, Alaska

    DOE PAGESBeta

    Roy Chowdhury, Taniya; Herndon, Elizabeth M.; Phelps, Tommy J.; Elias, Dwayne A.; Gu, Baohua; Liang, Liyuan; Wullschleger, Stan D.; Graham, David E.

    2014-11-26

    Arctic permafrost ecosystems store ~50% of global belowground carbon (C) that is vulnerable to increased microbial degradation with warmer active layer temperatures and thawing of the near surface permafrost. We used anoxic laboratory incubations to estimate anaerobic CO2 production and methanogenesis in active layer (organic and mineral soil horizons) and permafrost samples from center, ridge and trough positions of water-saturated low-centered polygon in Barrow Environmental Observatory, Barrow AK, USA. Methane (CH4) and CO2 production rates and concentrations were determined at 2, +4, or +8 C for 60 day incubation period. Temporal dynamics of CO2 production and methanogenesis at 2 Cmore » showed evidence of fundamentally different mechanisms of substrate limitation and inhibited microbial growth at soil water freezing points compared to warmer temperatures. Nonlinear regression better modeled the initial rates and estimates of Q10 values for CO2 that showed higher sensitivity in the organic-rich soils of polygon center and trough than the relatively drier ridge soils. Methanogenesis generally exhibited a lag phase in the mineral soils that was significantly longer at 2 C in all horizons. Such discontinuity in CH4 production between 2 C and the elevated temperatures (+4 and +8 C) indicated the insufficient representation of methanogenesis on the basis of Q10 values estimated from both linear and nonlinear models. Production rates for both CH4 and CO2 were substantially higher in organic horizons (20% to 40% wt. C) at all temperatures relative to mineral horizons (<20% wt. C). Permafrost horizon (~12% wt. C) produced ~5-fold less CO2 than the active layer and negligible CH4. High concentrations of initial exchangeable Fe(II) and increasing accumulation rates signified the role of iron as terminal electron acceptors for anaerobic C degradation in the mineral horizons.« less

  18. Stoichiometry and temperature sensitivity of methanogenesis and CO 2 production from saturated polygonal tundra in Barrow, Alaska

    SciTech Connect

    Roy Chowdhury, Taniya; Herndon, Elizabeth M.; Phelps, Tommy J.; Elias, Dwayne A.; Gu, Baohua; Liang, Liyuan; Wullschleger, Stan D.; Graham, David E.

    2014-11-26

    Arctic permafrost ecosystems store ~50% of global belowground carbon (C) that is vulnerable to increased microbial degradation with warmer active layer temperatures and thawing of the near surface permafrost. We used anoxic laboratory incubations to estimate anaerobic CO2 production and methanogenesis in active layer (organic and mineral soil horizons) and permafrost samples from center, ridge and trough positions of water-saturated low-centered polygon in Barrow Environmental Observatory, Barrow AK, USA. Methane (CH4) and CO2 production rates and concentrations were determined at 2, +4, or +8 C for 60 day incubation period. Temporal dynamics of CO2 production and methanogenesis at 2 C showed evidence of fundamentally different mechanisms of substrate limitation and inhibited microbial growth at soil water freezing points compared to warmer temperatures. Nonlinear regression better modeled the initial rates and estimates of Q10 values for CO2 that showed higher sensitivity in the organic-rich soils of polygon center and trough than the relatively drier ridge soils. Methanogenesis generally exhibited a lag phase in the mineral soils that was significantly longer at 2 C in all horizons. Such discontinuity in CH4 production between 2 C and the elevated temperatures (+4 and +8 C) indicated the insufficient representation of methanogenesis on the basis of Q10 values estimated from both linear and nonlinear models. Production rates for both CH4 and CO2 were substantially higher in organic horizons (20% to 40% wt. C) at all temperatures relative to mineral horizons (<20% wt. C). Permafrost horizon (~12% wt. C) produced ~5-fold less CO2 than the active layer and negligible CH4. High concentrations of initial exchangeable Fe(II) and increasing accumulation rates signified the role of iron as terminal electron acceptors for anaerobic C degradation in the mineral horizons.

  19. Stoichiometry and temperature sensitivity of methanogenesis and CO2 production from saturated polygonal tundra in Barrow, Alaska.

    PubMed

    Roy Chowdhury, Taniya; Herndon, Elizabeth M; Phelps, Tommy J; Elias, Dwayne A; Gu, Baohua; Liang, Liyuan; Wullschleger, Stan D; Graham, David E

    2015-02-01

    Arctic permafrost ecosystems store ~50% of global belowground carbon (C) that is vulnerable to increased microbial degradation with warmer active layer temperatures and thawing of the near surface permafrost. We used anoxic laboratory incubations to estimate anaerobic CO2 production and methanogenesis in active layer (organic and mineral soil horizons) and permafrost samples from center, ridge and trough positions of water-saturated low-centered polygon in Barrow Environmental Observatory, Barrow AK, USA. Methane (CH4 ) and CO2 production rates and concentrations were determined at -2, +4, or +8 °C for 60 day incubation period. Temporal dynamics of CO2 production and methanogenesis at -2 °C showed evidence of fundamentally different mechanisms of substrate limitation and inhibited microbial growth at soil water freezing points compared to warmer temperatures. Nonlinear regression better modeled the initial rates and estimates of Q10 values for CO2 that showed higher sensitivity in the organic-rich soils of polygon center and trough than the relatively drier ridge soils. Methanogenesis generally exhibited a lag phase in the mineral soils that was significantly longer at -2 °C in all horizons. Such discontinuity in CH4 production between -2 °C and the elevated temperatures (+4 and +8 °C) indicated the insufficient representation of methanogenesis on the basis of Q10 values estimated from both linear and nonlinear models. Production rates for both CH4 and CO2 were substantially higher in organic horizons (20% to 40% wt. C) at all temperatures relative to mineral horizons (<20% wt. C). Permafrost horizon (~12% wt. C) produced ~5-fold less CO2 than the active layer and negligible CH4 . High concentrations of initial exchangeable Fe(II) and increasing accumulation rates signified the role of iron as terminal electron acceptors for anaerobic C degradation in the mineral horizons. PMID:25308891

  20. Stoichiometry and temperature sensitivity of methanogenesis and CO2 production from saturated polygonal tundra in Barrow, Alaska

    DOE PAGESBeta

    Roy Chowdhury, Taniya; Herndon, Elizabeth M; Phelps, Tommy Joe; Elias, Dwayne A; Gu, Baohua; Liang, Liyuan; Wullschleger, Stan D; Graham, David E

    2015-01-01

    Arctic permafrost ecosystems store ~50% of global belowground carbon (C) that is vulnerable to increased microbial degradation with warmer active layer temperatures and thawing of the near surface permafrost. We used anoxic laboratory incubations to estimate anaerobic CO2 production and methanogenesis in active layer (organic and mineral soil horizons) and permafrost samples from center, ridge and trough positions of water-saturated low-centered polygon in Barrow Environmental Observatory, Barrow AK, USA. Methane (CH4) and CO2 production rates and concentrations were determined at 2, +4, or +8 C for 60 day incubation period. Temporal dynamics of CO2 production and methanogenesis at 2 Cmore » showed evidence of fundamentally different mechanisms of substrate limitation and inhibited microbial growth at soil water freezing points compared to warmer temperatures. Nonlinear regression better modeled the initial rates and estimates of Q10 values for CO2 that showed higher sensitivity in the organic-rich soils of polygon center and trough than the relatively drier ridge soils. Methanogenesis generally exhibited a lag phase in the mineral soils that was significantly longer at 2 C in all horizons. Such discontinuity in CH4 production between 2 C and the elevated temperatures (+4 and +8 C) indicated the insufficient representation of methanogenesis on the basis of Q10 values estimated from both linear and nonlinear models. Production rates for both CH4 and CO2 were substantially higher in organic horizons (20% to 40% wt. C) at all temperatures relative to mineral horizons (<20% wt. C). Permafrost horizon (~12% wt. C) produced ~5-fold less CO2 than the active layer and negligible CH4. High concentrations of initial exchangeable Fe(II) and increasing accumulation rates signified the role of iron as terminal electron acceptors for anaerobic C degradation in the mineral horizons.« less

  1. Utilization of remote sensing in Alaska permafrost studies

    NASA Technical Reports Server (NTRS)

    Hall, D. K.

    1981-01-01

    Permafrost related features such as: aufeis, tundra, thaw lakes and subsurface ice features were studied. LANDSAT imagery was used to measure the extent and distribution of aufeis in Arctic Slope rivers over a period of 7 years. Interannual extent of large aufeis fields was found to vary significantly. Digital LANDSAT data were used to study the short term effects of a tundra fire which burned a 48 sq km area in northwestern Alaska. Vegetation regrowth was inferred from Landsat spectral reflectance increases and compared to in-situ measurements. Aircraft SAR (Synethic Aperture Radar) imagery was used in conjunction with LANDSAT imagery used in conjunction with LANDSAT imagery to qualitatively determine depth categories for thaw lakes in northern Alaska.

  2. Arctic Summer Surface Energy Balance at Two Coastal Drained Lake Basins, Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Liljedahl, A.; Hinzman, L.; Harazono, Y.; Zona, D.; Oechel, W.

    2008-12-01

    We examined the partitioning of the summer surface energy balance at two coastal drained lake basins using measurements from two eddy covariance towers in Barrow, Alaska. Drained lake basins are a common land feature covering approximately one fourth of the Arctic Coastal Plain but have been given limited attention. Overall, wetlands are extensive in the region in spite of an annual precipitation close to a desert and a negative summer P-ET. Included in the analysis was summer 2007, which experienced unusually high air temperatures and low precipitation compared to the long term mean. During the five analyzed summers, most of the energy available at the ground surface was partitioned into sensible heat flux despite saturated or nearly saturated near-surface soils. The maritime conditions resulted in a cool and close to saturated air mass with a few exceptions on individual days. With a ground surface often warmer than the air above and limited air vapor pressure deficits, the dissipation of the available heat at the ground surface was mainly partitioned into sensible heat flux resulting in midday Bowen Ratios (sensible divided by latent heat flux) above unity. Total daily latent heat flux presented in mm of water varied between 0.2 - 4.2 mm/day with a Jun-Aug mean of 1.5 mm. In 80% of the analyzed days, mean midday evapotranspiration occurred below the equilibrium rate resulting in a Priestley-Taylor alpha value below unity. The equilibrium evaporation rates of inland arctic wetlands have previously shown to occur at or above equilibrium rate. Further, the energy balance partitioning of a wetland located in a maritime or continental climate show differences such as in the Bowen Ratio. It is therefore necessary to analyze coastal and inland areas separately when examining the hydrological response of wetlands to climate changes.

  3. Effects of experimentally-warmed tundra on diurnal gas exchange in Salix-, Carex, and Eriophorum in a high-arctic lowland oasis

    SciTech Connect

    Jones, M.H.; MacDonald, S.E. ); Henry, G.H.R. )

    1994-06-01

    Gas exchange was measured for the willow Salix arctica and two sede species. Carex qauatilus stans and Eriophorum angustifolium triste, at Alexandra Fiord, Ellesmere Island (78[degrees]52'N) in an experiment designed to stimulate climate change. The tundra was warmed using passive, open-topped experimental chambers that raised daily mean temperatures approx. 2[degrees] over two seasons. The chambers are part of the International Tundra Experiment (ITEX), the objective of which is to assess potential impacts of global warming on tundra plant communities. Salix arctica was measured in dry tundra and on adjacent wet meadow hummocks. The sedges were measured on hummocks and in hollows in the wet meadow only. Gas exchange was measured every four hours for 48 hours for each species. For S arctica, experimental warming had no effect in the dry tundra, but appeared to depress net assimilation (NA) in the wet meadow. Gas exchange parameters were slightly higher overall in the dry tundra for this species. For the sedges, the warming treatment had no major effect, although it caused some reduction of NA for Eriophorum on the hummocks. Gas exchange parameters were generally higher for Carex than for Eriophorum. No regular diurnal patterns of gas exchange were observed for any species.

  4. The Arctic clouds from model simulations and long-term observations at Barrow, Alaska

    NASA Astrophysics Data System (ADS)

    Zhao, Ming

    The Arctic is a region that is very sensitive to global climate change while also experiencing significant changes in its surface air temperature, sea-ice cover, atmospheric circulation, precipitation, snowfall, biogeochemical cycling, and land surface. Although previous studies have shown that the arctic clouds play an important role in the arctic climate changes, the arctic clouds are poorly understood and simulated in climate model due to limited observations. Furthermore, most of the studies were based on short-term experiments and typically only cover the warm seasons, which do not provide a full understanding of the seasonal cycle of arctic clouds. To address the above concerns and to improve our understanding of arctic clouds, six years of observational and retrieval data from 1999 to 2004 at the Atmospheric Radiation Management (ARM) Climate Research Facility (ACRF) North Slope of Alaska (NSA) Barrow site are used to understand the arctic clouds and related radiative processes. In particular, we focus on the liquid-ice mass partition in the mixed-phase cloud layer. Statistical results show that aerosol type and concentration are important factors that impact the mixed-phase stratus (MPS) cloud microphysical properties: liquid water path (LWP) and liquid water fraction (LWF) decrease with the increase of cloud condensation nuclei (CCN) number concentration; the high dust loading and dust occurrence in the spring are possible reasons for the much lower LWF than the other seasons. The importance of liquid-ice mass partition on surface radiation budgets was analyzed by comparing cloud longwave radiative forcings under the same LWP but different ice water path (IWP) ranges. Results show the ice phase enhance the surface cloud longwave (LW) forcing by 8˜9 W m-2 in the moderately thin MPS. This result provides an observational evidence on the aerosol glaciation effect in the moderately thin MPS, which is largely unknown so far. The above new insights are

  5. Future freshwater demands in the Arctic

    NASA Astrophysics Data System (ADS)

    White, D.; Strang, E. T.; Hinzman, L.; Alessa, L.; Kliskey, A.

    2004-12-01

    The overall objective of our research is to understand how humans rely on freshwater at local and regional scales in the Arctic, how these dependencies have changed in the recent past, and how they are likely to change in the future. This study will take place on the Seward Peninsula where climate induced changes in the hydrologic cycle are already being observed. This presentation will describe the human dependencies on freshwater in the Arctic. In particular, we will discuss the effects of inadequate quantity or quality of freshwater on Arctic inhabitants. The freshwater used by humans in the Arctic for drinking, cooking, and washing is derived in many cases from surface water, such as lakes and streams. Since the surface water frozen 6-9 months of the year in the Arctic, communities that rely on rivers and lakes must treat and store large volumes of water for use during winter. The stored water must be heated throughout the winter and distributed on an as-needed basis. Unfortunately, when not enough water can be gathered in the summer or stored in the winter, the entire community may be without freshwater. During these months, water must be collected by individuals from ice, snow, and rain. Collecting water during breakup can be dangerous. River ice is rotten, there is too little snow for snow mobiles, and the tundra is too soft all terrain vehicles. While the state of Alaska and Federal programs are making progress towards developing sustainable water sources for Alaska's Arctic communities, freshwater remains a precious commodity. Communities throughout the Arctic, including Canada and Russia, have similar problems with obtaining and purifying freshwater. As climate induced changes are being observed in the Arctic, the threat to the freshwater resource is now a greater concern than ever. This study is being funded under the NSF Arctic System Science Program, Human Dimensions of the Arctic (OPP-0328686).

  6. THE ROLE OF THERMAL REGIMEN IN TUNDRA PLANT COMMUNITY RESTORATION

    EPA Science Inventory

    Mineral extraction activities in the Arctic regions of the world produce long-lasting ecological disturbances. Assisted recovery from such disturbances may require restoration of the tundra thermal regime. We transplanted plugs of entire root zone and live tundra plants to a dist...

  7. Deriving Arctic Cloud Microphysics at Barrow, Alaska. Algorithms, Results, and Radiative Closure

    SciTech Connect

    Shupe, Matthew D.; Turner, David D.; Zwink, Alexander; Thieman, Mandana M.; Mlawer, Eli J.; Shippert, Timothy

    2015-07-01

    Cloud phase and microphysical properties control the radiative effects of clouds in the climate system and are therefore crucial to characterize in a variety of conditions and locations. An Arctic-specific, ground-based, multi-sensor cloud retrieval system is described here and applied to two years of observations from Barrow, Alaska. Over these two years, clouds occurred 75% of the time, with cloud ice and liquid each occurring nearly 60% of the time. Liquid water occurred at least 25% of the time even in the winter, and existed up to heights of 8 km. The vertically integrated mass of liquid was typically larger than that of ice. While it is generally difficult to evaluate the overall uncertainty of a comprehensive cloud retrieval system of this type, radiative flux closure analyses were performed where flux calculations using the derived microphysical properties were compared to measurements at the surface and top-of-atmosphere. Radiative closure biases were generally smaller for cloudy scenes relative to clear skies, while the variability of flux closure results was only moderately larger than under clear skies. The best closure at the surface was obtained for liquid-containing clouds. Radiative closure results were compared to those based on a similar, yet simpler, cloud retrieval system. These comparisons demonstrated the importance of accurate cloud phase classification, and specifically the identification of liquid water, for determining radiative fluxes. Enhanced retrievals of liquid water path for thin clouds were also shown to improve radiative flux calculations.

  8. Metagenomic survey for viruses in Western Arctic caribou, Alaska, through iterative assembly of taxonomic units.

    PubMed

    Schürch, Anita C; Schipper, Debby; Bijl, Maarten A; Dau, Jim; Beckmen, Kimberlee B; Schapendonk, Claudia M E; Raj, V Stalin; Osterhaus, Albert D M E; Haagmans, Bart L; Tryland, Morten; Smits, Saskia L

    2014-01-01

    Pathogen surveillance in animals does not provide a sufficient level of vigilance because it is generally confined to surveillance of pathogens with known economic impact in domestic animals and practically nonexistent in wildlife species. As most (re-)emerging viral infections originate from animal sources, it is important to obtain insight into viral pathogens present in the wildlife reservoir from a public health perspective. When monitoring living, free-ranging wildlife for viruses, sample collection can be challenging and availability of nucleic acids isolated from samples is often limited. The development of viral metagenomics platforms allows a more comprehensive inventory of viruses present in wildlife. We report a metagenomic viral survey of the Western Arctic herd of barren ground caribou (Rangifer tarandus granti) in Alaska, USA. The presence of mammalian viruses in eye and nose swabs of 39 free-ranging caribou was investigated by random amplification combined with a metagenomic analysis approach that applied exhaustive iterative assembly of sequencing results to define taxonomic units of each metagenome. Through homology search methods we identified the presence of several mammalian viruses, including different papillomaviruses, a novel parvovirus, polyomavirus, and a virus that potentially represents a member of a novel genus in the family Coronaviridae. PMID:25140520

  9. Evolving drainage networks and nutrient fluxes in continuous permafrost zones of interior and arctic Alaska

    NASA Astrophysics Data System (ADS)

    Koch, J. C.; Smith, R. L.; Gurney, K.; Wipfli, M.; Ewing, S. A.; Jorgenson, M. T.; Striegl, R. G.; Schmutz, J.

    2012-12-01

    It is generally accepted that permafrost thaw will release carbon and nutrients into high-latitude environments. However, utilization of these additions is highly dependent on hydrologic transport within ecosystems. Here we compare two headwater catchments in the interior Alaska and two sites further north on the Arctic Coastal Plain. All sites are underlain by continuous permafrost and summer warming leads to seasonal deepening of the active layer up to 0.3 to 1 m in early August. This annual thaw cycle promotes water and solute infiltration and storage, and often allows rapid movement of water and solutes near the organic/mineral and freeze/thaw soil boundaries. We present data from laboratory incubations, runoff and interflow sampling, and natural and manipulative stream nutrient additions. Our results indicate 1) the ability of runoff to access and thaw solute-rich water at the top of the permafrost, 2) the high concentrations of carbon, nitrogen, and phosphorous that can be delivered to aquatic ecosystems, and 3) the potential for rapid nutrient assimilation and cycling in ponds and low-order streams. We also provide evidence that rapid transport often limits actual cycling/assimilation rates. Understanding these coupled hydrological and biogeochemical processes is increasingly a focus of catchment and polar hydrology and will aid in predicting the effects of decadal-scale permafrost thaw and subsurface flowpath and drainage network evolution on nutrient fluxes and cycling.

  10. Metagenomic Survey for Viruses in Western Arctic Caribou, Alaska, through Iterative Assembly of Taxonomic Units

    PubMed Central

    Schürch, Anita C.; Schipper, Debby; Bijl, Maarten A.; Dau, Jim; Beckmen, Kimberlee B.; Schapendonk, Claudia M. E.; Raj, V. Stalin; Osterhaus, Albert D. M. E.; Haagmans, Bart L.; Tryland, Morten; Smits, Saskia L.

    2014-01-01

    Pathogen surveillance in animals does not provide a sufficient level of vigilance because it is generally confined to surveillance of pathogens with known economic impact in domestic animals and practically nonexistent in wildlife species. As most (re-)emerging viral infections originate from animal sources, it is important to obtain insight into viral pathogens present in the wildlife reservoir from a public health perspective. When monitoring living, free-ranging wildlife for viruses, sample collection can be challenging and availability of nucleic acids isolated from samples is often limited. The development of viral metagenomics platforms allows a more comprehensive inventory of viruses present in wildlife. We report a metagenomic viral survey of the Western Arctic herd of barren ground caribou (Rangifer tarandus granti) in Alaska, USA. The presence of mammalian viruses in eye and nose swabs of 39 free-ranging caribou was investigated by random amplification combined with a metagenomic analysis approach that applied exhaustive iterative assembly of sequencing results to define taxonomic units of each metagenome. Through homology search methods we identified the presence of several mammalian viruses, including different papillomaviruses, a novel parvovirus, polyomavirus, and a virus that potentially represents a member of a novel genus in the family Coronaviridae. PMID:25140520

  11. Relationship between environmental conditions and rates of coastal erosion in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Barnhart, K. R.; Anderson, R. S.; Overeem, I.; Wobus, C. W.; Clow, G. D.; Urban, F. E.; LeWinter, A. L.; Stanton, T. P.

    2012-12-01

    Rates of coastal cliff erosion are a function of the geometry and substrate of the coast; storm frequency, duration, magnitude, and wave field; and regional sediment sources. In the Arctic, the duration of sea ice-free conditions limits the time over which coastal erosion can occur, and sea water temperature modulates erosion rates where ice content of coastal bluffs is high. Predicting how coastal erosion rates in this environment will respond to future climate change requires that we first understand modern coastal erosion rates. Arctic coastlines are responding rapidly to climate change. Remotely sensed observations of coastline position indicate that the mean annual erosion rate along a 60-km reach of Alaska's Beaufort Sea coast, characterized by high ice content and small grain size, doubled from 7 m yr-1 for the period 1955-1979 to 14 m yr-1 for 2002-2007. Over the last 30 years the duration of the open water season expanded from ˜45 days to ˜95 days, increasing exposure of permafrost bluffs to seawater by a factor of 2.5. Time-lapse photography indicates that coastal erosion in this environment is a halting process: most significant erosion occurs during storm events in which local water level is elevated by surge, during which instantaneous submarine erosion rates can reach 1-2 m/day. In contrast, at times of low water, or when sea ice is present, erosion rates are negligible. We employ a 1D coastal cross-section numerical model of the erosion of ice-rich permafrost bluffs to explore the sensitivity of the system to environmental drivers. Our model captures the geometry and style of coastal erosion observed near Drew Point, Alaska, including insertion of a melt-notch, topple of ice-wedge-bounded blocks, and subsequent degradation of these blocks. Using consistent rules, we test our model against the temporal pattern of coastal erosion over two periods: the recent past (~30 years), and a short (~2 week) period in summer 2010. Environmental conditions used

  12. Decadally resolved quantitative temperature reconstruction spanning 5.6 ka at Kurupa Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Boldt, B. R.; Kaufman, D. S.; Briner, J. P.

    2012-12-01

    Pre-instrumental quantitative temperature records, fundamental for placing recent warming in the context of long-term, natural climate variability, are scarce in Arctic Alaska. New non-destructive high-resolution core scanning methods provide a means of constructing downcore inference models for various paleoclimate signals. Here we use visible reflectance spectroscopy (VIS-RS) to measure organic pigment (chlorophyll derivative) concentration in sediments from Kurupa Lake to quantitatively reconstruct air temperature in the north-central Brooks Range, Alaska during the past 5.6 ka. Kurupa Lake (N 68.35°, W -154.61°) is 29.7 km2, 40 m at maximum depth, and is fed by several tributaries, including meltwater from eight rapidly disappearing cirque glaciers. A 6.2-m-long core composed of finely laminated (sub-mm to 5 cm) coarse-grained clays to medium-grained silts was collected in 2010 from the primary depocenter of Kurupa Lake (depth = 34 m). The age model for the core is based on six radiocarbon ages and a Pu profile to capture the 1963 spike and 1953 onset of Pu deposition from atmospheric weapons testing. The split-core face was scanned with a Konica Minolta CM-2600d spectrometer at 2 mm intervals, corresponding to 1-2 years. The relative absorption band depth at 660-670 nm (RABD660-670) was used to quantify total sedimentary organic pigments (primarily diagenetic products of chlorophyll-a) as a proxy for primary productivity. Gridded temperature data from the NCEP reanalysis dataset were used for this study because regional weather stations in the Brooks Range are scarce and records discontinuous. The gridded data perform well in this area and are highly correlated (r = 0.88) with the instrumental record from Barrow. Mean May-through-October (warm half-year) temperature (5-year smoothed) from NCEP reanalysis data (130 years) correlates with inferred organic pigment content from Kurupa Lake (r = 0.76, p < 0.001). We chose k-fold cross-validation (k = 10) to

  13. Future Biome Projections in Alaska and East Russia

    NASA Astrophysics Data System (ADS)

    Hendricks, A.; Saito, K.; Bigelow, N. H.; Walsh, J. E.

    2014-12-01

    We projected Arctic biomes across a region including Alaska and Eastern Russia using the BIOME4 biogeochemical and biogeography vegetation model. BIOME4, which produces an equilibrium vegetation distribution under a given climate condition, was forced by CMIP5/PMIP3 climate data considered in IPCC AR5. We are exploring vegetation and permafrost distributions during the last 21,000 years and future projections (2100 C.E.) to gain an understanding of the effects of climate shifts on this complex subsystem. When forced with the baseline climatology, compiled from the University of Delaware temperature and precipitation climatology and ERA-40 sunshine data, our biome simulations were generally consistent with current vegetation observations in the study region. The biomes in this region are mostly evergreen and deciduous taiga capped by shrub and graminoid tundras to the north. The more noticeable differences were the tree line simulated north of the Brooks Range in Alaska and evergreen taiga in southwest Alaska where we know these biomes do not exist today. The projected changes in climate conditions in the region under a RCP8.5 climate scenario (significant warming upwards of 10°C by some models, an increase in precipitation by as much as 40%, and carbon dioxide concentration reaching approximately 940 ppm) drive shifts in Arctic biomes. The tree line shifts northward while shrub tundra and graminoid tundra regions decrease significantly. An intrusion of cool mixed, deciduous, and conifer forests above 60° north, especially in southwest Alaska, were marked and were not modeled for present day. Across eastern Russia, deciduous taiga begins to overtake evergreen taiga, except along the coastal regions where evergreen taiga remains the favored biome. The implications of vegetation shifts in the Arctic are vast and include effects on snow cover, soil properties, permafrost distribution, and albedo, not to mention impacts on local fauna and people of the Artic.

  14. 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.

  15. Modeling the spatio-temporal variability in subsurface thermal regimes across a low-relief polygonal tundra landscape: Modeling Archive

    DOE Data Explorer

    Peter E. Thornton; Jitendra Kumar; Colleen M. Iversen; Richard T. Mills; Gautam Bisht; Nathan Collier; Vladimir Romanovsky

    2016-01-27

    This Modeling Archive is in support of an NGEE Arctic discussion paper under review and available at http://www.the-cryosphere-discuss.net/tc-2016-29/. Vast carbon stocks stored in permafrost soils of Arctic tundra are under risk of release to atmosphere under warming climate. Ice--wedge polygons in the low-gradient polygonal tundra create a complex mosaic of microtopographic features. The microtopography plays a critical role in regulating the fine scale variability in thermal and hydrological regimes in the polygonal tundra landscape underlain by continuous permafrost. Modeling of thermal regimes of this sensitive ecosystem is essential for understanding the landscape behaviour under current as well as changing climate. We present here an end-to-end effort for high resolution numerical modeling of thermal hydrology at real-world field sites, utilizing the best available data to characterize and parameterize the models. We develop approaches to model the thermal hydrology of polygonal tundra and apply them at four study sites at Barrow, Alaska spanning across low to transitional to high-centered polygon and representative of broad polygonal tundra landscape. A multi--phase subsurface thermal hydrology model (PFLOTRAN) was developed and applied to study the thermal regimes at four sites. Using high resolution LiDAR DEM, microtopographic features of the landscape were characterized and represented in the high resolution model mesh. Best available soil data from field observations and literature was utilized to represent the complex hetogeneous subsurface in the numerical model. This data collection provides the complete set of input files, forcing data sets and computational meshes for simulations using PFLOTRAN for four sites at Barrow Environmental Observatory. It also document the complete computational workflow for this modeling study to allow verification, reproducibility and follow up studies.

  16. Sensitivity of permafrost carbon release to past climate change in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Gaglioti, B.; Mann, D. H.; Wooller, M. J.; Jones, B. M.; Farquharson, L. M.; Pohlman, J.

    2015-12-01

    Warming may cause arctic permafrost to thaw and release large stores of carbon (C) downstream and into the atmosphere. Documenting how permafrost-C release responded to prehistoric warming events can help determine its sensitivity to future climate change. We did this by first quantifying past climate change in Arctic Alaska over the last 15,000 years using oxygen isotope ratios in ancient wood cellulose, which is a proxy for summer temperatures and moisture sources. We then used radiocarbon (14C) age-offsets in lake sediment to determine how much permafrost C was being released over this same time period. A 14C age-offset is the difference between the true age of deposition determined by the 14C ages of delicate, terrestrial plant remains and the age of bulk sediment from the same stratigraphic layer. This bulk sediment contains ancient C derived from permafrost in the lake's watershed. Shifts in the magnitude of the age-offset over time provide a proxy for changes in the relative amount of permafrost C being released. Today, the age-offset in our study lake is 2,000 calibrated years before present (cal yr BP), which is the lowest it has been over the last 15,000 years. During the warmer-than-present, Bølling-Allerød period (BA; 14,700-12,900 cal yr BP), and the Holocene Thermal Maximum (HTM; 11,700-8,500 cal yr BP), the age offset reached 4,000-6,000 cal yr, indicating large inputs of ancient C to the lake via permafrost thaw. This enhanced input of ancient C was interrupted during the cold and dry Younger Dryas interval (YD; 12,900-11,700 cal yr BP). Interestingly, age-offsets during the YD were similar to today's, suggesting that the insulating peat layer now covering much of the LOP watershed is stabilizing permafrost C in the face of recent warming. However, this buffering capacity has a limit, and judging by the heightened influx of permafrost C during the HTM, this limit may be reached if summer temperatures warm a further 2-3°C. Temperature and

  17. Arctic continental shelf morphology related to sea-ice zonation, Beaufort Sea, Alaska

    USGS Publications Warehouse

    Reimnitz, E.; Toimil, L.; Barnes, P.

    1978-01-01

    Landsat-1 and NOAA satellite imagery for the winter 1972-1973, and a variety of ice and sea-floor data were used to study sea-ice zonation and dynamics and their relation to bottom morphology and geology on the Beaufort Sea continental shelf of arctic Alaska. In early winter the location of the boundary between undeformed fast ice and westward-drifting pack ice of the Pacific Gyre is controlled by major coastal promontories. Pronounced linear pressure- and shear-ridges, as well as hummock fields, form along this boundary and are stabilized by grounding, generally between the 10- and 20-m isobaths. Slippage along this boundary occurs intermittently at or seaward of the grounded ridges, forming new grounded ridges in a widening zone, the stamukhi zone, which by late winter extends out to the 40-m isobath. Between intermittent events along the stamukhi zone, pack-ice drift and slippage is continuous along the shelf edge, at average rates of 3-10 km/day. Whether slippage occurs along the stamukhi zone or along the shelf edge, it is restricted to a zone several hundred meters wide, and ice seaward of the slip face moves at uniform rates without discernible drag effects. A causal relationship is seen between the spatial distribution of major ice-ridge systems and offshore shoals downdrift of major coastal promontories. The shoals appear to have migrated shoreward under the influence of ice up to 400 m in the last 25 years. The sea floor seaward of these shoals within the stamukhi zone shows high ice-gouge density, large incision depths, and a high degree of disruption of internal sedimentary structures. The concentration of large ice ridges and our sea floor data in the stamukhi zone indicate that much of the available marine energy is expended here, while the inner shelf and coast, where the relatively undeformed fast ice grows, are sheltered. There is evidence that anomalies in the overall arctic shelf profile are related to sea-ice zonation, ice dynamics, and bottom

  18. The North Slope of Alaska and Tourism: Potential Impacts on the Arctic National Wildlife Refuge (ANWR)

    NASA Astrophysics Data System (ADS)

    Everett, L. R.

    2004-12-01

    The hydrocarbon industry of Alaska is currently the leading producer of revenue for the Alaskan state economy. Second only to hydrocarbons is the tourism industry. Tourism has been a viable industry since the 1890's when cruises touted the beauty of glaciers and icebergs along the Alaskan coastline. This industry has seen a steady growth for the past few decades throughout the state. The North Slope of Alaska, particularly Prudhoe Bay and the National Petroleum Reserve, has long been associated with hydrocarbon development and today displays a landscape dotted with gravel drill pads, gas and oil pipelines and housing for the oil workers. While tourism is not usually considered hand in hand with the hydrocarbon industry, it has mimicked the development of hydrocarbons almost since the beginning. Today one not only sees the effects of the oil industry on the North Slope, but also the tourist industry as planes unload dozens of tourists, or tour buses and private vehicles arrive daily via the Dalton Highway. In Deadhorse, hotels that once only housed the oil workers now welcome the tourist, offering tours of the oil fields and adjacent areas and have become jumping off sites for wilderness trips. Tourism will create jobs as well as revenue. However, at present, there are few restrictions or guidelines in place that will deal with the potential impacts of increased tourism. Because of this there are many concerns about the possible impacts tourism and the infrastructure development will have on the North Slope. To list several concerns: (1) What are the impacts of increased tourism and the infrastructure development? (2) What will the impacts be on the Arctic National Wildlife Refuge (ANWR), which sits a mere 60 miles to the east of Deadhorse? (3) Will hydrocarbon development in ANWR and the associated infrastructure exacerbate potential impact by encouraging greater use of the Refuge by tourists? (4) Will tourism itself have a negative impact on this fragile

  19. Sikuliqiruq: Ice dynamics of the Meade river - Arctic Alaska, from freezeup to breakup from time-series ground imagery

    USGS Publications Warehouse

    Beck, R.A.; Rettig, A.J.; Ivenso, C.; Eisner, Wendy R.; Hinkel, Kenneth M.; Jones, Benjamin M.; Arp, C.D.; Grosse, G.; Whiteman, D.

    2010-01-01

    Ice formation and breakup on Arctic rivers strongly influence river flow, sedimentation, river ecology, winter travel, and subsistence fishing and hunting by Alaskan Nat