Alaskan Arctic Coastal Plain Research Articles

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

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.

Mapping Polar Bear Maternal Denning Habitat in the National Petroleum Reserve–Alaska with an IfSAR Digital Terrain Model

The National Petroleum Reserve–Alaska (NPR-A) in northeastern Alaska provides winter maternal denning habitat for polar bears (Ursus maritimus) and also has high potential for recoverable hydrocarbons. Denning polar bears exposed to human activities may abandon their dens before their young are able to survive the severity of Arctic winter weather. To ensure that wintertime petroleum activities do not threaten polar bears, managers need to know the distribution of landscape features in which maternal dens are likely to occur. Here, we present a map of potential denning habitat within the NPR-A. We used a fine-grain digital elevation model derived from Interferometric Synthetic Aperture Radar (IfSAR) to generate a map of putative denning habitat. We then tested the map’s ability to identify polar bear denning habitat on the landscape. Our final map correctly identified 82% of denning habitat estimated to be within the NPR-A. Mapped denning habitat comprised 19.7 km2 (0.1% of the study area) and was widely dispersed. Though mapping denning habitat with IfSAR data was as effective as mapping with the photogrammetric methods used for other regions of the Alaskan Arctic coastal plain, the use of GIS to analyze IfSAR data allowed greater objectivity and flexibility with less manual labor. Analytical advantages and performance equivalent to that of manual cartographic methods suggest that the use of IfSAR data to identify polar bear maternal denning habitat is a better management tool in the NPR-A and wherever such data may be available.

Predicting breeding shorebird distributions on the Arctic Coastal Plain of Alaska

The Arctic Coastal Plain (ACP) of Alaska is an important region for millions of migrating and nesting shorebirds. However, this region is threatened by climate change and increased human development (e.g., oil and gas production) that have the potential to greatly impact shorebird populations and breeding habitat in the near future. Because historic data on shorebird distributions in the ACP are very coarse and incomplete, we sought to develop detailed, contemporary distribution maps so that the potential impacts of climate‐mediated changes and development could be ascertained. To do this, we developed and mapped habitat suitability indices for eight species of shorebirds (Black‐bellied Plover [Pluvialis squatarola], American Golden‐Plover [Pluvialis dominica], Semipalmated Sandpiper [Calidris pusilla], Pectoral Sandpiper [Calidris melanotos], Dunlin [Calidris alpina], Long‐billed Dowitcher [Limnodromus scolopaceus], Red‐necked Phalarope [Phalaropus lobatus], and Red Phalarope [Phalaropus fulicarius]) that commonly breed within the ACP of Alaska. These habitat suitability models were based on 767 plots surveyed during nine years between 1998 and 2008 (surveys were not conducted in 2003 and 2005), using single‐visit rapid area searches during territory establishment and incubation (8 June–1 July). Species‐specific habitat suitability indices were developed and mapped using presence‐only modeling techniques (partitioned Mahalanobis distance) and landscape environmental variables. For most species, habitat suitability increased at lower elevations (i.e., near the coast and river deltas) and decreased within upland habitats. Accuracy of models was high for all species, ranging from 65–98%. Our models predicted that the largest fraction of suitable habitat for the majority of species occurred within the National Petroleum Reserve‐Alaska, with highly suitable habitat also occurring within coastal areas of the Arctic National Wildlife Refuge west to Prudhoe Bay.

Thermokarst Lakes on the Arctic Coastal Plain of Alaska: Spatial and Temporal Variability in Summer Water Temperature

ABSTRACTIn summer 2010, water temperature profile measurements were made in 12 thermokarst lakes along a 150‐km long north–south transect across the Arctic Coastal Plain of northern Alaska. In shallow lakes, gradual warming of the water column to 1–4°C begins at the lake bed during decay of the ice cover in spring. Rapid warming follows ice‐off, with water temperature responding synchronously to synoptic weather variations across the area. Regionally, ice‐off occurs 2–4 weeks later on lakes near the coast. Inland lakes are warmer (13°C) in mid‐summer than those near the coast (7°C), reflecting the regional climate gradient and the maritime effect. All lakes are well mixed and largely isothermal, with some thermal stratification (< 2°C) occurring during calm, sunny periods in deeper lakes. In deep (6–9 m) lake‐bed depressions that are likely ice‐wedge troughs, water cools by conduction to the colder sediments below, while concurrent warming occurs in the upper water column. A spatially dense sample of near‐surface temperature measurements was collected from one lake over a short period and shows warmer (2–3°C) temperatures on the upwind, sheltered end of the lake. This study demonstrates that climatic gradients, meteorological conditions and basin characteristics impact lake temperature dynamics. Copyright © 2012 John Wiley & Sons, Ltd.

Soil moisture control over autumn season methane flux, Arctic Coastal Plain of Alaska

Abstract. Accurate estimates of annual budgets of methane (CH4) efflux in arctic regions are severely constrained by the paucity of non-summer measurements. Moreover, the incomplete understanding of the ecosystem-level sensitivity of CH4 emissions to changes in tundra moisture makes prediction of future CH4 release from the Arctic extremely difficult. This study addresses some of these research gaps by presenting an analysis of eddy covariance and chamber measurements of CH4 efflux and supporting environmental variables during the autumn season and associated beginning of soil freeze-up at our large-scale water manipulation site near Barrow, Alaska (the Biocomplexity Experiment). We found that the autumn season CH4 emission is significant (accounting for 21–25% of the average growing season emission), and that this emission is mostly controlled by the fraction of inundated landscape, atmospheric turbulence, and the decline in unfrozen water during the period of soil freezing. Drainage decreased autumn CH4 emission by a factor of 2.4 compared to our flooded treatment. Flooding slowed the soil freezing process which has implications for extending elevated CH4 emissions longer into the winter season.

Drained thaw lake basin recovery on the western Arctic Coastal Plain of Alaska using high-resolution digital elevation models and remote sensing imagery

The landscape on the Arctic Coastal Plain (ACP) of Alaska is dominated by thousands of thaw (thermokarst) lakes and associated drained thaw lake basins (DTLBs). Knowledge of the DTLBs benefits our understanding of thaw lake dynamics, carbon cycles, and paleo-climatic change on the ACP since the end of the Late Glacial. This study initializes the application of high-resolution digital elevation models (DEMs) into a systematic reconstruction of DTLBs on the western ACP and adjacent northern Arctic Foothills. The method combines a machine-based detection algorithm automating the delineation of basin paleoshorelines on IfSAR DEM data and a posterior quality control with the aid of high-resolution aerial photograph and Landsat-5 TM imagery. A total of ~3590km2 of thaw lakes and ~10130km2 of DTLBs were mapped, with an overall accuracy of 99.2% and a Kappa coefficient of 0.988. The delineated DTLB extents are conservative, as validated from eleven field-sampled paleoshorelines. A variety of topologic patterns such as merging, nesting, and overtopping are presented in the reconstructed DTLBs. Basin paleoshoreline levels are subject to average uncertainties of 0.4–0.7 m. The combined area of thaw lakes and DTLBs accounts for 57.1% of the western ACP and 23.2% of the northern Arctic Foothills in the study site. Regional analysis of several spatial and topographic characteristics demonstrates a distinct heterogeneity among the younger Outer Coastal Plain (YOCP), Outer Coastal Plain (OCP), Inner Coastal Plain (ICP), and the Arctic Foothills. Generally, the areal density of DTLBs decreases progressively on higher and older surfaces. The ICP has a lake–DTLB area ratio (0.37) greater than that in the other regions. DTLB bathymetry presents a positive correlation with surface elevation: basin maximum depths range from ~2.0m on the YOCP to ~ 8.0m on the Arctic Foothills. Given the reconstructed DTLBs, a total of 31.9 (±4.9) gigatons of net water drainage were estimated for the entire study area.

Modeling the subsurface thermal impact of Arctic thaw lakes in a warming climate

Warming air temperatures in the Arctic are modifying the rates of thermokarst processes along Alaska's Arctic Coastal Plain. The Arctic Coastal Plain is dominated by thaw lakes. These kilometer-scale lakes are the most visible surface features in the region, and they provide important habitats for migratory birds. The lakes are formed by thermokarst processes, and are therefore susceptible to change as warming continues. We present a 1D numerical model of permafrost and subsidence processes in order to investigate the subsurface thermal impact of thaw lakes of various depths, and to evaluate how this impact might change in a warming climate. Currently, most thaw lakes in the region are shallow (<∼2m deep), freeze to their base each winter, and are not underlain by permanently unfrozen ground (taliks). Field observations indicate that these shallow lakes have not greatly altered the thermal structure of the subsurface. Our model suggests that under a warming scenario, the number of lakes that do not freeze to their base during the winter, and are therefore underlain by taliks, will increase. Such changes could substantially alter the hydrology of the Arctic Coastal Plain.

Aircraft‐derived regional scale CO2 fluxes from vegetated drained thaw‐lake basins and interstitial tundra on the Arctic Coastal Plain of Alaska

AbstractThe landscape surface of the Barrow Peninsula of Alaska is a mosaic of small ponds, thaw lakes, different aged vegetated drained thaw‐lake basins (VDTLBs), and interstitial tundra which have been dynamically formed by both short‐ and long‐term processes. We used a combination of tower‐ and aircraft‐based eddy covariance measurements to characterize the spatial and temporal patterns of CO2, latent, and sensible heat fluxes along with MODIS NDVI, and were able to scale the aircraft‐based CO2 fluxes to the 1802 km2 Barrow Peninsula region. During typical 2006 summer conditions, the midday hourly CO2 flux over the region was −2.04 × 105 kg CO2 h−1. The CO2 fluxes among the interstitial tundra, Ancient, and Old VDTLBs, as well as between the Medium and Young VDTLBs were not significantly different. Combined, the interstitial tundra and Old and Ancient VDTLBs represent∼67% of the Barrow Peninsula surface area, accounting for ∼59% of the regional flux signal. Although the Medium and Young VDTLBs represent ∼11% of the surface area, they account for a large portion, ∼35%, of the total regional flux. The remaining ∼22% of the surface area are lakes and contributed the remaining ∼6% of the total regional flux. Previous studies treated vegetated areas of the region as a single surface type with measurements from a few study sites; doing so could underestimate the regional flux by ∼22%. Here, we demonstrate that aircraft‐based systems have the ability to cover large spatial scales while measuring the turbulent fluxes across a number of surfaces and combined with ground‐ and satellite‐based measurements provide a valuable tool for both scaling and validation of regional‐scale fluxes.

Fluctuations in lemming populations in north Yukon, Canada, 2007–2010

We estimated population density of brown lemmings ( Lemmus sibiricus (Kerr, 1792)), Greenland collared lemmings ( Dicrostonyx groenlandicus (Traill, 1823)), and tundra voles ( Microtus oeconomus (Pallas, 1776)) on Herschel Island from 2007 to 2010 by mark–recapture on three live-trapping areas. Limited data were also available from Komakuk Beach on the north Yukon coast. In contrast to most previous studies, brown and collared lemmings were partly out of phase. Brown lemmings on Herschel reached peak density in 2007–2008 and were low in 2009–2010, while collared lemmings were at peak density in 2007–2008 and again in 2010. Large adult male body size was characteristic of peak populations. Brown lemmings increased dramatically in the peak summer of 2008 and collared lemmings increased rapidly when winter breeding under the snow was successful in 2009–2010. By contrast, at Komakuk Beach, we could see no clear signs of fluctuations in these three species. Winter snow conditions may be too severe for population persistence on the coastal plain along the north coast of the Yukon. Further work is needed to unravel why peak lemming densities are so variable among sites and why lemming fluctuations are so pronounced on the arctic coastal plain of Alaska and virtually absent on the coastal plain of the north Yukon.

Breeding Ecology of Birds at Teshekpuk Lake: A Key Habitat Site on the Arctic Coastal Plain of Alaska

&lt;span style="font-family: 'Times New Roman';"&gt;The Teshekpuk Lake Special Area in the National Petroleum Reserve – Alaska (NPR-A) currently has no long-term protection from oil development. In this study, we provide novel information on nest density, productivity, and habitat use at Teshekpuk relative to a developed oilfield site at Prudhoe Bay, Alaska, to assess the importance of Teshekpuk for tundra-nesting birds and to provide recommendations regarding potential oil development. Mean annual nest density of all bird species combined was significantly higher at Teshekpuk than at Prudhoe Bay and was higher than any of five other sites with comparable data on the Alaskan Arctic Coastal Plain. Nest densities were significantly higher at Teshekpuk than at Prudhoe Bay for Lapland longspurs (&lt;em&gt;Calcarius lapponicus&lt;/em&gt;) and long-billed dowitchers (&lt;em&gt;Limnodromus scolopaceus&lt;/em&gt;), although those for semipalmated sandpipers (&lt;em&gt;Calidris pusilla&lt;/em&gt;) were higher at Prudhoe Bay. Total shorebird nest densities at Teshekpuk were among the highest of any sites in the region. At Teshekpuk, shorebirds nested preferentially in wet and emergent habitats, including flooded low-center polygons, non-patterned tundra, and &lt;em&gt;Carex aquatilis&lt;/em&gt;-dominated habitats. Therefore, we recommend that future oil infrastructure placement in this region avoid these habitats. Using data collected at Teshekpuk and Prudhoe Bay from 2005 to 2008, we modeled nest survivorship for 11 shorebird species and for Lapland longspurs. For longspurs, the best-supported models based on AIC&lt;/span&gt;&lt;span style="font-family: 'Times New Roman';"&gt;c &lt;/span&gt;&lt;span style="font-family: 'Times New Roman';"&gt;values indicated that nest survival was always higher at Teshekpuk, but it was also higher elsewhere in years of high lemming abundance and later in the nesting season. For shorebirds, the best-supported models indicated that nest survivorship was highly variable among years and sites. Uniparental-nesting shorebirds had lower nest survivorship shortly after nest initiation followed by a rapid increase, while biparental survivorship was consistently high throughout the nest lifetime. We recommend that disturbances to nesting habitat be minimized during early June, when vulnerability to nest failure is higher. Because of their high importance to Arctic breeding birds, we recommend that areas within the Teshekpuk Lake Special Area, including our study area and those that are currently under 10-year deferral, be considered for permanent protection.&lt;/span&gt;

Hydrogeomorphic processes of thermokarst lakes with grounded‐ice and floating‐ice regimes on the Arctic coastal plain, Alaska

AbstractThermokarst lakes cover &gt; 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed, water quality, and climatic data over a 35‐year period. Shoreline erosion rates due to permafrost degradation ranged from &lt; 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P − EL) with periods of full and nearly dry basins. Shorter‐term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long‐term record for only shallow lakes. Our analysis suggests that grounded‐ice lakes are ice‐free on average 37 days longer than floating‐ice lakes resulting in a longer period of evaporative loss and more frequent negative P − EL. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Alaskan Permafrost Groundwater Storage Changes Derived from GRACE and Ground Measurements

The Arctic is in transition from climate-driven thawing of permafrost. We investigate satellite-derived water equivalent mass changes, snow water equivalent with in situ measurements of runoff and ground-survey derived geoid models from 1999 through 2009. The Alaskan Arctic coastal plain groundwater storage (including wetland bog, thaw pond and lake) is increasing by 1.15 ± 0.65 km3/a (area-average 1.10 ± 0.62 cm/a), and Yukon River watershed groundwater storage is decreasing by 7.44 ± 3.76 km3/a (area‑average 0.79 ± 0.40 cm/a). Geoid changes show increases within the Arctic coastal region and decreases within the Yukon River watershed. We hypothesize these changes are linked to the development of new predominately closed- and possibly open-talik in the continuous permafrost zone under large thaw lakes with increases of lakes and new predominately open-talik and reduction of permafrost extent in the discontinuous and sporadic zones with decreases of thaw lakes.

Characterization of the carbon fluxes of a vegetated drained lake basin chronosequence on the Alaskan Arctic Coastal Plain

AbstractGreenhouse gas fluxes from vegetated drained lake basins have been largely unstudied, although these land features constitute up to 47% of the land cover in the Arctic Coastal Plain in northern Alaska. To describe current and to better predict future sink/source activity of the Arctic tundra, it is important to assess these vegetated drained lake basins with respect to the patterns of and controls on gross primary production (GPP), net ecosystem exchange, and ecosystem respiration (ER). We measured CO2 fluxes and key environmental variables during the 2007 growing season (June through August) in 12 vegetated drained lake basins representing three age classes (young, drained about 50 years ago; medium, drained between 50 and 300 years ago; and old, drained between 300 and 2000 years ago, as determined by Hinkel et al., 2003) in the Arctic Coastal Plain. Young vegetated drained lake basins had both the highest average GPP over the summer (11.4 gCO2 m−2 day−1) and the highest average summer ER (7.3 gCO2 m−2 day−1), while medium and old vegetated drained lake basins showed lower and similar GPP (7.9 and 7.2 gCO2 m−2 day−1, respectively), and ER (5.2 and 4 gCO2 m−2 day−1, respectively). Productivity decreases with age as nutrients are locked up in living plant material and dead organic matter. However, we showed that old vegetated drained lakes basins maintained relatively high productivity because of the increased development of ice‐wedge polygons, the formation of ponds, and the re‐establishment of very productive species. Comparison of the seasonal CO2 fluxes and concomitant environmental factors over this chronosequence provides the basis for better understanding the patterns and controls on CO2 flux across the coastal plain of the North Slope of Alaska and for more accurately estimating current and future contribution of the Arctic to the global carbon budget.

Modeling the Effects of Lakes and Wetlands on the Water Balance of Arctic Environments

AbstractLakes, ponds, and wetlands are common features in many low-gradient arctic watersheds. Storage of snowmelt runoff in lakes and wetlands exerts a strong influence on both the interannual and interseasonal variability of northern rivers. This influence is often not well represented in hydrology models and the land surface schemes used in climate models. In this paper, an algorithm to represent the evaporation and storage effects of lakes and wetlands within the Variable Infiltration Capacity (VIC) macroscale hydrology model is described. The model is evaluated with respect to its ability to represent water temperatures, net radiation, ice freeze–thaw, and runoff production for a variety of high-latitude locations. It is then used to investigate the influence of surface storage on the spatial and temporal distribution of water and energy fluxes for the Kuparuk and Putuligayuk Rivers, on the Alaskan arctic coastal plain. Inclusion of the lake and wetland algorithm results in a substantial improvement of the simulated streamflow hydrographs, as measured using the monthly Nash–Sutcliffe efficiency. Simulations of runoff from the Putuligayuk watershed indicate that up to 80% of snow meltwater goes into storage each year and does not contribute to streamflow. Approximately 46% of the variance in the volume of snowmelt entering storage can be explained by the year-to-year variation in maximum snow water equivalent and the lake storage deficit from the previous summer. The simulated summer lake storage deficit is much lower than the cumulative precipitation minus lake evaporation (−47 mm, on average) as a result of simulated recharge from the surrounding uplands.

Polar Bear Maternal Den Habitat in the Arctic National Wildlife Refuge, Alaska

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.

Distribution of Breeding Shorebirds on the Arctic Coastal Plain of Alaska

Available information on the distribution of breeding shorebirds across the Arctic Coastal Plain of Alaska is dated, fragmented, and limited in scope. Herein, we describe the distribution of 19 shorebird species from data gathered at 407 study plots between 1998 and 2004. This information was collected using a single-visit rapid area search technique during territory establishment and early incubation periods, a time when social displays and vocalizations make the birds highly detectable. We describe the presence or absence of each species, as well as overall numbers of species, providing a regional perspective on shorebird distribution. We compare and contrast our shorebird distribution maps to those of prior studies and describe prominent patterns of shorebird distribution. Our examination of how shorebird distribution and numbers of species varied both latitudinally and longitudinally across the Arctic Coastal Plain of Alaska indicated that most shorebird species occur more frequently in the Beaufort Coastal Plain ecoregion (i.e., closer to the coast) than in the Brooks Foothills ecoregion (i.e., farther inland). Furthermore, the occurrence of several species indicated substantial longitudinal directionality. Species richness at surveyed sites was highest in the western portion of the Beaufort Coastal Plain ecoregion. The broad-scale distribution information we present here is valuable for evaluating potential effects of human development and climate change on Arctic-breeding shorebird populations.

Incorporating uncertainty about species’ potential distributions under climate change into the selection of conservation areas with a case study from the Arctic Coastal Plain of Alaska

This analysis presents a conservation planning framework for decisions under uncertainty and applies it to the Arctic Coastal Plain of Alaska. Uncertainty arises from variable distributional shifts of species’ ranges due to climate change. The planning framework consists of a two-stage optimization model that selects a nominal conservation area network in the first stage and evaluates its performance under the climate scenarios in the second stage. The model is applied to eleven at-risk species in Alaska including the threatened Spectacled Eider and Steller’s Eider sea ducks and the polar bear. The 109th United States Congress and 2008 federal budget proposed opening for oil and gas development the “1002 Area” of the Arctic National Wildlife Refuge, which intersects the Plain. This analysis finds that, if Arctic Alaska experiences 1.5 °C of warming by 2040 (as predicted by the Intergovernmental Panel on Climate Change’s A2 scenario), then potential habitat will decrease significantly for eight of these at-risk species, including the polar bear. This analysis also shows that there is synergism between oil and gas development and climate change. For instance, climate change accompanied by no development of the 1002 Area results in an increase of potential habitat for Steller’s Eider. However, if development accompanies climate change, then there is a 20% decrease in that area. Further, this analysis quantifies the tradeoff between development and maintenance of suitable habitat for at-risk species.

InSAR detects possible thaw settlement in the Alaskan Arctic Coastal Plain

Satellite interferometric synthetic aperture radar (InSAR) has proven to be an effective tool for monitoring surface deformation from volcanoes, earthquakes, landslides, and groundwater withdrawal. This paper seeks to expand the list of applications of InSAR data to include monitoring subsidence possibly associated with thaw settlement over the Alaskan Arctic Coastal Plain. To test our hypothesis that InSAR data are sufficiently sensitive to detect subsidence associated with thaw settlement, we acquired all Japanese Earth Resources Satellite-1 (JERS-1) L-band data available for the summers of 1996, 1997, and 1998 over two sites on the Alaska North Slope. The least amount of subsidence for both study sites was detected in the interferograms covering the summer of 1996 (2–3 cm), interferograms from 1997 and 1998 revealed that about 3 cm of subsidence occurred at the northern Cache One Lake site, and about 5 cm of subsidence was detected at the southern Kaparuk River site. These preliminary results illustrate the capacity of the L-band (24 cm) wavelength JERS-1 radar data to penetrate the short Arctic vegetation to monitor subsidence possibly associated with thaw settlement of the active layer and (or) other hydrologic changes over relatively large areas.

THE FIRST PACHYCEPHALOSAURINE (DINOSAURIA) FROM THE PALEO-ARCTIC OF ALASKA AND ITS PALEOGEOGRAPHIC IMPLICATIONS

The last 15 years of field work along the beaches and bluffs of the Colville River, on Alaska's Arctic Coastal Plain, have produced a diverse record of high-latitude dinosaurs. Seven families and eight genera are documented with several other families and genera possibly being represented by less diagnostic remains and only a few scattered elements (Table 1; Nelms, 1989; Gangloff, 1994, 1998; Fiorillo et al., 1999; Fiorillo and Gangloff, 2000, 2001). Virtually all of the common major groups of theropods and ornithopods typical of the Late Cretaceous of northern North America are present. Most of the skeletal remains are found in rocks assigned to the Prince Creek Formation of the Colville Group (Detterman et al., 1963, 1975; Phillips, 1990). The diversity of the dinosaur record in Alaska has been significantly increased with the discovery of abundant tracks and trackways along the North Slope and Arctic Coastal Plain over the last six years. The majority of the ichnofossil record is contained in various terrestrial coal-bearing rocks assigned to the Early Cretaceous Nanushuk Group (Ahlbrandt et al., 1979). The dinosaur biozone spans the upper part of the Nanushuk group and all of the Colville Group, ranging from the mid to Late Cretaceous (Albian to Maastrichtian; Mull, 1985). The already diverse and abundant record of dinosaur skeletal fossils was increased by the discovery in 1999 of the first evidence of pachycephalosaurs from this region (Fig. 1). This taxon is now represented by a nearly complete left squamosal and the contiguous, posterior, basal part of the dome. The highly thickened bone with characteristic prismatic internal structure accompanied by the distinctive ornamentation diagnostic of this group allows for an unequivocal identification to the subfamily level. The specimen (UAM # AK-493-V-001, Fig. 2.2) is most of the left …

Satellite remote sensing classification of thaw lakes and drained thaw lake basins on the North Slope of Alaska

The purpose of this research was to map thaw lakes and drained thaw lake basins (DTLBs) on the North Slope of Alaska using satellite remote sensing. This research is the first to map DTLBs on a large scale for Alaska's Arctic Coastal Plain. Thaw lakes and DTLBs were classified from seven Landsat-7 scenes using texture analysis, spectral transformations, and image segmentation. The overall classification accuracy was 97.7% with a Kappa coefficient of 0.96. Thaw lakes had a producer accuracy of 99.1% and a user accuracy of 98.6%, while DTLBs had a producer accuracy of 93.8% and user accuracy of 98.1%. A total of 7054 km 2 of thaw lakes were mapped, accounting for 20.4% of the Arctic Coastal Plain; there were 8917 km 2 of DTLBs covering 25.7% of the study area. Continued research in the analysis of thaw lakes and DTLBs is crucial to our understanding of the global carbon cycle, atmospheric methane concentrations, heat flow and climate change.