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At least 469 records · Page 26Linked to original sources
USGS1981

Cretaceous Arctic silicoflagellates

Cretaceous silicoflagellate assemblages from Arctic Ocean USGS Core 437 show Vallacerta siderea the most abundant species; most species of Lyramula disappear halfway up the core; only L. burchardae, n. sp., persists into the upper sections. These occurrences are untypical of the few documented Cretaceous assemblages from other areas. A Campanian or Maestrichtian age is suggested by correlation, but the uniquely high abundance of V. siderea and lack of Corbisema suggests that a difference in both age and general environment could be involved. If Core 437 is latest Maestrichtian, then the evidence from this core would constrain the timing of the ocean-freshening model for the Cretaceous-Tertiary boundary extinctions. ?? 1981 A.M. Dowden, Inc.

Geo-Marine Letters↗
USGS2011

Data logging of body temperatures provides precise information on phenology of reproductive events in a free-living arctic hibernator

Precise measures of phenology are critical to understanding how animals organize their annual cycles and how individuals and populations respond to climate-induced changes in physical and ecological stressors. We show that patterns of core body temperature ( T b ) can be used to precisely determine the timing of key seasonal events including hibernation, mating and parturition, and immergence and emergence from the hibernacula in free-living arctic ground squirrels ( Urocitellus parryii ). Using temperature loggers that recorded T b every 20 min for up to 18 months, we monitored core T b from three females that subsequently gave birth in captivity and from 66 female and 57 male ground squirrels free-living in the northern foothills of the Brooks Range Alaska. In addition, dates of emergence from hibernation were visually confirmed for four free-living male squirrels. Average T b in captive females decreased by 0.5–1.0°C during gestation and abruptly increased by 1–1.5°C on the day of parturition. In free-living females, similar shifts in T b were observed in 78% ( n = 9) of yearlings and 94% ( n = 31) of adults; females without the shift are assumed not to have given birth. Three of four ground squirrels for which dates of emergence from hibernation were visually confirmed did not exhibit obvious diurnal rhythms in T b until they first emerged onto the surface when T b patterns became diurnal. In free-living males undergoing reproductive maturation, this pre-emergence euthermic interval averaged 20.4 days ( n = 56). T b -loggers represent a cost-effective and logistically feasible method to precisely investigate the phenology of reproduction and hibernation in ground squirrels.

Journal of Comparative Physiology B: Biochemical, ↗
USGS2025

Rapid recovery of an arctic lake ecosystem from a pulse disturbance caused by thermokarst failure

Due to rapid climate change, arctic ecosystems are experiencing an increase in disturbances including localized land-surface failures caused by melting ground ice (thermokarst failures). These failures result in the mass transport of sediment and organic materials into surface waters, with the potential to dramatically alter aquatic ecosystem function and biotic interactions. We coupled direct comparisons and long-term data of a suite of abiotic and biotic variables in a thermokarst-impacted lake and nearby reference lake to assess the impacts of thermokarst failure. After the thermokarst failure and relative to long-term averages, water transparency was substantially reduced. We hypothesized there would be subsequent changes to lower trophic levels and profound declines in fish foraging efficiency. However, these characteristics were within the range of natural variability and/or rapidly recovered to values within the range of long-term variability. In addition, although there was limited evidence of taxa-specific changes, we did not observe any strong changes in the total relative densities, growth rates, or composition of the bacterioplankton and zooplankton communities, benthic macroinvertebrates, or changes in fish diet, that could be attributed statistically to the thermokarst event. In sum, the thermokarst disturbance had substantial effects on water transparency and some lower trophic levels, which surprisingly were not manifested in higher trophic levels. Overall, the lake ecosystem appeared resistant to thermokarst disturbance with rapid recovery within two years after the disturbance.

Alaska↗
USGS2000

Coastal erosion vs riverline sediment discharge in the Arctic shelfx seas

This article presents a comparison of sediment input by rivers and by coastal erosion into both the Laptev Sea and the Canadian Beaufort Sea (CBS). New data on coastal erosion in the Laptev Sea, which are based on field measurements and remote sensing information and existing data on coastal erosion in the CBS as well as riverine sediment discharge into both the Laptev Sea and the CBS are included. Strong regional differences in the percentages of coastal ero- sion and riverine sediment supply are observed. The CBS is dominated by the riverine sediment discharge (64.45x106 t a-1) mainly of the Mackenzie River. which is the largest single source of sediments in the Arctic. Riverine sediment discharge into the Laptev Sea amounts to 24.10x106 t a-1, more than 70% of which are related to the Lena River. In comparison with the CBS. the Laptev Sea coast on average delivers approximately twice as much sediment mass per kilometer, a result of higher erosion rates due to higher cliffs and seasonal ice melting. In the Laptev Sea sediment input by coastal erosion (58.4x106 t a-1) is therefore more important than in the CBS and the ratio between riverine and coastal sediment input amounts to 0.4. Coastal erosion supplying 5.6x106 t a-1 is less significant for the sediment budget of the CBS where riverine sediment discharge exceeds coastal sediment input by a factor of ca. 10.

International Journal of Earth Sciences↗
USGS2015

Projected changes in wildlife habitats in Arctic natural areas of northwest Alaska

We project the effects of transitional changes among 60 vegetation and other land cover types (“ecotypes”) in northwest Alaska over the 21st century on habitats of 162 bird and 39 mammal species known or expected to occur regularly in the region. This analysis, encompassing a broad suite of arctic and boreal wildlife species, entailed building wildlife-habitat matrices denoting levels of use of each ecotype by each species, and projecting habitat changes under historic and expected accelerated future rates of change from increasing mean annual air temperature based on the average of 5 global climate models under the A1B emissions scenario, and from potential influence of a set of 23 biophysical drivers. Under historic rates of change, we project that 52 % of the 201 species will experience an increase in medium- and high-use habitats, 3 % no change, and 45 % a decrease, and that a greater proportion of mammal species (62 %) will experience habitat declines than will bird species (50 %). Outcomes become more dire (more species showing habitat loss) under projections made from effects of biophysical drivers and especially from increasing temperature, although species generally associated with increasing shrub and tree ecotypes will likely increase in distribution. Changes in wildlife habitats likely will also affect trophic cascades, ecosystem function, and ecosystem services; of particular significance are the projected declines in habitats of most small mammals that form the prey base for mesocarnivores and raptors, and habitat declines in 25 of the 50 bird and mammal species used for subsistence hunting and trapping.

Alaska↗
USGS2024

Wintering grounds leave their mark: Where birds winter influences genomic structure in Arctic nesting common eiders

Information about the distribution of genomic variation within and between nesting locations of waterfowl can aid in defining populations and conservation plans and inform harvest management. Identification of locations where shifts in allelic diversity occur is particularly important for Arctic nesting species nesting, a region currently experiencing rapid change associated with climate and other factors. Here, we build upon previous investigations on spatial patterns of genetic variation in a largely migratory, circumpolar breeding sea duck, the common eider ( Somateria mollissima ) through inclusion of additional sample locations and genomic markers. We analyzed double-digest restriction site-associated DNA sequences from 309 common eiders to estimate genetic variation within, and differentiation among, 21 nesting locations across North America. Our results corroborate previous evidence of four genetic groups that coincide with colonies that share similar winter areas. We found deeper genomic differences between common eiders wintering in the west (Pacific Ocean) versus the east (Atlantic Ocean and Hudson Bay). We also identified subtle structure, not previously recognized, within Hudson Bay nesting common eiders. Our findings add to evidence linking wintering areas and genomic differentiation in waterfowl, offering further insights for management of this culturally important sea duck species.

Conservation Genetics↗
USGS2015

Ontogenetic dynamics of infection with Diphyllobothrium spp. cestodes in sympatric Arctic charr Salvelinus alpinus (L.) and brown trout Salmo trutta L.

The trophic niches of Arctic charr and brown trout differ when the species occur in sympatry. Their trophically transmitted parasites are expected to reflect these differences. Here, we investigate how the infections of Diphyllobothrium dendriticum and D. ditremum differ between charr and trout. These tapeworms use copepods as their first intermediate hosts and fish can become infected as second intermediate hosts by consuming either infected copepods or infected fish. We examined 767 charr and 368 trout for Diphyllobothrium plerocercoids in a subarctic lake. The prevalence of D. ditremum was higher in charr (61.5%) than in trout, (39.5%), but the prevalence of D. dendriticum was higher in trout (31.2%) than in charr (19.3%). Diphyllobothrium spp. intensities were elevated in trout compared to charr, particularly for D. dendriticum . Large fish with massive parasite burdens were responsible for the high Diphyllobothrium spp. loads in trout. We hypothesize that fish prey may be the most important source for the Diphyllobothrium spp. infections in trout, whereas charr predominantly acquire Diphyllobothrium spp. by feeding on copepods. Our findings support previous suggestions that the ability to establish in a second piscine host is greater for D. dendriticum than for D. ditremum .

Lake Tavatn↗
USGS2020

Effects of experimental warming and nutrient enrichment on wetland communities at the Arctic’s edge

Global warming-related changes to freshwater ecosystems in Arctic and Subarctic regions have been magnified by nutrient input from increasing waterfowl populations. To gain insight into how these changes might affect ecosystem function, we conducted a mesocosm experiment in the Subarctic by enriching N and P (1 ×, 10 ×, and 20 × treatments) and increasing mean water temperatures ≤ 3°C. We measured responses of two species of larval amphibians, periphyton, and phytoplankton. Wood frog ( Rana sylvatica ) larvae developed quicker (odds ratio [OR] for 1°C increase = 0.903, 95% CI 0.892–0.912) and were more likely to metamorphose (OR 1.076, 95% CI 0.022–14.73) in warmer waters. Boreal chorus frogs ( Pseudacris maculata ) also developed quicker with warmer temperatures (OR 0.880, 95% CI 0.860–0.900), despite a non-significant trend toward reduced survival (OR 0.853, 95% CI 0.696–1.039). Periphyton and phytoplankton concentrations increased with nutrient additions, as did size of wood frog metamorphs. Periphyton and phytoplankton did not vary with temperature, but periphyton was limited by tadpole abundance. Our results highlight the potential for non-linear responses to ecosystem change, with species-specific consumer and ecosystem responses that depend on the magnitude of changes.

Manitoba↗
USGS2019

Towards determining spatial methane distribution on Arctic permafrost bluffs with an unmanned aerial system

Arctic permafrost stores vast amounts of methane (CH 4 ) in subsurface reservoirs. Thawing permafrost creates areas for this potent greenhouse gas to be released to the atmosphere. Identifying ‘hot spots’ of methane flux on a local scale has been limited by the spatial scales of traditional ground-based or satellite-based methane-sampling methods. Here we present a reliable and an easily replicable design using only off-the-shelf, cost-effective methane sensor components and an Unmanned Aerial System (UAS). Our results demonstrate the high efficiency of the design and the advantages of this methodology for environmental methane studies that are subjected to the high spatial variability of methane levels. On Barter Island, NE Alaska, we noted spikes in CH 4 concentrations coincident with topographic features or anomalies. Such spikes may be attributed to enhanced land/air transfer and may reveal zones of high methane production and/or minimal oxidation in areas of thermoerosional gullies along thawing coastal zones. Thermoerosional gullies represent hotspots that release significantly higher levels of methane than the surrounding areas, thus suggesting that point sampling is inadequate in characterizing methane releases and that increasing rates of permafrost thaw may result in increasing point sources of high CH 4 emissions.

SN Applied Sciences↗
USGS1972

Oil development and conservation in Arctic America

As in his earlier article to which reference is made, the author stresses the need for more background information and a much greater research effort before problems of environmental protection from oil developments in northern Alaska can be effectively tackled. Meanwhile, there are indications that the earlier estimates of around ten thousand million barrels should be raised—perhaps to about five times as much. There has moreover been a great increate also in the known and probable gas reserves in northern Canada—particularly in the Arctic Archipelago. In spite of planned automation, people will be needed for development—including Eskimos and Indians, whose interests will be widely protected under the Alaska Native Claims Settlement Act of December 1971. The International Biological Programme ‘Tundra Biome’ projects have accumulated much new information, including the results to be expected from disturbing the tundra seriously, and means of preventing or repairing damage to it. There is much interest in Alaska and Canada in protection of the northern environment, and in the former the US National Environmental Policy Act is already leading to stricter control of some developments.

Biological Conservation↗
USGS1972

Influence of grounding ice on the Arctic shelf of Alaska

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

Alaska↗
USGS2017

Anomalous radiocarbon ages from a Holocene detrital organic lens in Alaska and their implications for radiocarbon dating and paleoenvironmental reconstructions in the arctic

Eleven radiocarbon age determinations clearly show that a lens of Holocene fluvial organic debris on the Alaskan Arctic Coastal Plain contains mostly pre-Holocene organic material. Radio-carbon ages of identified plant macrofossils indicate the material was deposited about 9000 to 9500 yr B.P. Radiocarbon analyses of bulk samples from this deposit, however, range from 13,300 to 30,300 yr B.P. Most of the old organic matter seems to be in the smaller size fractions in the deposit, particularly in the fraction between 0.25 and 0.5 mm, but all size fractions are contaminated. Particular caution must be exercised in submitting bulk samples for radiocarbon dating from areas where conditions favor redeposition of isotopically "dead" carbon. ?? 1988.

Quaternary Research↗
USGS1971

Aircraft measurements of microwave emission from Arctic Sea ice

Measurements of the microwave emission from Arctic Sea ice were made with aircraft at 8 wavelengths ranging from 0.510 to 2.81 cm. The expected contrast in emissivities between ice and water was observed at all wavelengths. Distributions of sea ice and open water were mapped from altitudes up to 11 km in the presence of dense cloud cover. Different forms of ice also exhibited strong contrasts in emissivity. Emissivity differences of up to 0.2 were observed between two types of ice at the 0.811-cm wavelength. The higher emissivity ice type is tentatively identified as having been formed more recently than the lower emissivity ice.

Alaska↗
USGS1994

Seismic images of the Brooks Range fold and thrust belt, Arctic Alaska, from an integrated seismic reflection/refraction experiment

We describe results of an integrated seismic reflection/refraction experiment across the Brooks Range and flanking geologic provinces in Arctic Alaska. The seismic acquisition was unusual in that reflection and refraction data were collected simultaneously with a 700 channel seismograph system deployed numerous times along a 315 km profile. Shot records show continuous Moho reflections from 0–180 km offset, as well as numerous upper- and mid-crustal wide-angle events. Single and low-fold near-vertical incidence common midpoint (CMP) reflection images show complex upper- and middle-crustal structure across the range from the unmetamorphosed Endicott Mountains allochthon (EMA) in the north, to the metamorphic belts in the south. Lower-crustal and Moho reflections are visible across the entire reflection profile. Travel-time inversion of PmP arrivals shows that the Moho, at 33 km depth beneath the North Slope foothills, deepens abruptly beneath the EMA to a maximum of 46 km, and then shallows southward to 35 km at the southern edge of the range. Two zones of upper- and middle-crustal reflections underlie the northern Brooks Range above ~ 12–15 km depth. The upper zone, interpreted as the base of the EMA, lies at a maximum depth of 6 km and extends over 50 km from the range front to the north central Brooks Range where the base of the EMA outcrops above the metasedimentary rocks exposed in the Doonerak window. We interpret the base of the lower zone, at ~ 12 km depth, to be from carbonate rocks above the master detachment upon which the Brooks Range formed. The seismic data suggest that the master detachment is connected to the faults in the EMA by several ramps. In the highly metamorphosed terranes south of the Doonerak window, the CMP section shows numerous south-dipping events which we interpret as a crustal scale duplex involving the Doonerak window rocks. The basal detachment reflections can be traced approximately 100 km, and dip southward from about 10–12 km near the range front, to 14–18 km beneath the Doonerak window, to 26–28 km beneath the metamorphic belts in the central Brooks Range. The section documents middle- and lower-crustal involvement in the formation of the Brooks Range.

Alaska↗
USGS2017

Rapid response for invasive waterweeds at the arctic invasion front: Assessment of collateral impacts from herbicide treatments

The remoteness of subarctic and arctic ecosystems no longer protects against invasive species introductions. Rather, the mix of urban hubs surrounded by undeveloped expanses creates a ratchet process whereby anthropogenic activity is sufficient to introduce and spread invaders, but for which the costs of monitoring and managing remote ecosystems is prohibitive. Elodea spp. is the first aquatic invasive plant to become established in Alaska and has potential for widespread deleterious ecological and economic impacts. A rapid eradication response with herbicides has been identified as a priority invasion control strategy. We condu cted a multi-lake monitoring effort to assess collateral impacts from herbicide treatment for Elodea in high latitude systems. Variability in data was driven by seasonal dynamics and natural lake-to-lake differences typical of high latitude waterbodies, indicating lack of evidence for systematic impacts to water quality or plankton communities associated with herbicide treatment of Elodea . Impacts on native macrophytes were benign with the exception of some evidence for earlier onset of leaf senescence for lily pads( Nuphar spp.) in treated lakes. We observed a substantial increase in detected native flora richness after Elodea was eradicated from the most heavily infested lake, indicating potential for retention of native macrophyte communities if infestations are addressed quickly. While avoiding introductions through prevention may be the most desirable outcome, these applications indicated low risks of non-target impacts associated with herbicide treatment as a rapid response option for Elodea in high latitude systems.

Alaska↗
USGS2004

PCB impairs smoltification and seawater performance in anadromous Arctic charr ( Salvelinus alpinus )

The impacts of polychlorinated biphenyl (PCB) exposure on smoltification and subsequent seawater performance were investigated in hatchery-reared, anadromous Arctic charr ( Salvelinus alpinus ). The fish were subjected to a 2-month summer seawater residence, after which they were orally dosed with 0 (Control, C), 1 (Low Dose, LD) or 100 mg Aroclor 1254 kg −1 body mass (High Dose, HD) in November. They were then held in fresh water, without being fed (to mimic their natural overwintering in freshwater), until they had smolted in June the next year. The smolts were then transferred to seawater and fed to mimic their summer feeding residence in seawater, followed by a period without food in freshwater from August until maturation in October. Compared with C and LD charr, the HD charr had either a transient or a permanent reduction in plasma growth hormone, insulin-like growth factor-1, and thyroxin and triiodothyronine titers during the period of smoltification. These hormonal alterations in the HD charr corresponded with impaired hyposmoregulatory ability in May and June, as well as reduced growth rate and survival after transference to seawater. Consequently, fewer fish in the HD group matured in October compared to the other two treatments. The HD fish had a liver PCB concentration ranging between 14 and 42 mg kg −1 wet mass, whereas there were similar, and very low, liver PCB concentrations in LD and C fish throughout the smolting period. Our findings suggest that PCB might compromise mechanisms important for fitness in a fish species living in an extreme environment.

Comparative Biochemistry and Physiology, Part C: T↗
USGS2014

Reconstruction of historic sea ice conditions in a sub-Arctic lagoon

Historical sea ice conditions were reconstructed for Izembek Lagoon, Bering Sea, Alaska. This lagoon is a crucial staging area during migration for numerous species of avian migrants and a major eelgrass ( Zostera marina ) area important to a variety of marine and terrestrial organisms, especially Pacific Flyway black brant geese ( Branta bernicla nigricans ). Ice cover is a common feature of the lagoon in winter, but appears to be declining, which has implications for eelgrass distribution and abundance, and its use by wildlife. We evaluated ice conditions from a model based on degree days, calibrated to satellite observations, to estimate distribution and long-term trends in ice conditions in Izembek Lagoon. Model results compared favorably with ground observations and 26 years of satellite data, allowing ice conditions to be reconstructed back to 1943. Specifically, periods of significant (limited access to eelgrass areas) and severe (almost complete ice coverage of the lagoon) ice conditions could be identified. The number of days of severe ice within a single season ranged from 0 (e.g., 2001) to ≥ 67 (e.g., 2000). We detected a slight long-term negative trend in ice conditions, superimposed on high inter-annual variability in seasonal aggregate ice conditions. Based on reconstructed ice conditions, the seasonally cumulative number of significant or severe ice days correlated linearly with mean air temperature from January until March. Further, air temperature at Izembek Lagoon was correlated with wind direction, suggesting that ice conditions in Izembek Lagoon were associated with synoptic-scale weather patterns. Methods employed in this analysis may be transferable to other coastal locations in the Arctic.

Alaska↗
USGS2023

Incremental evolution of modeling a prognosis for polar bears in a rapidly changing Arctic

Updating predictions of the response of high-profile, at-risk species to climate change and anthropogenic stressors is vital for informing effective conservation action. Here, we review two prior generations of Bayesian network probability models predicting changes in global polar bear ( Ursus maritimus ) population status, and provide a contemporary update based on recent research findings and sea-ice projections by newer climate models. We compare predictions of polar bear population response from all 3 models among four circumpolar Arctic ecoregions, using sea ice projections based on three IPCC greenhouse gas emissions scenarios (SSP2.6, 4.5, 8.5). Consistent with the previous two model generations, polar bears will continue to experience increasing probability of declining or greatly declining populations throughout the 21st century, varying by emission scenario. Populations within the Polar Basin Divergent Ice Ecoregion have the highest predicted probability of declines, but predictions were slightly less dire relative to the previous model generation. Most of the influence, denoted by model sensitivity analysis, is from expected degradation and loss of sea ice and reduced access to marine prey. The lack of terrestrial prey adequate to substitute for loss of access to marine prey, as well as human-caused bear morality associated with hunting and defense of life and property encountered when polar bears are increasingly forced ashore also contributed to predicted declines. Although some tidewater glacial fjords and other localized onshore resources may provide local refugia, their benefit is transient. Our findings continue to inform priorities for inventory, monitoring, and research needs, and suggest that similar updates to models of other at-risk species can capitalize on the comparison framework we present here.

Ecological Indicators↗