Many Arctic marine predators are experiencing sustained changes in foraging success and body condition, likely driven by reduced sea ice and associated shifts in prey distribution, including the northward retraction of energyrich, ice-adapted species. For ringed seals (Pusa hispida) - an opportunistic mesopredator and primary prey of polar bears (Ursus maritimus) - the links between diet, environmental conditions, and body condition remain poorly characterized. We assessed the body condition and dietary indicators (blubber fatty acid composition) of 236 ringed seals harvested during the ice-covered period in 1996, 1999, 2001, and 2012-2015 from Amundsen Gulf, Canada. We explored relationships between ringed seal body condition, diet, winter environmental metrics (Arctic Oscillation Index [AOI], regional sea ice drift, and local thin sea ice accessibility), and their correlation with the body condition of 108 polar bears. Our results suggest that ringed seal body condition increased with dietary indicators of sea ice algae-associated prey, negative phases of AOI, thin sea ice accessibility, and sea ice drift, which creates pressure ridges and leads that enhance foraging habitat. Higher polar bear body condition was associated with higher ringed seal body condition in years with corresponding data. This study provides insights into the complex and cascading effects of environmental conditions on the foraging outcomes of Arctic marine predators. We suggest that shifts in marine predator foraging ecology will continue with climate warming, consistent with recent forecasts of sea ice and primary production, although the mechanisms and potential consequences for Arctic predators will depend on species-specific ecological plasticity and the magnitude of warming.

Barrow Canyon is a major conduit through which Pacific-origin water enters the Arctic Basin. Mooring data acquired across the mouth of Barrow Canyon from 2000 to 2022 have enabled direct computation of seawater transports. No significant decadal trend in volume transport of Barrow Canyon throughflow was observed, although an upward trend of Bering Strait throughflow has been reported. Annual heat transport through the canyon varied widely, ranging from 0.93 to 7.05 TW, and larger values of heat transport occurred more often in the 2010s compared to the 2000s. The interannual variability of heat transport was not correlated with the Bering Strait heat transport, even though most of the Pacific water inflow through the Bering Strait flows along an eastern path toward Barrow Canyon during summer. Instead, year-to-year variation in Barrow Canyon heat transport was driven by variation in summertime sea ice coverage of the northeastern Chukchi Sea, because early ice clearance reduces sensible heat loss to thawing ice and increases direct warming of the surface water via insolation. Using sea surface temperature and wind data from the Chukchi Sea, we derived a proxy for estimating volume and heat transport through Barrow Canyon over the last 40 years. Estimated heat transport in the canyon doubled between 1980s and 2010s likely because of decreasing sea ice presence in summer. This change in heat transport has been sufficient to explain the increase in the heat content of Pacific summer water in the Canada Basin over the same interval.

An analysis of ambient noise data collected from seven locations in the western Canadian Arctic at varying depths (30–350 m) during ice-free seasons over a period of five years (2018–2022) has been conducted. The measured noise level correlates well with wind speed after the removal of contaminated (sources other than wind) noise data. The characteristics of wind noise are predicted by fitting a multi-parameter empirical model to data. Results from the model are compared with existing empirical wind noise models and validated using data collected from one of the measurement locations.

Increased ship traffic due to climate change increases underwater noise in the Arctic. Therefore, accurate measurements of underwater radiated noise are necessary to map marine sound and quantify shipping's impact on the Arctic ecosystem. This paper presents a method to calculate opportunistic source levels (SLs) using passive acoustic data collected at six locations in the Western Canadian Arctic from 2018 to 2022. Based on Automatic Identification System data, acoustic data, and a hybrid sound propagation model, the SLs of individual ships were calculated within a 5 km radius of each measurement site. A total of 66 measurements were obtained from 11 unique vessels, with multiple measurements from the same vessel type contributing more SLs. For vessels with propeller cavitation, measured SLs correlated positively with vessel parameters, such as speed and length. SL and speed did not correlate well for vessels without propeller cavitation. The JOMOPANS-ECHO SL model produced good agreement with measured SL for certain ship types (container ships, a tanker, and a passenger vessel). However, significant differences between measurement and model are evident for certain polar-class ships that travel in the Arctic, indicating that more controlled SL measurements are needed.

Rapid climate change is altering Arctic ecosystems at unprecedented rates. These changes in the physical environment may open new corridors for species range expansions, with substantial implications for subsistence-dependent communities and sensitive ecosystems. Over the past 20 years, rising incidental harvest of Pacific salmon by subsistence fishers has been monitored across a widening range spanning multiple land claim jurisdictions in Arctic Canada. In this study, we connect Indigenous and scientific knowledges to explore potential oceanographic mechanisms facilitating this ongoing northward expansion of Pacific salmon into the western Canadian Arctic. A regression analysis was used to reveal and characterize a two-part mechanism related to thermal and sea-ice conditions in the Chukchi and Beaufort seas that explains nearly all of the variation in the relative abundance of salmon observed within this region. The results indicate that warmer late-spring temperatures in a Chukchi Sea watch-zone and persistent, suitable summer thermal conditions in a Beaufort Sea watch-zone together create a range-expansion corridor and are associated with higher salmon occurrences in subsistence harvests. Furthermore, there is a body of knowledge to suggest that these conditions, and consequently the presence and abundance of Pacific salmon, will become more persistent in the coming decades. Our collaborative approach positions us to document, explore, and explain mechanisms driving changes in fish biodiversity that have the potential to, or are already affecting, Indigenous rights-holders in a rapidly warming Arctic.

The Arctic Ice Monitoring (AIM) observatory has been maintained on the Chukchi Plateau at 75.1° N 168.0° W nearly continuously since 2003. The AIM site consists of a submerged mooring that, since October 2008, has been instrumented with a passive acoustic recorder to sample ambient sound, with a focus on marine mammal detections in the High Arctic. Year-long data sets for 2009, 2012, and 2014-2020 were analyzed for the presence of signals from Arctic species including bowhead and beluga whales, bearded seals, and walrus. Calls from subarctic ribbon seals were commonly detected in autumn months, suggesting they have expanded their distribution much further northward. Killer whale calls were detected in recent years providing evidence that they have moved further north into the Pacific Arctic. No other subarctic cetaceans were heard. Year-round passive acoustic sampling of sounds produced by marine mammals over a decadal timescale has enhanced our understanding of how climate-driven changes in biodiversity are affecting even the very High Arctic.

Abstract. This paper presents a systematic record of multi-year sea-ice thickness on the northern Canadian polar shelf, acquired during the winter of 2009–10. The data were acquired by submerged sonar positioned within Penny Strait where they measured floes drifting south from the notional “last ice area”. Ice was moving over the site until 10 December and fast thereafter. Old ice comprised about half of the 1669-km long survey. The average old-ice thickness within 25-km segments of the survey track was 3–4 m; maximum keels were 12–16 m deep. Floes with high average draft were of two types, one with interspersed low draft intervals and one without. The presence or absence of thin patches apparently distinguished aggregate floes comprised of sub-units of various ages and deformation states from units of more homogeneous age and deformation state. The former were larger and of somewhat lower mean thickness (1–5 km; 3.5–4.5 m) than the latter (400–600 m; 6.5–14 m). Calculated ice accretion onto the multi-year ice measured in autumn 2009 was used to seasonally adjust the observations to a date in late winter, when prior data are available. The adjusted mean thickness for all 25-km segments with 4 tenths or more old ice was 3.6 m (sample deviation of 0.4 m), a value indistinguishable within sampling error from values measured in the same area during the 1970s. The recently measured ice-draft distributions were also very similar to those from the 1970s.

SignificanceTemperature increases in Arctic regions have focused attention on permafrost degradation on land, whereas little is known about the dynamics of extensive glacial-age permafrost bodies now submerged under the vast Arctic Continental shelves. Repeated high-resolution bathymetric surveys show that extraordinarily rapid morphologic changes are occurring at the edge of the continental slope of the Canadian Beaufort Sea along what was once the seaward limit of relict Pleistocene permafrost. How widespread similar changes are on the Arctic shelves is unknown, as this is one of the first areas in the Arctic subjected to multiple multibeam bathymetric surveys. Rapid morphologic changes associated with active submarine permafrost thawing may be an important process in sculpturing the seafloor in other submarine permafrost settings.

Data from a four-mooring array deployed across the shelf and slope of Mackenzie Canyon, from 2016 to 2018, are used to characterize wind-driven upwelling and downwelling events and investigate their impact on the transport of water masses. We distinguish between coastal upwelling/downwelling forced by the along-coast wind stress, and canyon upwelling/downwelling associated with the wind stress curl in the Canada Basin. During coastal upwelling (downwelling), the isopycnals slope upward (downward) above the shelf bathymetry, and the normally westward-flowing shelf current is strengthened (reversed). During canyon upwelling (downwelling), the isopycnals slope upward (downward) progressing onshore relative to the background condition, and the cyclonic recirculation in the canyon is stronger (weaker), with an up-canyon (down-canyon) component on the upper slope. During periods of simultaneous coastal and canyon upwelling, Atlantic Water from the basin can be fluxed onto the shelf. These occurrences are dictated by the combination of three factors: the coastal upwelling strength, canyon upwelling strength, and the background depth of the offshore Pacific Water-Atlantic Water interface. Dense winter water is formed on the shelf by enhanced air-sea buoyancy flux during freeze-up and subsequent openings in the ice. During simultaneous coastal and canyon downwelling this water be fluxed offshore into the canyon, with the potential to ventilate the interior halocline.

Exploration of the continental slope of the Canadian Beaufort Sea has revealed a remarkable coalescence of slide scars with headwalls between 130 and 1100 m water depth (mwd). With increased depth, the scars widen and merge into one gigantic regional slide scar that is more than 100 km wide below similar to 1100 mwd. To understand the development of these features, five sites were investigated with an Autonomous Underwater Vehicle, which provided 1-m bathymetric grids and Chirp profiles, and surveyed with a Remotely Operated Vehicle. The morphologies are consistent with retrograde failures that occurred on failure planes located between 30 and 75 m below the modern seafloor. At issue is whether the continental slope in this area is preconditioned for failure. While rapid sedimentation during glacial periods, and the presence of shallow gas cannot be ruled out, given the geological environment, it is unclear that they are primary preconditioning factors. Evidence of widespread flushing of the slope with brackish waters, and observed flows of brackish water within slide scars, suggest fluid venting and overpressure may play a role in the development of the extensive slope failures seen along this margin. The impact of pore water salinity changes at the depth of the failure plane on slope stability has not been considered in marine settings previously.

The circumpolar Arctic ringed seal (Pusa hispida) occupies its fast-ice breeding habitat for four to five months during winter and the pack ice or open water of adjacent areas for the rest of the year. From 1971 - 78 and 1992 - 2019, we sampled approximately 100 ringed seals annually from western Prince Albert Sound (WPAS), the prime ringed seal fast-ice breeding habitat in Canada's Western Arctic, adjacent to primary overwinter foraging habitat in eastern Amundsen Gulf (EAG). As our metric of body condition, we measured ventral blubber depth corrected for body size. As our metrics of reproduction, we measured the annual ovulation rate of multiparous females and percent pups in the open-water harvest. We examined these biological parameters in relation to the winter Arctic Oscillation Index (winAOI) and the timing of sea ice clearance in EAG in spring. There were no significant effects of age or sample month (June or July) on adult blubber depth, but significant sex and year effects and, in females, ovulation status effects. Across the series, as we have observed previously through 2011, there was a sustained temporal declining trend in blubber depth in adults of both sexes. There was no temporal trend in residual blubber depth, no correlation between blubber depth and sea ice clearance date in EAG, and a quasi-cyclic pattern in blubber depth that tracked some of the phases of the winAOI. Annual ovulation rates were mainly in the 80% - 100% range and correlated with percent pups in the open-water harvest in the same year. Three (1974, 2005, 2012) of the 36 y had reproductive failures, when >= 50% of the multiparous females failed to ovulate. In each case, ovulation rates returned to normal within 1 - 3 y. Low annual ovulation rates were correlated with late sea ice clearance in EAG in spring, with two ovulation failure events taking place in years when spring sea ice clearance was delayed by five to six weeks. The most recent ovulation failure (2012) differed in that it came in an average ice year but at the end of a six-year sequence of negative residual mean blubber depths. Earlier spring sea ice clearance in WPAS, based on the observed rate of 3.8 d per decade, would on average not result in the physical loss of sea ice for pupping in this core habitat before 2140. The mechanisms involved in the sustained declining temporal trend in body condition, linkage with some phases of the winAOI, and the temporary but episodic failures of ovulation are complex and not fully explained by either the timing of sea ice clearance or the winAOI. Until the complex mix of factors, pressures and responses are understood, our ability to predict the impacts of a changing climate on ringed seals will remain limited.

The circumpolar Arctic ringed seal (Pusa hispida) occupies its fast-ice breeding habitat for four to five months during winter and the pack ice or open water of adjacent areas for the rest of the year. From 1971 – 78 and 1992 – 2019, we sampled approximately 100 ringed seals annually from western Prince Albert Sound (WPAS), the prime ringed seal fast-ice breeding habitat in Canada’s Western Arctic, adjacent to primary overwinter foraging habitat in eastern Amundsen Gulf (EAG). As our metric of body condition, we measured ventral blubber depth corrected for body size. As our metrics of reproduction, we measured the annual ovulation rate of multiparous females and percent pups in the open-water harvest. We examined these biological parameters in relation to the winter Arctic Oscillation Index (winAOI) and the timing of sea ice clearance in EAG in spring. There were no significant effects of age or sample month (June or July) on adult blubber depth, but significant sex and year effects and, in females, ovulation status effects. Across the series, as we have observed previously through 2011, there was a sustained temporal declining trend in blubber depth in adults of both sexes. There was no temporal trend in residual blubber depth, no correlation between blubber depth and sea ice clearance date in EAG, and a quasi-cyclic pattern in blubber depth that tracked some of the phases of the winAOI. Annual ovulation rates were mainly in the 80% – 100% range and correlated with percent pups in the open harvest in the same year. Three (1974, 2005, 2012) of the 36 y experienced reproductive failures, when over 50% of the multiparous females failed to ovulate. In each case, ovulation rates returned to normal within 1 – 3 y. Low annual ovulation rates were correlated with late sea ice clearance in EAG in spring, with two widespread ovulation failure events taking place in years when spring sea ice clearance was delayed by five to six weeks. The most recent ovulation failure (2012) differed in that it came in an average ice year but at the end of a six-year sequence of negative residual mean blubber depths. Earlier spring sea ice clearance in WPAS, based on the observed rate of 3.8 d per decade, would on average not result in the physical loss of sea ice for pupping in this core habitat before 2140. The mechanisms involved in the sustained declining temporal trend in body condition, linkage with some phases of the winAOI, and the temporary but episodic failures of ovulation are complex and not fully explained by either the timing of sea ice clearance or the winAOI. Until the complex mix of factors, pressures and responses are understood, our ability to predict the impacts of a changing climate on ringed seals will remain limited.

Data from a five-mooring array extending from the inner shelf to the continental slope in the vicinity of Mackenzie Canyon, Beaufort Sea are analyzed to elucidate the components of the boundary current system and their variability. The array, part of the Marine Arctic Ecosystem Study (MARES), was deployed from October 2016 to September 2017. Four distinct currents were identified: an eastward-directed flow adjacent to the coast; a westward-flowing, surface-intensified current centered on the outer-shelf; a bottom-intensified shelfbreak jet flowing to the east; and a recirculation at the base of the continental slope within the canyon. The shelf current transports - 0.12 +/- 0.03 Sv in the mean and is primarily wind-driven. The response is modulated by the presence of ice, with little-to-no signal during periods of nearly-immobile ice cover and maximum response when there is partial ice cover. The shelfbreak jet transports 0.03 +/- 0.02 Sv in the mean, compared to 0.08 +/- 0.02 Sv measured upstream in the Alaskan Beaufort Sea over the same time period. The loss of transport is consistent with a previous energetics analysis and the lack of Pacific-origin summer water downstream. The recirculation in the canyon appears to be the result of local dynamics whereby a portion of the westward-flowing southern limb of the Beaufort Gyre is diverted up the canyon across isobaths. This interpretation is supported by the fact that the low-frequency variability of the recirculation is correlated with the wind-stress curl in the Canada Basin, which drives the Beaufort gyre.

The southward freshwater flux through Nares Strait is an important component of the Arctic's freshwater budget. On short time scales, flow through the strait is dominated by the tides, and tidal dynamics may be important for the magnitude of the freshwater flux over longer periods. Here we build upon our existing knowledge of the tides in the region by exploring their propagation and vertical structure using data from four bottom-mounted Acoustic Doppler Current Profilers deployed in Nares Strait between 2003 and 2006. We observe that propagating barotropic semidiurnal tidal waves interact to create a standing wave pattern, explaining the abnormally large tidal amplitudes that are observed in this region. In the along-strait direction, semidiurnal tidal currents exhibit strong variations with depth. In contrast, the diurnal tides propagate northward through the strait as progressive waves, and the tidal currents are broadly depth invariant. Proximity of Nares Strait to the semidiurnal critical latitude and the topographical restriction imposed by the steep side wall of Ellesmere Island are primary drivers behind the observed vertical variability. In the upper part of the water column, baroclinic activity increases the tidal current amplitude by up to 25%. In the across-strait direction, a two-layer structure exists in both the diurnal and semidiurnal tidal flow, with a phase lag of approximately a quarter of a tidal cycle across the strait for the semidiurnal tide. Our results suggest that strong vertical motion exists against the side walls of Nares Strait, as the across-strait flow interacts with the steeply sloping bathymetry.

Long-term warming of the continental shelf of the Canadian Beaufort Sea caused by the transgression associated with the last deglaciation may be causing decomposition of relict offshore subsea permafrost and gas hydrates. To evaluate this possibility, pore waters from 118 sediment cores up to 7.3-m long were taken on the shelf and slope and analyzed for chloride concentrations and delta(18)0 and delta D composition. We observed downcore decreases in pore waters Cl- concentration in sediments from all sites from the inner shelf (<20-m water depth), from the shelf edge, from the outer slope (down to 1,000-m water depths), and from localized shelf features such as midshelf pingo-like features and inner shelf pockmarks. In contrast, pore water freshening is absent from all investigated cores of the Mackenzie Trough. Downcore pore waters Cl- concentration decreases indicate regional widespread freshwater seepage. Extrapolations to zero Cl- of pore water Cl- versus delta(18)0 regression lines indicate that freshwaters in these environments carry different isotope signatures and thus are sourced from different reservoirs. These isotopic signatures indicate that freshening of shelf sediments pore waters is a result of downward infiltration of Mackenzie River water, freshening of shelf edge sediments is due to relict submarine permafrost degradation or gas hydrate decomposition under the shelf, and freshening of slope sediments is consistent with regional groundwater flow and submarine groundwater discharge as far as 150 km from shore. These results confirm ongoing decomposition of offshore permafrost and suggest extensive current groundwater discharge far from the coast. Plain Language Summary The continental shelves around the Arctic Ocean were exposed to very low temperatures during the last glacial period more than 12,000 years ago. Precipitation that infiltrated these areas froze in the soils as permafrost. When climate warmed at the end of the glacial period, sea level rose and inundated the shelves warming them up. The warming may be reaching the now submarine permafrost and inducing its melting. This permafrost decomposition may be detected as freshwater seeping into the seafloor. In this study, we found evidence that in the Canadian Beaufort Sea not only permafrost is decomposing and seeping into the seafloor but also current groundwater discharge into the seafloor occurs at distances as far as 150 km from the current shore, likely routed by the permafrost presence in the shelf as a frozen lid. Active water discharge onto sediments may induce sediment instabilities that result in landslides, which can trigger tsunamis. In addition, sediment instabilities are a geohazard for sea-based infrastructure.

The Canadian Arctic Archipelago is a key conduit for comparatively fresh Arctic waters flowing to the Atlantic. Model estimates of the freshwater outflow, which is strongly correlated with the volume flux, contain major uncertainties because most existing models exclude tides, marginally resolve the internal Rossby radius, or both. At the same time, barotropic tidal models preclude stratified flow effects. Here we assess the relative importance of barotropic and baroclinic processes to water mass transformation, friction, and energy losses motivated by processes observed in a fine-scale survey in the central Archipelago. A sharp separation of warmed Canada Basin water and locally formed water is observed over a long sill in a narrow channel and coincides with an internal hydraulic jump caused by the mean flow. Tidal currents, however, modulate the jump, as demonstrated by both scale analysis and a two-dimensional simulation. The jump, together with internal tides propagating as Kelvin waves, leads to isopycnal displacements up to 50m. The generation of these internal Kelvin waves has a leading-order role in a regional energy budget. It is small, however, relative to bottom boundary layer dissipation, which accounts for an estimated 50% of the total tidal energy losses. Consequently, adding tides needs to be a priority for regional models. Plain Language Summary Satellite and in situ observations indicate that the western Arctic Ocean is growing fresher. One of two pathways that this freshwater can take to the Atlantic Ocean is the Canadian Arctic Archipelago, which includes many constrictions that induce energetic turbulence. Predicting this outflow is a great challenge to large-scale numerical predictions due to poor parameterization of this mixing and friction, with consequences for global climate prediction. Using high-spatial-resolution observations of salinity, temperature, and velocity, we show the importance of mean flow and tidal processes in the straits in causing turbulence and dissipation. In particular, we show evidence that radiating internal waves, breaking hydraulic lee waves, and bottom friction all play leading-order roles in the energy budget and mixing of water in the region.

Satellite observations sustained since 1979 have been the primary source of information to reveal Arctic Ocean sea ice extent is diminishing rapidly. Sea ice is also thinning based on historical surface and near-surface records and more recent satellite retrievals. There is a new “normal” environment in the Arctic environment with substantial socio-economic impacts. A key question is: What are the spatial and temporal characteristics of the sea ice thickness distribution throughout the annual cycle, and what is the evolving inter-annual trend? Arctic Ocean sea ice conditions have been determined with passive microwave radiometer, active scatterometer and other satellite instrument measurements recorded by a continuing series of satellites. An important feature of the continuous time series measurements has been the overlap of each new satellite dataset with ongoing measurements so as to provide adequate time intervals for calibration and validation. Satellite instrument diversity has provided both coarse spatial resolution measurements over the entire Arctic Ocean for long-period time series and limited-duration fine spatial resolution data over selected regions for navigation and other applications. Satellite observations of Arctic Ocean sea ice will continue to increase in importance because predictability of sea ice is poor and societal interest is great. Unfortunately, however the sustainability of some critical elements of the current Arctic Ocean satellite measurement suite beyond 2020 remains uncertain, e.g., after the CryoSat-2 and ICESat-2 missions have concluded.