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At least 217 records · Page 12Linked to original sources
USGS1996

Geographic variation in migratory behavior of greater white-fronted geese ( Anser albifrons )

We studied the migration and winter distribution of adult Greater White-fronted Geese ( Anser albifrons frontalis ) radio-marked on the Yukon-Kuskokwim Delta (YKD) and Bristol Bay Lowlands (BBL) of Alaska from 1987 to 1992. The major autumn staging site for geese from both breeding areas was the Klamath Basin on the California/Oregon border. However, temporal use of this area differed markedly between populations. Geese from the BBL arrived at the Klamath Basin nearly 30 days before geese from the YKD and departed before most YKD geese had arrived. Ninety percent of BBL geese used the Klamath Basin in autumn, whereas 30% of YKD geese bypassed the Klamath Basin during autumn and instead flew directly to the Central Valley of California. Nearly all BBL geese migrated directly from the Klamath Basin to wintering areas in Mexico, bypassing the Central Valley. Ninety percent of the BBL geese wintered in Mexico, as opposed to <20% of the YKD geese. Wetlands of the Interior Highlands in the state of Chihuahua, particularly Laguna Babicora, were used by >90% of the radio-marked geese in Mexico. Marshes along the West Coast comprised the other important wintering habitat in Mexico. The Sacramento Valley of California was the predominant wintering area for YKD geese. BBL geese migrated north from Mexico into the San Joaquin Valley or Sacramento-San Joaquin Delta of California by the last week of January. Fifty-five percent of the BBL population used the Klamath Basin in spring, but many birds staged in eastern Oregon and western Idaho. In contrast, geese from the YKD staged almost exclusively in the Klamath Basin during spring before flying to staging areas in Alaska. Breeding allopatry and temporal partitioning on staging and wintering areas likely has contributed to the evolution of previously described phenotypic differences between these populations. These two populations, along with the Tule Greater White-fronted Goose (A. a. gambeli), may constitute a portion of a Rassenkreis, a group of subspecies connected by clines, each ecotype of which has independent conservation needs.

The Auk↗
USGS2001

The National Petroleum Reserve-Alaska (NPRA) data archive

The area currently known as the National Petroleum ReserveAlaska was originally designated in 1923 as Naval Petroleum Reserve No. 4 (NPR4). It was one of four U.S. regions thought to contain significant amounts of oil that were to be reserved for national crises. Geographic and geologic knowledge of the NPR4 was only superficial in 1923. Earlier exploration, however, had shown that the region contained the ingredients necessary for oil accumulations to exist: source rocks, reservoir rocks, and geologic structures that could trap petroleum. Oil seeps on the coast and the size of the area (some 37,000 square miles, about the size of Indiana) reinforced the notion that significant quantities of petroleum were present.

Fact Sheet↗
USGS2005

Murre eggs ( Uria aalge and Uria lomvia ) as indicators of mercury contamination in the Alaskan marine environment

Sixty common murre ( Uria aalge ) and 27 thick-billed murre ( Uria lomvia ) eggs collected by the Seabird Tissue Archival and Monitoring Project (STAMP) in 1999−2001 from two Gulf of Alaska and three Bering Sea nesting colonies were analyzed for total mercury (Hg) using isotope dilution cold vapor inductively coupled mass spectrometry. Hg concentrations (wet mass) ranged from 0.011 μg/g to 0.357 μg/g (relative standard deviation = 76%), while conspecifics from the same colonies and years had an average relative standard deviation of 33%. Hg levels in eggs from the Gulf of Alaska (0.166 μg/g ± 0.011 μg/g) were significantly higher ( p < 0.0001) than in the Bering Sea (0.047 μg/g ± 0.004 μg/g). Within the Bering Sea, Hg was significantly higher ( p = 0.0007) in eggs from Little Diomede Island near the arctic than at the two more southern colonies. Although thick-billed and common murres are ecologically similar, there were significant species differences in egg Hg concentrations within each region ( p < 0.0001). In the Bering Sea, eggs from thick-billed murres had higher Hg concentrations than eggs from common murres, while in the Gulf of Alaska, common murre eggs had higher concentrations than those of thick-billed murres. A separate one-way analysis of variance on the only time−trend data currently available for a colony (St. Lazaria Island in the Gulf of Alaska) found significantly lower Hg concentrations in common murre eggs collected in 2001 compared to 1999 ( p = 0.017). Results from this study indicate that murre eggs may be effective monitoring units for detecting geographic, species, and temporal patterns of Hg contamination in marine food webs. The relatively small intracolony variation in egg Hg levels and the ability to consistently obtain adequate sample sizes both within and among colonies over a large geographic range means that monitoring efforts using murre eggs will have suitable statistical power for detecting environmental patterns of Hg contamination. The potential influences of trophic effects, physical transport patterns, and biogeochemical processes on these monitoring efforts are discussed, and future plans to investigate the sources of the observed variability are presented.

Environmental Science & Technology↗
USGS1972

Energy resources of the United States

Estimates are made of United States resources of coal, petroleum liquids, natural gas, uranium, geothermal energy, and oil from oil shale. The estimates, compiled by specialists of the U.S. Geological Survey, are generally made on geologic projections of favorable rocks and on anticipated frequency of the energy resource in the favorable rocks. Accuracy of the estimates probably ranges from 20 to 50 percent for identified-recoverable resources to about an order of magnitude for undiscovered-submarginal resources. The total coal resource base in the United States is estimated to be about 3,200 billion tons, of which 200-390 billion tons can be considered in the category identified and recoverable. More than 70 percent of current production comes from the Appalachian basin where the resource base, better known than for the United States as a whole, is about 330 billion tons, of which 22 billion tons is identified and recoverable. Coals containing less than 1 percent sulfur are the premium coals. These are abundant in the western coal fields, but in the Appalachian basin the resource base for low-sulfur coal is estimated to be only a little more than 100 billion tons, of which 12 billion tons is identified and recoverable. Of the many estimates of petroleum liquids and natural-gas resources, those of the U.S. Geological Survey are the largest because, in general, our estimates include the largest proportion of favorable ground for exploration. We estimate the total resource base for petroleum liquids to be about 2,900 billion barrels, of which 52 billion barrels is identified and recoverable. Of the total resource base, some 600 billion barrels is in Alaska or offshore from Alaska, 1,500 billion barrels is offshore from the United States, and 1,300 billion barrels is onshore in the conterminous United States. Identified-recoverable resources of petroleum liquids corresponding to these geographic units are 11, 6, and 36 billion barrels, respectively. The total natural-gas resource of the United States is estimated to be about 6,600 trillion cubic feet, of which 290 trillion cubic feet is identified and recoverable. In geographic units comparable to those for petroleum liquids, the resource bases are 1,400, 3,400, and 2,900 trillion cubic feet, and the identified-recoverable resources are 31, 40, and 220 trillion cubic feet, respectively. Uranium resources in conventional deposits, where uranium is the major product, are estimated at 1,600,000 tons of U3O8, of which 250,000 tons is identified and recoverable. A potential byproduct resource of more than 7 million tons of U3O8, is estimated for phosphate rock, but none of this resource is recoverable under present economic conditions. The resources of heat in potential geothermal energy sources are poorly known. The total resource base for the United States is certainly greater than 10 22 calories, of which only 2.5 ? 10 18 calories can be considered identified and recoverable at present. Oil shale is estimated to contain 26 trillion barrels of oil. None of this resource is economic at present, but if prices increase moderately, 160-600 billion barrels of this oil could be shifted into the identified-recoverable category.

Circular↗
USGS2006

Atlas of relations between climatic parameters and distributions of important trees and shrubs in North America - Alaska species and ecoregions

Climate is the primary factor in controlling the continental-scale distribution of plant species, although the relations between climatic parameters and species' ranges is only now beginning to be quantified. Preceding volumes of this atlas explored the continental-scale relations between climatic parameters and the distributions of woody plant species across all of the continent of North America. This volume presents similar information for important woody species, groups of species, and ecoregions in more detail for the State of Alaska. For these analyses, we constructed a 25-kilometer equal-area grid of modern climatic and bioclimatic parameters for North America from instrumental weather records. We obtained a digital representation of the geographic distribution of each species or ecoregion, either from a published source or by digitizing the published distributions ourselves. The presence or absence of each species or ecoregion was then determined for each point on the 25-kilometer grid, thus providing a basis for comparison of the climatic data with the geographic distribution of each species or ecoregion. The relations between climate and these distributions are presented in graphical and tabular form.

Alaska↗
USGS2008

Distribution and spawning dynamics of capelin (Mallotus villosus) in Glacier Bay, Alaska: A cold water refugium

Pacific capelin (Mallotus villosus) populations declined dramatically in the Northeastern Pacific following ocean warming after the regime shift of 1977, but little is known about the cause of the decline or the functional relationships between capelin and their environment. We assessed the distribution and abundance of spawning, non-spawning adult and larval capelin in Glacier Bay, an estuarine fjord system in southeastern Alaska. We used principal components analysis to analyze midwater trawl and beach seine data collected between 1999 and 2004 with respect to oceanographic data and other measures of physical habitat including proximity to tidewater glaciers and potential spawning habitat. Both spawning and non-spawning adult Pacific capelin were more likely to occur in areas closest to tidewater glaciers, and those areas were distinguished by lower temperature, higher turbidity, higher dissolved oxygen and lower chlorophyll a levels when compared with other areas of the bay. The distribution of larval Pacific capelin was not sensitive to glacial influence. Pre-spawning females collected farther from tidewater glaciers were at a lower maturity state than those sampled closer to tidewater glaciers, and the geographic variation in the onset of spawning is likely the result of differences in the marine habitat among sub-areas of Glacier Bay. Proximity to cold water in Glacier Bay may have provided a refuge for capelin during the recent warm years in the Gulf of Alaska.

Fisheries Oceanography↗
USGS1985

DATA ACQUISITION AND APPLICATIONS OF SIDE-LOOKING AIRBORNE RADAR IN THE U. S. GEOLOGICAL SURVEY.

The Side-Looking Airborne Radar (SLAR) program encompasses a multi-discipline effort involving geologists, hydrologists, engineers, geographers, and cartographers of the U. S. Geological Survey (USGS). Since the program began in 1980, more than 520,000 square miles of aerial coverage of SLAR data in the conterminous United States and Alaska have been acquired or contracted for acquisition. The Geological Survey has supported more than 60 research and applications projects addressing the use of this technology in the earth sciences since 1980. These projects have included preparation of lithographic reproductions of SLAR mosaics, research to improve the cartographic uses of SLAR, research for use of SLAR in assessing earth hazards, and studies using SLAR for energy and mineral exploration through improved geologic mapping.

Conference Paper↗
USGS2019

Detrital zircon geochronology along a structural transect across the Kahiltna assemblage in the western Alaska Range: Implications for emplacement of the Alexander-Wrangellia-Peninsular terrane against North America

The Kahiltna assemblage in the western Alaska Range consists of deformed Upper Jurassic and Cretaceous clastic strata that lie between the Alexander-Wrangellia-Peninsular (AWP) terrane to the south, and the Farewell and other peri-cratonic terranes to the north. Differences in detrital zircon populations and sandstone petrography allow geographic separation of the strata into two different successions, each consisting of multiple units, or petrofacies, with distinct provenance and lithologic characteristics. The northwestern succession was largely derived from older, inboard peri-cratonic terranes and correlates along strike to the southwest with the Kuskokwim Group. The southeastern succession is characterized by volcanic and plutonic rock detritus derived from Late Jurassic igneous rocks of the AWP terrane and mid to Late Cretaceous arc related igneous rocks and is part of a longer belt to the southwest and northeast, here named the Koksetna-Clearwater belt. The two successions remained separate depositional systems until the Late Cretaceous, when the northwestern succession overlapped the southeastern succession at about 81 Ma and they were deformed together by about 80 Ma by southeast-verging fold-and-thrust style deformation interpreted to represent final accretion of the AWP terrane along the southern Alaska margin. We interpret the tectonic evolution of the Kahiltna successions as a progression from forearc sedimentation and accretion in a south-facing continental magmatic arc to arrival and partial underthrusting of the backarc flank of an active, south-facing island arc system (AWP terrane). A modern analogue is the ongoing collision and partial underthrusting of the Izu-Bonin-Marianas island arc beneath the Japan Trench-Nankai Trough on the east side of central Japan.

Alaska↗
USGS2021

U–Pb zircon eruption age of the Old Crow tephra and review of extant age constraints

Eruption of the Old Crow tephra deposited ~200 km 3 of volcanic ash throughout Alaska and the northwestern Yukon (eastern Beringia), providing an isochronous marker across the region on a scale unique in the Pleistocene. The Old Crow tephra represents a critical temporal piercing point used extensively to link geographically disparate stratigraphic sections and the paleo-environmental records they contain. Although the canonical age of the Old Crow suggests eruption during the transition between the glacial and interglacial periods of Marine Isotope Stages (MIS) 5 and 6 at ~125 ka, recent U–Th–Pb and (U–Th)/He zircon dating of the tephra suggests eruption at ~200 ka, within MIS 7. If accurate, this revised eruption age begets significant change to existing models describing the geologic and biotic evolution of Beringia in the Pleistocene. Thus, confidently knowing the age of the tephra is critical to its time-stratigraphic utility and for past and future work in the region where the tephra has been found. With this contribution, we review existing Old Crow age constraints and present an eruption age for the tephra determined via high spatial resolution ion microprobe U–Pb surface analysis on zircon crystals isolated from source-proximal (<500 km from plausible source) pumiceous pyroclasts of the tephra. By dating only glass-mantled crystals isolated from discrete pumice clasts, we limit the potential for sample contamination from exotic crystals and resulting age bias. The young population of dates from this dataset corroborate previous radiometric dates and confirm Old Crow eruption within late MIS 7 at 207 ± 13 ka.

Alaska↗
USGS1988

Neutralizing monoclonal antibodies recognize antigenic variants among isolates of infectious hematopoietic necrosis virus

eutralizing monoclonal antibodies were developed against strains of infectious hematopoietic necrosis virus (IHNV) from steelhead trout Salmo gairdneri in the Deschutes River of Oregon, chinook salmon Oncorhynchus tshawytscha in the Sacramento River of California, and rainbow trout Salmo gairdneri reared in the Hagerman Valley of Idaho, USA. These antibodies were tested for neutralization of 12 IHNV isolates obtained from salmonids in Japan, Alaska, Washington, Oregon, California, and Idaho. The antibodies recognized antigenic variants among the isolates and could be used to separate the viruses into 4 groups. The members of each group tended to be related by geographic area rather than by source host species, virulence, or date of isolation.

Diseases of Aquatic Organisms↗
USGS2023

Geologic map of Okmok Volcano

The geologic map and description of map units presented here cover approximately 880 km2 of northeastern Umnak Island, Aleutian Islands, Alaska. This report focuses on Okmok Volcano and its eruptive products and updates the mid-20th-century geologic map of Byers (1959). Mapped deposits reflect the state of the volcano just prior to the 2008 eruption. Published information about other portions of Umnak Island geology, including Mount Recheshnoi and Mount Vsevidof, can be found in Byers (1959). The 2008 eruption and its deposits are described in Larsen and others (2009, 2013, 2015). Okmok Volcano is one of 54 historically active volcanoes in the Alaska–Aleutian volcanic arc that stretches across southern mainland Alaska and the Aleutian Islands (fig. 1; Wood and Kienle, 1990; Miller and others, 1998; Cameron and others, 2020). The highest point of the modern Okmok Caldera is along the caldera’s northern rim, 967 m in elevation, and formally named “Mount Okmok” (U.S. Board on Geographic Names, www.usgs.gov/core-science-systems/ngp/boardon-geographic-names/domestic-names). Okmok Volcano dominates the northeastern portion of Umnak Island, which is 100 km southwest of Unalaska/Dutch Harbor and 1,400 km southwest of Anchorage (figs. 1, 2). The Port of Dutch Harbor on Unalaska Island produces the highest volume of seafood for any port in the United States (see fisheries.noaa.gov/resource/document/fisheries-united-states-2018-report). Unalaska city and the Port of Dutch Harbor have been impacted by ash fall and drifting ash clouds from Okmok Volcano’s explosive eruptions as recently as 2008. Holocene and late Pleistocene volcanic rocks and deposits of Okmok Volcano rest upon glaciated Tertiary volcanic and sedimentary rocks (Byers, 1959). The first geologic mapping expedition to Okmok Volcano was by the U.S. Geological Survey (USGS) after the 1945 eruption, largely in response to concerns about volcanic hazards to U.S. military activities in the Aleutians Islands (Byers and others, 1947, 1959; Byers and Brannock, 1949; Byers, 1955, 1959, 1961). The State of Alaska conducted further mapping and geochemical studies as part of its geothermal exploration program in the 1980s (Nye, 1983; Nye and Reid, 1986; Motyka and others, 1993). Additional modern geological work focused on Okmok Volcano and the rest of Umnak Island to address the geochemistry and origin of primary Aleutian arc magmas and subduction zone mass recycling (Marsh, 1982; Brophy and Marsh, 1986; Nye and Reid, 1986; Myers and Marsh, 1987; Miller and others, 1992; Fournelle and others, 1994; Kay and Kay, 1994). In 1998, the Alaska Volcano Observatory (AVO) began a multi-year effort to expand geophysical monitoring in the central Aleutians Islands, including at Okmok Volcano. As part of this effort, AVO geologists from the University of Alaska Fairbanks Geophysical Institute (UAF/GI), the Alaska Division of Geological & Geophysical Surveys (DGGS), and USGS also began a renewed effort to document Okmok Volcano’s recent eruption products. The project started with reconnaissance fieldwork to document and sample products from the 1997 eruption within Okmok Caldera. This evolved into an effort to produce an updated geologic map of Okmok Volcano and gather more information about its eruptive history and hazards. Three significant eruptions occurred at Okmok Volcano in 1958, 1997, and 2008—after fieldwork had been conducted for the original 1:63,360-scale geologic map produced by Byers (1959)—resulting in new volcanic deposits not previously described. Okmok Volcano is one of the most frequently active volcanoes in the Aleutian volcanic arc. Seismic and geodetic monitoring indicate ongoing unrest at Okmok Volcano since at least 1997. Geodetic observations of inflation before and after the 1997 and 2008 eruptions indicate a nearly continuous input of new magma from a depth consistent with frequent eruptions of basalt and basaltic andesite magmas over the past 200 years (Larsen and others, 2013; Lu and others, 2000, 2003, 2005; Mann, 2002; Mann and others, 2002). To better understand the likelihood and character of future eruptions from Okmok Volcano, it is necessary to understand its past behavior, including eruptions since the first geologic map was published by Byers (1959).

Alaska↗
USGS1982

Habitat suitability index models: Cutthroat trout

Cutthroat trout, Salmo clarki, are a polytypic species consisting of several geographically distinct forms with a broad distribution and a great amount of genetic diversity (Hickman 1978; Behnke 1979). Behnke (1979) recognized 13 extant subspecies: Coastal cutthroat (S. c. clarki) in coastal streams from Prince William Sound, Alaska to the Eel Rlver in California; mountain cutthroat (~. ~. alpestris) in upper Columbia and F~Dser River drainages of British Columbia; west slope cutthroat (S. c. lewisi) in the upper Columbia, Salmon, Clearwater, South Saskatchewan and upper Missouri drainages of Montana and Idaho; an undescribed subspecies in the Alvord basin, Oregon; Lahonton cutthroat (S. c ..henshawi), Pauite cutthroat (S. c. seleniris), and an undescribed- subspecies in the Humboldt River drafnage of the Lahontan basin of Nevada and California; Yellowstone cutthroat (S. c. bouvieri) in the Yellowstone drainage of Wyoming and Montana and the Snake River drainage of Wyoming, Idaho, and Nevada; an undescribed subspecies (fine spotted) in the upper Snake River, Wyoming; Bonneville cutthroat (S. c. utah) in the Bonneville basin in Utah, Nevada, Idaho, and Wyoming; Colorado River cutthroat (~. ~. pleuriticus) in the Colorado River drainage in Wyoming, Utah, New Mexico, and Colorado; greenback cutthroat (S. c. stomias) in the South Platte and Arkansas River systems; and Rio Grande cutthroat (~. ~. virginalis) in the Rio Grande River drainage of Colorado and New Mexico. Many of these 13 subspecies are included on Federal or State endangered or threatened species lists. Temperature and chemical preferences, migration, and other ecological and life history attributes vary among cutthroat subspecies (Behnke 1979). Differences in growth rate (Carlander 1969; Scott and Crossman 1973; Behnke 1979) and food preferences have also been reported (Trojnar and Behnke 1974) between some subspecies.

FWS/OBS↗
USGS2016

Estimating flood magnitude and frequency at gaged and ungaged sites on streams in Alaska and conterminous basins in Canada, based on data through water year 2012

Estimates of the magnitude and frequency of floods are needed across Alaska for engineering design of transportation and water-conveyance structures, flood-insurance studies, flood-plain management, and other water-resource purposes. This report updates methods for estimating flood magnitude and frequency in Alaska and conterminous basins in Canada. Annual peak-flow data through water year 2012 were compiled from 387 streamgages on unregulated streams with at least 10 years of record. Flood-frequency estimates were computed for each streamgage using the Expected Moments Algorithm to fit a Pearson Type III distribution to the logarithms of annual peak flows. A multiple Grubbs-Beck test was used to identify potentially influential low floods in the time series of peak flows for censoring in the flood frequency analysis. For two new regional skew areas, flood-frequency estimates using station skew were computed for stations with at least 25 years of record for use in a Bayesian least-squares regression analysis to determine a regional skew value. The consideration of basin characteristics as explanatory variables for regional skew resulted in improvements in precision too small to warrant the additional model complexity, and a constant model was adopted. Regional Skew Area 1 in eastern-central Alaska had a regional skew of 0.54 and an average variance of prediction of 0.45, corresponding to an effective record length of 22 years. Regional Skew Area 2, encompassing coastal areas bordering the Gulf of Alaska, had a regional skew of 0.18 and an average variance of prediction of 0.12, corresponding to an effective record length of 59 years. Station flood-frequency estimates for study sites in regional skew areas were then recomputed using a weighted skew incorporating the station skew and regional skew. In a new regional skew exclusion area outside the regional skew areas, the density of long-record streamgages was too sparse for regional analysis and station skew was used for all estimates. Final station flood frequency estimates for all study streamgages are presented for the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probabilities. Regional multiple-regression analysis was used to produce equations for estimating flood frequency statistics from explanatory basin characteristics. Basin characteristics, including physical and climatic variables, were updated for all study streamgages using a geographical information system and geospatial source data. Screening for similar-sized nested basins eliminated hydrologically redundant sites, and screening for eligibility for analysis of explanatory variables eliminated regulated peaks, outburst peaks, and sites with indeterminate basin characteristics. An ordinary least‑squares regression used flood-frequency statistics and basin characteristics for 341 streamgages (284 in Alaska and 57 in Canada) to determine the most suitable combination of basin characteristics for a flood-frequency regression model and to explore regional grouping of streamgages for explaining variability in flood-frequency statistics across the study area. The most suitable model for explaining flood frequency used drainage area and mean annual precipitation as explanatory variables for the entire study area as a region. Final regression equations for estimating the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent annual exceedance probability discharge in Alaska and conterminous basins in Canada were developed using a generalized least-squares regression. The average standard error of prediction for the regression equations for the various annual exceedance probabilities ranged from 69 to 82 percent, and the pseudo-coefficient of determination (pseudo-R 2 ) ranged from 85 to 91 percent. The regional regression equations from this study were incorporated into the U.S. Geological Survey StreamStats program for a limited area of the State—the Cook Inlet Basin. StreamStats is a national web-based geographic information system application that facilitates retrieval of streamflow statistics and associated information. StreamStats retrieves published data for gaged sites and, for user-selected ungaged sites, delineates drainage areas from topographic and hydrographic data, computes basin characteristics, and computes flood frequency estimates using the regional regression equations.

Alaska↗
USGS2015

Temporal patterns in adult salmon migration timing across southeast Alaska

Pacific salmon migration timing can drive population productivity, ecosystem dynamics, and human harvest. Nevertheless, little is known about long-term variation in salmon migration timing for multiple species across broad regions. We used long-term data for five Pacific salmon species throughout rapidly warming southeast Alaska to describe long-term changes in salmon migration timing, interannual phenological synchrony, relationships between climatic variation and migratory timing, and to test whether long-term changes in migration timing are related to glaciation in headwater streams. Temporal changes in the median date of salmon migration timing varied widely across species. Most sockeye populations are migrating later over time (11 of 14), but pink, chum, and especially coho populations are migrating earlier than they did historically (16 of 19 combined). Temporal trends in duration and interannual variation in migration timing were highly variable across species and populations. The greatest temporal shifts in the median date of migration timing were correlated with decreases in the duration of migration timing, suggestive of a loss of phenotypic variation due to natural selection. Pairwise interannual correlations in migration timing varied widely but were generally positive, providing evidence for weak region-wide phenological synchrony. This synchrony is likely a function of climatic variation, as interannual variation in migration timing was related to climatic phenomenon operating at large- (Pacific decadal oscillation), moderate- (sea surface temperature), and local-scales (precipitation). Surprisingly, the presence or the absence of glaciers within a watershed was unrelated to long-term shifts in phenology. Overall, there was extensive heterogeneity in long-term patterns of migration timing throughout this climatically and geographically complex region, highlighting that future climatic change will likely have widely divergent impacts on salmon migration timing. Although salmon phenological diversity will complicate future predictions of migration timing, this variation likely acts as a major contributor to population and ecosystem resiliency in southeast Alaska.

Alaska↗
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.

Alaska↗
USGS2009

The National Map - Elevation

The National Elevation Dataset (NED) is the primary elevation data product produced and distributed by the USGS. The NED provides seamless raster elevation data of the conterminous United States, Alaska, Hawaii, and the island territories. The NED is derived from diverse source data sets that are processed to a specification with a consistent resolution, coordinate system, elevation units, and horizontal and vertical datums. The NED is the logical result of the maturation of the long-standing USGS elevation program, which for many years concentrated on production of topographic map quadrangle-based digital elevation models. The NED serves as the elevation layer of The National Map, and provides basic elevation information for earth science studies and mapping applications in the United States. The NED is a multi-resolution dataset that is updated bimonthly to integrate newly available, improved elevation source data. NED data are available nationally at grid spacings of 1 arc-second (approximately 30 meters) for the conterminous United States, and at 1/3 and 1/9 arc-seconds (approximately 10 and 3 meters, respectively) for parts of the United States. Most of the NED for Alaska is available at 2-arc-second (about 60 meters) grid spacing, where only lower resolution source data exist. Part of Alaska is available at the 1/3-arc-second resolution, and plans are in development for a significant upgrade in elevation data coverage of the State over the next 5 years. Specifications for the NED include the following: *Coordinate system: Geographic (decimal degrees of latitude and longitude), *Horizontal datum: North American Datum of 1983 (NAD 83), *Vertical datum: North American Vertical Datum of 1988 (NAVD 88) over the conterminous United States and varies in other areas, and *Elevation units: Decimal meters.

Fact Sheet↗
USGS1989

Iterative techniques for characterizing marine bird habitats with time-series of satellite images

Demonstrating long-term habitat use of marine habitats by seabirds is often complicated by short-term changes in habitat locations, persistence, and age. This paper describes iterative techniques for characterizing non-static habitats, such as meso-scale (10-100 km) ocean eddies and fronts, using time-series of satellite images that define sea surface conditions. Seabird use of satellite-detected habitats was compared using survey data and imagery from the Gulf of Alaska and southeastern United States. Time-series examination of satellite images combined with long-term seabird censuses allow 1) estimation of the successional state (age) of some marine habitats, 2) detection of recurring habitats, 3) geographically-referenced measurement of habitat location and areal extent, 4) identification of consistently-used habitats, and 5) demonstration of time-dependent use by seabirds associated with seasonal or annual variation in habitat availability.

Colonial Waterbirds↗
USGS2003

Protocols for long-term monitoring of seabird ecology in the Gulf of Alaska

Seabird populations will need to be monitored for many years to assess both recovery and ecological conditions affecting recovery. Detailed studies of individual seabird colonies and marine ecosystems in the Gulf of Alaska have been conducted by the U.S. Geological Survey and U.S. Fish and Wildlife Service under the auspices of damage assessment and restoration programs of the Trustee Council. Much has been learned about factors influencing seabird populations and their capacity to recover from the spill in the Gulf of Alaska. As the restoration program moves toward long-term monitoring of populations, however, protocols and long-term monitoring strategies that focus on key parameters of interest and that are inexpensive, practical, and applicable over a large geographic area need to be developed.

Alaska↗