Eastern Interior Alaska Research Articles

AirSWOT InSAR Mapping of Surface Water Elevations and Hydraulic Gradients Across the Yukon Flats Basin, Alaska

AbstractAirSWOT, an experimental airborne Ka‐band interferometric synthetic aperture radar, was developed for hydrologic research and validation of the forthcoming Surface Water and Ocean Topography (SWOT) satellite mission (to be launched in 2021). AirSWOT and SWOT aim to improve understanding of surface water processes by mapping water surface elevation (WSE) and water surface slope (WSS) in rivers, lakes, and wetlands. However, the utility of AirSWOT for these purposes remains largely unexamined. We present the first investigation of AirSWOT WSE and WSS surveys over complex, low‐relief, wetland‐river hydrologic environments, including (1) a field‐validated assessment of AirSWOT WSE and WSS precisions for lakes and rivers in the Yukon Flats Basin, an Arctic‐Boreal wetland complex in eastern interior Alaska; (2) improved scientific understanding of surface water flow gradients and the influence of subsurface permafrost; and (3) recommendations for improving AirSWOT precisions in future scientific and SWOT validation campaigns. AirSWOT quantifies WSE with an RMSE of 8 and 15 cm in 1 and 0.0625 km2 river reaches, respectively, and 21 cm in lakes. This indicates good utility for studying hydrologic flux, WSS, geomorphic processes, and coupled surface/subsurface hydrology in permafrost environments. This also suggests that AirSWOT supplies sufficient precision for validating SWOT WSE and WSS over rivers, but not lakes. However, improvements in sensor calibration and flight experiment design may improve precisions in future deployments as may modifications to data processing. We conclude that AirSWOT is a useful tool for bridging the gap between field observations and forthcoming global SWOT satellite products.

Hypereumelanistic Horned Grebe Observed in Eastern Interior Alaska

Hypereumelanistic Horned Grebe Observed in Eastern Interior Alaska

Observations of Migrating Golden Eagles (Aquila chrysaetos) in Eastern Interior Alaska Offer Insights On Population Size and Migration Monitoring

Abstract Migratory Golden Eagles (Aquila chrysaetos) from Alaska winter across a vast region of western North America, much of which is undergoing rapid change from a diversity of indirect and direct human activities. To address recent conservation concerns, we are studying the year-round movements of migratory Golden Eagles from interior and northern Alaska to identify and evaluate potential risks to their survival. We are also developing new survey techniques to estimate population size and trends. As part of our ongoing studies, we observed migrating Golden Eagles in spring and autumn 2014 during field investigations to locate Golden Eagle capture sites in eastern interior Alaska, and in spring 2015 during capture activities. We observed large numbers of Golden Eagles in both spring and autumn, suggesting that the Mentasta Mountains are an important migration corridor for this species. Further, our observations, including 1364 migrating Golden Eagles in October 2014, suggested that the Alaska Golden Ea...

Movement patterns and space use of maternal grizzly bears influence cub survival in Interior Alaska

Abstract Foraging decisions and movement strategies by animals often involve a trade-off between meeting nutritional demands and minimizing risk of predation. We evaluated the influence of space use and movement patterns of maternal female grizzly bears (Ursus arctos) on cub (defined as first year of life) survival in eastern Interior Alaska, USA, during 2008–2012. We monitored 9 GPS radiocollared females that produced 28 cubs in 12 litters (x¯ litter size = 2.3, range = 2–3). The estimated annual cub survival rate was 0.39 (95% CI = 0.20–0.57). In all cases the entire litter survived or died prior to den entrance. All cubs in a litter died either concurrently or within 14 days in 5 of 7 litters lost. Sixty-nine percent of cub mortality occurred between 31 May and 16 June. We did not document cub mortality before 31 May. Females with surviving cubs remained within 1 km of the den for a longer period following emergence than those that lost cubs. Between den emergence and the onset of vegetation gree...

Wolf kill rates across winter in a low-density moose system in Alaska

Wolf (Canis lupus) kill rates are fundamental to understanding predation, but are not well known at low moose (Alces alces) densities. We investigated kill rates of 6 wolf packs (2–10 wolves/pack) during 2 winters on the Yukon Flats, a region of eastern Interior Alaska where moose were the sole ungulate prey of wolves occurring at densities <0.2 moose/km2. Our objectives were to compare kill rates with those from areas of greater moose densities, and to determine potential trends in kill rates across the winter. We located moose killed by wolves in February–March 2009, and November 2009–March 2010 using aerial tracking techniques and global positioning system (GPS) location clusters. Wolves killed more moose in early than late winter (βMONTH = −0.02 moose/pack/day, 95% CI = −0.01 to −0.04), and kill rate estimates (mean, 95% CI) were greatest in November (0.033 moose/wolf/day, 0.011–0.055) and least in February (0.011, 0.002–0.02). Kill rates were similar between February and March 2009 (0.019 moose/wolf/day, 0.01–0.03) and 2010 (0.018, 0.01–0.03). Prey composition was primarily adult females (39%) and young-of-the-year (35%). We attribute an elevated kill rate in early winter to predation on more vulnerable young-of-the-year. Kill rates in our study were similar to those from other studies where moose occurred at greater densities. We suggest that very few, if any, wolf–moose systems in Alaska and the Yukon experience a density-dependent phase in the functional response, and instead wolves respond numerically to changes in moose density or availability in the absence of alternative prey. Through a numerical response, wolf predation rates may approximate the annual growth potential of the moose population, contributing to persistent low densities of moose and wolves on the Yukon Flats. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Vowels of Upper Tanana Athabascan

This paper provides a detailed phonetic, synchronic description of the oral vowels of Upper Tanana, an Athabascan language spoken in eastern interior Alaska and the western Yukon Territory. Upper Tanana has, depending on the dialect, six or seven oral monophthongs that can be modified for (low) tone, nasalization, and length. Previous accounts are auditory. They disagree regarding the articulation of two of the vowels (which we represent as /ɘ/ and /ʌ/), and raise the question of whether ‘length’ indicates a quantity or a quality distinction. In contrast to earlier accounts, we provide acoustic measurements of F1, F2, and the duration of the vowels of two Alaskan dialects of Upper Tanana: Northway and Tetlin. We find that the phonetic realization of one of the vowels is quite different from the earlier auditory descriptions. For the other vowels and for the quantity distinction, our findings support earlier descriptions while supplying new details. Several co-articulation effects, previously undescribed, are also identified.

SIMULATING THE INFLUENCES OF VARIOUS FIRE REGIMES ON CARIBOU WINTER HABITAT

Caribou are an integral component of high-latitude ecosystems and represent a major subsistence food source for many northern people. The availability and quality of winter habitat is critical to sustain these caribou populations. Caribou commonly use older spruce woodlands with adequate terrestrial lichen, a preferred winter forage, in the understory. Changes in climate and fire regime pose a significant threat to the long-term sustainability of this important winter habitat. Computer simulations performed with a spatially explicit vegetation succession model (ALFRESCO) indicate that changes in the frequency and extent of fire in interior Alaska may substantially impact the abundance and quality of winter habitat for caribou. We modeled four different fire scenarios and tracked the frequency, extent, and spatial distribution of the simulated fires and associated changes to vegetation composition and distribution. Our results suggest that shorter fire frequencies (i.e., less time between recurring fires) on the winter range of the Nelchina caribou herd in eastern interior Alaska will result in large decreases of available winter habitat, relative to that currently available, in both the short and long term. A 30% shortening of the fire frequency resulted in a 3.5-fold increase in the area burned annually and an associated 41% decrease in the amount of spruce-lichen forest found on the landscape. More importantly, simulations with more frequent fires produced a relatively immature forest age structure, compared to that which currently exists, with few stands older than 100 years. This age structure is at the lower limits of stand age classes preferred by caribou from the Nelchina herd. Projected changes in fire regime due to climate warming and/or additional prescribed burning could substantially alter the winter habitat of caribou in interior Alaska and lead to changes in winter range use and/or population dynamics.

Moose Mortality in Eastern Interior Alaska

We investigated causes of mortality and the physical condition of moose (Alces alces gigas) in a multiple-predator system in eastern interior Alaska, USA, from 1998 to 2000. We identified the sources of mortality of calf and cow moose and collected fecundity and fitness data to obtain information on range quality and carrying capacity. Radiocollars were placed on 30 cow moose in 1998 and on 62 moose calves in 1998 (n = 29) and 1999 (n = 33). Estimates of fecundity and fitness parameters indicated that reproductive potential for moose was high, with a twinning rate of 63%, a pregnancy rate of 89%, and above-average body sizes of female and neonate moose. We inferred that range quality may not be a significant limiting factor for this population. We documented low neonate survival through the first 14 weeks of life (28%). Predation was responsible for 92% of known calf mortality; black bears (Ursus americanus; 45%) and grizzly bears (Ursus arctos; 39%) were the major causes of mortality. Despite low population densities in this region, grizzly bears were an important predator on neonates as well as adult female moose. Mean annual calf and adult female moose survival (20% and 88%, respectively) were similar to rates reported in other low-density moose populations in North America. We also estimated from 7 to 12% of the population was harvested annually by humans, and of that, illegal cow harvest constituted at least 33%. Our data suggest that low calf survival, adult mortality from wolf (Canis lupus) and grizzly bear predation, illegal cow harvest, and low predator harvest, all act in concert to maintain this moose population at a low density.

Potential analogues for paleoclimatic variations in eastern interior Alaska during the past 14,000 yr: atmospheric-circulation controls of regional temperature and moisture responses

The paleoclimatic history of a region can be viewed as a series of surface temperature and moisture anomalies through time. The effects of changes in large-scale climatic controls (e.g., insolation, major circulation controls) can be mediated by the influence of smaller-scale controls (e.g., topographic barriers, coastlines); this may result in heterogenous surface climatic responses at the regional and sub-regional scale. Divergent paleoclimatic trajectories between regions may be explainable in terms of such meso-scale patterns. Using modern analogues for paleoclimate we examine how the sequence of climatic variations in eastern interior Alaska during the interval 12,000–0 14 C yr BP could have been generated by specific atmospheric circulation patterns. Fossil-pollen and lake-level records document the long-term trends in temperature and effective moisture for the region. Water-balance modelling provides additional estimates of paleoprecipitation. Synoptic climatological patterns are described using the modern (instrumental) record of upper-level and sea-level pressure, surface temperature, and precipitation. At 12,000 14 C yr BP, eastern interior Alaska was cooler and drier than present, a situation generated today by a southward displacement of the jet stream. Conditions warmer and drier than present at 9000 14 C yr BP may have been generated by increased ridging north of Alaska and a weakened westerly circulation. Warmer, wetter conditions than present possibly prevailed in the late-middle Holocene; these might reflect ridging over Alaska and troughing further west. Cool, wet conditions feature enhanced westerly flow into Alaska through an eastward shift in the east Asian trough and positive pressure anomalies in the North Pacific; they may be analogous to cold periods of the Little Ice Age. The analogues demonstrate how surface conditions in other parts of Beringia may sometimes be similar to, while at other times different from those in the eastern interior. These broader spatial patterns provide hypotheses about past climates that can be tested with paleoclimatological data. For example, the widespread positive temperature anomalies associated with the warm/dry (9000 14 C yr BP) analogue fit with the expansion northward of the eastern Siberian treeline. The anomalously cool conditions in northeast Siberia associated with the warm/wet analogue may explain the continued (late-middle Holocene) treeline advance in Alaska while there was retreat in Siberia.

Pliocene terrace gravels of the ancestral Yukon River near Circle, Alaska: Palynology, paleobotany, paleoenvironmental reconstruction and regional correlation

Gravels deposited by the ancestral Yukon River are preserved in terrace remnants on the margins of the Yukon River valley near the village of Circle in east-central Alaska. Plant fossils recovered from sandy silt lenses within these gravels include cones and needles of Picea and Larix and a variety of seeds. Seed types include several taxa which no longer grow in Alaska, such as Epipremnum, Prunus and Weigela. Pollen types recovered from these deposits represent tree and shrub taxa that grow in interior Alaska today, such as Picea, Larix, Betula and Alnus, as well as several taxa that no longer grow in interior Alaska today, such as Pinus, Tsuga, Abies and Corylus. Pollen of herb taxa identified include Gramineae, Cyperaceae, Caryophyllaceae, Compositae, Polemonium and Epilobium. The fossil flora from the gravels near Circle are similar and probably age-equivalent to the flora recovered from the Nenana Gravel in the Alaska Range 250 km to the south. Palynological and tectonic evidence summarized in this paper now suggests that the Nenana Gravel was deposited during the early and middle Pliocene. The presence of plant fossils of Tsuga, Abies, Pinus, Weigela and Prunus suggests that the mean annual temperature (MAT) of eastern interior Alaska during the early and middle Pliocene was perhaps 7–9°C warmer and less continental than today's MAT of −6.4°C.

The Distribution of Some Small Mammals in Eastern Interior Alaska

The Distribution of Some Small Mammals in Eastern Interior Alaska