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The Bering Sea is undergoing major changes from increasing winter temperatures to the north, extreme minimum sea‐ice years in 2018 and 2019, through to an ecosystem reorganisation and negative impacts on communities' economic and subsistence food resources. These events have emerged under a global warming background, with positive feedback processes through a weakened atmospheric Alaskan Arctic Front (AAF) that promotes a self‐reinforcing process of sea‐ice loss, warmer air and sea temperatures, a wavy jet stream, and southerly winds. Interannual variability is still important: during 2021–2024 the Aleutian Low‐pressure system was regionally dominant in supporting a strong AAF, and sea‐ice conditions were observed close to the climatological mean. Before 2017, the AAF, consisting of cold dry air mass to the north and moist relatively warm air mass to the south, was a barrier to northward movement of storms, keeping the northern Bering/Chukchi seas with a cold Arctic climate. That historical situation is ending. Of critical importance is the probable reoccurrence of low Bering Sea sea‐ice years over the next decades and related ecosystem impacts. We propose that radically low sea ice will have a frequency of one to three 2018‐like low sea‐ice events per decade in the coming two decades, based on a historical meteorological analysis and ensemble climate model projections. Arctic temperatures to the north are increasing, weakening their contribution to the AAF. A weakened AAF and low sea‐ice years needs the winter Aleutian low pressure system to be far to the west of its average position, with southerly rather than northeasterly winds, warm years and low sea‐ice extent. From 1948 to 2024 meteorological records, this western location occurred with a range of zero to three times per decade. Communities need to plan for a response to intermittent occurrence of 2018‐like extreme sea‐ice loss and their ecosystem impacts over the coming decades. [ABSTRACT FROM AUTHOR]

Subsurface eddies, characterized by their cores located within or below the pycnocline, can transport materials over long distances in the ocean's interior. Observations of these eddies are sparse, limiting our understanding of their regional distribution and detailed horizontal structures, particularly in high‐latitude areas. The Bering Sea, situated in the subarctic region, is among the world's most productive areas and significantly influences the Arctic Ocean's state, thereby impacting climate change. In this study, we utilize ultrahigh resolution (approximately 10 m) data to investigate the distribution and characteristics of subsurface eddies in the Aleutian Basin, Bering Sea. We detected 44 subsurface eddies in 13 survey transects and analyzed their morphological and hydrographic characteristics, spatial distribution, propagation, and transport. The results show that the average core radius of the subsurface eddies is about 11.62 km and they exhibit complex structures in both the core and flank regions. The dichothermal layer cold‐core eddies are prevalent in the deep‐water region of the Bering Sea, contributing approximately 1.76 Sv poleward and westward transport in the subsurface layer. This is the first three‐dimensional depiction of subsurface eddies in the Bering Sea, revealing that the prevalence of subsurface eddies in the Bering Sea may have been negligent, with significant implications for the hydrographic and biogeochemical properties of both the Bering Sea and the Arctic Ocean. More detailed comprehensive and long‐term observations should be made to assess the global impact of subsurface eddies in the future. Plain Language Summary: Eddies are ubiquitous in the ocean, with subsurface eddies being a type characterized by their temperature, salinity, and maximum velocity core located within the ocean's interior. However, detailed knowledge of these eddies is limited due to the lack of systematic observations. Sporadic observations and low‐resolution studies have shown that these eddies can transport tracers such as heat, salinity, and nitrate for a long distance and can induce sharp vertical displacements at their flanks, thereby exerting a strong influence on ocean circulation, climate, and biological production. In this study, we use an ultrahigh‐resolution (about 10 m) technology, that is, seismic oceanography, and utilize concurrent temperature and current velocity measurements to depict the three‐dimensional distribution and characteristics of subsurface eddies in the deep region of the Bering Sea. The results indicate that subsurface eddies are more prevalent and their detailed structures are more complex than previously thought. Our findings suggest that these eddies significantly impact the hydrographic and biogeochemical characteristics of the subsurface layer of the Bering Sea and potentially the Arctic Ocean. More detailed comprehensive observations should be made to assess the role of subsurface eddies in ocean circulation, climate, and biological production in the future. Key Points: An ultrahigh‐resolution 3D observation reveals that subsurface eddies are prevalent in the Aleutian Basin, Bering SeaThese subsurface eddies are classified into dichothermal and mesothermal layer eddies with distinct core depth and originThe structures of these subsurface eddies are complex; most are submesoscale, with some exhibiting submesoscale filaments [ABSTRACT FROM AUTHOR]

Arctic sea ice has provided a historical barrier for killer whale (Orcinus orca) entry, but that barrier is now depleting as the sea ice melts due to global climate change. This study used passive acoustic monitoring to describe changes in broad-scale killer whale presence in the U.S. Arctic associated with declining sea ice. Passive acoustic data were analyzed for killer whale calls from eight monitoring sites throughout the Alaska Chukchi, northern Bering, and western Beaufort seas from 2011 to 2019 and correlated with sea ice coverage. Killer whale acoustic presence was significantly correlated with sea ice coverage in the U.S. Arctic at two sites directly north and south of the Bering Strait (p = 0.04, t7 = − 5.34; p = 0.03, t7 = − 4.42), and increased as sea ice decreased in the North Slope region along the Northern Alaska coast (p < 0.01, t7 = 4.49). We also observed shifts in the spring arrival of killer whale calling over the time period of the study, which correlated with the timing of sea ice retreat. Killer whales shifted their time of arrival an average of 50 days earlier in the North Slope region and 32 days earlier in the Bering Strait region over the study period with 16.2 days (± 6.6 SD) lag between sea ice retreat and the first killer whale detection. These results point to an increased presence of an apex predator in the U.S. Arctic, which has the potential to impact the trophic dynamics of this region. [ABSTRACT FROM AUTHOR]

High statistical significance of water temperature at the sea bottom T and depth D for distribution of pacific cod in the West Bering Sea fishing zone is found in several tested models tuned on the data of bottom trawl surveys conducted in the period between 1977 and 2021 not deeper than 400 m. The vector autoregressive spatio-temporal (VAST) models which included nonlinear dependencies of cod catches from T and D have the best generalization ability. Correlation between predicted by VAST models and observed distribution density of cod in the test data set are higher than that in simpler models trained using the full set of data. The VAST models produce continuous time series of cod biomass with estimates of their uncertainty and statistical weights of the model configurations relative to the test data. After stacking with statistical weights and previously published estimates of biomass, the obtained time series allow to estimate dynamics of biological processes deviations from stationary assumptions and to estimate approximately the volume of “extra” cod not considered by these processes in the Bayesian State-Space Surplus Production Model. The portion of “extra” cod increased sharply above 40 % in 2016 and reached the maximum of 49 % by 2018, then began to decrease. Sharp changes in the main EOF modes for T are revealed in these years. Thus, the hypothesis of cod redistribution in the Bering Sea due to changes of the cold pool area at the bottom was tested for the first time by statistical methods in space. Due to high errors of forecasts based on analysis of biological processes only, there is impossible to predict accurately dynamics of the cod biomass without predicting the water temperature distribution at the bottom of shelf.

Background: The deep-sea acorn worm Quatuoralisia malakhovi belongs to the phylum Hemichordata, class Enteropneusta, family Torquaratoridae, which was described in 2005. Owing to their epibenthic lifestyle and deep-sea habitat features, torquaratorids differ anatomically from shallow-water acorn worms; however, their morphology and fine structure are poorly studied. We have the opportunity to make three complete detailed series of histological sections of Q. malakhovi and to study the microscopic anatomy, histology and fine structure of the reproductive system of this acorn worm using scanning and transmission electron microscopy. Results: The sexes of Q. malakhovi are separate and indistinguishable externally. The lobed testes occupy the dorsal side of the genital wings and distinctly bulge into the peribranchial cavity by their mature lobes. The central part of the testis is always submerged into the genital wing and opens via a single gonad pore. The monociliary muscle cells stretch along the external wall of the testis and surround the gonad pore, probably taking part in the contraction of the testis lobes for spawning. The germinative epithelium of the testis contains spermatogenic cells at different stages of development and interstitial cells. Yolk cells are not found. Interstitial cells embrace the spermatogonia and spermatogenic columns, providing horizontal compartmentalization of the germinative epithelium, and contain numerous phagosomes with remnants of degenerating spermatogenic cells. The testis wall contains haemal lacunae, which are usually located on the side opposite the gonad pore. We describe the fine structure of spermatogonia, spermatocytes clustered in spermatogenic columns, spermatids, and spermatozoa. Spermatozoa are of the ectaquasperm type and consist of an acorn-shaped head and a flagellum 18–25 µm long. The sperm head includes a beak-shaped acrosomal part, a spherical nucleus and a midpiece containing a ring of 5 or rarely 6 mitochondria. Conclusions: The male reproductive system and sperm structure of Q. malakhovi, a representative of the family Torquaratoridae, have a number of differences from shallow-water acorn worms; however, the spermatogenesis and sperm structure of Q. malakhovi generally follow the pattern of the other three enteropneust families, and the phylogenetic significance of these deviations should be the subject of further research. [ABSTRACT FROM AUTHOR]

Recent studies have documented poleward shifts in heavily targeted fish stocks on the Bering Sea Shelf. This study investigated whether commercial fishing vessels in the region have also shifted their distribution poleward in recent years. We used Vessel Management System data generated between January 1, 2013, and December 31, 2022, to identify regions over the shelf where vessel activity increased (emerging hot spots) and where it decreased (emerging cold spots) during this time period. We hypothesized that emerging hot spots would occur at the northern edge of the vessel operating range, while emerging cold spots would occur at the southern edge. Overall, northward shifts in vessel distribution were most evident during October–February and July–August, when the range of emerging hots spots was centered 204–515 km to the N, NE, or NW of the center of the range of emerging cold spots. The trend was strongest in August, when emerging hot spots were widespread in the Northern Bering Sea. We did not attempt to identify factors driving these distributional shifts, but the timing of shifts did coincide with the busiest fishing seasons over the Bering Sea Shelf and, in part, the open seasons for walleye pollock (Gadus chalcogrammus). If groundfish populations continue to move poleward with climate change, this study may serve as a window into the early stages of a long-term redistribution of commercial fishing effort in the Bering Sea, a region supporting one of the largest fishing industries in the world. [ABSTRACT FROM AUTHOR]

For the first time, the isotopic composition and concentration of dissolved inorganic carbon in waters of the western Bering Sea (Koryak shelf and Chukotka continental slope, and Commander Islands, depth range 10–4100 m) have been analyzed. The [DIC] values vary from 1900 μmol/kg in the summer waters of the Koryak shelf to 2510 μmol/kg in the deep waters in the area of the Commander Islands. The δ13С values of DIC in productive summer waters exceed +1‰ and reach +3.08‰ in Koryak shelf surface waters. The depth of the carbon isotope minimum (–0.7‰) is ≈500 m. The model calculations were made taking into account the physical processes (isotopic exchange with atmospheric CO2 and conservative mixing). The calculations show that the δ13С(DIC) and [DIC] values in the main water column are governed by oxidation of organic matter. The predominance of primary production occurs only in the surface (<20 m) waters of the Bering Sea. The DIC concentrations increase to depths of ≈1000 m and remain approximately constant (2430 ± 30 μmol/kg), exceeding [DIC] levels in deep Pacific waters. A "physical carbon pump" model is proposed, in which the main role in the accumulation and redistribution of DIC within the water column is attributed to winter waters of the Bering Sea. [ABSTRACT FROM AUTHOR]

Recent concerns that commercial bottom trawling can contribute to a significant release of sequestered marine carbon have highlighted a need for research in this area. Here, a Before-After Control-Impact (BACI) experimental design was utilized in a previously untrawled area of the eastern Bering Sea. Six pairs of experimental and control corridors were sampled before, after, and 1 year after a trawl disturbance. Each experimental corridor was fished four consecutive times over ∼12 h with a commercial otter trawl. Results were contextualized with minimum detectable effects (MDE), and showed no evidence of a trawl effect on total organic carbon (P  = .999, MDE ± 0.05% TOC), total nitrogen (P  = .999, MDE ± 0.02% TN), δ13C, and δ15N isotope ratios and sediment size classes. Interannual changes observed in δ15N, sand, silt, and clay are attributed to natural variation. The study suggests that the characteristics of the study site, such as storm disturbances, high sand content, and low carbon content, limited the bottom-trawl effect on sediment composition following this initial trawl disturbance. The findings highlight the importance of site-specific studies that account for local conditions to support best management practices for commercial bottom trawling. [ABSTRACT FROM AUTHOR]

Ice-associated seals rely on sea ice for a variety of activities, including pupping, breeding, molting, and resting. In the Arctic, many of these activities occur in spring (April through June) as sea ice begins to melt and retreat northward. Rapid acceleration of climate change in Arctic ecosystems is therefore of concern as the quantity and quality of suitable habitat is forecast to decrease. Robust estimates of seal population abundance are needed to properly monitor the impacts of these changes over time. Aerial surveys of seals on ice are an efficient method for counting seals but must be paired with estimates of the proportion of seals out of the water to derive population abundance. In this paper, we use hourly percent-dry data from satellite-linked bio-loggers deployed between 2005 and 2021 to quantify the proportion of seals hauled out on ice. This information is needed to accurately estimate abundance from aerial survey counts of ice-associated seals (i.e., to correct for the proportion of animals that are in the water, and so are not counted, while surveys are conducted). In addition to providing essential data for survey 'availability' calculations, our analysis also provides insights into the seasonal timing and environmental factors affecting haul-out behavior by ice-associated seals. We specifically focused on bearded (Erignathus barbatus), ribbon (Histriophoca fasciata), and spotted seals (Phoca largha) in the Bering and Chukchi seas. Because ringed seals (Phoca (pusa) hispida) can be out of the water but hidden from view in snow lairs analysis of their 'availability' to surveys requires special consideration; therefore, they were not included in this analysis. Using generalized linear mixed pseudo-models to properly account for temporal autocorrelation, we fit models with covariates of interest (e.g., day-of-year, solar hour, age and sex class, wind speed, barometric pressure, temperature, precipitation) to examine their ability to explain variation in haul-out probability. We found evidence for strong diel and within-season patterns in haul-out behavior, as well as strong weather effects (particularly wind and temperature). In general, seals were more likely to haul out on ice in the middle of the day and when wind speed was low and temperatures were higher. Haul-out probability increased through March and April, peaking in May and early June before declining again. The timing and frequency of haul-out events also varied based on species and age-sex class. For ribbon and spotted seals, models with year effects were highly supported, indicating that the timing and magnitude of haul-out behavior varied among years. However, we did not find broad evidence that haul-out timing was linked to annual sea-ice extent. Our analysis emphasizes the importance of accounting for seasonal and temporal variation in haul-out behavior, as well as associated environmental covariates, when interpreting the number of seals counted in aerial surveys. [ABSTRACT FROM AUTHOR]

The degree to which walleye pollock (Gadus chalcogrammus , hereafter pollock) move between the US and Russian zones of the Bering Sea is a key source of uncertainty for fisheries management. To study transboundary migrations across the US–Russia maritime boundary and explore how climate variability might influence these migrations, four seafloor-mounted echosounder moorings were deployed from July 2019 to August 2020 in the northwestern Bering Sea. The observations indicated that a substantial amount of pollock moves between the US and Russia seasonally, with a period of southeast movement into the US as winter as sea ice forms and northwest movement into Russia in early summer as waters warm. Over the deployment period, 2.3-times more pollock backscatter moved into the US zone in fall and winter than exited the subsequent spring and summer. We hypothesize that the difference in the net movement between regions was driven by pollock moving farther into Russia during the historically warm conditions at the start of deployment period and reduced northwest return migration the following summer when temperatures were relatively cooler. This supports the hypothesis that temperature affects pollock distribution, and that continued warming will lead to a larger proportion of the stock in Russian waters. [ABSTRACT FROM AUTHOR]

A comparative morphological analysis has been conducted for antlered sculpins of the genus Enophrys from three remote regions: the Sea of Japan, the Sea of Okhotsk, and the Bering Sea. Variations in their body color pattern and also meristic and measurable characters have been analyzed. As the analysis has shown, antlered sculpins from the Sea of Japan differ significantly from the two other samples in their body color, some head proportions, and the size and location of the fins D1, D2, A, V, and P. Differences on the subspecies level (CD > 1.28) have been found for five of the studied characters and a hiatus (differences on the species level) for one character (depth of D1). The data we obtained confirm the previously published assumption that the fish from the Sea of Japan possibly belong to the species E. namiyei. [ABSTRACT FROM AUTHOR]

Long-term dynamics of the food base for nekton in the deep-sea waters of the western Bering Sea are analyzed on the data of ecosystem surveys in 1986–2022. The main patterns of species composition and structure are determined for the main taxonomic groups of zooplankton and their production is evaluated. These features are influenced by climateoceanographic and biocenotic factors, with priority of the climate-oceanographic ones, whereas the biocenotic factors are conditioned by them. As an example of biocenotic impact, the effect of chaetognats on copepods is considered. Trophic characteristics of the most abundant species of pacific salmon (chum salmon Oncorhynchus keta and pink salmon O. gorbuscha) and their consumption of zooplankton production were estimated for 2020–2022. Comparing productivity and grazing of the main zooplankton groups, there is concluded that pacific salmon consume a small portion from seasonal production of their prey, therefore, food competition between the species of pacific salmon is absent in the deep-sea waters.

Changes to Earth's climate affect organisms globally; in marine systems, these impacts are seen through warming water temperatures, ocean acidification, hypoxia and frequent marine heatwaves. These effects may lead to the movement of species to more favourable conditions. While climate‐driven movement is well studied at the adult stage, how the early life stages of marine fish will respond to future variability is less clear. Many fish species are constrained by specific spawning locations or phenology. Spawning in certain locations allows for local retention of offspring, while precise timing can facilitate transport of offspring to nursery locations through seasonal circulation patterns. Our research investigates how changing oceans impact the location and timing of spawning of Bering Sea groundfishes over the next century. We used ROMS SST and SSS model output and NOAA survey data in species distribution models to hindcast and project distributions and centre of gravity for eggs and larvae of six groundfish species. Our analyses found that most of our study species exhibit flexible geography. However, the speed and direction of egg and larval movement did not track the speed and direction of their respective thermal niches. Hence, the projected distributional patterns of adult stages may be limited by their early life stages. This response is likely to be mirrored globally by other species with planktonic eggs and larvae. These results indicate that life history considerations are critical for the management of commercially important species, as effects on early life stages are strongly connected to the success or failure of adult populations. [ABSTRACT FROM AUTHOR]

The short-tailed albatross (Phoebastria albatrus) is a rare bird species today, numbers of which declined significantly in the Holocene due to human hunting activities. Bones of albatrosses from archaeological sites of Chukotka, Kamchatka, and the Aleutian Islands, and from coastal sediments of the Commander Islands were used to analyze the content of stable carbon and nitrogen isotopes in bone collagen. The analysis showed that the isotopic niches of Aleutian and Commander albatrosses diverged during the Holocene. Short-tailed albatrosses of the Aleutian Islands are closer to Holocene albatrosses of Vancouver Island (Canada) in the isotopic characteristics. [ABSTRACT FROM AUTHOR]

The isotope parameters and sources of freshwater components for the subsurface, intermediate, and deep water of the western Bering Sea were estimated using the isotope (δ18О, δD) data for 177 seawater samples. We show that subsurface, dichothermal and, partially, intermediate water (<1000 m) are freshened by regional precipitation. For these waters, the next equations of relations between delta and salinity values were obtained: δ18О = [0.390 ± 0.018]S – 13.521 ± 0.613 and δD = [3.07 ± 0.08]S – 107 ± 2.74. Deeper (1000–2500 m) water is also freshened by precipitation but from the more southern region (≈40°–45° S). The deepest water (2800–4300 m) retain their isotope signal obtained via freshening by Antarctic glacier ice meltwater. The distribution of isotope parameters with the depth shows that vertical mixing at depths of ≈1000–2500 m takes place. This process should influent the redistribution of nutrients, dissolved oxygen, organic matter, and other components in water of the western Bering Sea. The isotope composition of water passing into the Arctic Ocean halocline (S = 33.1) from the Bering Sea are δ18О = –0.61‰ and δD = –5.4‰. [ABSTRACT FROM AUTHOR]

Predominantly Western-based biomedical models of successful aging have been used to research, understand, and explain successful aging among diverse populations. With an increasingly heterogeneous older adult population nationwide, scholars have been exploring Indigenous understandings of successful aging. To add to the accumulation of knowledge of diverse Alaska Native populations, this study involved semi-structured qualitative interviews with 20 Unangan Elders from the Aleutian and Pribilof Islands. This community-based participatory research study explores the aging experiences and conceptualization of successful aging of these Elders from this remote and culturally distinct region of Alaska. Thematic analysis was employed to identify themes related to successful aging within this specific region, which supported our previous four themes, or characteristics, of Alaska Native successful aging: physical health, social support and emotional well-being, generativity as a traditional way of life, and community engagement and Inidgenous cultural generativity. Each of these themes or characteristics of Eldership is intertwined and together support successful aging within two remote communities in the Bering Sea. The findings of this study illuminate how Alaska Native Elders can live in geographically diverse regions of the State, yet the values and teachings they possess on successful aging possess the same cultural values and teachings. This study highlighted two new emerging constructs that influence Alaska Native Elders' successful aging based on geographical location. Findings contribute to the thematic saturation of the four main successful aging domains while outlining the importance of future research to conduct deeper investigations into the role of environment and history on Elders' perceptions and understanding of aging. [ABSTRACT FROM AUTHOR]

From 1982–1990 to 2006–2010 in the western part of the Bering Sea biomass of the walleye pollock Gadus chalcogrammus decreased by almost an order of magnitude, from 7.2 to 0.7 million tons. However, in the last decade (2011–2020) its biomass increased to the long-term average value (4.0 million tons). In the eastern part of the sea, the pollock biomass dynamics was of the wave-like nature with the highest value in 1982–1990 and the lowest, in 2006–2010. The food spectrum of the walleye pollock is wide and includes 16 taxonomic groups of aquatic organisms. The main part of average annual food mass consumed by pollock in the Bering Sea in 1982–2020 consisted of zooplankton (74.1%). During different study periods, annual feed consumption varied from 91.1 to 373.0 (average 239.3) million tons per year. Significant fluctuations in the volume of food consumed are mainly associated with the dynamics of the species' biomass. [ABSTRACT FROM AUTHOR]

Over the past four decades, temporal variability in March sea ice area (SIA) within the Bering Sea occasionally contradicts prevailing northeasterly wind, raising doubt about the primary regulatory role of wind speed in governing maximum SIA. We argue that at least two spatial modes, extracted through the Empirical Orthogonal Function analysis, are necessary to explain the variations in the maximum SIA in the Bering Sea. Wind field emerges as the primary regulator of EOF1, governing both the direct influence of wind divergence (WD) and the indirect influence of meridional heat transport on sea ice. EOF2 is directly governed by ocean heat transport (OHT). Considering only the direct impact on sea ice, the OHT is directly responsible for the maximum SIA changes in 1995–2007, while in 2008–2014, the wind field is the largest driver. Since 2015, historically low SIA is attributed to significantly enhanced wind convergence and reduced zonal heat transport in the Gulf of Anadyr. Wind field directly controls the maximum SIA for less than half of the observation time, with OHT driving the rest. Declining trends observed in both WD and OHT suggests a future distribution pattern for the maximum SIA in the Bering Sea, characterized by an increase in the east and a decrease in the west. Long‐term retreat of sea ice on the western side of the Bering Sea is anticipated to exert significant impacts on local ecosystems, commercial activities, and even indigenous communities. Plain Language Summary: Over the past 43 years, interpreting maximum sea ice area fluctuations in the Bering Sea involves understanding a combined response to wind field and ocean heat transport (OHT). Disentangling these processes is challenging due to the significant coupling between the ocean, atmosphere, and sea ice. We found that wind field, traditionally seen as the dominant force, directly impacts sea ice changes for less than 50% of the observation period. However, in view of the fact that OHT is susceptible to the influence of wind patterns, it can be concluded that wind field emerges as the primary modulating factor when indirect effects are taken into account. The characteristics of long‐term light ice years in the Bering Sea over the last 10 years are the result of the combined effects of enhanced wind convergence outside the Bering Sea continental shelf and reduced eastward heat transport in the Gulf of Anadyr. In addition, we also predicted the future distribution characteristics of sea ice in the Bering Sea. Key Points: The direct influence exerted by wind field on local sea ice coverage is observed to be relatively constrained in the Bering SeaThe fluctuation in the March sea ice area (SIA) has been interpreted as a combined response to local wind divergence (WD) and zonal heat transportThe recent protracted light‐ice years is due to the intensification of wind convergence and the abatement of eastward heat transport [ABSTRACT FROM AUTHOR]

A multidisciplinary survey was carried out in the Pacific Arctic and sub-Arctic regions of the North Pacific Ocean on the Korean icebreaking research vessel Araon. During this survey, ichthyoplankton fishes in the Pacific Arctic and sub-Arctic region ranged from the Bering Sea to the northern Chukchi Shelf in summer. The most dominant species was Gadus chalcogrammus, followed by Pleuronectes quadrituberculatus and Boreogadus saida. Gadus chalcogrammus and P. quadrituberculatus were particularly abundant near the Bering Sea and Bering Strait, whereas B. saida was dominant in the Chukchi Sea. Hierarchical cluster analysis revealed four distinct ichthyoplankton communities in Pacific Arctic and sub-Arctic regions based on geographical regions. However, Eleginus gracilis, which was previously known to be seen between latitudes 66.5 °N and 69.5 °N, was found above 70 °N, suggesting that its distribution extends further north. Furthermore, we noticed that Benthosema glaciale, which is usually found in the Atlantic sector of Arctic Ocean, was observed in the northern Chukchi Sea. In addition to these unusual species distributions, several species that are mainly observed in coastal areas are observed in the Chukchi Sea region. The observed influx of various uncommon fish species into the Chukchi Sea can be attributed to multiple factors, including freshwater inflow from the East Siberian Sea and the intrusion of warm Atlantic and Pacific waters, which are strongly affected by global warming. Consequently, it is imperative to conduct rigorous monitoring of the Pacific Arctic region, with a particular focus on the Chukchi Sea, to better understand the implications of global warming. [ABSTRACT FROM AUTHOR]

Foraging specialisations are common in animal populations, because they increase the rate at which individuals acquire food from a known and reliable source. Foraging plasticity, however, may also be important in variable or changing environments. To better understand how seabirds might respond to changing environmental conditions, we assessed how plastic the foraging behaviours of short-tailed shearwaters (Ardenna tenuirostris) were during their non-breeding season. To do this, we tracked 60 birds using global location sensing loggers (GLS) over a single year between 2012 and 2016 with the exception of 8 individuals that were tracked over 2 consecutive years. Birds predominantly foraged in either the Sea of Okhotsk/North Pacific Ocean (Western strategy) or the southeast Bering Sea/North Pacific (Eastern strategy). The eight birds tracked for 2 consecutive years all returned to the same core areas, indicating that these birds were faithful to foraging areas between years, although the time spent there varied, probably in response to local changes in food availability. Overall, 50% of the birds we tracked left their core area towards the end of the non-breeding period, moving into the Chukchi Sea, suggesting that the birds have flexible intra-seasonal foraging strategies whereby they follow prey aggregations. We hypothesise that seasonal declines in chlorophyll a concentrations in their primary core foraging areas coincide with changes in the availability of large-bodied krill, an important food source for short-tailed shearwaters. Decreasing prey abundance likely prompts the movement of birds out of their core foraging areas in search of food elsewhere. This strategy, through which individuals initially return to familiar areas but disperse if food is limited, provides a mechanism that allows the birds to respond to the effects of climate variability. [ABSTRACT FROM AUTHOR]

The McKay's Bunting (Plectrophenax hyperboreus) is endemic to Alaska, breeds solely on the remote and uninhabited St. Matthew and Hall islands (332 km2) in the central Bering Sea, and is designated as a species of high conservation concern due to its small population size and restricted range. A previous hypothesized population estimate (~2,800 to 6,000 individuals) was greatly increased (~31,200 individuals) after systematic surveys of the species' entire breeding range in 2003, establishing McKay's Bunting as one of the rarest passerines in North America. In 2018, we replicated the 2003 surveys and used density surface models to estimate breeding season densities, distributions, and population change over the intervening time period. Our results indicate that the McKay's Bunting population declined by 38% (95% CI: 27 to 48%) from ~31,560 to 19,481 individuals since 2003. Spatial model predictions showed no areas with an increase of birds on either St. Matthew or Hall islands but revealed declines across 13% (42 km2) of St. Matthew Island. Declines disproportionately occurred both in marginal habitats with reduced rocky nesting substrate and in high-density hotspots along the coast of St. Matthew Island. The total area occupied by breeding adults decreased by 8%, and high-density hotspots shifted inland from the coast of St. Matthew Island to higher elevations on both islands, the latter potentially responses to exceptionally warm weather and reduced spring snow cover in 2018. Additionally, we observed low numbers of predators and interspecific competitors in 2018, suggesting that these did not cause the decline. Our findings indicate that McKay's Bunting meets international standards for elevating its conservation status from Least Concern to Endangered based on the International Union for Conservation of Nature Red List of Threatened Species ranking criteria. Additional population monitoring and studies to identify the causal mechanisms of the recent population decline of this rare species could assist future population assessments. [ABSTRACT FROM AUTHOR]

Abstract Background Climate change is reshaping Bering Sea crab distributions and recent population declines have elevated the urgency in understanding spatial dynamics in relation to management boundaries. While pop-up satellite archival tags (PSATs) can provide fishery-independent movement information, a high level of spatial resolution is needed to evaluate small-scale (i.e., 10 s of km) movements of crabs. Because PSATs drift at the surface prior to acquisition of a satellite-estimated location (via Argos), the accuracy of pop-up location (i.e., animal terminal position) estimates depends on the ability to accurately estimate drift error. We deployed PSATs (n = 36) on fixed-position moorings in Bristol Bay and Marmot Bay, Alaska to validate a new method to estimate tag pop-up location and an associated error ellipse that uses in situ drift data from surfaced tags to estimate drift error. Estimated pop-up location was compared to the location of tag surfacing (i.e., the tag’s fixed position) and to an alternative estimate (i.e., an early satellite-estimated location). Additional tags were deployed on mature male red king crab (Paralithodes camtschaticus) in Bristol Bay during 2020 (n = 84) and 2021 (n = 90) to compare estimates of tag drift error and crab displacement derived using the method. Results For red king crab tags with pop-up location estimates in 2020 (n = 79) and 2021 (n = 46), mean drift error was 9% and 44% of mean crab displacement, respectively. For fixed-position PSATs with pop-up location estimates (n = 27), mean distance between the estimated pop-up location and the tag’s fixed position was 2.0 km, representing a mean improvement in accuracy of 51% over alternative estimates. Corresponding error ellipse estimates either encompassed the tag’s fixed position (n = 11) or their boundaries were a mean distance of 1.3 km (n = 16) from the fixed position. Conclusions Our method improves pop-up location estimates for PSAT-tagged animals and is particularly well suited for crabs and other slow-moving benthic marine species. The improved estimates enhance PSAT utility for addressing management and ecological questions that require a fine spatial resolution, such as movement near management boundaries or defining essential habitat for important life history events.

Russian shelf is one of the most important areas for hydrocarbon forecast and mineral resources development. The main features of the geological structure of the shelves of the Far Eastern seas are discussed in the paper. The most promising basins on the Okhotsk shelf are located around Sakhalin island where the majority of the hydrocarbon fields have been discovered. The Bering and the Japan shelf has not been sufficiently studied by now but nevertheless has high oil and gas potential.The main focus is made on the geological and geophysical data, licensing, lithological and stratigraphic structure, seismic interpretation, oil and gas fields distribution. The structuraltectonic zoning of the entire Far Eastern region has been done in order to identify zones of deep troughs with thick sedimentary cover to predict the sources of hydrocarbon generation.

Mean patterns of atmospheric circulation over the Bering Sea in 4 seasons: winter (January-March), spring (April-June), summer (July-September) and autumn (OctoberDecember) are described using the author’s typification of synoptic situations. Frequency of all 6 types of synoptic situations is calculated and the predominant types are determined, by season. Mean values of the meridional and zonal indices of atmospheric circulation and the number and intensity of cyclones in the Bering Sea area are calculated for each season in the period 1995–2022. Cyclonic activity and direction and intensity of general wind transfer, particularly intensity of winter and summer monsoons, are considered separately for the western and eastern parts of the Bering Sea. Interannual variations of all these parameters are traced. For all seasons, the wind transfer over the entire area is determined by cyclonic activity in the western Bering Sea: the higher activity leads to weaker monsoon in winter (northeasterly) and summer (southwesterly) but strengthening in spring (southeasterly) and autumn (northwesterly). Since the middle 1990s, autumns and winters in the Bering Sea became warmer (with the warmest period in the late 2010s when southeasterlies prevailed in winter), but springs became colder (southeastern wind transfer in early 2000s changed to the northeastern one in late 2010s), with no definite tendency for summer, when the meridional index of atmospheric circulation was rather stable and the zonal index had a negative trend (weakening of westerlies). Trends and cycles of oceanographic conditions in the northwestern Bering Sea generally coincided with the changes in wind transfer in any season.

Results of trawl surveys in the Okhotsk Sea and western Bering Sea conducted aboard RV TINRO and RV Professor Kaganovsky in the autumn of 2023 are analyzed. Data on spatial distribution, abundance and biomass of fish species, cephalopods and jellyfishes in the epipelagic layer are presented. Contemporary status of the epipelagic nekton communities is examined. Quantitative distribution and biological state of pink salmon is described in details.

Based on the high-precision isotopic composition and concentration of dissolved inorganic carbon (DIC) in the Bering Sea waters, their scopes and pathways are estimated in the Pacific sector of the Arctic Ocean. Although δ13С(DIC) and [DIC] are not classical conservative tracers, these parameters show the presence of both Atlantic and Pacific marine waters similar to the Bering Sea waters in the basin of the East Siberian Sea, which is a zone of active interaction of river and marine waters. The spatial distribution of Pacific and Atlantic and river waters is estimated using a three-component mixing model along two sections of the East Siberian Sea. The Pacific component propagates from east to west approximately to 160° E (probably, more westward) skirting Wrangel Island not only from the north but also probably from the south. The East Siberian Sea contains waters similar to the Bering Sea summer surface waters of the open sea, which are removed to the northern shelf by the circular Bering Sea Current, and to the upper intermediate waters, which can be involved in the zone of the northern sea shelf due to upwelling or active mixing. [ABSTRACT FROM AUTHOR]

The results of analysis on the feeding patterns and assessment of the trophic levels and niches in two Zoarcidae species Bothrocara brunneum and B. zestum from the deep-water areas in the Sea of Okhotsk and the Pacific Ocean off the Lesser Kuril Ridge have been reported. Both species feed on various benthic and mesobenthic forage organisms including crustaceans, mesopelagic fishes, cephalopods, bivalved mollusks, polychaetes, and echinoderms. Despite the dominant food component variability across different water areas, crustaceans represent the major food group. In addition, both fish species have similar food sources and, therefore, trophic niches. It is proven by estimation with the standard ellipse area method via the Bayesian probability, showing rather similar widths of trophic niches: 17.7 for B. zestum and 16.6 for B. brunneum. The actual values for stable nitrogen isotope ratios (δ15N) in food components indicate a wide range of trophic levels in the analyzed species: from 2.08 to 4.36 in B. zestum and from 1.97 to 4.42 in B. brunneum, which can prove their plasticity in selecting the food items. The ranges of values for the stable carbon isotope ratios (δ13C) in food components indicating the basal food sources reached 15.04 to 23.43‰ for B. zestum and 15.07 to 23.43‰ for B. brunneum. The survey-based new information on two species feeding was obtained to determine their roles in the trophic structures of ecosystems in the studied water areas. [ABSTRACT FROM AUTHOR]

Worm-like endosymbionts were found in the hepatic region of the digestive tract of the deep-sea acorn worm Quatuoralisia malakhovi Ezhova et Lukinykh, 2022 (family Torquaratoridae) from the Bering Sea. The symbionts were assigned to the taxon Nemertodermatida on the basis of histological examination. Torquaratoridae are similar in feeding type to holothuroids, which have also been found to have Xenacoelomorpha endosymbionts. [ABSTRACT FROM AUTHOR]

The digestive system was anatomically studied in the deep-sea enteropneust Quatuoralisia mala-khovi. It was shown that lateral collar lips are twisted in such a way that they form a ciliary groove that leads to an internal channel, through which collected detritus particles are transferred to peripheral pharyngeal channels. The size of the selected particles ranges from 1–6 to 100–200 μm, which corresponds to feeding on the remains of planktonic diatoms. A fecal cord was observed to act as an anchor that holds the heavily watered jelly-like body of Torquaratoridae at the sea floor during feeding. [ABSTRACT FROM AUTHOR]

Oceanic N2O is a major source of atmospheric N2O gas and is involved in global warming and ozone depletion. It is thought to be mainly produced by nitrification, denitrification and nitrifier denitrification processes mediated by ammonia‐oxidizing bacteria, ammonia‐oxidizing archaea (AOA) and denitrifying bacteria. The Bering Sea, especially its continental shelf area, is considered a typical source of atmospheric N2O. During the 7th Chinese National Arctic Research Expedition (CHINARE2016), the distributions of N2O and ammonia‐oxidizing microorganisms (AOOs) in the Bering Sea continental shelf and abyssal basin water were investigated. At a depth of 50∼900 m within the abyssal basin, the in‐situ ammonia oxidation process, particularly performed by AOA, exhibits considerable potential for the formation of supersaturated N2O. Meanwhile, beneath the oxygen minimum zone (depth range is approximately 800∼1,000 m), supersaturated N2O is primarily driven by mixing processes, while the ammonia oxidation mediated by AOA also contributes to a certain extent. In addition, the N2O distribution characteristic exhibits a substantial disparity between the southern and northern Bering Sea shelves, with the former characterized as a mild sink and the latter as a weak source. The water column of the Bering Sea demonstrates a considerable potential for generating supersaturated N2O through ammonia oxidation, as corroborated by the current study. Plain Language Summary: Nitrous oxide (N2O) is an important trace greenhouse gas that also acts as an ozone destroyer. The ocean is one of the main sources of N2O to the atmosphere. As a marginal sea of the Pacific Ocean with high productivity, the distribution mechanism of N2O is very complex affected by water masses mixing and intricate biogeochemical cycle processes. And the N2O flux of Bering Sea has distinct spatio‐temporal variability. In this study, by incorporating previous research conclusions on the nitrogen cycle, we investigate the distribution mechanism of N2O and functional genes of ammonia oxidizing microorganisms in the Bering Sea to elucidate the potential contribution of individual nitrogen cycle processes to N2O supersaturation and which kinds of ammonia oxidation microorganisms are involved in this contribution, thus illustrating the distribution mechanisms of N2O in the northern Bering Sea. The flux of Bering Sea in summer was estimated based on the distribution mechanism of N2O. This findings were helpful to understand the mechanism of N2O metabolism in the Bering Sea and improve the accuracy of Marine N2O flux estimation. Key Points: The source‒sink characteristics of N2O in Bering Sea express obvious spatial and temporal variabilityAmmonia oxidation could potentially play a crucial role in the formation of N2O in the deep waters of the Bering Abyssal BasinThe distribution mechanisms of N2O in the southern and northern shelves of the Bering Sea exhibit distinct characteristic [ABSTRACT FROM AUTHOR]

Typical patterns of the water temperature distribution in the upper mixed layer of the Bering Sea in winter are determined on all available oceanographic data obtainedby research institutions of Russia, Japan, USA, and China. Previously [Luchin, 2023], the data were sorted to two sets presenting «cold» and «warm» winters. The proper set includes 2,492 oceanographic stations and the latter one – 2,130 stations. Spatial distribution of the temperature has some common patterns for both sets: the highest values (3–4 to 5–6 оC) are observed at the central and eastern passages between Aleutian Islands, primarily reflecting the Pacific waters invasion to the sea, then these waters are involved into the large-scale cyclonic gyre over the deep-water basin and transported along the continental slope that is indicated by 3оC isotherm. However, different types of the temperature distribution are well distinguished by prominent difference of its values that is amounted in 1.0–1.5о, up to 3–4о at the northwestern coast including the western part of the eastern Bering Sea slope. A wide set of potential predictors for interannual variability of thermal and dynamic conditions in the Bering Sea are examined using correlation analysis,including the global and regional climatic indices. There is concluded that the winter temperature fields are formed by several key factors, as the warm Pacific waters advection, the basin-scale cyclonic circulation, the vertical and lateral water mixing in the Aleutian sounds and at the continental slope, and fall-winter cooling of the surface layer driven by air–sea heat exchange.

Year-to-year variations of temperature in the upper mixed layer are considered for the ice-free waters of the Bering Sea in cold season (from December to March) using all data of the deep-sea oceanographic observations available to date (12,430 stations for the period from 1943 to 2022). Series of annual mean fields of the mixed layer temperature in December-March were decomposed by applying the empirical orthogonal function (EOF); dynamics of the first two components of decomposition (described in sum 50.4 % of the initial fields variability) are analyzed. The first component (32.4 % of variation) indicates synchronous oscillations over the entire sea area with the maximum contribution at the continental slope. The second component (18.0 % of variance) reflects opposite oscillations in two vast regions of the sea located along the continental slope from Cape Navarin to Alaska Peninsula and in the western, central and southern parts of the deep basin. The following statistically significant periodic oscillations are revealed by spectral analysis: quasi-biennial and those with periods of 4, 7, and 17–20 year for the 1st EOF and quasi-biennial and those with periods of 3 and 4 year for the 2nd EOF. A statistically significant linear trend to warming is detected for the time coefficient of the 1st EOF in the period of 1958–2022. Approximation of this coefficient dynamics with 6-degree polynomial function (polynomial trend) shows a tendencies to the mixed layer cooling in winters of 1969–1972 and 1992–2004 but the opposite tendencies to warming in 1973–1991 and 2005–2022. Variations of time coefficient for the 2nd EOF correspond to opposite tendencies in the areas with positive and negative values of this EOF. For the period from 1958 to 2022, winters in the Bering Sea are classified by the mixed layer temperature, taking into account the contribution of the 1st EOF only, as «warm» (1958, 1959, 1963, 1964, 1966, 1979, 1982, 1985, 1987, 1997, 2001, 2003, 2004, 2015–2018, 2020, and 2022), «normal» (1960–1962, 1965, 1967, 1968, 1970, 1971, 1974, 1978, 1980, 1981, 1983, 1986, 1989–1994, 1996, 1998, 2005–2007, 2011, 2013, 2014, 2019, and 2021), «cold» (1969, 1972, 1973, 1975–1977, 1984, 1988, 1995, 1999, 2000, 2002, 2008, and 2010), and extremely cold (2009 and 2012).

Warm water inflow from the Northeast Pacific has always been considered a crucial factor in early winter freeze-up in the Bering Sea. There is a strong correlation between changes in sea surface temperature (SST) on the eastern Bering Sea shelf and sea ice area in December. However, there is still limited research on the impact of Pacific inflow on SST on the eastern Bering Sea shelf, resulting in insufficient measurements of the impact of Pacific inflow on early freeze-up. In this article, the definition of marine heatwaves (MHW) is used to extract warm events (with a threshold of the 70th percentile) and cold events (with a threshold of the 30th percentile) from the eastern Bering Sea shelf in November. Self-organizing map (SOM) technology is utilized to classify extracted cold and warm events and the mixed-layer heat budget is ultimately used to explore the factors that generate and maintain these cold and warm events. Between 1993 and 2021, a total of 12 warm and 12 cold events are extracted and their cumulative intensity is found to be strongly correlated with the interannual variation in SST by 99.8%, indicating that these warm and cold events are capable of characterizing the interannual variation in SST. Among the 12 warm events, 9 of them can be attributed to abnormal warming of seawater before November and only 3 events are attributed to warm water inflow from the Northeast Pacific. During the development of warm events, there are only two events in which the warm inflow from the Northeast Pacific has a more profound regulatory effect on warm events in November. Moreover, both generation and regulatory factors of cold events are the net air–sea heat flux. Statistics indicate that the warm water inflow from the Northeast Pacific has a limited effect on SST on the eastern Bering Sea shelf during the early freeze-up period. Changes in local SST are more influenced by the residual heat before November and by local net air–sea heat flux. However, we highlight that long-term ocean heatwaves occurring in the Northeast Pacific can enlarge the residual heat of seawater in the eastern Bering Sea shelf before November, thereby impacting early freeze-up. The frequency of such events has significantly increased in the past decade, causing notable changes in the climate and ecosystem of the Bering Sea. Therefore, it is crucial to continue closely monitoring the occurrence and development of such events in the future. [ABSTRACT FROM AUTHOR]

Microalgae are the main source of the omega‐3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), essential for the healthy development of most marine and terrestrial fauna including humans. Inverse correlations of algal EPA and DHA proportions (% of total fatty acids) with temperature have led to suggestions of a warming‐induced decline in the global production of these biomolecules and an enhanced importance of high latitude organisms for their provision. The cold Arctic Ocean is a potential hotspot of EPA and DHA production, but consequences of global warming are unknown. Here, we combine a full‐seasonal EPA and DHA dataset from the Central Arctic Ocean (CAO), with results from 13 previous field studies and 32 cultured algal strains to examine five potential climate change effects; ice algae loss, community shifts, increase in light, nutrients, and temperature. The algal EPA and DHA proportions were lower in the ice‐covered CAO than in warmer peripheral shelf seas, which indicates that the paradigm of an inverse correlation of EPA and DHA proportions with temperature may not hold in the Arctic. We found no systematic differences in the summed EPA and DHA proportions of sea ice versus pelagic algae, and in diatoms versus non‐diatoms. Overall, the algal EPA and DHA proportions varied up to four‐fold seasonally and 10‐fold regionally, pointing to strong light and nutrient limitations in the CAO. Where these limitations ease in a warming Arctic, EPA and DHA proportions are likely to increase alongside increasing primary production, with nutritional benefits for a non‐ice‐associated food web. [ABSTRACT FROM AUTHOR]

An analysis of water exchange between the Bering (Pacific Ocean) and Chukchi (Arctic Ocean) seas in the summer was carried out using satellite data on sea level, geostrophic currents, and measurement data of water transport in the Bering Strait. It is shown that there is good agreement (r = 0.85, July–October 1997−2019) between the velocities of geostrophic currents (satellite data) and measurements of water transport (buoy station data) through the Bering Strait. It has been established that the temporal variability of water transport through the Bering Strait is determined by sea level variations in the southern part of the Chukchi Sea (66°–68° N, 170°–172° W). Strengthening of the eastern (western) winds is accompanied by a decrease (increase) in the sea level in the southern part of the Chukchi Sea and, as a result, an increase (decrease) in the flow of water through the Bering Strait. An increase (decrease) in the flow of the Yukon River is accompanied by a rise (decrease) in sea level and changes in water circulation in the northern Bering Sea and the southern Chukchi Sea. [ABSTRACT FROM AUTHOR]

Ferromanganese crusts found in the Bering Sea on the Volcanology Massif, Alpha Fault Zone, and Shirshov Submarine Ridge that cover the surface of rocky volcanic structures are most likely the product of postvolcanic activity. The results indicate that the studied ferromanganese formations developed under the influence of two factors: slow precipitation of metals from ordinary seawater and metal-enriched hydrothermal solutions. In microstructural and mineralogical terms, the composition of Fe–Mn crusts of the Bering Sea proved rather monotonous. The ore part is represented mainly by ferruginous vernadite and, rarely, hematite in combination with amorphous silica, and to a lesser extent, montmorillonite, calcite, and aragonite. The manganese mineral todorokite, considered a reliable sign of hydrothermal origin of ore crusts, was not detected in our samples. In the studied samples, the reduced cerium anomaly (0.87) was established only in one sample, and in other samples, its value varies within 1.08–1.89, which is typical of the upper horizons in the ocean water column. At the same time, the europium anomaly is close to neutral, so in seven samples, its value is 0.96–1.03 (average 1.0) and only in three samples is it slightly elevated (1.05–1.07), which can be considered a very weak sign of hydrothermal activity. In addition, the presence of gold microinclusions in the ferromanganese phase can indirectly indicate the possible influence of hydrothermal factor on the crust composition. [ABSTRACT FROM AUTHOR]

The eastern North Pacific right whale (NPRW) is the most endangered population of whale and has been observed north of its core feeding ground in recent years with low sea ice extent. Sea ice and water temperature are important drivers for zooplankton dynamics within the whale's core feeding ground in the southeastern Bering Sea, seasonally forming stable fronts along the shelf that give rise to distinct zooplankton communities. A northward shift in NPRW distribution driven by changing distribution of prey resources could put this species at increased risk of entanglement and vessel strikes. We modeled the abundance of NPRW prey, Calanus glacialis, Neocalanus, and Thysanoessa species, using a dynamic biophysical food web model of nine zooplankton guilds in the Bering shelf zooplankton community during a period of warming (2006–2016). This model is unique among prior zooplankton studies from the region in that it includes density dependence, thereby allowing us to ask whether species interactions influence zooplankton dynamics. Modeling confirmed the importance of sea ice and ocean temperature to zooplankton dynamics in the region. Density‐independent growth drove community dynamics, while dependent factors were comparatively minimal. Overall, Calanus responded to environment terms, with the strength and direction of response driven by copepodite stage. Neocalanus and Thysanoessa responses were weaker, likely due to their primary occurrence on the outer shelf. We also modeled the steady‐state (equilibrium) abundance of Calanus in conditions with and without wind gusts to test whether advection of outer shelf species might disrupt the steady‐state dynamics of Calanus abundance; the results did not support disruption. Given the annual fall sampling design, we interpret our results as follows: low‐ice‐extent winters induced stronger spring winds and weakened fronts on the shelf, thereby advecting some outer shelf species into the study region; increased development rates in these warm conditions influenced the proportion of C. glacialis copepodite stages over the season. Residual correlation suggests missing drivers, possibly predators, and phytoplankton bloom composition. Given the continued loss of sea ice in the region and projected continued warming, our findings suggest that C. glacialis will move northward, and thus, whales may move northward to continue targeting them. [ABSTRACT FROM AUTHOR]

Many mobile marine taxa are changing their distributions in response to climate change. Such movements pose a challenge to fisheries monitoring and management, particularly in systems where climate‐adaptive and ecosystem‐based management objectives are emphasized. While shifts in species distributions can be discerned from long‐term fisheries‐independent monitoring data, distilling coherent patterns across space and time from such datasets can be challenging, particularly for transboundary stocks. One approach for identifying dominant patterns of spatiotemporal variation that has been widely used in physical atmospheric and oceanographic studies is empirical orthogonal function (EOF) analysis, wherein spatiotemporal variation is separated into time‐series of annual factor loadings and spatial response maps. Here, we apply an extension of EOF analysis that has been modified for compatibility with biological sampling data to a combined US–Russian fisheries‐independent survey dataset that spans the eastern (United States) and western (Russia) Bering Sea shelf to estimate dominant patterns of spatiotemporal variation for 10 groundfish species at a shelf‐wide scale. EOF identified one axis of variability that was coherent with the extent of cold (≤0°C) near‐bottom waters (the cold pool) previously shown to be a key influence on species distributions and ecosystem structure for the Bering Sea. However, the leading axis of variability identified by our EOF analysis was characterized by low frequency changes in the distributions of several species over longer time scales. Our analysis has important implications for predicting variation in species distributions over time and demonstrates a widely applicable method for leveraging combined fisheries‐independent survey datasets to characterize community‐level responses to ecosystem change at basin‐wide scales. [ABSTRACT FROM AUTHOR]