Eastern Beaufort Sea Research Articles

A New Snailfish of the Genus Careproctus (Cottiformes: Liparidae) from the Beaufort Sea

A new species of Careproctus is described on the basis of two individuals collected from the eastern Beaufort Sea during the U.S.–Canada 2013 Transboundary Cruise. It is distinguished from all known species of Careproctus primarily by its elongate deeply exserted filamentous rays in the middle part of the pectoral fin, an unlobed dorsal fin, protruding snout, and counts of dorsal- (58–60) and anal-fin rays (52–54) and vertebrae (64–65). The two known specimens were collected at depths of 488–599 m. Among other liparids of the Arctic and North Pacific Oceans, the new species is most similar to Careproctus mica, from which it can be readily distinguished by the filamentous rays of the pectoral fin and higher counts of median-fin rays and vertebrae.

Potential exposure of beluga and bowhead whales to underwater noise from ship traffic in the Beaufort and Chukchi Seas

Sea ice loss associated with a changing climate is resulting in increased levels of ship traffic in the Arctic, which in turn is causing increased underwater noise levels and associated impacts on marine life. Estimating the possible, present levels of exposure of marine life to underwater noise is a crucial step in understanding and managing contemporary exposures and underwater noise levels, and will inform future planning actions and mitigation. In this study, we examined the overlap between modeled underwater noise from ship traffic from 2015 to 2017 and monthly utilization distributions of beluga (Delphinapterus leucas) and bowhead whales (Balaena mysticetus) calculated from satellite telemetry data collected between 1995 and 2018 in the Beaufort and Chukchi seas. We first modeled noise propagation from observed vessel traffic in the Pacific Arctic from Amundsen Gulf in the east to Bering Strait in the west. We modeled the propagation loss of underwater noise from different classes of vessels that were transiting the area, and then applied these values to actual ship tracks (derived from satellite automatic identification system data) to model monthly noise footprints between July and October in each year between 2015 and 2017. We overlaid the monthly noise footprints with monthly 50% utilization distributions for satellite-tagged eastern Beaufort Sea beluga whales (1993–1997, 2004–2006) and Bering-Chukchi-Beaufort bowhead whales (2006–2018). Vessel traffic and its associated underwater noise were highest in all months in the southern Chukchi Sea near Bering Strait, particularly along the Russian and Alaskan coastlines. In comparison, traffic was lower in the western Canadian Arctic and in offshore areas; within the western Canadian Arctic, traffic was higher in August and September than in July and October. In July, low ship traffic resulted in low levels of overlap between modeled underwater noise and the utilization distributions for both whale species because the whales tend to use habitats in the eastern Beaufort Sea and Amundsen Gulf. Conversely, in August through September, there was medium to high overlap between underwater noise and the distributions for both species as ship traffic increased in those months and the distribution of both species began shifting towards the Chukchi Sea. Both beluga and bowhead whales migrate through areas with the highest levels of traffic in the Pacific Arctic, and are potentially exposed to a high number of acoustic disturbance events in three national jurisdictions. Without proactive vessel management and effective mitigation measures, acoustic disturbance of whales is expected to increase, and eventually expand to more months of the year, as ship traffic continues to increase in step with increases in the length of the open water season.

Upriver sightings of beluga whales (Delphinapterus leucas) follow storm surges and high water in the Mackenzie Delta, Northwest Territories, Canada

Each summer, Eastern Beaufort Sea beluga whales (Delphinapterus leucas (Pallas, 1776)) form a large congregation in the Tarium Niryutait Marine Protected Area (TNMPA) in the Mackenzie River estuary, a behaviour thought to be linked to warm, freshwater conditions. In 2018, >50 belugas were observed upriver near Aklavik in the Mackenzie River Delta. Community members noted that this upriver occurrence of belugas was unusual and suggested that wind-driven high water levels in the Mackenzie River were a primary driver. We investigated this explanation by searching past communications and reports for documentation of beluga sightings upriver and identifying storm surges and water-level changes at six hydrometric stations in the Mackenzie River Delta. We found three previous occurrences of belugas upriver dating back to 2000, all of which followed prominent surges in river level attributable to coastal storms. Although acknowledging a small sample size, we suggest that upriver occurrences of beluga whales warrant further investigation through extension of the TNMPA beluga monitoring program. As climate-driven changes cause more frequent and intense Arctic storm surges, we expect storm events to increasingly overlap with the annual summer beluga congregation. This may cause upriver movements to become more common, and population-level implications are not known.

Sea-ice and water dynamics and moonlight impact the acoustic backscatter diurnal signal over the eastern Beaufort Sea continental slope

Abstract. A 2-year-long time series of currents and acoustic backscatter from an acoustic Doppler current profiler, moored over the eastern Beaufort Sea continental slope from October 2003 to September 2005, were used to assess the dynamics and variability of the sound-scattering layer. It has been shown that acoustic backscatter is dominated by a synchronized diel vertical migration (DVM) of zooplankton. Our results show that DVM timings (i) were synchronous with sunlight and (ii) were modified by moonlight and sea ice, which attenuates light transmission to the water column. Moreover, DVM is modified or completely disrupted during highly energetic current events. Thicker ice observed during winter–spring 2005 lowered the backscatter values but favored extending DVM toward the midnight sun. In contrast to many previous studies, DVM occurred through the intermediate water layer during the ice-free season of the midnight sun in 2004. In 2005, the midnight-sun DVM was likely impacted by a high acoustic scattering generated by suspended particles. During full moon at low cloud cover, the nighttime moonlight illuminance led to zooplankton avoidance of the subsurface layer, disrupting DVM. Moreover, DVM was disrupted by upwelling, downwelling, and eddy passing. We suggest that these deviations are consistent with DVM adjusting to avoid enhanced water dynamics. For upwelling and downwelling, zooplankton likely respond to the along-slope water dynamics dominated by surface- and depth-intensified flow, respectively. This drives zooplankton to adjust DVM by aggregating in the low or upper intermediate water layer for upwelling and downwelling, respectively. The baroclinic eddy reversed DVM below the eddy core.

Variation in the diet of beluga whales in response to changes in prey availability: insights on changes in the Beaufort Sea ecosystem

The eastern Beaufort Sea (EBS) beluga whaleDelphinapterus leucaspopulation has experienced a 20 yr decline in inferred growth rates of individuals, which is hypothesized to have resulted from changes in prey availability. We used fatty acid signatures and stable isotope ratios to reconstruct the proportional contributions of 14 prey species to the diets of 178 beluga whales from 2011 to 2014. Prey estimates using quantitative fatty acid signature analysis suggest that EBS beluga whales primarily consume Arctic codBoreogadus saida, a species highly sensitive to climate change. Prey estimates varied with year and sex and size class of the whales, with large males consuming the highest proportions of Arctic cod, and females consuming the highest proportions of capelinMallotus villosus. Estimated proportional contributions of Arctic cod to beluga diet decreased from 2011 to 2014, coinciding with an increase in capelin. Belugas consumed the highest proportions of capelin and the lowest proportions of cod in 2014, the same year in which body condition indices were lowest in the whales. We hypothesize that changing conditions in the Beaufort Sea ecosystem may result in a decreased consumption of Arctic cod by belugas and increased consumption of capelin, which may result in a decline in condition. This may predominately affect females and juveniles since they consume the highest proportions of capelin; however, long-term monitoring is needed for confirmation. Understanding inter-annual variation in prey, and the longer-term nutritional implications of shifting from an Arctic cod- to a capelin-dominated diet should be a priority for monitoring EBS predators.

Spatial patterns, environmental correlates, and potential seasonal migration triangle of polar cod (Boreogadus saida) distribution in the Chukchi and Beaufort seas

Polar cod (Boreogadus saida) is a key forage fish in the Arctic marine ecosystem and provides an energetic link between lower and upper trophic levels. Despite its ecological importance, spatially explicit studies synthesizing polar cod distributions across research efforts have not previously been conducted in its Pacific range. We used spatial generalized additive models to map the distribution of polar cod by size class and relative to environmental variables. We compiled demersal trawl data from 21 cruises conducted during 2004–2017 in the Chukchi and Beaufort seas, and investigated size-specific patterns in distribution to infer movement ecology of polar cod as it develops from juvenile to adult life stages. High abundances of juvenile polar cod (≤ 70 mm) in the northeastern Chukchi Sea and western Beaufort Sea were separated from another region of high abundance in the eastern Beaufort Sea, near the US and Canadian border, suggesting possible population structure in the Pacific Arctic. Relating environmental correlates to polar cod abundance demonstrated that temperature and salinity were related to juvenile distribution patterns, while depth was the primary correlate of adult distribution. A comparison of seasonal 2017 abundances of polar cod in the southern Chukchi Sea found low demersal abundance in the spring when compared to the summer. Seasonal differences in polar cod abundance suggest that polar cod migration may follow a classical ‘migration triangle’ route between nursery grounds as juveniles, feeding grounds as subadults, and spawning grounds as adults, in relation to ice cover and seasonal production in the Chukchi Sea.

Mapping and Understanding the Role of Seabed Morphology in Relation to Beluga Whale (Delphinapterus leucas) Hotspots and Habitat Use in the Mackenzie Estuary, NT

The Tarium Niryutait Marine Protected Area within the Mackenzie Estuary provides a critical summer habitat for the Eastern Beaufort Sea (EBS) beluga whales (Delphinapterus leucas). Given the lack of seabed characterization in the Mackenzie Estuary, there is a need to characterize key features and governing processes that may influence or drive beluga habitat use. Thus, we sample and describe the Mackenzie Estuary seabed and examine the influence of ice conditions, fluvial processes and wave interactions to define seabed processes and spatially defined habitats. Lastly, we examine how beluga selects specific seabed characteristics or habitat types. Seabed mapping, sediment sampling and delineation of seafloor features are used to define the seabed habitat. The majority of the seabed consists of medium to coarse-grained silt and is void of any bathymetric variations and disturbances. Five seabed habitat zones were defined: (1) featureless and flat, (2) scours and disturbed, (3) sandy shoal, (4) deep channel and (5) longshore bars. Beluga observations analysed retrospectively from 1972 to 1992 were associated with the featureless and flat seabed habitat 72% of the time. However, a preference for the sandy shoal habitat provides some indication there are substrates in the estuary which are suitable for whales to rub against (to scrape off moulting skin), supporting the hypothesis there are certain habitats that may attract belugas during the annual moult.

Environmental drivers of beluga whale Delphinapterus leucas habitat use in the Mackenzie Estuary, Northwest Territories, Canada

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 626:209-226 (2019) - DOI: https://doi.org/10.3354/meps13011 Environmental drivers of beluga whale Delphinapterus leucas habitat use in the Mackenzie Estuary, Northwest Territories, Canada K. Scharffenberg1,*, D. Whalen2, M. Marcoux1,3, J. Iacozza4, G. Davoren1, L. Loseto1,4 1Dept of Biological Sciences, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada 2Natural Resources Canada, Geological Survey of Canada, Dartmouth, Nova Scotia B2Y 4A2, Canada 3Freshwater Institute, Fisheries and Oceans Canada, Winnipeg, Manitoba R3T 2N6, Canada 4Dept of Environment & Geography, University of Manitoba, Winnipeg, Manitoba R3T 2N2, Canada *Corresponding author: scharffk@myumanitoba.ca ABSTRACT: Understanding drivers of habitat use and selection of mobile species is critical for understanding the impacts of climate change and formulating management plans. Eastern Beaufort Sea beluga whales Delphinapterus leucas form large summering aggregations in the warm, fresh waters of the Mackenzie Estuary, Northwest Territories, Canada; however, the environmental factors driving spatial and temporal patterns of habitat use within the estuary are not fully understood. We used passive acoustic monitoring to record beluga presence during their summer aggregation (June-August) at known congregation areas and locations with unique oceanographic features in Kugmallit Bay in the Mackenzie River Estuary, while simultaneously recording environmental and oceanographic data. The effectiveness of hydrophones at determining beluga presence/absence was validated using shore-based observations. Multiple logistic regression was used to assess the influence of environmental conditions on presence/absence of belugas. Results indicate that temporal patterns of habitat use varied by location, and were influenced by environmental conditions such as temperature, salinity, and wind speed. Belugas did not frequent commonly used locations during periods with high-speed winds and moved farther into the estuary during periods of cold oceanic influxes. This study provides support for hypotheses that belugas use the location for moulting or to provide a thermal advantage for young belugas. This information can be used to inform decisions by northern communities and policy makers, thus aiding in management of the Beaufort Sea beluga population. KEY WORDS: Passive acoustic monitoring · Oceanography · Estuarine ecology · Arctic Full text in pdf format Supplementary material PreviousNextCite this article as: Scharffenberg K, Whalen D, Marcoux M, Iacozza J, Davoren G, Loseto L (2019) Environmental drivers of beluga whale Delphinapterus leucas habitat use in the Mackenzie Estuary, Northwest Territories, Canada. Mar Ecol Prog Ser 626:209-226. https://doi.org/10.3354/meps13011 Export citation Mail this link - Contents Mailing Lists - RSS Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 626. Online publication date: September 12, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Body condition indicators: Assessing the influence of harvest location and potential thresholds for application in beluga monitoring

• Sex-specific beluga body condition models account for size, age, location, and year. • Belugas from entrapment events can serve as thresholds for body condition indicators. • Spatial variability was detected and requires consideration in the use of indicators. • This study aims to develop blubber thickness and girth as body condition indicators. Monitoring marine protected areas requires simplifying complex marine ecosystems into a suite of indicators. The Tarium Niryutait Marine Protected Area (TN MPA), the first MPA in the Canadian Arctic is located in the Inuvialuit Settlement Region, NT and is selecting indicators for monitoring. Proposed health indicators for the TN MPA species of interest, the Eastern Beaufort Sea (EBS) beluga, include the body condition metrics blubber thickness and girth. Sex-specific body condition models for both metrics were developed to account for age, size, location, and timing of harvest from belugas harvested from 2000 to 2015. Models were tested to determine if the spatial variation is detected in the condition of belugas between the three areas of the TN MPA and between belugas harvested inside to outside of the TN MPA. Lastly, we assessed belugas from entrapment events to determine if indicator thresholds could be developed. Three of the indicators (girth male, girth female, blubber thickness male) contain both temporal and spatial factors, signalling the significant influence of year and harvest location on condition. Male belugas harvested from the western area of the TN MPA had smaller mean blubber thickness and girth compared to the other TN MPA areas, whereas there was no significant difference in female condition across the TN MPA. There was a significant difference inside and outside the TN MPA for all four indicators, with larger mean blubber thickness inside the TN MPA, females exhibiting larger mean girth and males exhibiting smaller mean girth inside the TN MPA. Indicators confirm that belugas from entrapment events had significantly lower body condition than belugas harvested during the summer and can serve as thresholds for condition indicators. This study provides guidance on the selection and use of condition indicators for their application in monitoring the TN MPA and demonstrates that careful consideration is required for indicator development and selection.

Body condition impacts blood and muscle oxygen storage capacity of free-living beluga whales (Delphinapterus leucas).

Arctic marine ecosystems are currently undergoing rapid environmental changes. Over the past 20 years, individual growth rates of beluga whales (Delphinapterus leucas) have declined, which may be a response to climate change; however, the scarcity of physiological data makes it difficult to gauge the adaptive capacity and resilience of the species. We explored relationships between body condition and physiological parameters pertaining to oxygen (O2) storage capacity in 77 beluga whales in the eastern Beaufort Sea. Muscle myoglobin concentrations averaged 77.9 mg g-1, one of the highest values reported among mammals. Importantly, blood haematocrit, haemoglobin and muscle myoglobin concentrations correlated positively to indices of body condition, including maximum half-girth to length ratios. Thus, a whale with the lowest body condition index would have ∼27% lower blood (26.0 versus 35.7 ml kg-1) and 12% lower muscle (15.6 versus 17.7 ml kg-1) O2 stores than a whale of equivalent mass with the highest body condition index; with the conservative assumption that underwater O2 consumption rates are unaffected by body condition, this equates to a >3 min difference in maximal aerobic dive time between the two extremes (14.3 versus 17.4 min). Consequently, environmental changes that negatively impact body condition may hinder the ability of whales to reach preferred prey sources, evade predators and escape ice entrapments. The relationship between body condition and O2 storage capacity may represent a vicious cycle, in which environmental changes resulting in decreased body condition impair foraging, leading to further reductions in condition through diminished prey acquisition and/or increased foraging efforts.

Intestinal polycyclic aromatic hydrocarbon-DNA adducts in a population of beluga whales with high levels of gastrointestinal cancers.

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) were disposed directly into the Saguenay River of the St. Lawrence Estuary (SLE) by local aluminum smelters (Quebec, Canada) for 50 years (1926-1976). PAHs in the river sediments are likely etiologically related to gastrointestinal epithelial cancers observed in 7% of 156 mature (>19-year old) adult beluga found dead along the shorelines. Because DNA adduct formation provides a critical link between exposure and cancer induction, and because PAH-DNA adducts are chemically stable, we hypothesized that SLE beluga intestine would contain PAH-DNA adducts. Using an antiserum specific for DNA modified with several carcinogenic PAHs, we stained sections of paraffin-embedded intestine from 51 SLE beluga (0-63 years), 4 Cook Inlet (CI) Alaska beluga (0-26 years), and 20 beluga (0-46 years) living in Arctic areas (Eastern Beaufort Sea, Eastern Chukchi Sea, Point Lay Alaska) and aquaria, all with low PAH contamination. Stained sections showed nuclear light-to-dark pink color indicating the presence of PAH-DNA adducts concentrated in intestinal crypt epithelial lining cells. Scoring of whole tissue sections revealed higher values for the 51 SLE beluga, compared with the 20 Arctic and aquarium beluga (P = 0.003). The H-scoring system, applied to coded individual photomicrographs, confirmed that SLE beluga and CI beluga had levels of intestinal PAH-DNA adducts significantly higher than Arctic and aquarium beluga (P = 0.003 and 0.02, respectively). Furthermore, high levels of intestinal PAH-DNA adducts in four SLE beluga with gastrointestinal cancers, considered as a group, support a link of causality between PAH exposure and intestinal cancer in SLE beluga. Environ. Mol. Mutagen. 60:29-41, 2019. Published 2018. This article is a U.S. Government work and is in the public domain in the USA.

Deglacial floods in the Beaufort Sea preceded Younger Dryas cooling

A period of cooling about 13,000 years ago interrupted about 2,000 years of deglacial warming. Known as the Younger Dryas (YD), the event is thought to have resulted from a slowdown of the Atlantic meridional overturning circulation in response to a sudden flood of Laurentide Ice Sheet meltwater that reached the Nordic Seas. Oxygen isotope evidence for a local source of meltwater to the open western North Atlantic from the Gulf of St Lawrence has been lacking. Here we report that the eastern Beaufort Sea contains the long-sought signal of 18O-depleted water. Beginning at ~12.94 ± 0.15 thousand years ago, oxygen isotopes in the planktonic foraminifera from two sediment cores as well as sediment and seismic data indicate a flood of meltwater, ice and sediment to the Arctic via the Mackenzie River that lasted about 700 years. The minimum in the oxygen isotope ratios lasted ~130 years. We suggest that the floodwater travelled north along the Canadian Archipelago and then through the Fram Strait to the Nordic Seas, where freshening and freezing near sites of deep-water formation would have suppressed convection and caused the YD cooling by reducing the meridional overturning.

Beluga whales (Delphinapterus leucas), environmental change and marine protected areas in the Western Canadian Arctic

Two Arctic Marine Protected Areas (MPAs) (Tarium Niryutait and Anguniaqvia niqiqyuam) have been established in the Western Canadian Arctic, including the first in the Arctic, with conservation objectives directed to protect and maintain healthy beluga (Delphinapterus leucas) populations. The MPAs support the continued access of Inuvialuit (Western Arctic Inuit) to harvest beluga whales for food security and cultural purposes. The land claim and co-management framework for the Inuvialuit Settlement Region support the long term monitoring and management plans for this beluga population. We draw upon over 40 years of monitoring of the Eastern Beaufort Sea (EBS) beluga whale population and consider the utility of biological indicators for MPA management. In particular we focus on the conservation of a beluga population whose home range extends far beyond MPA boundaries (transboundary population with summer core area in excess of 36, 000 Km2). We conclude that the EBS beluga whales are effective indicators of environmental change, but that we have limited understanding of the temporal and spatial relationships between beluga responses to processes that drive environmental change. Management bodies are challenged with implementing indicators that measure the impacts of ‘non-manageable’ stressors such as climate change, and by uncertainty in the mechanistic relationships that drive biological indicators. Given that Inuvialuit continue to be astute observers of the environment and changing conditions, our assessment suggests that Indigenous knowledge will continue to enhance the development and interpretation of beluga whale indicators for use in MPA monitoring and management.

“That’s how we know they’re healthy”: the inclusion of traditional ecological knowledge in beluga health monitoring in the Inuvialuit Settlement Region

Belugas (Delphinapterus leucas) from the Eastern Beaufort Sea (EBS) population are harvested annually in the Inuvialuit Settlement Region (ISR) during their seasonal migration past coastal communities and harvest camps. The beluga harvest monitoring program is a flagship program of the ISR’s Fish and Marine Mammal Community Monitoring Program, and it has provided critical information about beluga health and observed changes in the EBS population. This study aimed to develop a suite of local indicators of beluga health that bridged traditional ecological knowledge (TEK) about beluga condition, illness, and disease, with western science through the co-production of knowledge. Community members from Inuvik, Paulatuk, and Tuktoyaktuk with beluga harvesting and preparation experience were engaged to characterize beluga health from an Inuvialuit perspective. Inuvialuit knowledge about the environment and beluga health, values about hunting beluga, and Inuvialuit cosmology — the foundation of the knowledge syste...

Diet and feeding observations from an unusual beluga harvest in 2014 near Ulukhaktok, Northwest Territories, Canada

The Eastern Beaufort Sea (EBS) beluga (Delphinapterus leucas) population are an important traditional food for the Inuit of the Inuvialuit Settlement Region, Northwest Territories (NT) Canada. In 2...

A multi-species synthesis of satellite telemetry data in the Pacific Arctic (1987–2015): Overlap of marine mammal distributions and core use areas

We collated available satellite telemetry data for six species of ice-associated marine mammals in the Pacific Arctic: ringed seals (Pusa hispida; n = 118), bearded seals (Erignathus barbatus, n = 51), spotted seals (Phoca largha, n = 72), Pacific walruses (Odobenus rosmarus divergens, n = 389); bowhead whales (Balaena mysticetus, n = 46), and five Arctic and sub-arctic stocks of beluga whales (Delphinapterus leucas, n = 103). We also included one seasonal resident, eastern North Pacific gray whales (Eschrichtius robustus, n = 12). This review summarized the distribution of daily locations from satellite-linked transmitters during two analysis periods, summer (May–November) and winter (December–April), and then examined the overlap among species. Six multi-species core use areas were identified during the summer period: 1) Chukotka/Bering Strait; 2) Norton Sound; 3) Kotzebue Sound; 4) the northeastern Chukchi Sea; 5) Mackenzie River Delta/Amundsen Gulf; and 6) Viscount Melville Sound. During the winter period, we identified four multi-species core use areas: 1) Anadyr Gulf/Strait; 2) central Bering Sea; 3) Nunivak Island; and 4) Bristol Bay. During the summer period, four of the six areas were centered on the greater Bering Strait region and the northwestern coast of Alaska and included most of the species we examined. The two remaining summer areas were in the western Canadian Arctic and were largely defined by the seasonal presence of Bering-Chukchi-Beaufort stock bowhead whales and Eastern Beaufort Sea stock beluga whales, whose distribution overlapped during both summer and winter periods. During the winter period, the main multi-species core use area was located near the Gulf of Anadyr and extended northwards through Anadyr and Bering Straits. This area is contained within the Bering Sea “green belt”, an area of enhanced primary and secondary productivity in the Bering Sea. We also described available telemetry data and where they can be found as of 2017. These data are important for understanding ice-associated marine mammal movements and habitat use in the Pacific Arctic and should be archived, with appropriate metadata, to ensure they are available for future retrospective analyses.

Qualitative risk assessment of impact of Toxoplasma gondii on health of beluga whales, Delphinapterus leucas from the Eastern Beaufort Sea, Northwest Territories

In recent years, the protozoan parasite Toxoplasma gondii has increasingly been recognized in Arctic fauna, including beluga whales (Delphinapterus leucas) in the Eastern Beaufort Sea (EBS), Northw...

Wind-forced depth-dependent currents over the eastern Beaufort Sea continental slope: Implications for Pacific water transport

Pacific water contributes significantly to the Arctic Ocean freshwater budget. Recent increases in Arctic freshwater flux, also affected by the Pacific-derived Arctic water, impact the Atlantic overturning circulation with implications for global climate. The interannual variability of the Pacific water outflow remains poorly understood, partly due to different branches of the Pacific water flow in the Arctic Ocean. The shelfbreak current over the Beaufort Sea continental slope transports ~50% of the Pacific-derived water eastward along the Beaufort Sea continental slope towards the Canadian Archipelago. The oceanographic mooring deployed over the eastern Beaufort Sea continental slope in October 2003 recorded current velocities through depths of 28–108 m until September 2005. Data analysis revealed that these highly energetic currents have two different modes of depth-dependent behaviour. The downwelling-favourable wind associated with cyclones passing north of the Beaufort Sea continental slope toward the Canadian Archipelago generates depth-intensified shelfbreak currents with along-slope northeastward flow. A surface Ekman on-shore transport and associated increase of the sea surface heights over the shelf produce a cross-slope pressure gradient that drives an along-slope northeastward barotropic flow, in the same direction as the wind. In contrast, the upwelling-favourable wind associated with deep Aleutian Low cyclones over the Alaskan Peninsula and/or Aleutian Island Arc leads to surface-intensified currents with along-slope westward flow. This northeasterly wind generates a surface Ekman transport that moves surface waters offshore. The associated cross-slope pressure gradient drives an along-slope southwestward barotropic flow. The wind-driven barotropic flow generated by upwelling and downwelling is superimposed on the background bottom-intensified shelfbreak current. For downwelling, this flow amplifies the depth-intensified background baroclinic circulation with enhanced Pacific water transport towards the Canadian Archipelago. For upwelling, the shelfbreak current is reversed, which results in surface-intensified flow in the opposite direction. These results are supported by numerical simulations.

Trends in sea-ice cover within bowhead whale habitats in the Pacific Arctic

The range of the Bering-Chukchi-Beaufort (BCB) population of bowhead whales (Balaena mysticetus) extends across the seasonally ice-covered waters of the Pacific Arctic region. The majority of whales summer in the eastern Beaufort Sea and winter in the Bering Sea, migrating across the Chukchi Sea in fall and spring. As arctic sea-ice extent rapidly diminishes, the increasing length and variability of the open water season is changing bowhead habitat substantially, with many areas now regularly ice-free when whales are present. This study examines changes in the number of open water days (OWD) between 1979 and 2014 within annual bowhead whale core-use areas as defined by satellite tagging data, and within the western Beaufort Sea (140–157°W; to 72°N) sampled by fall aerial surveys. Ice cover has decreased more in the core-use areas in the northern extent of the range than in core-use areas in the southern extent. The numbers of OWD within the core-use areas near Point Barrow and along the northern Chukotka Coast during peak use have increased by 13 and 10 days/decade, respectively. The most dramatic reductions in sea-ice cover have taken place in the western Beaufort Sea where the number of OWD on the shelf and slope have increased by 20 and 25 days/decade, respectively. In contrast, sea-ice cover has not significantly changed within the winter core-use area near the Gulf of Anadyr. Using aerial survey data, we found that bowheads in the Beaufort Sea during the fall migration have a preference for being closer to shore than to the ice edge, and that their distance to shore decreases as the fraction of open water increases. This distribution may be due to increased feeding opportunities closer to shore as a result of greater upwelling along the shelf break when the ice cover is farther from shore. Furthermore, the aerial survey data also revealed a substantial shift westward toward Point Barrow in the whales’ use of the western Beaufort Sea during fall in the period 1997–2014 compared to 1982–1996. The extent and timing of sea-ice coverage has changed relatively little over time in the Bering Sea. Bowheads typically migrate north prior to spring ice melt and retreat; therefore, large changes in the timing of the spring migration are not expected. We anticipate that bowheads will spend increasingly more time within summer and fall feeding areas, delaying their arrival to wintering areas in the Bering Sea. Reduced ice coverage and thickness in the southern Chukchi Sea may make wintering there more common in the future. Summer and fall movements may be more variable as productivity and zooplankton aggregations in existing feeding areas are altered in response to sea ice thinning and retreat, and as new areas become available.

Sea-ice thickness in the coastal northeastern Chukchi Sea from moored ice-profiling sonar

ABSTRACTTime series ice-draft data were obtained from moored ice-profiling sonar (IPS), in the coastal northeastern Chukchi Sea during 2009/10. Time series data show seasonal growth of sea-ice draft, occasionally interrupted by coastal polynya. The sea-ice draft distribution indicates a slightly lower abundance of thick, deformed ice compared with the eastern Beaufort Sea. In January, a rapid increase in the abundance of thick ice coincided with a period of minimal drift indicating compaction again the coast and dynamical thickening. The overall mean draft and corresponding derived thickness are 1.27 and 1.38 m, respectively. The evolution of modal ice thickness observed can be explained mostly by thermodynamic growth. The derived ice thicknesses are used to estimate heat losses based on ERA-interim data. Heat losses from the raw, 1 s IPS data are ~50 and 100% greater than those calculated using IPS data averaged over spatial scales of ~20 and 100 km, respectively. This finding demonstrates the importance of subgrid-scale ice-thickness distribution for heat-loss calculation. The heat-loss estimate based on thin ice data derived from AMSR-E data corresponds well with that from the 1 s observed ice-thickness data, validating heat-loss estimates from the AMSR-E thin ice-thickness algorithm.