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Research about Alaska

Source-linked reports with geographic coverage including Alaska.

At least 109 records · Page 6Linked to original sources
USGS2025

Mechanisms influencing thermal refuges and territory occupancy by collared pikas during summer and winter

Collared pikas ( Ochotona collaris ) are cold adapted alpine lagomorphs of western Canada and Alaska, USA, that are vulnerable to direct and indirect effects of climate change. However, how and to what extent such changes influence persistence for this species is not well understood, particularly at fine spatial scales. Our goal was to evaluate how microclimate and microhabitat characteristics influence occupancy of collared pikas. We quantified thermal conditions during both summer and winter to test hypotheses about potential drivers of pika persistence. We recorded den occupancy and territory characteristics, including in situ measurements of den microclimate, across three study areas with contrasting climate gradients in southcentral and interior Alaska during 2017–2022. We examined changes in pika den occurrence by estimating annual colonization and extinction rates with a Bayesian dynamic occurrence model with forage availability, rock size, and multiple den temperature metrics as the explanatory variables. Our top model indicated that daily maximum temperature during both summer and winter best predicted den persistence and larger rocks had a moderating effect on warm summer den temperatures. This information helps to advance understanding about the mechanistic links between climate and population persistence for small mammal species under a rapidly changing arctic climate.

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USGS2025

Accounting for seasonal patterns in bird availability prevents biased population trend estimates with advancing spring phenology

Advancing spring phenology has been observed around the world, including changes in the timing of breeding of birds. When singing rates are tied to breeding stage, the rate at which birds are available for detection by surveyors can also show seasonal patterns that may shift with spring phenology. As the timing of peak bird availability changes over years, monitoring programs that do not account for changing availability could incorrectly conclude that there is a change in population size. We used a 20-yr point-count dataset to test for relationships between bird availability and spring vegetation phenology for 27 species in boreal Alaska. Nine of 22 migratory species showed a significant effect of day of spring (DOS) on availability, usually with availability declining over the survey window (late spring and early summer). In contrast, 3 of 5 resident species showed availability increasing over the survey window. We then conducted a simulation study to evaluate how changing spring phenology could affect estimates of population trend under a static survey window. We found that including DOS in the model as a covariate of availability prevented bias in the trend estimates and did not reduce precision. However, when the model ignored the effect of DOS on availability, population trend estimates were often significantly biased when spring phenology was advancing. Our study adds to previous evidence that bird availability is often related to spring phenology, and demonstrates that failing to account for seasonal changes in availability could result in the spurious estimation of a population trend when spring phenology changes over time. In some cases, the bias could be large enough to change species status assessments under IUCN Red List Criteria. Monitoring programs for birds and other taxa with seasonally varying availability could avoid bias by simply measuring and modeling the relationship between DOS and availability.

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USGS2025

Energetic value of Arctic forage-sized fish with implications for a nearshore seabird predator

Arctic cod ( Boreogadus saida , also called polar cod) are considered the single most important Arctic forage fish due to their high abundance and nutritional quality. Because Arctic cod are strongly ice associated and prefer colder waters, their frequency in coastal waters has declined with warming, decreasing availability to nearshore predators. To consider the nutritional quality of alternative prey, we measured energy density and estimated whole-body energy of forage-size (39–200 mm) fishes collected during summers 2021–2023 ( n = 274). The fishes sampled included 16 potential prey species from Foggy Island Bay (70.3°N, 147.5°W, near Prudhoe Bay) and Lion Bay (70.2°N, 146.4°W, near Flaxman Island), northern Alaska. Dry weight energy densities ranged from 16.2 to 27.5 kJ g -1 (mean ± SD = 22.0 ± 1.73 kJ g -1 , n = 274) across individuals. Of common species, Arctic cod had the highest mean energy density (24.3 ± 1.1 kJ g -1 , n = 25) and fourhorn sculpin ( Myoxocephalus quadricornis ) had the lowest (19.7 ± 0.8 kJ g -1 , n = 20). To account for size differences among prey species, whole-body energy of typical fish sizes available to predators were modeled using whole-body energy to length relationships and length distributions. Juvenile salmonids (e.g., ciscoes and whitefishes) provided the most energy per individual and were four-fold greater than smaller-bodied Arctic cod. Predators that consume juvenile ciscoes and whitefishes may be more resilient to declines in Arctic cod availability than predators with smaller gapes.

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USGS2025

Reducing bias in shorebird nest survival rates across a large Arctic landscape

Reproductive success is a key demographic parameter that can have profound impacts on a species' population trend. Indeed, poor reproductive success has been suggested as a contributing factor to the declines observed in many species of birds, including Arctic-breeding shorebirds. However, the available information on Arctic-breeding shorebird nest survival is restricted to a limited number of non-random locations where proximity to human settlements and traditional invasive monitoring techniques may artificially alter nest predation rates and, thus, bias results. To accurately assess reproductive success, unbiased estimates are needed. In this study, we monitored 96 shorebird nests (six species) at 41 randomly selected sites across a large Arctic landscape (1219 km 2 area of the Arctic National Wildlife Refuge) using minimally invasive techniques (i.e. single nest visits, temperature loggers and cameras) in 2019 and 2022. Overall, daily survival was 0.975 (95% CI: 0.955–0.987), which translates to a 53% (95% CI: 32–72%) probability of a shorebird nest surviving the median (25 days) incubation period for the studied species. Camera footage indicated Arctic Foxes Vulpes lagopus were the primary nest predator (85% of identified predation events), but Parasitic Jaegers Stercorarius parasiticus and Sandhill Cranes Grus canadensis also contributed to nest loss. In both years, greater nest failure occurred in the northwest and northcentral regions of our study area, potentially the result of greater shorebird abundance and density-dependent predation rates. Nest survival rates obtained in this study were the same as those obtained in a previous large geographical study that monitored shorebird nests across numerous small, non-randomly selected, high-density shorebird field sites that employed intensive human monitoring techniques. However, site-specific and annual differences in predator and shorebird species and densities make direct comparisons to previous studies difficult. Continued monitoring using methods that minimize bias and are consistent across time are needed to accurately measure true changes in nest survival rates that may occur under a changing climate and with increased human development.

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USGS2025

Near-surface material and topography generate anomalous high-frequency ground motion amplification in Chugiak, Alaska

An ∼3 km long nodal array oriented approximately east–west was deployed in Chugiak, Alaska, by the U.S. Geological Survey during 2021. The array intersects with the permanent NetQuakes station NP.ARTY, where peak ground acceleration (PGA) value of 1.98 g was recorded during the 2018 M w 7.1 Anchorage, Alaska, earthquake, in sharp contrast to the PGA of ∼0.3 g at a site just 4 km to the west. Seismic data for M w 1.8–4.3 aftershocks from the M w 7.1 event recorded by the nodal array confirm the anomalously large ground motions obtained at NP.ARTY as well as similar amplifications at nodes within ∼1 km to the east. Here, we performed 0–10 Hz 3D finite‐difference simulations, including high‐resolution surface topography, to explore the cause of the unexpectedly large amplification. As expected, the simulations computed with a regional 3D tomography velocity model severely underpredict the 0–10 Hz acceleration records at almost all sites. Adding a near‐surface low‐velocity taper to 300 m depth amplifies the accelerations by up to a factor of 5 and enables a reasonable match between the nodal data and simulations at sites to the west of NP.ARTY. However, this model still underpredicts the spectral energy in the area covered by glacial sediments by up to an order of magnitude. The addition of a till layer using a depth‐dependent shear‐wave velocity ( ⁠⁠ V s ) profile along with a homogeneous, 8 m thick low‐velocity layer with V s = 250 m/s representing the kame terraces improves the fit to data to within a factor of 2 at nodes located on top of the glacial sediments. Our study shows that the anomalously large high‐frequency amplification recorded at and near NP.ARTY can be explained by a combination of topographic effects and near‐surface low‐velocity material with amplification effects on the high‐frequency ground motion by up to about 40% and an order of magnitude, respectively.

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USGS2025

Interacting sea-level rise, sea-ice loss, storm flooding, erosion, and permafrost thaw threaten ecosystems, wildlife, and communities on the Yukon-Kuskokwim Delta

The Yukon-Kuskokwim Delta has the largest intertidal wetland in North America, is a globally critical breeding area for waterbirds, and is home to the largest regional indigenous population in the Arctic. Here, coastal tundra ecosystems, wildlife, and indigenous communities are highly vulnerable to sea-ice loss in the Bering Sea, sea-level rise, storm flooding, erosion, and collapsing ground from permafrost thaw caused by climate warming. These drivers interact in non-linear ways to increase flooding, salinization, and sedimentation, and thus, alter ecosystem trajectories and broader landscape evolution. Rapid changes in these factors over decadal time scales are highly likely to cause transformative shifts in coastal ecosystems across roughly 70% of the outer delta this century. We project saline and brackish ecotypes on the active delta floodplain with frequent sedimentation will maintain dynamic equilibrium with sea-level rise and flooding, slightly brackish ecotypes on the inactive floodplain with infrequent flooding and low sedimentation rates will be vulnerable to increased flooding and likely transition to more saline and brackish ecotypes, and fresh lacustrine and lowland ecotypes on the abandoned floodplain with permafrost plateaus will be vulnerable to thermokarst, salinization and flooding that will shift them toward brackish ecosystems. This will greatly affect bird nesting and foraging habitats, with both winners and losers. Already, some Yup'ik communities are facing relocation of their low-lying villages. The societal challenges and consequences of adapting to these changing landscapes are enormous and will require a huge societal effort.

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USGS2025

Warming Alaskan rivers affect first-year growth in critical northern food fishes

Arctic and subarctic rivers are warming rapidly, with unknown consequences for migratory fishes and the human communities dependent on them. To date, few studies have provided a comprehensive assessment of possible climate change impacts on the hydrology and temperature of Arctic rivers at the regional scale, and even fewer have connected those changes to multiple fish species with input and guidance from Indigenous communities. We used climate, hydrologic, and fish-growth simulations of historical (1990–2021) and future (2034–2065) young-of-year (YOY) growth potential of Chinook salmon ( Oncorhynchus tshawytscha ) and Dolly Varden ( Salvelinus malma ) for seven river basins in the Arctic-Yukon-Kuskokwim (AYK) region of Alaska, USA and Yukon Territory, Canada. Historically, summer water temperatures of all river basins remained below thresholds regarded as deleterious for Chinook salmon (14.6 °C) and Dolly Varden (16 °C), even in the warmest years. However, by the mid-century, Chinook salmon growth was limited, with declines in the warmest years in most river basins. Conversely, Dolly Varden are expected to benefit, with a near-doubling in growth projections in all river basins. This suggests that there may be an increase in suitable habitat for Dolly Varden by mid-century. The results highlight species-specific consequences of climate change and can guide future research on refugia for these species of cultural and subsistence importance to Indigenous communities in the AYK region and throughout the Arctic.

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USGS2025

Climate change and infrastructure development drive ice-rich permafrost thaw in Point Lay (Kali), Alaska

Permafrost thaw and thermokarst development pose urgent challenges to Arctic communities, threatening infrastructure and essential services. This study examines the reciprocal impacts of permafrost degradation and infrastructure in Point Lay (Kali), Alaska, drawing on field data from ∼60 boreholes, measured and modeled ground temperature records, remote sensing analysis, and community interviews. Field campaigns from 2022–2024 reveal widespread thermokarst development and ground subsidence driven by the thaw of ice-rich permafrost. Borehole analysis confirms excess-ice contents averaging ∼40%, with syngenetic ice wedges extending over 12 m deep. Measured and modeled ground temperature data indicate a warming trend, with increasing mean annual ground temperatures and active layer thickness (ALT). Since 1949, modeled ALTs have generally deepened, with a marked shift toward consistently thicker ALTs in the 21st century. Remote sensing shows ice wedge thermokarst expanded from <5% in 1949 to >60% in developed areas by 2019, with thaw rates increasing tenfold between 1974 and 2019. In contrast, adjacent, undisturbed tundra exhibited more consistent thermokarst expansion (∼0.2% yr −1 ), underscoring the amplifying role of infrastructure, surface disturbance, and climate change. Community interviews reveal the lived consequences of permafrost degradation, including structural damage to homes, failing utilities, and growing dependence on alternative water and wastewater strategies. Engineering recommendations include deeper pile foundations, targeted ice wedge stabilization, aboveground utilities, enhanced snow management strategies, and improved drainage to mitigate ongoing infrastructure issues. As climate change accelerates permafrost thaw across the Arctic, this study highlights the need for integrated, community-driven adaptation strategies that blend geocryological research, engineering solutions, and local and Indigenous knowledge.

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USGS2025

Selected special conditions affecting peak streamflow and extreme floods in Alaska through water year 2022

The U.S. Geological Survey, in cooperation with the Alaska Department of Transportation and Public Facilities, inventoried selected special conditions for annual peak flows and identified extreme floods at streamgages in Alaska through water year 2022 to facilitate hydrologic analysis. Special conditions identified from U.S. Geological Survey gaging records and basin characteristics included regulation and diversion, urbanization, indeterminate drainage areas, drainage areas less than the minimum used in regional analyses, glacial lake outburst floods, other outburst floods, and snowmelt floods. For peak flows that occurred during calendar years 1980–2019, an atmospheric river dataset was used to identify atmospheric river presence or absence on the dates peak flows occurred. Extreme floods (defined as peak flows exceeding the 1-percent annual exceedance probability flood magnitude or an empirical measure of relative magnitude using Creager’s coefficient C) were identified and associated with flood-generating mechanisms using the other inventoried special conditions and other information. The gaging record contained glacial lake outburst floods at 15 streamgages and other types of outburst floods at 10 streamgages. Non-outburst peak flows in Alaska resulted from a mixture of rainfall and melt-based flood-generating mechanisms in all but the most rain-dominated seasonal flow regime. Melt-based flood-generating mechanisms included snowmelt, high-elevation snow and ice melt, or rain-on-snow events. Atmospheric rivers were common in Alaska and conterminous basins in Canada, occurring in that region on 67 percent of the days in the calendar year 1980–2019 period. Atmospheric rivers were more common on the days of peak flows and even more common on the days of non-outburst extreme floods. The percentage of days when an atmospheric river was present increased to 78 percent for the days of peak flows in that period and to 83 percent for the days of non-outburst extreme floods in that period. Of 149 extreme floods in the gaging record, 38 were generated by outburst floods. Of the non-outburst extreme floods, 72 percent were generated by rainfall and 26 percent were generated by melt-based processes or a combination of rainfall and melt-based processes. Flood-generating mechanisms could not be determined for the final 2 percent of the non-outburst extreme floods because the month and day of the peak flows were unknown and no other information was available. Secondary factors strongly associated with extreme floods included antecedent rain and streamflow conditions and warm storm conditions that produced rain instead of snow or generated snowmelt.

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USGS2025

Constraining snow water equivalent of wet snowpacks in southeast Alaska

Quantifying snow water equivalent (SWE) with ground-penetrating radar (GPR) in a warming climate is complicated by the incidence and variability of liquid water in snow. Snow surveys conducted during the melt season serve as a valuable analog to conditions under future warming. Here, we determine the variability of wet snowpack properties (relative permittivity and density) to quantify their impact on SWE estimates using GPR. We collected spatially continuous snowpack measurements with 400 MHz GPR in 2012 and 2021 across repeat transects (~150 km each year) along with spring and summer snow depth and density measurements from snow pits and snow cores. Snow relative permittivity values ranged between 2.06 – 2.62 in 2012 and 2.11 – 5.11 in 2021, resulting in calculated volumetric liquid water content (LWC) between 1.7% – 5.7% in 2012 and 2.1% – 16% in 2021. This variability in snow relative permittivity results in SWE uncertainties between 8% – 33%, with more extreme cases reaching 13% – 45%. We attribute this uncertainty to spatial and temporal variability in liquid water content when using GPR to estimate SWE. As snowpacks become wetter with rising atmospheric temperatures, GPR surveys should include in-situ relative permittivity measurements to reduce depth and SWE interpretation uncertainties.

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USGS2025

‘The fish that stop’: Drivers of historical decline for Pacific cod and implications for modern management in an era of rapidly changing climate

n the Gulf of Alaska, a series of marine heat waves depleted Pacific cod ( Gadus macrocephalus ) biomass to the lowest abundance ever recorded and led to the fishery’s closure in 2020. Although the fishery has been productive for decades, this collapse may have historical precedents. Traditional knowledge holders refer to cod as ‘the fish that stop’, and there is a suggested period of decline in the 1930s. Here we conduct a catch reconstruction of the early commercial fishery (1864–1950), confirming a rapid catch decline in the 1920s and 1930s. Next, we evaluate evidence for possible drivers. We document changes to demand and technology that contributed to declining catch. However, we also find both qualitative and quantitative evidence of depletion, suggesting catch declines were not driven entirely by social factors. Overfishing may have contributed to localized catch declines as evidenced by declining catch rates in heavily fished localities. We also find evidence for climate as a driver of regional decline, with the period of catch decline characterized by up to 2°C higher temperatures as compared to the earlier period of high fisheries production. Our analysis underscores the importance of understanding long-term drivers of fisheries productivity and the value of linking fisheries and climate histories.

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USGS2025

Cryptic ice wedge networks in Holocene peat, Yukon-Kuskokwim Delta, Alaska

The Yukon-Kuskokwim Delta (YKD), covering ~75,000 km 2 of Alaska's discontinuous permafrost zone, has a historic (1902–2023) mean annual air temperature of ~−1°C and was previously thought to lack ice wedge networks. However, our recent investigations near Bethel, Alaska, revealed numerous near-surface ice wedges. Using 20 cm resolution aerial orthoimagery from 2018, we identified ~50 linear km of ice wedge troughs in a 60 km 2 study area. Fieldwork in 2023 and 2024 confirmed ice wedges up to ~1.5 m wide and ~2.5 m in vertical extent, situated on average 0.9 m below the tundra surface ( n = 29). Ground-penetrating radar (GPR) detected additional ice wedges beyond those visible in the remote sensing imagery, suggesting an underestimation of their true abundance. Coring of polygonal centers revealed late-Quaternary deposits, including thick early Holocene peat, late-Pleistocene ice-rich silts (reworked Yedoma), charcoal layers from tundra fires, and the Aniakchak CFE II tephra (~3600 cal yrs BP). Stable water isotopes from Bethel's wedge ice (mean δ 18 O = −15.7 ‰, δ 2 H = −113.1 ‰) indicate a relatively enriched signature compared to other Holocene ice wedges in Alaska, likely due to warmer temperatures and maritime influences. Expanding our mapping across the YKD using high-resolution satellite imagery from 2012 to 2024, we estimate that the Holocene ice wedge zone encompasses ~30% of the YKD tundra region. Our findings demonstrate that ice wedge networks are more widespread across the YKD than previously recognized, emphasizing both the resilience and vulnerability of the region's warm, ice-rich permafrost. These insights are crucial for understanding permafrost responses to climate change and assessing agricultural potential and development in the region.

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USGS2025

2024 Surprise Inlet landslides: Insights from a prototype landslide‐triggered tsunami monitoring system in Prince William Sound, Alaska

Alaska's coastal communities face growing landslide hazards owing to glacier retreat and extreme weather intensified by the warming climate, yet hazard monitoring remains challenging. As part of ongoing experimental monitoring in Prince William Sound, we detected three large landslides (0.5–2.3 M m 3 ) at Surprise Inlet on 20 September 2024, within the span of an hour. These events were identified in near real-time through seismic data and later confirmed using satellite imagery, tidal records, and infrasound. The landslides generated a modest tsunami, and a 4 cm wave was recorded by a tide gauge 18 km away, marking the first recorded landslide to reach water since monitoring began in this region in 2021. Here, we examine the detection and interpretation of these landslides using multiple data sources and modeling. We demonstrate the effectiveness of this regional seismic monitoring system and show how complementary instrumentation, where available, can enhance detection capabilities.

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USGS2025

Timing of Steller’s Eider remigial molt has delayed over 26-year span

The Steller’s Eider is a sea duck that uses specific molting areas in lagoons in southwest Alaska, and these molting populations have declined in recent decades. The annual flight feather molt is a significant stage in avian life-history. The focus of this study was to characterize the phenology of Steller’s Eider flight feather molt timing and explore if molt timing is (1) earlier, (2) remained unchanged, or (3) is delayed. We developed a flight feather growth function throughout molt using data from captive birds. We used measurements from free-ranging birds over a 26-year period to investigate variation in molt start dates among sexes, years, and locations. Results indicate that fall molt timing has delayed over 26 years for Steller’s Eiders in our study area. We speculate that drivers of observed change in timing may be related to changes in seasonal Arctic environmental conditions. Our findings can be used by managers to inform timing of population surveys.

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USGS2025

Linking fire radiative power to land cover, fire history, and environmental setting in Alaska, 2003–2022

Background Fire radiative power (FRP) shows promise as a diagnostic and predictive indicator of fire behavior and post-fire effects in Alaska, USA. Aims To investigate relationships between FRP, vegetation functional groups, and environmental settings in Alaska (2003–2022) under various fire history conditions. Methods We tested for distinctness of MODIS FRP distributions associated with vegetation classes and fire legacies (frequency and number of previous burns). We used a random forest model to examine relative importance of vegetation class for FRP versus bottom-up biophysical and temporal parameters. Key results FRP distributions are statistically distinct among vegetation functional groups with contrasting fuel biomass, or within functional groups with contrasting burn characteristics. Location and topography, which constrain vegetation class, strongly determine FRP, and fire history is of lesser importance over the 19-year analysis period. Conclusions FRP can be used to identify wildfire consumption in dissimilar vegetation classes but is highly conditioned by geographic location. The complex and evolving vegetation composition of post-fire boreal landscapes precludes a clear association of expected FRP at distinct stages of recovery. Implications These results can inform further study of FRP as an indicator of fire behavior and fuel consumption and for informing dynamics of post-fire recovery across Alaska.

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