Eastern Beaufort Sea Research Articles

Harvester selection and observed mercury levels in Eastern Beaufort Sea and Western Hudson Bay beluga whales (Delphinapterus leucas)

Mercury in marine biota has been extensively studied across Inuit Nunaat because it bioaccumulates and biomagnifies in high trophic level species, such as the beluga whale (Delphinapterus leucas), or qilalugaq in Inuktut. Qilalugaait (pl) are a staple in many coastal Inuit communities, including Tuktoyaktuk, Northwest Territories and Arviat, Nunavut. We examine how total mercury (THg) concentrations in two beluga populations are influenced by biased sampling resulting from local harvester preferences. We examined historical THg in skin, muscle, and liver (1980's to 2022) together with local qualitative interviews from two beluga-harvesting communities. Age and length bins were used to compare similar sized and aged whales between locations, where males (350 - 400 cm, and 20–30 years) and females (330–400 cm, and 15–30 years) were segregated. The interviews revealed distinct preferences whereby harvesters in Tuktoyaktuk actively sought larger (length) male whales, whereas harvesters in Arviat, selected wide and even range across size and sex. These local preferences were also evident in the historical dataset, with the median age and lengths were 31 years and 389.0 cm in Tuktoyaktuk (n = 461) and 23 and 336.0 cm in Arviat (n = 146). For males, mean and median THg concentrations were higher in beluga harvested from Tuktoyaktuk than Arviat in all three tissues with age and lengths combined, yet in the selected age and length bins, there was no difference in mean and median THg in the muscle tissue, and in median liver THg. There were significant differences in mean and median skin THg and in mean liver THg concentrations between males. In female whales, THg concentrations did not differ between Tuktoyaktuk and Arviat (in ages and lengths combined and in selected age bins across all tissues), excluding median muscle THg concentration. This study indicated that differences in THg concentrations that were previously observed resulted from hunter preferences in these two communities.

Geographic variation in simple contact calls of Canadian beluga whales (Delphinapterus leucas)

AbstractBeluga whales, Delphinapterus leucas, are a highly social species with a complex and diverse vocal repertoire. Although extensively studied and classified, to date few attempts have been made to examine geographic variation in their calls. In this study, we examined geographic variation in simple contact calls (SCCs), specifically those that consist only of broadband pulsed trains, among four Canadian beluga populations from the Eastern Beaufort Sea (EBS), the Eastern High Arctic‐Baffin Bay, St. Lawrence Estuary (SLE), and the Western Hudson Bay. Five acoustic parameters were measured for each call and compared among populations using multivariate discriminant analysis. Results of our study indicate that there is a degree of variation in SCCs among these four populations, with the most geographically distant populations of the SLE and EBS displaying the greatest degrees of dissimilarity in SCC structure relative to geographically closer populations. Further, these results align with genetic variation of Canadian beluga populations previously described in the literature. This study is the first descriptive population comparison of SCCs for beluga and establishes a baseline for continued work into this developing area of research.

Do beluga whales truly migrate? Testing a key trait of the classical migration syndrome

BackgroundMigration enables organisms to access resources in separate regions that have predictable but asynchronous spatiotemporal variability in habitat quality. The classical migration syndrome is defined by key traits including directionally persistent long-distance movements during which maintenance activities are suppressed. But recently, seasonal round-trip movements have frequently been considered to constitute migration irrespective of the traits required to meet this movement type, conflating common outcomes with common traits required for a mechanistic understanding of long-distance movements. We aimed to test whether a cetacean ceases foraging during so-called migratory movements, conforming to a trait that defines classical migration.MethodsWe used location and dive data collected by satellite tags deployed on beluga whales (Delphinapterus leucas) from the Eastern Beaufort Sea population, which undertake long-distance directed movements between summer and winter areas. To identify phases of directionally persistent travel, behavioural states (area-restricted search, ARS; or Transit) were decoded using a hidden-Markov model, based on step length and turning angle. Established dive profiles were then used as a proxy for foraging, to test the hypothesis that belugas cease foraging during these long-distance transiting movements, i.e., they suppress maintenance activities.ResultsBelugas principally made directed horizontal movements when moving between summer and winter residency areas, remaining in a Transit state for an average of 75.4% (range = 58.5–87.2%) of the time. All individuals, however, exhibited persistent foraging during Transit movements (75.8% of hours decoded as the Transit state had ≥ 1 foraging dive). These data indicate that belugas actively search for and/or respond to resources during these long-distance movements that are typically called a migration.ConclusionsThe long-distance movements of belugas do not conform to the traits defining the classical migration syndrome, but instead have characteristics of both migratory and nomadic behaviour, which may prove adaptive in the face of unpredictable environmental change. Such patterns are likely present in other cetaceans that have been labeled as migratory. Examination of not only horizontal movement state, but also the vertical behaviour of aquatic animals during directed movements is essential for identifying whether a species exhibits traits of the classical migration syndrome or another long-distance movement strategy, enabling improved ecological inference.

Beluga Whale Body Condition: Evaluating environmental variables on beluga body condition indicators in the Tarium Niryutait MPA, Beaufort Sea.

The development of indicators as tools for ecosystem monitoring is a key step in the management of Marine Protected Areas (MPAs). This study uses previously developed sex-specific body condition indices, blubber thickness and girth, to assess temporal changes in body condition from 2000 to 2015 in harvested Eastern Beaufort Sea (EBS) beluga whales (Delphinapterus leucas). Specifically, the goals were to (1) examine seasonal and inter-annual trends of beluga body condition indicators over the harvest season; (2) evaluate associations of body condition indicators across sexes; and (3) test annual means of each body condition index for correlations to regional scale environmental drivers, (i.e. the Pacific Decadal Oscillation (PDO) and sea-ice minimum (SIM) in the Beaufort Sea). Significant seasonal changes in male blubber thickness and female girth indices demonstrated the importance of short term seasonal drivers. Whilst inter-annual changes in girth and blubber thickness indices revealed longer-term changes, that were correlated between males and females. Only the male girth index had significant relationships with environmental drivers: a negative relationship with the PDO at a zero-year lag ,and a negative relationship with the SIM at a two-year lag. [more in manuscript]

I know what you did last winter: Bowhead whale anomalous winter acoustic occurrence patterns in the Beaufort Sea, 2018–2020

Global warming is affecting the Arctic at a faster pace than the rest of the world, causing an urgent need to monitor ecosystems to detect possible climate-related changes. To this end, five passive acoustic datasets were recorded in the southern Amundsen Gulf (eastern Beaufort Sea) from September 2018 to September 2020 and analyzed for Bering-Chukchi-Beaufort (BCB) bowhead whale calls using a combination of automated and manual detections. Results indicate a large variation in bowhead occurrence patterns between the two years. For 2018–2019, we obtained the first evidence of bowheads overwintering in what is typically their summer foraging ground. Examination of the following year’s recordings sheds light on whether this interruption in bowhead annual migration was an anomaly or part of an ongoing phenological shift due to climate change. Time series of remotely sensed sea ice concentration at the study area were considered over the last seven years in interpreting differences in migratory behavior of the whales. Statistical quantification of seasonal patterns and habitat preferences of bowheads, based on the 2018–2019 acoustic data, are presented to provide context to BCB bowhead ecology. Passive acoustic monitoring is an indispensable tool in discerning whale responses to a changing ocean in the Arctic.

Summer distribution and habitat preference of beluga whale social groups in the Eastern Beaufort Sea

In social animals, group composition can cause variations in individual needs that can influence responses to habitat trade-offs, such as predator exposure or foraging opportunities. The Eastern Beaufort Sea beluga whales ( Delphinapterus leucas (Pallas, 1776)) form different group types and cover multiple habitat types in summer. This study compares the habitat preference of three beluga social group types: (1) individual belugas, (2) groups of adults, and (3) groups with at least one calf. Observations were collected during aerial surveys in July and August 2019. For each month, beluga distribution was analyzed with hierarchical generalized additive models, as a function of group type and four covariates: sea surface temperature, bathymetry, slope, and distance to the coastline. Group type, water temperature, and bathymetric features best explained beluga distribution. In July, groups of adults preferred the continental shelf, whereas individual belugas and groups with calves preferred the continental slope. In August, groups of adults and groups with calves were found in Amundsen Gulf at similar depths. For both months, individual belugas associated more with deeper and colder areas. The preferences often corresponded to previously published distributions of the beluga's main prey species, suggesting that foraging opportunities and size-related energy requirements strongly influence habitat use.

Projected changes in sea ice and the navigability of the Arctic Passages under global warming of 2 ℃ and 3 ℃

Although a rapid decrease in sea ice due to global warming has improved the navigable potential of the Arctic passages, the extent to which this area will become viable for commercial shipping in the future remains unclear. This study investigated the accessibility of the Northern Sea Route and Northwest Passage under global warming of 2°C and 3°C. We applied the Polar Operational Limit Assessment Risk Indexing System to measure navigability by considering the impacts of sea ice and ice resistance of ships. Except for the Parry Channel, surface air temperature is positive in the Seas along two passages in September under 2℃ warming. With global warming of 3°C, the warming area extends northward, and the concentration of sea ice drops below 20%. The thickness of the sea ice is still substantial in the eastern Beaufort Sea and the waters within the Canadian Arctic Archipelago and north of Greenland, both of which can restricting the opening of the Arctic passages. Temperature increases cause sea ice to be younger and are more pronounced in the seas on the European side of the Arctic. The results indicate that changes in sea ice improve the navigability of the Arctic passages. Ships in Polar Class 6 may be unimpeded along two Arctic passages in November from 2℃ warming onward, whereas ordinary ships may be capable of passing the Northern Sea Route with global warming of 3℃, with maximum potential in September. This study provides an important reference for planning global shipping in the Arctic in the future, even with some uncertainty in the model projections.

Специфика грязевулканической дегазации Земли с катастрофическими последствиями

In the natural gas-saturated geosystems, diverse causal relationships (chains) of various hazardous and catastrophic phenomena are formed that occur under the direct triggering effect of the Earth degassing processes. The level of natural threats to human life and the safe functioning of industrial objects increases under the influence of self-ignition and gas explosions, one of the main causes of which is the electrization of air and electrostatic discharges. To ensure the safety of the homosphere, it is necessary to conduct special studies to take into account the threats from potentially explosive processes of degassing of the Earth. The mud volcanic mechanism of the Earth degassing has a larger scale of distribution and insufficiently studied specificity of manifestation forms compared to those existing at the present level of knowledge. Due to the insufficient level of knowledge about the number of potentially hazardous natural objects, additional studies can lead to a radical revision of their genesis. In particular, as the result of detailed studies of heaving mounds on the bottom of the eastern Beaufort Sea, many of them were recognized by the Geological Survey of Canada as mud volcanoes. An analysis was made of the number of powerful gas blowouts and explosions with the formation of giant craters on the Yamal Peninsula in 2014-2021. The authors came to the conclusion that the genesis of several of them has all the signs of mud volcanism with cryogenic specificity, in which, due to the presence of the cryosphere, pieces of frozen rock of predominantly clay composition are ejected instead of liquefied clay mass. It is required to identify potentially hazardous gas-saturated objects and understand their genesis. This will allow to reduce the risks of uncontrolled gas blowouts that threaten the functioning of the infrastructure of the oil and gas industry in the Arctic, and make a negative contribution to the climate changes, as well as to switch to the rational use of the gas contained in these objects.

Exposure and behavioral responses of tagged beluga whales (Delphinapterus leucas) to ships in the Pacific Arctic

AbstractArctic marine mammals face a multitude of challenges linked to climate change, including increasing anthropogenic noise from ship traffic. The beluga whale (Delphinapterus leucas), a predominately Arctic endemic cetacean, relies heavily on acoustic communication, with documented overlap between their vocalizations and hearing range and ship noise. Some belugas migrate through areas with the highest levels of ship traffic in the Pacific Arctic and exposure to ship noise is highly probable. Here, we document the responses of nine satellite‐tagged Eastern Beaufort Sea belugas to encounters with ships in the Beaufort, Chukchi, and Bering Seas during July–December 2018. We report 177 occasions when ships were within 125 km of tagged belugas and quantified changes in lateral and vertical movements to investigate individual behavioral responses to ship approaches within 50 km (n = 23). Belugas' swim speed was negatively correlated with ship distance, showing possible changes in swim speed up to 79 km away. Changes in lateral and vertical movements, indicating disruption of behavior, were observed when some ships passed within 50 km. These findings corroborate previous studies that have shown behavioral responses of belugas to ships at distances far beyond visual range, implying belugas react to low‐amplitude ship noise near ambient levels.

Synoptic-scale variability in the Beaufort High and spring ice opening in the Beaufort Sea

This study examines the role of synoptic-scale variability in the Beaufort High in spring ice opening in the Beaufort Sea using data over the 2000–2019 period. A few days before ice opening in spring, the Beaufort High begins to strengthen, deform, and shift eastward from the Chukchi Sea to the western Canadian Arctic Archipelago due to warming in eastern Siberia, and the Aleutian Low is also enhanced. The pressure gradient between the Aleutian Low and the Beaufort High increases rapidly, promoting strong southeasterly winds. As the Beaufort High shifts eastward, the anticyclonic sea ice circulation in the Beaufort Sea tends to be an asymmetrical gyre; as a result, sea ice in the eastern Beaufort Sea is exported toward the western Beaufort Sea without supplementation from the north. Sea ice volume budget analysis indicates that when southeasterly winds are prevailing, wind-forced ice advection and divergence dominate the ice opening in the southeastern Beaufort Sea. Although both the basal and lateral melting are promoted during the ice opening, their contributions to the reduction of ice volume are negligible.

Delineation of Eastern Beaufort Sea Sub-regions Using Self-Organizing Maps Applied to 17 Years of MODIS-Aqua Data

Satellite observations are an integral component of long-term Arctic Ocean monitoring and help identifying changes resulting from climate warming. A Self-Organizing Maps (SOM) approach was applied to four-day composite satellite images of the Eastern Beaufort Sea (EBS) acquired by the MODerate resolution Imaging Spectroradiometer over the period 2003–2019. Using sea-surface temperature (SST), suspended particulate matter concentration (SPM) and chlorophyll-a concentration (Chl-a) as input the EBS was partitioned into six biogeochemical regions. The SOM approach revealed region-specific mean conditions and seasonal cycles for all properties, particularly for SPM and Chl-a. Three of the six regions, located on the continental shelf, had the highest SST, SPM and Chl-a with earlier maxima compared to the remaining three regions which comprised the shelf edge, Canada Basin and Amundsen Gulf. While mean and maximum SST did not exhibit significant trends over the 17 years of observations, the annual maximum SST in Amundsen Gulf was reached significantly earlier in recent years compared to the start of the time series. With the exception of Amundsen Gulf, sea-ice concentration (SIC) derived from microwave satellites declined throughout the study area; monthly trends showed dramatic SIC declines in regions on the shelf during May and June, and in Canada Basin during August. Correlation analysis of properties within and between regions showed that SST and SIC were driven by large scale processes while SPM and Chl-a showed regional features. SST and Chl-a in the regions nearest the Mackenzie River showed a strong relationship during seasonal warming. The SOM approach, applied to 17 years of satellite data, revealed spatially distinct marine units with unique characteristics, emphasizing the need for regional considerations when assessing the impact of climate warming in the Arctic Ocean.

Environmental drivers of beluga whale distribution in a changing climate: a case study of summering aggregations in the Mackenzie Estuary and Tarium Niryutait Marine Protected Area

During summer, the Eastern Beaufort Sea beluga whale ( Delphinapterus leucas (Pallas, 1776)) population aggregates in the waters of the Mackenzie Estuary and Tarium Niryutait Marine Protected Area (TNMPA). Guided by local communities’ priorities, this study aimed to better understand beluga summer habitat selection and to examine whether shifts in beluga distribution are expected under a changing climate. We used a resource selection function (RSF) based on aerial survey data and satellite remote sensing images to estimate the likelihood of beluga presence as a function of environmental conditions. The RSF revealed that belugas selected warm and turbid waters, with suspended particulate matter concentrations and sea surface temperatures ranging above average estuarine values. These specific conditions support hypotheses on the ecological roles of estuaries for belugas such as providing a thermal advantage for their calves or for beluga epidermal moulting. Using a diachronic analysis, we found a distribution shift towards coastal and inshore waters, areas already experiencing effects of climate change. Thus, the current distribution may reflect beluga responses to a changing climate, selecting warmer and more turbid areas. Our finding provides insight into current and evolving beluga habitat and habitat selection under a changing climate, which may help inform beluga management in the TNMPA.

Group characteristics and spatial organization of the Eastern Beaufort Sea beluga whale (Delphinapterus leucas) population using aerial photographs

While it is known that beluga whales ( Delphinapterus leucas (Pallas, 1776)) are social animals, sociality within populations remains complex and poorly understood. Using aerial photographs taken in mid-July and early August 2019, we examined group characteristics and spatial organization of the Eastern Beaufort Sea beluga population in two distinct summering areas: (1) the continental shelf and offshore region of the southeast Beaufort Sea and (2) the inshore of the Mackenzie Estuary. Observations revealed that the mean group size was similar in both environments. A piecewise regression analysis showed that belugas were found to be most frequently within 24.6 m of another beluga in the offshore and within 22.0 m in the inshore. The mean interindividual distance of groups composed of subadults and (or) adults was greater than that of groups including younger whales in both environments. Also, the swimming direction of individuals in a group differed less in the offshore than in the inshore. We suggest that habitat shapes the types of activity conducted and that spatial cohesion within groups persists across environmental conditions but changes with age composition. By identifying elements of social structure and important areas for Eastern Beaufort Sea belugas, our results highlight the value of habitat conservation.

Bowhead whale calf detections in the western Beaufort sea during the open water season, 2012–2019

Successful reproduction is essential to a species existence. Here we summarize Bering–Chukchi–Beaufort (BCB) bowhead whale (Balaena mysticetus Linnaeus, 1758) calf distribution, ratio of calf to adult sightings, and encounter rate from data collected during line–transect aerial surveys conducted from July to October 2012–2019 in the western Beaufort Sea (140°W–157°W). During 223,000 on effort km, a total of 274 calves were seen: 100 in summer (July–August) and 174 in fall (September–October), compared with nearly 3,200 non-calves. Calves were widely distributed in the study area in August and September, with distribution in July largely east of 150°W and distribution in October west of 143°W. Calf ratios and encounter rates appear to follow a 3–4 year cycle. Most calves (240/274; 88%) were seen near an adult assumed to be the maternal female, but 9% (26/274) of all calves were observed unaccompanied at the surface and 3% (8/274) were observed with large whales at the surface but not close by. Of the total calves detected, 60% (165/274) were observed after circling was initiated, highlighting the importance of closely investigating all bowhead whale sightings if identification of calves is critical to project goals. Bowhead whale calf data from the eastern Beaufort Sea and Amundsen Gulf in August 2019 are also summarized.

Year-Round Dive Characteristics of Male Beluga Whales From the Eastern Beaufort Sea Population Indicate Seasonal Shifts in Foraging Strategies

Dive behavior represents multiple ecological functions for marine mammals, but our understanding of dive characteristics is typically limited by the resolution or longevity of tagging studies. Knowledge on the time-depth structures of dives can provide insight into the behaviors represented by vertical movements; furthering our understanding of the ecological importance of habitats occupied, seasonal shifts in activity, and the energetic consequences of targeting prey at a given depth. Given our incomplete understanding of Eastern Beaufort Sea (EBS) beluga whale behavior over an annual cycle, we aimed to characterize dives made by belugas, with a focus on analyzing shifts in foraging strategies. Objectives were to (i) characterize and classify the range of beluga-specific dive types over an annual cycle, (ii) propose dive functions based on optimal foraging theory, physiology, and association with environmental variables, and (iii) identify whether belugas undergo seasonal shifts in the frequency of dives associated with variable foraging strategies. Satellite-linked time-depth-recorders (TDRs) were attached to 13 male belugas from the EBS population in 2018 and 2019, and depth data were collected in time series at a 75 s sampling interval. Tags collected data for between 13 and 357 days, including three tags which collected data across all months. A total of 90,211 dives were identified and characterized by twelve time and depth metrics and classified into eight dive types using a Gaussian mixed modeling and hierarchical clustering analysis approach. Dive structures identify various seasonal behaviors and indicate year-round foraging. Shallower and more frequent diving during winter in the Bering Sea indicate foraging may be energetically cheaper, but less rewarding than deeper diving during summer in the Beaufort Sea and Arctic Archipelago, which frequently exceeded the aerobic dive limit previously calculated for this population. Structure, frequency and association with environmental variables supports the use of other dives in recovery, transiting, and navigating through sea ice. The current study provides the first comprehensive description of the year-round dive structures of any beluga population, providing baseline information to allow improved characterization and to monitor how this population may respond to environmental change and increasing anthropogenic stressors.

Blubber cortisol in four Canadian beluga whale populations is unrelated to diet

Changing conditions in the Arctic have had severe consequences for many marine mammals. In this study, we examined blubber cortisol using radioimmunoassay in 4 Canadian beluga whaleDephinapterus leucaspopulations. The endangered Cumberland Sound population had higher cortisol levels (mean ± SE: 0.65 ± 0.11 ng g-1) than populations not at risk: Eastern Beaufort Sea (0.31 ± 0.03 ng g-1; p < 0.001), Eastern High Arctic-Baffin Bay (0.32 ± 0.09 ng g-1; p = 0.004), and Western Hudson Bay (0.44 ± 0.04 ng g-1; p = 0.004). To evaluate if measured cortisol differences were due to differences in diet, we compared stable isotope ratios of carbon and nitrogen (δ13C and δ15N) and dietary fatty acids among populations. Beluga whales from Eastern Beaufort Sea had lower δ13C (p ≤ 0.017) and higher δ15N (p < 0.001) values than other measured populations, while Western Hudson Bay beluga dietary fatty acid profiles differed from other measured populations (p < 0.001). Population and sex were significant predictors of blubber cortisol (p ≤ 0.017). Females exhibited higher cortisol than males. Despite diet differences among populations, neither stable isotopes nor fatty acids were significant predictors of cortisol, suggesting differences in cortisol levels were unrelated to diet. Other factors, such as increased risk of predation, hunting pressure, vessel traffic, or differences in baseline blubber cortisol concentrations may be contributing to elevated cortisol levels in Cumberland Sound beluga whales. Measuring blubber cortisol in combination with chemical indicators of diet provides a useful method for monitoring population health and can be used to inform management and conservation.

Microplastics in beluga whale (Delphinapterus leucas) prey: An exploratory assessment of trophic transfer in the Beaufort Sea

Microplastics (MPs, <5 mm in length) have been identified as emerging contaminants in marine environments, with ingestion by a variety of biota being of increasing concern. Few studies exist on MP ingestion in Arctic fish, and there are currently no such data from the Beaufort Sea. We investigated MP abundance in five ecologically valuable species from three sampling sites in the Eastern Beaufort Sea to evaluate possible trophic-level pathways of MPs from prey to beluga whales. Polymer analysis confirmed that 21% of fish gastrointestinal tracts (n = 116) contained microplastic particles. Fish that contained MPs had a mean abundance of 1.42 ± 0.44 particles per individual and an overall mean abundance of 0.37 ± 0.16 particles. No plastic particles >5 mm were found, and 78% of the particles observed were fibers. Based on energetic needs, we estimate that individual beluga may ingest between 3800 and 145,000 microplastics annually through trophic transfer, with uncertain health implications.

Ringed Seal Diet and Body Condition in the Amundsen Gulf region, Eastern Beaufort Sea

Diet from stomach contents and body condition from morphometric measurements were obtained for 169 (108 stomachs analysed) ringed seals (Pusa hispida) for the Amundsen Gulf region in the western Canadian Arctic from 2015 to 2018. Sampling was from subsistence-harvested seals from the three communities of Paulatuk (spring, summer, and autumn), Sachs Harbour (summer), and Ulukhaktok (winter), Northwest Territories. Stomach contents were separated through sieves and by hand, and taxa identified to the lowest taxonomic level possible and weighed. Stomachs were fullest (by weight and prey count) in the autumn, which suggests that foraging was most intense and successful at that time. A total of 93 prey taxa, including 17 fish and 76 invertebrate species were identified. Several fish and invertebrate species were regularly found together, the most common being Arctic cod (Boreogadus saida), sand lance (Ammodytes hexapterus), capelin (Mallotus villosus), and hyperiid amphipods (Themisto spp.). Condition measurements inferred from blubber thickness, although showing considerable variation among sites and years, had a seasonal relationship with maximal depth during the autumn and winter. Overall, the diet of ringed seals in Amundsen Gulf was broadly similar to those reported from other areas while also indicating some degree of regional specificity. When compared to the diet of ringed seals in the same area in the 1980s, the results presented here were more diverse, with new or increased numbers of subarctic species (e.g., saffron cod, Eleginus gracilis) found in the samples. This finding is a likely consequence of climate warming, as increasing numbers of subarctic species move north with warming ocean temperatures in the Arctic.

Bowhead whales overwinter in the Amundsen Gulf and Eastern Beaufort Sea.

The bowhead whale is the only baleen whale endemic to the Arctic and is well adapted to this environment. Bowheads live near the polar ice edge for much of the year and although sea ice dynamics are not the only driver of their annual migratory movements, it likely plays a key role. Given the intrinsic variability of open water and ice, one might expect bowhead migratory plasticity to be high and linked to this proximate environmental factor. Here, through a network of underwater passive acoustic recorders, we document the first known occurrence of bowheads overwintering in what is normally their summer foraging grounds in the Amundsen Gulf and eastern Beaufort Sea. The underlying question is whether this is the leading edge of a phenological shift in a species' migratory behaviour in an environment undergoing dramatic shifts due to climate change.

The Regional Ice Ocean Prediction System v2: a pan-Canadian ocean analysis system using an online tidal harmonic analysis

Abstract. Canada has the longest coastline in the world and includes diverse ocean environments, from the frozen waters of the Canadian Arctic Archipelago to the confluence region of Labrador and Gulf Stream waters on the east coast. There is a strong need for a pan-Canadian operational regional ocean prediction capacity covering all Canadian coastal areas in support of marine activities including emergency response, search and rescue, and safe navigation in ice-infested waters. Here we present the first pan-Canadian operational regional ocean analysis system developed as part of the Regional Ice Ocean Prediction System version 2 (RIOPSv2) running in operations at the Canadian Centre for Meteorological and Environmental Prediction (CCMEP). The RIOPSv2 domain extends from 26∘ N in the Atlantic Ocean through the Arctic Ocean to 44∘ N in the Pacific Ocean, with a model grid resolution that varies between 3 and 8 km. RIOPSv2 includes a multivariate data assimilation system based on a reduced-order extended Kalman filter together with a 3D-Var bias correction system for water mass properties. The analysis system assimilates satellite observations of sea level anomaly and sea surface temperature, as well as in situ temperature and salinity measurements. Background model error is specified in terms of seasonally varying model anomalies from a 10-year forced model integration, allowing inhomogeneous anisotropic multivariate error covariances. A novel online tidal harmonic analysis method is introduced that uses a sliding-window approach to reduce numerical costs and allow for the time-varying harmonic constants necessary in seasonally ice-infested waters. Compared to the Global Ice Ocean Prediction System (GIOPS) running at CCMEP, RIOPSv2 also includes a spatial filtering of model fields as part of the observation operator for sea surface temperature (SST). In addition to the tidal harmonic analysis, the observation operator for sea level anomaly (SLA) is also modified to remove the inverse barometer effect due to the application of atmospheric pressure forcing fields. RIOPSv2 is compared to GIOPS and shown to provide similar innovation statistics over a 3-year evaluation period. Specific improvements are found near the Gulf Stream for all model fields due to the higher model grid resolution, with smaller root mean squared (rms) innovations for RIOPSv2 of about 5 cm for SLA and 0.5 ∘C for SST. Verification against along-track satellite observations demonstrates the improved representation of mesoscale features in RIOPSv2 compared to GIOPS, with increased correlations of SLA (0.83 compared to 0.73) and reduced rms differences (12 cm compared to 14 cm). While the RIOPSv2 grid resolution is 3 times higher than GIOPS, the power spectral density of surface kinetic energy provides an indication that the effective resolution of RIOPSv2 is roughly double that of the global system (35 km compared to 66 km). Observations made as part of the Year of Polar Prediction (2017–2019) provide a rare glimpse at errors in Arctic water mass properties and show average salinity biases over the upper 500 m of 0.3–0.4 psu in the eastern Beaufort Sea in RIOPSv2.