Eastern Hudson Bay Research Articles

Enhanced interannual variability of the May North Atlantic Oscillation and its impact on summer sea ice in the North Atlantic after the mid-2000s

Based on data diagnosis and numerical experiments, this study investigated the changes in the interannual properties of the May North Atlantic Oscillation (NAO) and their impact on summer (June–July) sea ice in the North Atlantic during 1979–2021. Results showed statistically significant increase in the interannual variability of the May NAO after the mid-2000s, which had remarkably enhanced impact on summer sea ice in the eastern Hudson Bay (EHB) and the western Labrador Sea (WLS). During 2005–2021, corresponding to a positive phase of the May NAO, anomalous surface westerly or northwesterly winds prevailed over the Hudson Bay and Labrador Sea in May. This led to statistically significant increase in sea ice in both the EHB and the WLS in May via dynamic processes (favoring southeastward movement of the sea ice) and thermal processes (changing surface turbulent heating and shortwave radiation). In comparison with the situation in May, the increase in sea ice in the EHB developed further during summer mainly via thermal processes (positive feedback between the increased sea ice and shortwave radiation). In contrast, amplitude of the increased sea ice in the WLS was comparable between May and summer. Dynamic processes (southeastward movement of sea ice), which was induced by a barotropic anomalous high in the troposphere centered over the Labrador Peninsula, favored the increase in sea ice in summer in the WLS. The tripole sea surface temperature anomalies in the North Atlantic and increased snowpack on the Labrador Peninsula in May, triggered by the positive phase of the May NAO, played an important role in the formation of the anomalous high. During 1979–2004, the surface wind, snowpack, and tripole sea surface temperature anomalies in May, triggered by the May NAO, were relatively weak, leading to statistically insignificant changes in summer sea ice in the EHB and WLS.

Climate variations in eastern Hudson bay over the past 3000 years

Palynological analyses of the marine sediment core AMD0509-20 collected north of Whapmagoostui-Kuujjuarapik in Nunavik were performed to investigate past changes in climate and sea-surface conditions based on pollen and spores and dinoflagellate cysts, respectively. Our results show relatively warm sea-surface temperatures before 2600 BP, about 2 °C higher than at present in summer, in addition to higher salinity suggesting relatively low freshwater inputs, thus low precipitation over the watershed. After 2400 years BP, an abrupt drop in sea-surface temperatures was recorded, followed by a decrease in salinity particularly pronounced until ∼2000 years BP. After 1600 years BP, summer sea-surface temperatures and salinity stabilized around current values. The changes recorded in surface waters during the late Holocene can be associated with a regional shift in the hydroclimatic regime that led to a gradual decline of spruce (Picea) in pollen assemblages.

Size‐dependent community patterns differ between microbial eukaryotes and bacteria in a permafrost lake–river–sea continuum

AbstractMicrobial communities play a crucial role in ecosystem functioning, with contributions that can vary among taxonomic domains and size fractions. However, microbial assembly processes for bacteria and eukaryotes are seldom characterized together using size fractionation, especially in flowing waters. Here, we used amplicon sequencing combined with physicochemical measurements to determine how size fractionated (small fraction 0.22–3 μm; large fraction > 3 μm) community structure and diversity varied over a subarctic river continuum. We sampled the Sheldrake River, a 25 km river flowing through degrading discontinuous permafrost, from its lacustrine source through subarctic forest shrub tundra to its discharge plume in eastern Hudson Bay (Nunavik, Canada). Microbial community structure differed by size fraction and among habitats, with differences in the variables potentially driving community structure among size fractions and microbial domains. For the small size fraction, colored dissolved organic matter was a significant covariate of community variation for both bacteria and eukaryotes, consistent with the influence of landscape gradients. There were contrasting diversity patterns along the lake–river transect between bacterial size fractions. An abundance‐based approach indicated that for all communities, assembly processes were dominated by homogeneous selection, while an incidence‐based method showed dominance of heterogeneous selection for bacteria and homogenizing dispersal for microbial eukaryotes. Our findings show how different components of riverine microbial communities can have divergent patterns along the downstream continuum to the sea.

Provenance of middle to late Pleistocene tills in Illinois, U.S.A.: evidence for long-distance (∼ 2000 km) ice transport during two successive glaciations

ABSTRACTZircons extracted from 567 granitic cobbles, in middle to late Pleistocene tills of the Lake Michigan Lobe in Illinois, provide a remarkably consistent Archean age of ∼ 2.7 Ga, with 87% dating between 2.6 and 2.8 Ga. This finding suggests a persistent glacial flow path of the southern Laurentide ice sheet from the Superior Province into the Lake Michigan basin during Marine Isotope Stage 6 (Illinois Episode) and Marine Isotope Stage 2 (Wisconsin Episode). Based on published crystalline bedrock ages in the Canadian Shield, these cobbles are interpreted to have been transported as much as ∼ 2000 km southwestward from the Quebec–Labrador ice dome, east of Hudson Bay, to the ice-sheet terminus in central to southern Illinois, USA. Some of the glacial flow likely skirted eastern Hudson Bay (source of Omar erratics) and southern James Bay, and traversed outcrops of Huronian jasper conglomerate and diamictite along the north shore of Lake Huron. Transport across the Paleozoic strata may have been enhanced, in part, by an ice stream that advanced across relatively soft and water-saturated sediments that underlie the Lake Michigan basin. The Lake Michigan basin, although present earlier in some form, was likely significantly eroded and overdeepened by accelerated glacial flow and erosion during MIS-6, further constraining the southern Laurentide Ice Sheet (LIS) flow path and influencing its subsequent flow during the last glaciation. As the Lake Michigan Lobe thinned and radiated out from the Lake Michigan basin, topographic effects led to separation of sublobes during the LIS advance to its southernmost extent.

Content in fatty acids and carotenoids in phytoplankton blooms during the seasonal sea ice retreat in Hudson Bay complex, Canada

The Hudson Bay complex (HBC) is home to numerous indigenous communities that traditionally have relied heavily on its marine resources. The nutritional quality and stocks of the entire HBC food web depend in large part on the phytoplankton production of bioactive molecules (long chain polyunsaturated fatty acids and carotenoids) and their transfer through trophic levels. The purpose of this study was thus to determine which molecules were produced during spring phytoplankton blooms, as well as the environmental factors driving this production. We investigated 21 stations in 5 sub-regions of the HBC. At the time of sampling, the sub-regions studied had different environmental settings (e.g., ice cover, nutrients, seawater salinity and temperature) conditioning their bloom stages. Pre- and post-bloom stages were associated with relatively low concentrations of bioactive molecules (either fatty acids or carotenoids). In contrast, the highest concentrations of bioactive molecules (dominated by eicosapentaenoic acid and fucoxanthin) were associated with the diatom bloom that typically occurs at the ice edge when silicates remain available. Interestingly, the large riverine inputs in eastern Hudson Bay led to a change in protist composition (larger contribution of Dinophyceae), resulting in lower while more diverse content of bioactive molecules, whether fatty acids (e.g., α-linolenic acid) or carotenoids (e.g., peridinin). As greater stratification of the HBC is expected in the future, we suggest that a mixotrophic/heterotrophic flagellate-based food web would become more prevalent, resulting in a smaller supply of bioactive molecules for the food web.

Landfast sea ice in Hudson Bay and James Bay

Through analysis of Canadian Ice Service ice charts, we have characterized the temporal and spatial variability of landfast sea ice (or fast ice) surrounding Hudson Bay and James Bay from 2000 to 2019. Over this 19-year period, we observed contrasting changes in fast-ice persistence between the western and eastern sides of Hudson Bay and James Bay. Fast ice in western Hudson Bay and James Bay trended towards later freeze-up and earlier break-up that resulted in a shortening of the fast-ice season at a rate of 6 days/decade. Contrastingly, eastern Hudson Bay and James Bay showcased relatively earlier freeze-up and delayed break-up, and an overall trend towards a longer fast-ice season at a rate of 8 days/decade. The general trend in air temperature followed a similar spatial pattern to the changing fast-ice persistence; however, the timing of fast-ice break-up did not have a strong relationship with the thawing-degree days during spring. Variations in fast-ice area showed latitudinal and meridional gradients, with greater fast-ice area in eastern Hudson Bay and James Bay compared to the west. Given the overall warming trend in the Arctic, observing areas of decreasing fast-ice persistence is unexpected; however, this study highlights the role of regional factors, such as coastal orientation and bathymetry, in controlling the stability, growth and decay of fast ice.

Atmospherically forced sea-level variability in western Hudson Bay, Canada

Abstract. In recent years, significant trends toward earlier breakup and later freeze-up of sea ice in Hudson Bay have led to a considerable increase in shipping activity through the Port of Churchill, which is located in western Hudson Bay and is the only deep-water ocean port in the province of Manitoba. Therefore, understanding sea-level variability at the port is an urgent issue crucial for safe navigation and coastal infrastructure. Using tidal gauge data from the port along with an atmospheric reanalysis and Churchill River discharge, we assess environmental factors impacting synoptic to seasonal variability of sea level at Churchill. An atmospheric vorticity index used to describe the wind forcing was found to correlate with sea level at Churchill. Statistical analyses show that, in contrast to earlier studies, local discharge from the Churchill River can only explain up to 5 % of the sea-level variability. The cyclonic wind forcing contributes from 22 % during the ice-covered winter–spring season to 30 % during the ice-free summer–fall season due to cyclone-induced storm surges generated along the coast. Multiple regression analysis revealed that wind forcing and local river discharge combined can explain up to 32 % of the sea-level variability at Churchill. Our analysis further revealed that the seasonal cycle of sea level at Churchill appears to be impacted by the seasonal cycle in atmospheric circulation rather than by the seasonal cycle in local discharge from the Churchill River, particularly post-construction of the Churchill River diversion in 1977. Sea level at Churchill shows positive anomalies for September–November compared to June–August. This seasonal difference was also revealed for the entire Hudson Bay coast using satellite-derived sea-level altimetry. This anomaly was associated with enhanced cyclonic atmospheric circulation during fall, reaching a maximum in November, which forced storm surges along the coast. Complete sea-ice cover during winter impedes momentum transfer from wind stress to the water column, reducing the impact of wind forcing on sea-level variability. Expanding our observations to the bay-wide scale, we confirmed the process of wind-driven sea-level variability with (i) tidal-gauge data from eastern Hudson Bay and (ii) satellite altimetry measurements. Ultimately, we find that cyclonic winds generate sea-level rise along the western and eastern coasts of Hudson Bay at the synoptic and seasonal timescales, suggesting an amplification of the bay-wide cyclonic geostrophic circulation in fall (October–November), when cyclonic vorticity is enhanced, and Hudson Bay is ice-free.

Structural Characterization of Dissolved Organic Matter in Permafrost Peatland Lakes

Thermokarst lakes result from the thawing of ice-rich permafrost and are widespread across northern landscapes. These waters are strong emitters of methane, especially in permafrost peatland regions, where they are stained black by high concentrations of dissolved organic matter (DOM). In the present study, we aimed to structurally characterize the DOM from a set of peatland thermokarst lakes that are known to be intense sites of microbial decomposition and methane emission. Samples were collected at different depths from three thermokarst lakes in the Sasapimakwananisikw (SAS) River valley near the eastern Hudson Bay community of Kuujjuarapik–Whapmagoostui (Nunavik, Canada). Samples were analyzed by spectrofluorometry, Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and elemental analysis. Fluorescence analyses indicated considerable amounts of autochthonous DOM in the surface waters of one of SAS 1A, indicating a strong bioavailability of labile DOM, and consequently a greater methanogenic potential. The three lakes differed in their chemical composition and diversity, suggesting various DOM transformations phenomena. The usefulness of complementary analytical approaches to characterize the complex mixture of DOM in permafrost peatland waters cannot be overlooked, representing a first step towards greater comprehension of the organic geochemical properties of these permafrost-derived systems.

Changes in Fog, Ice Fog, and Low Visibility in the Hudson Bay Region: Impacts on Aviation

Fog and low visibility present a natural hazard for aviation in the Hudson Bay region. Sixteen communities on the eastern and western shores of Hudson and James Bays, Canada, were selected for fog, ice fog, and low visibility statistical analyses for a range of 21 to 62 year time series. Both fog hours and ice fog hours were found to be in general decline, with some locations experiencing statistically significant declines. Spatial asymmetries for fog and ice fog were observed among the various areas within the Hudson Bay region. The more northerly locations in this study experienced statistically significant declines in fog hours while the southerly locations’ declines were not significant. Fog was significantly declining in some western Hudson Bay locations during spring and fall and in James Bay during winter and summer, but minimal trends were observed in eastern Hudson Bay. For ice fog hours, all of the locations in the western shore of Hudson Bay experienced a significant decline in winter while only one-third of the locations in eastern shores were found to be declining significantly during winter. Blowing snow, snow, ice and fog were the leading causes for reduced and low visibilities at the majority of the locations. Other factors such as rain contributed a minor role to low visibility.

Atmospheric Forcing Drives the Winter Sea Ice Thickness Asymmetry of Hudson Bay

AbstractRecently, we highlighted the presence of a strong west‐east asymmetry in sea ice thickness across Hudson Bay that is driven by cyclonic circulation. Building on this work, we use satellite altimetry and a unique set of in situ observations of ice thickness from three moored upward looking sonars to examine the role of atmospherically driven ice dynamics in producing contrasting regional ice thickness patterns. Ultimately, north‐northwesterly winds coupled with numerous reversals during winter 2016/2017 led to thicker ice in southern Hudson Bay, while enhanced west‐northwesterly winds during winter 2017/2018 led to thicker ice in eastern Hudson Bay that delayed breakup and onset of the summer shipping season to coastal communities. Extending the analysis over the 40‐year satellite observation period, we find that these two different patterns of atmospheric forcing alter the timing of breakup by 30 days in eastern Hudson Bay and offer some skill in seasonal predictions of breakup.

Permafrost aggradation along the emerging eastern coast of Hudson Bay, Nunavik (northern Québec, Canada)

AbstractEmerging polar coasts have different geothermal regimes than those in submergence. While the scientific community is mainly concerned with rapidly eroding permafrost coastlines in sedimentary formations where relative sea level is rising, much less research has been dedicated to permafrost dynamics in emergent coastal regions where post‐glacial uplift is ongoing. The eastern Hudson Bay coast of Nunavik (northern Québec, Canada) is undergoing glacio‐isostatic uplift at a current emergence rate of about 13 mm/yr, outpacing the current global sea‐level rise (~3 mm/yr) and progressively exposing new land to climate conditions favorable for permafrost formation. To observe incipient permafrost in the shore zone over time, in 2005 we strategically installed a thermistor cable down to a depth of 23 m at a high‐tide level site. We detected the formation and the continuing deepening of permafrost near the surface. Freezing of the ground was also favored by a succession of several cold years in Nunavik since 2010. The near 0°C temperature profile at greater depths also reveals the cooling influence of deep Hudson Bay waters on the shore zone ground temperature regime and the probable presence of subsea permafrost offshore of the measurement site.

Hudson Bay Climate Change and Local Winter Wind Circulation

The meteorological mechanisms causing the recent increase in winter wind speed on Hudson Bay are investigated by examining the NARR dataset (The North American Regional Reanalysis Model) for the past several decades. Winter seasonal changes for atmospheric variables are examined and their interconnections are studied. Yearly mean near-surface temperatures are analyzed from 1948 to denote a rapid warming over Hudson Bay from late 1998 onwards. The surface albedo, air temperatures, mean sea level pressure and wind vector anomalies from 1998 to 2015 have also been studied. The comparison of the 1000 hPa wind vector mean and departures from 1981-2010 (normal period) averages have shown an intensification of anti-cyclonic anomaly pattern over most parts of Hudson Bay. The structure of the wind vector anomalies has revealed a contrast between cyclonic and anti-cyclonic local wind circulations mostly in the east, north and north-west regions along with wind speed increasing at 10 m, increases in near-surface air temperature and decreasing of the surface albedo. The anomalies of the wind vector analysing at different pressure levels show the change in wind direction mostly from northwesterly (zonal wind weakening) to south and easterlies. The polar jet wind vectors at 200 mb during anomaly time (1998-2015) have revealed the changes in magnitude and position. During winter anomaly time, the polar jet at 200 mb has been shifted mostly from rather mean colder north westerly currents to the rather warmer south and easterly anomaly currents over Hudson Bay areas. The yearly historical total accumulated Hudson Bay ice coverage during 1980-2015, using Canadian Ice Service data has shown a slight reduction in the north, north-west and eastern Hudson Bay. The linear regressions of the winter temperature anomaly at 2 m against albedo anomaly, alongside the wind speed anomaly at 10 m against air temperature at 2 m, have shown a relationship between these variables. Also, there is a statistically meaningful relation between decreased albedo and increased evaporation.

Periphytic diatom community structure in thermokarst ecosystems of Nunavik (Québec, Canada)

Climate change is causing rapid permafrost degradation across Arctic and subarctic regions, resulting in changes in the size, abundance, and structure of thermokarst (thaw) ponds and lakes. The main objectives of this study were to analyze periphytic diatom communities and their affinity to vegetation substrates in thermokarst ecosystems located in the eastern Hudson Bay region and to establish a first inventory of diatom assemblages and the associated littoral vegetation in these systems. Some generalist diatom species, including Tabellaria flocculosa, occupied all ecological niches in the water bodies. In contrast, genera such as Eunotia and Pinnularia were more specialized and generally concentrated on moss substrates. Shoreline vegetation and thermokarst pond/lake littoral morphology (slope) resulted in limnological conditions that differed between sites and ultimately affected diatom community structure. Our results show that both shoreline vegetation and diatom communities are diverse in thermokarst...

Sea ice thickness in the Eastern Canadian Arctic: Hudson Bay Complex & Baffin Bay

Past observations of sea ice thickness in the Eastern Canadian Arctic (ECA) have generally been restricted to drill-hole measurements at a few local sites on landfast ice. Here we use data from the laser altimeter ICESat and the radar altimeter Cryosat-2 to present a 14-year record (2003–2016) of high-resolution and spatially extensive ice thickness observations for the ECA and identify 12 sub-regions with distinct patterns. The mean sea ice growth rate within the seasonally ice-covered ECA from November to April is 23cmmo−1 (565km3mo−1), with the fastest increase in thickness occurring through strong ice convergence and deformation in eastern Hudson Bay and Foxe Basin. Our results demonstrate characteristically asymmetrical distributions of sea ice thickness in both Hudson Bay and Baffin Bay, but in opposing directions. In Hudson Bay the spring ice cover is 40cm thicker in the eastern region compared to the northwestern region, whereas in Baffin Bay the ice is 20cm thicker in the western half of the bay compared to the eastern half. In Hudson Bay we find that years with strong and positive ice drift vorticity (i.e. cyclonic and convergent conditions) correlate with increasingly asymmetrical sea ice covers, with the level of west-east asymmetry varying from 2 to 11cm per 100km. However, in Baffin Bay the ice drift vorticity is typically negative (i.e. anticyclonic and divergent) with no obvious link to the asymmetry of the spring ice cover. Finally, we estimate that large interannual variations in spring sea ice volume within the ECA lead to ±15% variations in the volume of freshwater available at the ocean surface during summer.

Recent trends and variability in river discharge across northern Canada

Abstract. This study presents an analysis of the observed inter-annual variability and inter-decadal trends in river discharge across northern Canada for 1964–2013. The 42 rivers chosen for this study span a combined gauged area of 5.26 × 106 km2 and are selected based on data availability and quality, gauged area and record length. Inter-annual variability in river discharge is greatest for the eastern Arctic Ocean (coefficient of variation, CV = 16 %) due to the Caniapiscau River diversion into the La Grande Rivière system for enhanced hydropower production. Variability is lowest for the study area as a whole (CV = 7 %). Based on the Mann–Kendall test (MKT), no significant (p > 0.05) trend in annual discharge from 1964 to 2013 is observed in the Bering Sea, western Arctic Ocean, western Hudson and James Bay, and Labrador Sea; for northern Canada as a whole, however, a statistically significant (p < 0.05) decline of 102.8 km3 25 yr−1 in discharge occurs over the first half of the study period followed by a statistically significant (p < 0.05) increase of 208.8 km3 25 yr−1 in the latter half. Increasing (decreasing) trends in river discharge to the eastern Hudson and James Bay (eastern Arctic Ocean) are largely explained by the Caniapiscau diversion to the La Grande Rivière system. Strong regional variations in seasonal trends of river discharge are observed, with overall winter (summer) flows increasing (decreasing, with the exception of the most recent decade) partly due to flow regulation and storage for enhanced hydropower production along the Hudson and James Bay, the eastern Arctic Ocean and Labrador Sea. Flow regulation also suppresses the natural variability of river discharge, particularly during cold seasons.

Review of killer whale (Orcinus orca) ice entrapments and ice-related mortality events in the Northern Hemisphere

In January 2013, a group of killer whales (Orcinus orca) was discovered in an ice entrapment in eastern Hudson Bay, Canada. The whales escaped the entrapment after several days, which ended the discussion on response options. The event did, however, highlight the need for a better understanding of killer whale entrapments to guide future responses. We conducted a literature review of ice entrapment and ice-induced stranding mortality events for killer whales in the Northern Hemisphere and identified 17 events dating from 1840 to 2013, ranging from a single whale to more than 20. Ice entrapments occurred in both pack ice (mobile ice) and fast ice (ice which forms and remains fast along the coast), with most records (70 %) coming from midlatitude regions with seasonal ice cover (e.g., Sea of Okhotsk and eastern Canada). Most events resulted in mortality, and time to mortality depended on ice conditions with whales surviving longer in fast-ice entrapments, where ice is more stable than in mobile ice.

Distribution and use of brood-rearing and moulting sites of the Atlantic population of Canada Geese (<em>Branta canadensis</em>) in Nunavik, Quebec

The Atlantic population of Canada Geese (Branta canadensis) nests in the coastal lowlands of eastern Hudson Bay and southwestern Ungava Bay in Nunavik, Quebec. Although many aspects of the nesting ecology of this and other northern populations of Canada Geese have been studied and published, there is a paucity of information on the use of brood-rearing and moulting sites. Based on 18 years of band and recapture data from an ongoing banding program, this paper presents the distribution of brood-rearing and moulting sites and the use of these sites over time. Along Hudson Bay and Ungava Bay, the most important brood-rearing and moulting areas are the stretch of coastal lowlands between the Mariet River and Shallow Bay and between Rivière aux Feuilles and Virgin Lake, respectively. Of all adult geese captured during the banding program (n = 41 924), 7.5% (standard error [SE] 0.13%) were recaptures, that is, birds that had previously been caught and banded; annual recapture rates ranged from 5.1% to 11.4%. The mean and median distances between the site of first recapture and the original site of capture were 4.3 km (SE 0.22 km) and 1.5 km, respectively. Juveniles moved, on average, 5.4 km farther than adults and males moved 1.4 km farther than females. Among geese banded as juveniles, males moved twice as far as females: 11.5 km versus 5.7 km.

Estimating the abundance of the Southern Hudson Bay polar bear subpopulation with aerial surveys

The Southern Hudson Bay (SH) polar bear subpopulation occurs at the southern extent of the species’ range. Although capture–recapture studies indicate abundance was likely unchanged between 1986 and 2005, declines in body condition and survival occurred during the period, possibly foreshadowing a future decrease in abundance. To obtain a current estimate of abundance, we conducted a comprehensive line transect aerial survey of SH during 2011–2012. We stratified the study site by anticipated densities and flew coastal contour transects and systematically spaced inland transects in Ontario and on Akimiski Island and large offshore islands in 2011. Data were collected with double-observer and distance sampling protocols. We surveyed small islands in James Bay and eastern Hudson Bay and flew a comprehensive transect along the Quebec coastline in 2012. We observed 667 bears in Ontario and on Akimiski Island and nearby islands in 2011, and we sighted 80 bears on offshore islands during 2012. Mark–recapture distance sampling and sight–resight models yielded an estimate of 860 (SE = 174) for the 2011 study area. Our estimate of abundance for the entire SH subpopulation (943; SE = 174) suggests that abundance is unlikely to have changed significantly since 1986. However, this result should be interpreted cautiously because of the methodological differences between historical studies (physical capture–recapture) and this survey. A conservative management approach is warranted given previous increases in duration of the ice-free season, which are predicted to continue in the future, and previously documented declines in body condition and vital rates.

Microsatellite assessment of walrus (<i>Odobenus rosmarus rosmarus</i>) stocks in Canada

Walruses in Canada are currently subdivided into seven stocks based on summering areas; Western Jones Sound (WJS), Baffin Bay (BB), Penny Strait-Lancaster Sound (PS-LS), North Foxe Basin (N-FB), Central Foxe Basin (C-FB), Hudson Bay Davis Strait (HB-DS) and Southern and Eastern Hudson Bay (SE-HB). In this study, walrus were sampled from six of the seven stocks (SE-HB samples were not available) and genotyped at 10 microsatellite loci. All stocks were genetically diverse (average heterozygosity of 0.58) with no evidence of inbreeding (average FIS of 0.03). We detected significant genetic differentiation among the stocks and a pattern of genetic spatial autocorrelation that suggests a moderate effect of geographic distance on gene flow among stocks. Bayesian clustering suggested the six recognized stocks were elements of two larger genetic clusters - a northern Arctic population (containing BB, WJS, and PS-LS stocks) and a central Arctic population (containing C-FB, N-FB, and HB-DS stocks). These populations are moderately differentiated (FST = 0.07), but based on evidence of contemporary movement from assignment tests, are not completely isolated. There was support for maintaining the WJS stock and a combined BB+PS-LS stock, although the latter conclusion is based on a small sample size. Similarly, there was some evidence suggesting separation of the Foxe Basin stocks from the HB-DS but not the N-FB from the C-FB stock. However, given that there are morphological and chemical differences between N-FB and C-FB stocks, there is currently insufficient evidence to support a revision of the current stock designations.

Low calcium carbonate saturation state in an Arctic inland sea having large and varying fluvial inputs: The Hudson Bay system

AbstractThe Hudson Bay system (HBS) is a shallow inland sea in the Arctic, composed of Hudson Strait, Foxe Basin/Channel, James Bay, and Hudson Bay. Dissolved inorganic carbon (DIC) and total alkalinity (TA) measurements were used to investigate the state of ocean acidification, specifically calcium carbonate saturation states (Ω) and pH. The freshwater sources were identified from the relationship between oxygen isotope composition (δ18O) and salinity to understand the role of freshwater in ocean acidification. The saturation state of seawater with respect to calcium carbonate (Ω) in surface water (<10 m) of the HBS was strongly influenced by river runoff. Aragonite under‐saturation (Ωarg < 1) was observed in the surface water of the south‐eastern Hudson Bay, where the river runoff fraction was high (>10%). The watershed characteristics, however, influenced the alkalinity of river runoff in different parts of Hudson Bay, which contributed to Ω variation in the coastal region. In southwestern Hudson Bay where the watershed is dominated by limestone, Ω was higher compared to eastern Hudson Bay, where the watershed consists of an igneous rock formation. In deeper waters, low Ω is caused by remineralization of organic matter. The highest DIC concentrations (>2300 µmol/kg) were observed in the depths of central Hudson Bay with a pHtotal of 7.49 and Ωarg of 0.37. Over 67% and 22% of the bottom water of Hudson Bay was undersaturated with respect to aragonite and calcite respectively, despite Hudson Bay being very shallow (less than 250 m deep). The aragonite saturation horizon in the central Hudson Bay was around 50 m.