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1. Bowhead and beluga whale acoustic detections in the western Beaufort Sea 2008–2018

   https://doi.org/10.1371/journal.pone.0253929  

   Stafford, Kathleen M. ; Citta, John J. ; Okkonen, Stephen R. ; Zhang, Jinlun ( June 2021 , PLOS ONE)

   Halliday, William David (Ed.)

   The Distributed Biological Observatory (DBO) was established to detect environmental changes in the Pacific Arctic by regular monitoring of biophysical responses in each of 8 DBO regions. Here we examine the occurrence of bowhead and beluga whale vocalizations in the western Beaufort Sea acquired by acoustic instruments deployed from September 2008-July 2014 and September 2016-October 2018 to examine inter-annual variability of these Arctic endemic species in DBO Region 6. Acoustic data were collected on an oceanographic mooring deployed in the Beaufort shelfbreak jet at ~71.4°N, 152.0°W. Spectrograms of acoustic data files were visually examined for the presence or absence of known signals of bowhead and beluga whales. Weekly averages of whale occurrence were compared with outputs of zooplankton, temperature and sea ice from the BIOMAS model to determine if any of these variables influenced whale occurrence. In addition, the dates of acoustic whale passage in the spring and fall were compared to annual sea ice melt-out and freeze-up dates to examine changes in phenology. Neither bowhead nor beluga whale migration times changed significantly in spring, but bowhead whales migrated significantly later in fall from 2008–2018. There were no clear relationships between bowhead whales and the environmental variables, suggesting that themore »DBO 6 region is a migratory corridor, but not a feeding hotspot, for this species. Surprisingly, beluga whale acoustic presence was related to zooplankton biomass near the mooring, but this is unlikely to be a direct relationship: there are likely interactions of environmental drivers that result in higher occurrence of both modeled zooplankton and belugas in the DBO 6 region. The environmental triggers that drive the migratory phenology of the two Arctic endemic cetacean species likely extend from Bering Sea transport of heat, nutrients and plankton through the Chukchi and into the Beaufort Sea.« less
2. Changes in gray whale phenology and distribution related to prey variability and ocean biophysics in the northern Bering and eastern Chukchi seas

   https://doi.org/10.1371/journal.pone.0265934  

   Moore, Sue E. ; Clarke, Janet T. ; Okkonen, Stephen R. ; Grebmeier, Jacqueline M. ; Berchok, Catherine L. ; Stafford, Kathleen M. ( April 2022 , PLOS ONE)

   Ummenhofer, Caroline (Ed.)

   Changes in gray whale ( Eschrichtius robustus ) phenology and distribution are related to observed and hypothesized prey availability, bottom water temperature, salinity, sea ice persistence, integrated water column and sediment chlorophyll a , and patterns of wind-driven biophysical forcing in the northern Bering and eastern Chukchi seas. This portion of the Pacific Arctic includes four Distributed Biological Observatory (DBO) sampling regions. In the Bering Strait area, passive acoustic data showed marked declines in gray whale calling activity coincident with unprecedented wintertime sea ice loss there in 2017–2019, although some whales were seen there during DBO cruises in those years. In the northern Bering Sea, sightings during DBO cruises show changes in gray whale distribution coincident with a shrinking field of infaunal amphipods, with a significant decrease in prey abundance (r = -0.314, p<0.05) observed in the DBO 2 region over the 2010–2019 period. In the eastern Chukchi Sea, sightings during broad scale aerial surveys show that gray whale distribution is associated with localized areas of high infaunal crustacean abundance. Although infaunal crustacean prey abundance was unchanged in DBO regions 3, 4 and 5, a mid-decade shift in gray whale distribution corresponded to both: (i) a localized increase in infaunalmore »prey abundance in DBO regions 4 and 5, and (ii) a correlation of whale relative abundance with wind patterns that can influence epi-benthic and pelagic prey availability. Specifically, in the northeastern Chukchi Sea, increased sighting rates (whales/km) associated with an ~110 km (60 nm) offshore shift in distribution was positively correlated with large scale and local wind patterns conducive to increased availability of krill. In the southern Chukchi Sea, gray whale distribution clustered in all years near an amphipod-krill ‘hotspot’ associated with a 50-60m deep trough. We discuss potential impacts of observed and inferred prey shifts on gray whale nutrition in the context of an ongoing unusual gray whale mortality event. To conclude, we use the conceptual Arctic Marine Pulses (AMP) model to frame hypotheses that may guide future research on whales in the Pacific Arctic marine ecosystem.« less
3. Mapping vessel traffic patterns in the ice-covered waters of the Pacific Arctic

   https://doi.org/10.1007/s10584-023-03568-3  

   Kapsar, Kelly ; Gunn, Grant ; Brigham, Lawson ; Liu, Jianguo ( July 2023 , Climatic Change)

   Recent climate change has caused declines in ice coverage which have lengthened the open water season in the Arctic and increased access to resources and shipping routes. These changes have resulted in more vessel activity in seasonally ice-covered regions. While traffic is increasing in the ice-free season, the amount of vessel activity in the marginal ice zone (ice concentration 15–80%) or in pack ice (>80% concentration) remains unclear. Understanding patterns of vessel activities in ice is important given increased safety challenges and environmental impacts. Here, we couple high-resolution ship tracking information with sea ice thickness and concentration data to quantify vessel activity in ice-covered areas of the Pacific Arctic (northern Bering, Chukchi, and western Beaufort Seas). This region is a geo-strategically critical area that contains globally important commercial fisheries and serves as a corridor for Arctic access for wildlife and vessels. We find that vessel traffic in the marginal ice zone is widely distributed across the study area while vessel traffic in pack ice is concentrated along known shipping routes and in areas of natural resource development. Of the statistically significant relationships between vessel traffic and both sea ice concentration and thickness, over 99% are negative, indicating that increasingmore »sea ice is associated with decreasing vessel traffic on a monthly time scale. Furthermore, there is substantial vessel traffic in areas of high concentration for bowhead whales (Balaena mysticetus), and traffic in these areas increased four-fold during the study period. Fishing vessels dominate vessel traffic at low ice concentrations, but vessels categorized as Other, likely icebreakers, are the most common vessel type in pack ice. These findings indicate that vessel traffic in areas of ice coverage is influenced by distant policy and resource development decisions which should be taken into consideration when trying to predict future vessel-ice interactions in a changing climate.

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4. Warming and Freshening of the Pacific Inflow to the Arctic From 1990‐2019 Implying Dramatic Shoaling in Pacific Winter Water Ventilation of the Arctic Water Column

   https://doi.org/10.1029/2021GL092528  

   A. Woodgate, Rebecca ; Peralta‐Ferriz, Cecilia ( May 2021 , Geophysical Research Letters)

   The Pacific inflow to the Arctic traditionally brings heat in summer, melting sea ice; dense waters in winter, refreshing the Arctic’s cold halocline; and nutrients year‐round, supporting Arctic ecosystems. Bering Strait moorings from 1990 to 2019 find increasing (0.010 ± 0.006 Sv/yr) northward flow, reducing Chukchi residence times by ∼1.5 months over this period (record maximum/minimum ∼7.5 and ∼4.5 months). Annual mean temperatures warm significantly (0.05 ± 0.02°C/yr), with faster change (∼0.1°C/yr) in warming (June/July) and cooling (October/November) months, which are now 2°C to 4°C above climatology. Warm (≥0°C) water duration increased from 5.5 months (the 1990s) to over 7 months (2017), mostly due to earlier warming (1.3 ± 0.7 days/yr). Dramatic winter‐only (January–March) freshening (0.03 psu/yr) makes winter waters fresher than summer waters. The resultant winter density change, too large to be compensated by Chukchi sea‐ice processes, shoals the Pacific Winter Water (PWW) equilibrium depth in the Arctic from 100–150 to 50–100 m, implying PWW no longer ventilates the Arctic’s cold halocline at 33.1 psu.
5. Diet energy density estimated from isotopes in predator hair associated with survival, habitat, and population dynamics

   https://doi.org/10.1002/eap.2751  

   Rode, Karyn D. ; Taras, Brian D. ; Stricker, Craig A. ; Atwood, Todd C. ; Boucher, Nicole P. ; Durner, George M. ; Derocher, Andrew E. ; Richardson, Evan S. ; Cherry, Seth G. ; Quakenbush, Lori ; et al ( December 2022 , Ecological Applications)

   Sea ice loss is fundamentally altering the Arctic marine environment. Yet there is a paucity of data on the adaptability of food webs to ecosystem change, including predator–prey interactions. Polar bears (Ursus maritimus) are an important subsistence resource for Indigenous people and an apex predator that relies entirely on the under‐ice food web to meet its energy needs. In this study, we assessed whether polar bears maintained dietary energy density by prey switching in response to spatiotemporal variation in prey availability. We compared the macronutrient composition of diets inferred from stable carbon and nitrogen isotopes in polar bear guard hair (primarily representing summer/fall diet) during periods when bears had low and high survival (2004–2016), between bears that summered on land versus pack ice, and between bears occupying different regions of the Alaskan and Canadian Beaufort Sea. Polar bears consumed diets with lower energy density during periods of low survival, suggesting that concurrent increased dietary proportions of beluga whales (Delphinapterus leucas) did not offset reduced proportions of ringed seals (Pusa hispida). Diets with the lowest energy density and proportions from ringed seal blubber were consumed by bears in the western Beaufort Sea (Alaska) during a period when polar bear abundancemore »declined. Intake required to meet energy requirements of an average free‐ranging adult female polar bear was 2.1 kg/day on diets consumed during years with high survival but rose to 3.0 kg/day when survival was low. Although bears that summered onshore in the Alaskan Beaufort Sea had higher‐fat diets than bears that summered on the pack ice, access to the remains of subsistence‐harvested bowhead whales (Balaena mysticetus) contributed little to improving diet energy density. Because most bears in this region remain with the sea ice year round, prey switching and consumption of whale carcasses onshore appear insufficient to augment diets when availability of their primary prey, ringed seals, is reduced. Our results show that a strong predator–prey relationship between polar bears and ringed seals continues in the Beaufort Sea. The method of estimating dietary blubber using predator hair, demonstrated here, provides a new metric to monitor predator–prey relationships that affect individual health and population demographics.

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