Foxe Basin Research Articles

Unstitching the Past: An Experimental and Microwear Investigation of Dorset (Paleo-Inuit) Needles from the Foxe Basin Region

For Paleo-Inuit cultures, needles are arguably one of the most important artefact types, as they were used to create warm, waterproof clothing that is essential for survival in Arctic environments. This, in combination with the prevalence of needles within archaeological collections, has prompted many researchers to the topic of Paleo-Inuit needles. However, the majority of their studies have approached the material using traditional, typological methodology. A pilot study conducted by Siebrecht et al. (2021) demonstrated that, while needles from several Dorset Paleo-Inuit culture (c. 800 – 1300 AD) sites in the Foxe Basin region were previously considered as typologically identical, microwear analysis highlighted variation in how they would have been made and used over time and across sites. The pilot study also noted variation, across sites, in certain typological attributes, such as needle eye shape, distal end shape, and cross-section shape. The present study aims to expand on these discoveries by considering possible reasons for variability in the attribute of needle cross-section shape. Methodologically, we use microwear analysis, experimental archaeology, and ethnographic collaboration. With this approach, we were able to explore Dorset needle making and sewing practices in more detail than has been possible in prvevious, purely typology-focused studies. Our results showed no observable pattern between cross-section shape and the material being sewn but may reveal links between needle size and the material being sewn, a correlation in different polish types and the duration of needle use, as well as insights into the possible sewing techniques used by Dorset groups. Our study thus offers a fresh perspective on this topic and points to new directions for this area of Arctic archaeological research.

Ordovician conodont biostratigraphy of northwestern Baffin Island, Nunavut, Canada, with new insights into the age and diachronism of the Ship Point Formation in the Foxe Basin

Northwestern Baffin Island, Nunavut, Canada, preserves the stratigraphic record in the northern margin of the Foxe Basin. The Ordovician succession exposed on an unnamed peninsula west of Steensby Inlet, northwestern Baffin Island includes the Lower and Middle Ordovician Ship Point Formation and Upper Ordovician Frobisher Bay and Amadjuak formations. Nearly 7000 conodont specimens recovered from six sections on this peninsula allow the establishment of seven conodont zones throughout this succession: Rossodus manitouensis Taxon-range Zone, Acodus deltatus–Oneotodus costatus Assemblage Zone, Oepikodus communis Interval Zone, and Cooperignathus aranda–Jumudontus gananda Assemblage Zone in units 2 and 3 of the Ship Point Formation, correlative to the upper Tremadocian and Floian, Lower Ordovician; Phragmodus polonicus Taxon-range Zone confined to unit 4 of the Ship Point Formation, correlative to the middle Darriwilian, Middle Ordovician; and Appalachignathus delicatuluss– Belodina confluens and Belodina confluens–Periodon grandis Assemblage zones limited to the Frobisher Bay and Amadjuak formations, respectively, correlative to the lower Katian, Upper Ordovician. The establishment of these conodont zones proves that (1) the Ship Point Formation in the Foxe Basin is not a continuous stratigraphic unit but has a stratigraphic interval missing that is assignable to the Dapingian and lower Darriwilian, Middle Ordovician; (2) the base of the Ship Point Formation is diachronous in the Foxe Basin, which is correlated to the upper Tremadocian on northwestern Baffin Island but to the upper Floian on Melville Peninsula; and (3) the strata younger than lower Amadjuak Formation have been eroded in this area.

Climate-related range shifts in Arctic-breeding shorebirds.

To test whether the occupancy of shorebirds has changed in the eastern Canadian Arctic, and whether these changes could indicate that shorebird distributions are shifting in response to long-term climate change. Foxe Basin and Rasmussen Lowlands, Nunavut, Canada. We used a unique set of observations, made 25 years apart, using general linear models to test if there was a relationship between changes in shorebird species' occupancy and their species temperature Index, a simple version of a species climate envelope. Changes in occupancy and density varied widely across species, with some increasing and some decreasing. This is despite that overall population trends are known to be negative for all of these species based on surveys during migration. The changes in occupancy that we observed were positively related to the species temperature index, such that the warmer-breeding species appear to be moving into these regions, while colder-breeding species appear to be shifting out of the regions, likely northward. Our results suggest that we should be concerned about declining breeding habitat availability for bird species whose current breeding ranges are centered on higher and colder latitudes.

Differences in individual bowhead whale Balaena mysticetus habitat use, foraging dive depth and diet during the peak feeding season

Shifts in zooplankton quantity and quality caused by climate change could challenge the ability of bowhead whales to meet their energetic requirements. When facing such selection pressure, intra-population variation dampens the negative effects and provides population-level resilience. Previous studies observed inter-individual diet variation in bowhead whales, but the mechanism responsible for the variation was undetermined. We investigated foraging variability in Eastern Canada-West Greenland bowhead whales using dietary biomarkers (stable isotopes, fatty acids) and movement data (satellite telemetry with time-depth recorders) from the same individuals. We found that bowhead whale individuals using distinct summer and fall foraging habitats displayed differences in horizontal movements, foraging dive depth, and diet. For individuals using the Canadian Arctic Archipelago habitat (Foxe Basin, Gulf of Boothia, Prince Regent Inlet, Lancaster Sound and Admiralty Inlet, Nunavut), they performed long distance movements across regions, and their foraging dive depth was generally shallow, but increased from July to November. These whales displayed higher δ13C and δ15N values and ratios of C16:1n7/C16:0. Individuals using the West Baffin Bay habitat (Cumberland Sound, Baffin Bay, Davis Strait) were more localized in their horizontal movements and consistent over time in their foraging dive depth, which was generally deeper. These whales displayed lower δ13C and δ15N values and ratios of C16:1n7/C16:0. Overall, this inter-individual variation in diet and foraging behaviour could indicate some niche variation which would be beneficial for the population under changing habitats and prey availability.

Revised marine reservoir offset (ΔR) values for molluscs and marine mammals from Arctic North America

Appropriate marine–terrestrial reservoir offset (ΔR) values are essential for accurate calibration of marine radiocarbon dates. However, ΔR values are only valid for the specific calibration curve that their calculation is based on. Here, we present revised ΔR values for the Marine20 calibration curve from Arctic North America, based on previously published 14C dates on pre‐bomb live‐collected marine molluscs (n = 124) and cetaceans (beluga whales; tooth dentine; n = 12), and bowhead whale–driftwood age comparisons from the same glacio‐isostatically uplifted shorelines (n = 18). Molluscan‐based ΔR are: Chukchi/Beaufort sea coasts, 265±116 14C years; NW Canadian Arctic Archipelago, 188±91 14C years; NE Baffin Island, 81±18 14C years; SE Baffin Island, 14±58 14C years; Hudson Strait, −73±64 14C years; Ungava Bay, 0±86 14C years; Foxe Basin, 175±89 14C years; Hudson Bay, −21±72 14C years; James Bay, 209±114 14C years; West Greenland, −93±111 14C years. Species‐specific marine mammal ΔR terms are 107±59 14C years for beluga and 24±58 14C years for bowheads. Our revised ΔR values are applicable for as long as the same broad oceanographic conditions (circulation, ventilation) have persisted, i.e. through the Holocene. While molluscan values are applicable to other marine carbonate (e.g. foraminifera), cetacean ΔR are valid only for the species they were calculated for and should not be applied to other marine mammals. Importantly, the ΔR terms calculated here are only valid for Marine20 and should not be used with earlier or later calibration curves.

Bottom-associated phytoplankton bloom and its expansion in the Arctic Ocean.

Phytoplankton production in the Arctic Ocean is increasing due to global warming-induced sea ice loss, which is generally assessed through satellite observations of surface chlorophyll. Here we show that a diatom bloom can occur near the seafloor rather than at the surface in the open Arctic Ocean. Light can reach the seafloor underlying nutrient-rich bottom water after the spring bloom because the surface water becomes oligotrophic and increases transparency in the region of shallow Arctic shelf. Our microcosm experiment demonstrated that diatoms formed a bloom when sediments on the shelf region, which contained abundant viable diatom cells, were exposed to even weak light reaching the seafloor (~1% of the surface irradiance). Repeated shipboard observations in the shelf region suggested that such bottom-associated blooms occurred occasionally and the primary production was significantly underestimated by satellite observations. The average bottom irradiance (2003-2017) in the Arctic Ocean is particularly promoted in summer in the eastern East Siberian Sea and the Foxe Basin, which were ice-covered throughout the year until the 1990s. Our results imply that hidden bottom-associated blooms are now widespread across the shallow Arctic shelf region.

An assessment of mercury and its dietary drivers in fur of Arctic wolves from Greenland and High Arctic Canada

Mercury has become a ubiquitous hazardous element even ending up in pristine areas such as the Arctic, where it biomagnifies and leaves especially top predators vulnerable to potential health effects. Here we investigate total mercury (THg) concentrations and dietary proxies for trophic position and habitat foraging (δ15N and δ13C, respectively) in fur of 30 Arctic wolves collected during 1869–1998 in the Canadian High Arctic and Greenland. Fur THg concentrations (mean ± SD) of 1.46 ± 1.39 μg g −1 dry weight are within the range of earlier reported values for other Arctic terrestrial species. Based on putative thresholds for Hg-mediated toxic health effects, the studied Arctic wolves have most likely not been at compromised health. Dietary proxies show high dietary plasticity among Arctic wolves deriving nutrition from both marine and terrestrial food sources at various trophic positions. Variability in THg concentrations seem to be related to the wolves' trophic position rather than to different carbon sources or regional differences (East Greenland, the Foxe Basin and Baffin Bay area, respectively). Although the present study remains limited due to the scarce, yet unique historic study material and small sample size, it provides novel information on temporal and spatial variation in Hg pollution of remote Arctic species.

Bowhead whales and whaling in the central and eastern Canadian Arctic, 1970-2021

The history of bowhead whaling and hunt management in the eastern and central Canadian Arctic is reviewed. Subsistence hunting of bowhead whales by Inuit resumed in the 1990s under co-management arrangements that were part of land-claims settlement agreements. Removals by whaling in both Canada and Greenland have been accounted for in IWC Scientific Committee assessments of the Eastern Canada–West Greenland (EC-WG) stock, but Canada, having withdrawn from IWC membership in 1982, has no legal obligation to consider IWC management advice. From 1994-2021 the total reported catch of bowheads in the central and eastern Canadian Arctic was 39 (not including struck-and-lost whales or whales that died from incidental entanglement in fishing gear). Sixteen different communities, most of which had a long history of bowhead whaling prior to the arrival of commercial whalers, took at least one bowhead over that 27-year period. More than half of the recent catches have been by the communities of Igloolik, Sanijarak, Naujaat and Coral Harbour, all in the Foxe Basin–Repulse Bay–northern Hudson Bay region where at least occasional hunting of bowheads by local people had persisted until well into the 1970s. Greenland’s reported landed catches totaled from 2009-2015, with no successful hunts reported since 2015. Well over a third of the whales landed by both countries combined have been mature females, the most valuable class in terms of potential for population increase. Several factors in addition to hunting and entanglement in fishing gear are likely affecting EC-WG bowheads, including increased exposure to killer whale predation (linked to the massive reduction in sea ice) and other changes in ecological conditions driven primarily by climate change (e.g. more industrial activity, more vessel traffic, more noise). Recent analyses suggest the EC-WG stock of bowheads has grown considerably since the end of commercial whaling, with best estimates of current abundance in the range of 6000-7000 individuals. Even though the population appears capable of sustaining present levels of removal and disturbance, it is important for monitoring efforts to continue in both Canada and Greenland, with regular Indigenous participation. Local observations and traditional knowledge can be valuable sources of information on animal health, behaviour and phenology.

Polar bear diet composition reveals spatiotemporal distribution of Arctic marine mammals across Nunavut, Canada

Climate warming and associated physical and biological changes will likely force widespread species redistribution, particularly in polar environments. However, tracking such distributional shifts is difficult. The dietary habits of apex predators, like polar bears (Ursus maritimus), may provide early signals of distributional change in prey populations. We used harvest-based sampling to investigate the spatial feeding patterns of polar bears across Nunavut from 2010 to 2018 (n = 1570) and identify spatiotemporal clusters of different prey based on predator diet estimates. Quantitative fatty acid signature analysis and the Getis-Ord Gi* statistic identified spatial clusters of high or low dietary proportions (i.e., “hot spots” and “cold spots”) reflecting seasonal and spatial availability of prey. Ringed seal (Pusa hispida) was the primary prey of bears throughout Nunavut followed by bearded seal (Erignathus barbatus), although proportional consumption varied spatially. A consistent ringed seal consumption hot spot was found in Gulf of Boothia indicating the importance of year-round availability of ringed seals. Spatial clusters of bearded seal and Atlantic walrus (Odobenus rosmarus rosmarus) throughout Foxe Basin suggested overlapping seasonal distributions and high regional abundance. Bears had consistently high dietary levels of harbour seal (Phoca vitulina) around Southampton Island and along the western coast of Hudson Bay suggesting a possible year-round concentration of this prey. Hot spots of harp seal (Pagophilus groenlandicus) consumption were evident throughout Davis Strait and a spring-summer hot spot around Jones Sound was consistent with harp seal migratory patterns. Year-round beluga whale (Delphinapterus leucas) hot spots were found along eastern Baffin Island and southern Viscount Melville Sound providing new knowledge of local conditions that promote polar bear predation or scavenging. Narwhal (Monodon monoceros) were less susceptible to predation with only one spatial cluster of high consumption appearing during spring-summer in Barrow Strait. Bowhead whale (Balaena mysticetus) hot spots occurred around south-western Foxe Basin and seasonally in southern Viscount Melville Sound suggesting carcasses are locally accessible to bears and may act as a supplemental food source in particular areas and seasons. The congruence of polar bear feeding habits and known prey distribution suggests polar bears serve as ecological indicators and ongoing monitoring of their diets may reveal regional and broad-scale changes in prey population distributions and Arctic ecosystem functioning.

Prey selection of polar bears in Foxe Basin, NU, Canada: evidence of dietary flexibility in a specialized predator

AbstractEcological flexibility of a species reflects its ability to cope with environmental change. Although polar bears (Ursus maritimus) are experiencing changes in foraging opportunities due to sea ice loss, regional prey availability and environmental conditions will influence the rate and severity of these effects. We examined changes in polar bear diet and the influence of sea ice characteristics in Foxe Basin over an 18-year period. We combined previous fatty acid data from bears harvested from 1999 to 2003 (n = 82) with additional data from 2010 to 2018 (n = 397). Polar bear diets were diverse; however, ringed seal (Pusa hispida) was the primary prey throughout the sample period. Prey contribution varied temporally and spatially, and by intrinsic factors, while the frequency of prey in diets varied over time suggesting that diet estimates reflect the variability in available prey. Bowhead whale (Balaena mysticetus), although still a minor dietary component, has more than doubled in frequency of occurrence in diets in recent years in association with increased scavenging opportunities. Higher dietary levels of beluga whale (Delphinapterus leucas) and harbour seal (Phoca vitulina) were linked to later breakup date suggesting heavier ice conditions may promote access to both prey species. The flexible foraging strategies of bears in Foxe Basin may help mitigate their vulnerability to changes in prey distribution and habitat conditions. Our results provide insights into the importance of alternative and supplemental food sources for polar bears during phenological changes in ice conditions that will likely have consequences to Arctic community structure as warming continues.

Middle Dorset communal living at Alarniq, northern Foxe Basin, Inuit Nunangat (Arctic Canada)

Our understanding of Dorset communal living is largely derived from the Late Dorset period when longhouses are prevalent throughout the Eastern Arctic. However, based on the recent identification of large multi-family dwellings that date to the Middle Dorset period communal living was seemingly a significant part of Dorset lifeways much earlier. To date, few such dwellings have been excavated, and none have been published in detail. In 2015 a large Middle Dorset multi-family dwelling, Feature 9, was excavated at Alarniq, northern Foxe Basin, Nunavut— one of the largest Dorset sites found across the Eastern Arctic. Feature 9 is the fourth large Middle Dorset multi-family dwelling recorded at Alarniq and radiocarbon dates indicate that these dwellings were not a short-term phenomenon, but instead were built (and rebuilt) at the site for several centuries. Unlike Late Dorset longhouses, which appear to be warm season occupations containing few artifacts and faunal material, Feature 9 was occupied during the cold season, perhaps even year-round, and contained abundant artifacts and faunal material. Undoubtedly, it is an enlarged version of the more typical winter dwelling used in the region. However, since all known large Middle Dorset multi-family dwellings are associated with dwellings of a more typical size they may have also served as gathering spaces, in some ways resembling qaqqiq used in traditional Inuit society.

Hudson Strait Platform and Basins Tectono-Sedimentary Element, Northeast Canada

Abstract The Hudson Strait Platform and basins Tectono-Sedimentary Element (HSPB TSE) is part of a major topographical feature that connects Hudson Bay and Foxe Basin with the Labrador Sea in the Canadian Arctic. The Paleozoic succession (Ordovician–Silurian) unconformably overlies the Precambrian basement and reaches a maximum preserved thickness of less than 600 m on the islands. High-resolution marine seismic data indicate that the offshore part of the Hudson Strait is underlain by several fault-controlled sub-basins with a half-graben geometry. The sedimentary succession in the sub-basins is thicker than the one preserved in nearby islands, and includes an upper sedimentary package for which the nature and age remain poorly constrained. Upper Ordovician source rocks have been mapped onshore. Known potential reservoir rocks consist of Ordovician clastics and Ordovician–Silurian reefs and dolostones.

Multi‐Century Impacts of Ice Sheet Retreat on Sea Level and Ocean Tides in Hudson Bay

AbstractPast and modern large‐scale ice sheet loss results in geographically variable sea level changes. At present, in Hudson Bay, Canada, sea level is decreasing due to glacial isostatic adjustment, which represents a departure from the globally averaged sea level rise. However, there are large uncertainties in future sea level trends with further polar ice sheet retreat in the coming centuries. Sea level changes affect ocean tides considerably because tides are highly sensitive to changes in bathymetry. Here, we present multi‐century sea level projections associated with a suite of past and future ice loss scenarios and consider the impact of these changes on ocean tides using an established tidal model. Modern tides in Hudson Bay are poorly resolved due to large uncertainties in bathymetry. To establish an initial condition for our simulations, we constrain bathymetry in the bay using tide observations. Due to gravitational, Earth rotational and deformational effects, Greenland ice loss will produce a small sea level fall in the bay, while Antarctic ice loss will produce a larger than average sea level rise. Our results show that the response of the Antarctic ice sheet to climate change strongly impacts the magnitude and sign of future sea level and tidal amplitude changes in the region, with the largest changes predicted in Hudson Strait and Foxe Basin. We emphasize that further constraints on bathymetry and accurate projections of sea level and tides in Hudson Bay are imperative for assessing the associated impacts on coastal communities and ecosystems.

Simulating changes in polar bear subpopulation growth rate due to legacy persistent organic pollutants – Temporal and spatial trends

Although atmospheric concentrations of many conventional persistent organic pollutants (POPs) have decreased in the Arctic over the past few decades, levels of most POPs and mercury remain high since the 1990s or start to increase again in Arctic areas, especially polar bears. So far, studies generally focused on individual effects of POPs, and do not directly link POP concentrations in prey species to population-specific parameters. In this study we therefore aimed to estimate the effect of legacy POPs and mercury on population growth rate of nineteen polar bear subpopulations. We modelled population development in three scenarios, based on species sensitivity distributions (SSDs) derived for POPs based on ecotoxicity data for endothermic species. In the first scenario, ecotoxicity data for polar bears were based on the HC50 (the concentration at which 50% of the species is affected). The other two scenarios were based on the HC5 and HC95. Considerable variation in effects of POPs could be observed among the scenarios. In our intermediate scenario, we predicted subpopulation decline for ten out of 15 polar bear subpopulations. The estimated population growth rate was least reduced in Gulf of Boothia and Foxe Basin. On average, PCB concentrations in prey (in μg/g toxic equivalency (TEQ)) posed the largest threat to polar bear subpopulations, with negative modelled population growth rates for the majority of subpopulations. We did not find a correlation between modelled population changes and monitored population trends for the majority of chemical-subpopulation combinations. Modelled population growth rates increased over time, implying a decreasing effect of PCBs, DDTs, and mercury. Polar bear subpopulations are reportedly still declining in four out of the seven subpopulations for which sufficient long-term monitoring data is available, as reported by the IUCN-PBSG. This implies that other emerging pollutants or other anthropogenic stressors may affect polar bear subpopulations.

Low-altitude aerial thermography for the archaeological investigation of arctic landscapes

Remotely-piloted aircraft (RPA) thermography is one of the least utilized remote-sensing methods in archaeology, yet it has great potential for visualizing subsurface archaeological features. Given the logistic constraints of remote fieldwork, arctic archaeologists have much to gain from this portable and effective remote-sensing application. This paper presents a novel methodological approach for the collection, processing, and analysis of RPA thermal imagery in the Canadian High Arctic that accounts for the unique environmental and logistic challenges of RPA applications in polar regions. The development of this approach is based on a case study of two Pre-Inuit (4500–1000 B.P.) archaeological sites from the Foxe Basin region, Nunavut. The presented workflow demonstrates the effectiveness of RPA thermography in archaeological feature detection in an Arctic-tundra setting. Thermal detection of several previously unidentified subsurface features in Foxe Basin suggest that surface feature visibility is lower than previously anticipated, calling attention to potential judgemental biases in pedestrian archaeological surveys in Arctic contexts. Based on the utility of low-altitude thermography for visualizing the internal structures of Tuniit dwellings, this paper proposes that thermography facilitates archaeological spatial analysis beyond feature prospection. RPA thermography is a non-destructive and economic remote-sensing solution to some of the persistent logistic challenges to fieldwork in remote locations that often inhibit large-scale archaeological analyses not only in the Canadian Arctic, but remote Arctic-Alpine regions worldwide.

Impact of tidal dynamics on diel vertical migration of zooplankton in Hudson Bay

Abstract. Hudson Bay is a large seasonally ice-covered Canadian inland sea connected to the Arctic Ocean and North Atlantic through Foxe Basin and Hudson Strait. This study investigates zooplankton distribution, dynamics, and factors controlling them during open-water and ice cover periods (from September 2016 to October 2017) in Hudson Bay. A mooring equipped with two acoustic Doppler current profilers (ADCPs) and a sediment trap was deployed in September 2016 in Hudson Bay ∼190 km northeast from the port of Churchill. The backscatter intensity and vertical velocity time series showed a pattern typical for zooplankton diel vertical migration (DVM). The sediment trap collected five zooplankton taxa including two calanoid copepods (Calanus glacialis and Pseudocalanus spp.), a pelagic sea snail (Limacina helicina), a gelatinous arrow worm (Parasagitta elegans), and an amphipod (Themisto libellula). From the acquired acoustic data we observed the interaction of DVM with multiple factors including lunar light, tides, and water and sea ice dynamics. Solar illuminance was the major factor determining migration pattern, but unlike at some other polar and subpolar regions, moonlight had little effect on DVM, while tidal dynamics are important. The presented data constitute the first-ever observed DVM in Hudson Bay during winter and its interaction with the tidal dynamics.

The Potential of Space-Based Sea Surface Salinity on Monitoring the Hudson Bay Freshwater Cycle

Hudson Bay (HB) is the largest semi-inland sea in the Northern Hemisphere, connecting with the Arctic Ocean through the Foxe Basin and the northern Atlantic Ocean through the Hudson Strait. HB is covered by ice and snow in winter, which completely melts in summer. For about six months each year, satellite remote sensing of sea surface salinity (SSS) is possible over open water. SSS links freshwater contributions from river discharge, sea ice melt/freeze, and surface precipitation/evaporation. Given the strategic importance of HB, SSS has great potential in monitoring the HB freshwater cycle and studying its relationship with climate change. However, SSS retrieved in polar regions (poleward of 50°) from currently operational space-based L-band microwave instruments has large uncertainty (~ 1 psu) mainly due to sensitivity degradation in cold water (<5°C) and sea ice contamination. This study analyzes SSS from NASA Soil Moisture Active and Passive (SMAP) and European Space Agency (ESA) Soil Moisture and Ocean Salinity(SMOS) missions in the context of HB freshwater contents. We found that the main source of the year-to-year SSS variability is sea ice melting, in particular, the onset time and places of ice melt in the first couple of months of open water season. The freshwater contribution from surface forcing P-E is smaller in magnitude comparing with sea ice contribution but lasts on longer time scale through the whole open water season. River discharge is comparable with P-E in magnitude but peaks before ice melt. The spatial and temporal variations of freshwater contents largely exceed the remote sensed SSS uncertainty. This fact justifies the use of remote sensed SSS for monitoring the HB freshwater cycle.

Changing surface radiation and energy budgets of the Hudson Bay Complex using the North American regional reanalysis (NARR) model

Monthly and annual component fluxes of the surface radiation and energy budgets for the two-decade period from 1997 to 2016 are compared with the climate normal period (1981–2010) for the marine system consisting of James Bay, Hudson Bay, Hudson Strait and Foxe Basin using estimates from the North American regional reanalysis model. Reflected solar radiation has declined unevenly, primarily offshore of major rivers, in polynyas and along shore leads, both during earlier melt and later freeze up. Annually, net radiation increases are driven by albedo decreases during the summer. Over 94% of the increases in ocean heat gain during the melt season are due to increases in absorbed sunlight. Large enhanced oceanic heat losses in the late fall are almost entirely consumed by intensified convective losses of both sensible and latent heat. All the seas within the Hudson Bay Complex show a reduced rate of ocean warming over the past two decades. This outcome can be partially reconciled with the observation that all water bodies are experiencing enhanced losses of energy during extended ice-free winters that exceed enhanced gains of energy during the extended ice-free summers. The implications of seasonal changes in ice cover for future climate are discussed.

Correlates of seasonal change in the body condition of an Arctic top predator.

Climate-driven sea ice loss has led to changes in the timing of key biological events in the Arctic, however, the consequences and rate of these changes remain largely unknown. Polar bears (Ursus maritimus) undergo seasonal changes in energy stores in relation to foraging opportunities and habitat conditions. Declining sea ice has been linked to reduced body condition in some subpopulations, however, the specific timing and duration of the feeding period when bears acquire most of their energy stores and its relationship to the timing of ice break-up is poorly understood. We used community-based sampling to investigate seasonality in body condition (energy stores) of polar bears in Nunavut, Canada, and examined the influence of sea ice variables. We used adipose tissue lipid content as an index of body condition for 1,206 polar bears harvested from 2010-2017 across five subpopulations with varying seasonal ice conditions: Baffin Bay (October-August), Davis Strait and Foxe Basin (year-round), Gulf of Boothia and Lancaster Sound (August-May). Similar seasonal patterns were found in body condition across subpopulations with bears at their nadir of condition in the spring, followed by fat accumulation past break-up date and subsequent peak body condition in autumn, indicating that bears are actively foraging in late spring and early summer. Late season feeding implies that even minor advances in the timing of break-up may have detrimental effects on foraging opportunities, body condition, and subsequent reproduction and survival. The magnitude of seasonal changes in body condition varied across the study area, presumably driven by local environmental conditions. Our results demonstrate how community-based monitoring of polar bears can reveal population-level responses to climate warming in advance of detectable demographic change. Our data on the seasonal timing of polar bear foraging and energy storage should inform predictive models of the effects of climate-mediated sea ice loss.

The use of hair as a proxy for total and methylmercury burdens in polar bear muscle tissue

Polar bears (Ursus maritimus) are an ecologically important species in the Arctic, whose health, and that of the people whose livelihoods depend on them, are increasingly affected by climate change and the bioaccumulation of contaminants such as mercury (Hg). Although methylmercury (MeHg) is the toxic form of Hg that biomagnifies up food webs, risk assessment studies typically only report on total Hg (THg) concentrations because it is cheaper to quantify. Furthermore, hair is commonly analysed for THg in polar bear as well as human risk assessment studies because it is relatively non-invasive to collect, yet we know little of how THg and MeHg concentrations differ between hair and muscle tissues. In this study, we quantified THg and MeHg concentrations in hair and muscle from 44 polar bears (24 sub-adults: 9 females, 15 males; 18 adults: 5 females, 13 males, and 2 males of unknown age group), harvested in 2015 and 2016 from four subpopulations in Nunavut, Canada (Davis Strait, n = 3; Gulf of Boothia, n = 8; Baffin Bay, n = 15; Foxe Basin, n = 18). We found only moderately positive correlations (0.4 ≤ r ≤ 0.5) between THg concentrations in hair and THg and MeHg concentrations in muscle. Further, 75% and 88% of THg was MeHg in hair and muscle, respectively. High concentrations of THg in hair - 71% of the samples were above the suggested neurochemical no observed effect level for polar bears - suggest some of the bears may be adversely affected by Hg-related health effects. Despite this, all MeHg concentrations in muscle (0.1 to 0.4 mg/kg (wet weight, ww)) were below the consumption maximum Hg concentration of 0.5 mg/kg (ww) set by Canadian health authorities.