Labrador Coast Research Articles

Life-stage-dependent supergene haplotype frequencies and metapopulation neutral genetic patterns of Atlantic cod, Gadus morhua, from Canada's Northern cod stock region and adjacent areas.

Among highly migratory fish species, nursery areas occupied by juveniles often differ from adult habitats. To better understand the spatial dynamics of Canada's Northern cod stock, juveniles caught off the east coast of Newfoundland and Labrador were compared to adults from the same region as well as individuals from other areas in Atlantic Canada using double-digest restriction site-associated DNA sequencing-derived single nucleotide polymorphisms. A reduced proportion of homozygotes with a chromosomal inversion located in linkage group 1 (LG1) was detected between juvenile and adult samples in the Northern cod stock region, potentially indicating age-dependent habitat use or ontogenetic selection for attributes associated with the many genes located in LG1. No selectively neutral genetic differences were found between samples from the Northern cod stock; nevertheless, significant differences were found between some of these samples and cod collected from St. Pierre Bank, Bay of Fundy, Browns Bank and the southern Scotian Shelf. Clustering analysis of variants at neutral loci provided evidence for three major genetic units: (a) the Newfoundland Atlantic Coast, (b) eastern and southern Gulf of St. Lawrence and Burgeo Bank and (c) the Bay of Fundy, Browns Bank and southern Scotian Shelf. Both adaptive and neutral population structure within the Northern cod stock should be considered by managers to promote demographic rebuilding of the stock.

87 million years of recorded history in Labrador: Birth, life, and sleep of the Kiglapait Intrusion

ABSTRACTThe Kiglapait Intrusion on the north coast of Labrador is a bowl-shaped body dominated by troctolite about 3500 km3 in initial volume and was created during an intrusive event perhaps lasting thousands of years. It was emplaced into anorthosite and metasedimentary rocks at an estimated roof depth of 9.6 km and a magma depth of 8.4 km; hence with a floor at 18 km depth. The primary magma for the intrusion is thought to have been of harzburgite composition; a large volume of olivine crystallized in transit, to the extent that the magma became saturated with plagioclase by the time it reached the site of emplacement or soon after. To test this hypothesis, piston-cylinder experiments were made at 5–15 kbar in graphite using the Kiglapait Intrusion bulk composition with Fo-rich olivine added. Results at 13 kbar yielded saturation with garnet, olivine, spinel, orthopyroxene, clinopyroxene, plagioclase, and melt. This assemblage is compatible with a lherzolite solidus at 1375 °C. A postulated harzburgite solidus at 15 kbar would be hotter, perhaps 1410 °C. Partial melt from this harzburgite rising into a hot, thinned lithosphere is presumed to have shed large amounts of olivine to produce the plagioclase-saturated troctolitic basal Lower Zone of the intrusion. Conditions of emplacement are schematically developed in ternary Al–Ca–Fe diagrams. Some high-pressure experimental compositions of clino- and orthopyroxene are metastably enriched in Al but do not affect the interpretation of the magmatic history. We show that olivine fractionation will pass through the compositions of these aluminous minerals to reach a relatively evolved saturation with only plagioclase and olivine, resulting in the voluminous Lower Zone of troctolite. The amount of olivine crystallized to reach this result is calculated, using multiphase Rayleigh fractionation and a standard MELTS routine, to between 30% and 50%. Previously published argon-argon mineral dates on hornblende, biotite, and feldspars have captured a cooling history from ∼1258 °C to the ambient ∼100 °C over the time interval 1307 to 1220 Ma, hence the 87 million year history claimed in the title.

Diversity in Labrador Inuit sled dog diets: Insights from δ13C and δ15N analysis of dog bone and dentine collagen

Sled dogs were an integral part of Labrador Inuit life from the initial expansion and settlement of northeastern Canada to the present day. Tasked with pulling sleds and assisting people with other subsistence activities in the winter, dogs required regular provisioning with protein and fat. In this paper, we conduct stable carbon and nitrogen isotope ratio analysis of the skeletal remains of dogs (n = 35) and wild fauna (n = 68) from sites located on the north and south coasts of Labrador to characterize dog provisioning between the 15th to early 19th centuries. In addition, we analyse bone (n = 20) and dentine (n = 4) collagen from dogs from Double Mer Point, a communal house site in Hamilton Inlet to investigate how dog diets intersected with Inuit subsistence and trade activities at a local level. We find that dog diets were largely composed of marine mammal protein, but that dogs on the north coast consumed more caribou and fish relative to dogs from the central and south coast sites. The diets of dogs from Double Mer Point were the most heterogenous of any site, suggesting long-distance movement of people and/or animals along the coast.

Golden cod persist through climate change

This “golden cod” (left) from Gilbert Bay, off the coast of Labrador, Canada, is easily recognized by commercial harvesters because of its distinctive “golden” coloration; this fish is technically an Atlantic cod (Gadus morhua), though it is much darker than cod from the adjoining northern population (right). Atlantic cod is a population-rich species, incorporating tremendous intraspecific biodiversity, and is prized by North Atlantic fisheries. The northern cod stock, which collapsed and was placed under a fishing moratorium in 1992, has not recovered owing in part to colder-than-normal ocean temperatures in the Labrador Sea. Remarkably, while northern cod experienced high rates of natural mortality during the 1990s, the Gilbert Bay cod population grew. This golden cod spent its entire life (~17 years) in Gilbert Bay, living 6 months of the year just meters beneath sea ice in sub-zero temperatures. It therefore experienced much colder conditions, and for longer time periods, than other Atlantic cod. During summer, however, golden cod take advantage of the short growth season in the shallow waters that warm quickly within the protection of the bay.

Assessing the Usefulness of Iceberg Electromagnetic Backscatter Modeling Using a C-Band SAR Classifier

This letter presents the validation of an electromagnetic (EM) backscatter model of icebergs at C-band by comparing the performances of target classifiers trained with both modeled and real synthetic aperture radar (SAR) data. Simulated SAR data were obtained in a combination of imaging beam modes and scene parameters to produce 216 simulated Sentinel-1 C-band SAR images. Parameters consisted of Sentinel-1 IW1 (33.1°) and IW3 (43.1°) beam modes with varying wind speed (5 and 10 m/s), wind direction (0°, 45°, and 90°), and target orientation (0°, 45°, and 90°). Simulations were created from an EM SAR simulator called GRECOSAR, which took 3-D profiles of iceberg and ship targets and parameters necessary to closely mimic the real scenes. 3-D models of three icebergs were captured in a field study off the coast of Bonavista, Newfoundland, and Labrador, Canada in June 2017. Three generic ship models were sourced from an online inventory and scaled to a size equivalent to that of the iceberg targets. Real SAR image data were drawn from in-house data set collected from a complementary research program. Classifiers including support vector machine (SVM), Random Forest (RanFor), k-nearest neighbor (kNN), and neural network (NN) were trained with targets from modeled SAR data and then gradually mixed with real SAR data. Target classifier performance from the modeled target data was shown to be similar to classifiers trained entirely from real SAR data. The similarity in accuracy provides an indication of the validity of the modeled SAR data for this specific application.

Cross‐Isobath Freshwater Exchange Within the North Atlantic Subpolar Gyre

AbstractThe amount of cross‐isobath freshwater exchange within the North Atlantic subpolar gyre is estimated from numerical modelling simulations. A regional configuration of the Nucleus for European Modelling of the Ocean model is used to carry out three simulations with horizontal resolutions of 1/4°, 1/12°, and 1/4° with a 1/12° nested domain. Freshwater transport is calculated across five isobaths in six regions for three distinct water masses. Fresh Polar Water is only transported offshore from the western coast of Greenland and the southern coast of Labrador; other regions have onshore transport of freshwater or little offshore transport. The salty water masses of Irminger and Labrador Sea Water typically have onshore transport, acting to promote subsurface freshening of the Labrador Sea. The freshwater transport via the Polar Water mass experiences a large degree of seasonal variability, while the Irminger and Labrador Sea Water masses do not. Decomposing the freshwater transport into the mean and turbulent components indicates that most regions and water masses have stronger freshwater transport associated with the mean flow while the turbulent flow in often the opposite direction. The only water mass and region where the mean and turbulent freshwater transport act in the same direction is Polar Water along the western margin of Greenland. Model resolution plays an important role in determining cross‐isobath exchange as our results from an identically forced simulation at 1/4° has reduced seasonal cycles, reduced transport, and sometimes transport in the opposite direction when compared against the 1/12° resolution simulations.

Two Neoarchean tectonothermal events on the western edge of the North Atlantic Craton, as revealed by SIMS dating of the Saglek Block, Nain Province, Labrador

The Saglek Block forms the northern part of the Nain Province and underwent widespread metamorphism at c. 2.7 Ga, producing the dominant gneissosity and intercalation of supracrustal sequences. Zircon dating of gneiss samples collected along 80 km of the Labrador coast from Ramah Bay in the north to Hebron Fjord in the south confirms the widespread extent of high-grade metamorphism between 2750 and 2700 Ma. In addition, a distinct event between 2550 and 2510 Ma produced felsic melt with peritectic garnet in metavolcanic gneiss and granoblastic recrystallization in mafic granulite. Ductile deformation of granite emplaced at c. 2550 Ma indicates that this later event involved a degree of tectonism during high- T metamorphism. Such tectonism may be related to a hypothesized post-2.7 Ga juxtaposition of the predominantly Eoarchean Saglek Block against the Mesoarchean Hopedale Block, along a north–south boundary that extends from the coast near Nain to offshore of Saglek Bay. Evidence of reworking of c. 2.7 Ga gneisses by c. 2.5 Ga tectonothermal activity has been found elsewhere on the margins of the North Atlantic Craton, of which the Nain Province represents the western margin. In particular, a recent suggestion that c. 2.5 Ga metamorphic ages along the northern margin of the North Atlantic Craton in SW Greenland may record the final assembly of the craton could also apply to the western margin as represented by the rocks of the Nain Province. Supplementary material: Plots and geochemical data are available at https://doi.org/10.6084/m9.figshare.c.4567934

“Where the Mysterious and the Undefined Breathes and Lives”: Kathleen Winter’s Annabel as Intersex Text

Kathleen Winter’s Annabel (2010) tells the story of Wayne Blake, a hermaphrodite born in the village of Croydon Harbour on the southeast Labrador coast. In this land of extremes, Wayne’s body defies classification, and its multiplicity not only signifies “the emptiness of signs” but also unhinges the narratives of the people and the land that come into contact with him. His intersex body defies the social norms of his parents’ societies, the linguistic parameters of self-identification, and the supposed laws of nature by which so many of these characters live their lives. Yet as the novel progresses, almost everyone and everything in this landscape come to share Wayne’s multiplicity. As a result, this article argues, Annabel is an intersex text in which everything is revealed to be more than one thing at any given time, a philosophy of people and places also found in the ecocriticism of Glen A. Love and Lawrence Buell.

A trap with light-emitting diode (LED) lights: Evaluating the effect of location and orientation of lights on the catch rate of snow crab (Chionoecetes opilio)

This study investigated the effect of installing underwater light-emitting diode (LED) lights in different locations (close and distant to the trap entrance) and orientations (normal and upside down direction) inside baited traps targeting snow crab (Chionoecetes opilio) off the coast of Newfoundland and Labrador, Canada. Four experimental treatments were evaluated in comparison with traditional baited traps (control). Our results showed each of the experimental treatments produced significantly higher (39%–57%; 48% on average) catch per unit effort (CPUE) compared to the control traps, with no significant differences for both legal and sublegal-sized crab among the different experimental treatments. Longer soak times significantly increased the CPUE of the illuminated traps, but did not affect the catch rate of the control traps. Our results also indicated crab size frequency distributions were independent of experiment treatments. Our results suggest that fishing enterprises could improve their catching performance by adding LED lights to their traps, but the location and orientation of the lights appears unimportant.

On the interplay between downwelling, deep convection and mesoscale eddies in the Labrador Sea

In this study, an idealized eddy-resolving model is employed to examine the interplay between the downwelling, ocean convection and mesoscale eddies in the Labrador Sea and the spreading of dense water masses. The model output demonstrates a good agreement with observations with regard to the eddy field and convection characteristics. It also displays a basin mean net downwelling of 3.0 Sv. Our analysis confirms that the downwelling occurs near the west Greenland coast and that the eddies spawned from the boundary current play a major role in controlling the dynamics of the downwelling. The magnitude of the downwelling is positively correlated to the magnitude of the applied surface heat loss. However, we argue that this connection is indirect: the heat fluxes affect the convection properties as well as the eddy field, while the latter governs the Eulerian downwelling. With a passive tracer analysis we show that dense water is transported from the interior towards the boundary, predominantly towards the Labrador coast in shallow layers and towards the Greenland coast in deeper layers. The latter transport is steered by the presence of the eddy field. The outcome that the characteristics of the downwelling in a marginal sea like the Labrador Sea depend crucially on the properties of the eddy field emphasizes that it is essential to resolve the eddies to properly represent the downwelling and overturning in the North Atlantic Ocean, and its response to changing environmental conditions.

The Grenfell Mission and American Support in Newfoundland and Labrador, 1890s–1940s ed. by Jennifer J. Connor and Katherine Side

Reviewed by: The Grenfell Mission and American Support in Newfoundland and Labrador, 1890s–1940s ed. by Jennifer J. Connor and Katherine Side Peter L. Twohig Jennifer J. Connor and Katherine Side, eds. The Grenfell Mission and American Support in Newfoundland and Labrador, 1890s–1940s. McGill-Queen's/Associated Medical Services Studies in the History of Medicine, Health, and Society. Montreal: McGill/Queen's University Press, 2019. xvi + 392 pp. Ill. $34.95 (978-0-7735-5487-0). There are a handful of critical studies, biographies, journal articles, theses, and doctoral dissertations that explore aspects of the Grenfell Mission that brought health, education, and other services to northern Newfoundland and coastal Labrador. So what does an edited collection such as the one curated by Jennifer J. Connor and Katherine Side add to this literature? The short answer is quite a lot. Health and other social services were delivered through a patchwork of arrangements in Newfoundland and Labrador, which was independent of Canada until 1949. Health, education, and social services were all woefully underdeveloped or nonexistent. The Grenfell Mission, which became the International Grenfell Association (IGA) in 1914, stepped into this gap to meet some of the basic needs of the residents. The IGA ran a network of institutions, including hospitals and nursing stations, in northern Newfoundland and along the Labrador coast, encompassing some 1,500 miles (2,400 kilometers) of coastline in a very unforgiving environment. [End Page 624] The book is divided into two parts. The first part has four chapters that explore the political and social context of the IGA and Newfoundland and Labrador. James Hiller, one of Newfoundland's most eminent historians, provides a very cogent chapter on Wilfred Grenfell and Newfoundland that provides essential context for understanding the man and his mission. Hiller describes the IGA as a "colony within a colony" (p. 44) suggesting both the scope of its activities and its distinctive identity in Newfoundland. In her chapter on Grenfell, race, and missions, Jennifer Connor highlights how the IGA was, in the broadest sense, part of a number of social movements that were a response to the problems of uneven economic development, underdeveloped state infrastructure, and a variety of other issues. Ronald Numbers explores the relationship between Grenfell and John Harvey Kellogg, a leading health reformer, both of whom shared an interest in the "gospel of right living" (p. 269). Kellogg, as Numbers noted, existed on the border between reputable and disreputable practice, and Grenfell carefully managed this so as not to disrupt his mission. The fragility of the Grenfell mission is ably illustrated in the chapter by Heidi Coombs-Thorne, who has authored many fine studies of nursing in the IGA. She analyzes how the actions of a single person associated with the mission nearly undid Grenfell's efforts and unraveled the network that he had carefully cultivated for twenty years. The next six chapters explore the work and activities of the mission to varying degrees of success. All of them are interesting in their own ways and reveal a good deal about the scope of the work. There are essays on sports history, clothing distribution, and education, as well as two essays focused on health care. One unusual omission is any consideration of the religious aspect of the "mission," except for several references to "muscular Christianity." This oversight is a significant one, and the collection would have been enriched through the inclusion of such a chapter or encouraging contributors to address this key aspect of the mission's work. This is particularly true when one remembers that the essays are not solely focused on health care but extend into other arenas of activity and also the important place of religion in organizing Newfoundland society in these years. It is an old saw to complain that edited collections are characterized by an uneven quality. I would have liked the chapters to engage more fully with one another and build on one another. For example, Jennifer Connor notes that what distinguished the IGA was its focus "English-speaking, white Anglo-Saxon Protestants" rather than "non-white, non-Christian, Indigenous peoples" (p. 49), a point that Grenfell emphasized in his efforts to secure both funds and...

Postglacial relative sea-level histories along the eastern Canadian coastline

We have assembled a database of Relative Sea Level (RSL) data points from the eastern coast of Canada from Hudson Bay to the border with the USA. In compiling this database we have critically reviewed 1092 radiocarbon dated samples from raised beaches, isolation basins, intertidal and marine deposits, and archaeological indicators to produce 405 sea-level index points and 687 sea-level limiting points. Our comprehensive, systematic, and quality-controlled RSL database allowed for the reconstruction of the postglacial evolution of 34 regions of eastern Canada providing new basin-scale insights into the processes driving RSL changes in the last ∼16 ka. The combination of a database of sea-level index points with an innovative empirical-Bayesian spatio-temporal statistical model provided new insights into rates and magnitude of the spatially-variable glacial isostatic adjustment (GIA), which dominated the postglacial RSL evolution in this sector of North America. A continuous postglacial RSL fall is observed at latitudes ≥ ∼50° N with higher rates (up to 35 mm a−1) recorded in southeastern Hudson Bay. At lower latitudes, the evolution is non-monotonic with RSL that dropped to a spatially variable early-Holocene lowstand, followed by a mid-Holocene highstand and, eventually, a gradual drop to present RSL. This pattern is particularly evident in the St Lawrence corridor. Along the majority of the Newfoundland, New Brunswick and western Nova Scotia coasts, a late-Pleistocene/early-Holocene RSL lowstand was followed by a continuous rise through the Holocene. At the margin of the former ice-sheet (i.e. eastern Nova Scotia), our data identify a continuous RSL rise through the Holocene. These records are characterized by decreasing rates of RSL rise through time, commencing with a rapid rise during the early Holocene (up to ∼17 mm a−1), a slowdown in the mid-Holocene (average rates ≤ ∼9 mm a−1), and a further reduction in the late Holocene (average rates < 2 mm a−1). Finally, our database allowed the identification of regions, including the Labrador coast and part of the St Lawrence corridor, where further investigations are required to better constrain the RSL evolution and improve our ability to assess the variability of RSL histories.

Atlantic and Pacific halibut co‐management initiatives by Canadian fishermen's organizations

AbstractMany fisheries managers and neoliberal fisheries economists promote Individual Transferable Quotas (ITQs) as a solution to the race for fish which can cause rent dissipation under competitive quota or open access fisheries. These actors consider the Canadian Pacific halibut ITQ fishery an example of successful achievement of these objectives. However, critics note the weak performance of this management model in distribution of benefits, increased capital costs to fishermen, deteriorating safety conditions, reductions in crew income and barriers to entry. They point to the layup system which successfully managed effort in the Pacific halibut fishery for four decades prior to the introduction of ITQs. A system similar to the layup has been used for Atlantic halibut since 2013, initiated by the Fish Food and Allied Workers (FFAW) representing owner‐operator license holders in the halibut fishery off the coast of western Newfoundland and southern Labrador. The FFAW rejected the two halibut management plan options presented to them by Fisheries and Oceans Canada: the status quo (a competitive 12‐hr “derby” fishery) or IQs, likely leading to ITQs. Instead, the FFAW worked with license holders to develop a management plan that required harvesters to choose between different fishing periods that spread fishing opportunities over time. This approach improved conservation results, delivered strong economic returns, distributed benefits widely to active fishermen, and allowed an even flow into the market. The authors consider the advantages of these Canadian east and west coast halibut co‐management systems and their broader application.

A Comparison of Numerically Modelled Iceberg Backscatter Signatures with Sentinel-1 C-Band Synthetic Aperture Radar Acquisitions

Use of machine learning to develop algorithms for distinguishing iceberg and vessel targets requires large validated data sets that are often costly, time consuming and, in some cases, inaccessible. Generating electromagnetic (EM) backscatter models of iceberg and ship targets can be a vital step in developing a robust iceberg/ship classification algorithm. In this work, EM backscatter models for icebergs are developed using an EM backscatter modelling tool called GRECOSAR and compared with ground truth data. The imaging scene consists of iceberg targets surrounded by the ocean surface. The 3D computer aided design models of the icebergs were obtained using LiDAR and multi-beam sonar data collected during a field program off the coast of Salvage, Newfoundland and Labrador, Canada. While profiling the iceberg targets, a synthetic aperture radar (SAR) image from Sentinel-1A was captured and compared with the simulated SAR images. Comparisons made in terms of total radar cross section (TRCS) and the SAR signature of the targets generally indicate credible simulations. Simulated SAR images were generated at low and high dielectric conditions to mimic cold and melt iceberg surfaces. Variability of the TRCS and morphology as a function of target orientation highlights the usefulness of EM modelling in developing robust iceberg/ship classifiers.

Meltwater and seasonality influence on Subpolar Gyre circulation during the Holocene

Dinoflagellate cyst assemblages in a marine sediment core from the Iceland Basin were used to carry out qualitative and quantitative assessments of upper ocean conditions in the northern branch of the Subpolar Gyre (SPG) during the Holocene. The data revealed that the early Holocene, i.e. prior to ~6.8 kyr B.P., experienced elevated summer sea surface temperatures (SST). In contrast, winter SST was lower compared to modern conditions. This stronger-than-present seasonality revealed by our data thus shows the influence of the early Holocene insolation forcing. Higher seasonality also dominated the reconstructed sea surface salinity (SSS) in the same period, with lower salinity during both summers and winters. The lower SSS suggests freshwater advection into the SPG, and the dinoflagellate cyst content from this interval indicates a dominant sourcing from the Canadian Labrador coast, and thus the eastern margin of the Laurentide Ice Sheet. Within this interval of low SSS, the onset of the Holocene Climate Optimum stands out by its distinct “marine” assemblage components and associated high summer SST and relative SSS increase between 9.3 and 7.8 kyr B.P. A prominent shift in the overall assemblage composition occurs at ~6.8 kyr B.P., with lower seasonality in sea surface conditions from that time onwards. Increased summer and winter SSS suggest that this change is linked to the halted influence of meltwater from the Laurentide Ice Sheet, a westward shift of the subpolar front and a contracted SPG allowing an easier northward movement of southern-sourced North Atlantic waters, contributing to and consequently sustained by the spin-up of the overturning circulation. The subpolar front appears to gradually have moved slightly eastward again between 2.8 and 1.9 kyr B.P. towards its modern-day position, with a subtle increase of elements characterized by a typical East Greenland Current signature in the Iceland Basin. Finally, spectral analyses indicate that a range of periodicities may be present in the new SSS and SST records, most notably a 2000-yr periodicity in SSS changes, although none of the periodicities are dominant in both records or throughout the time interval covered by the records.

Semiautomated Segmentation of Sentinel-1 SAR Imagery for Mapping Sea Ice in Labrador Coast

This study aims at proposing a semiautomated sea ice segmentation workflow utilizing Sentinel-1 synthetic aperture radar imagery. The workflow consists of two main steps. First, preferable features in sea ice interpretation were determined with a random forest feature selection method. Second, an unsupervised graph-cut image segmentation was performed. The workflow was tested on 13 Sentinel-1A images from January to June 2016, and the results were evaluated on open water segmentation per ice charts provided by Canada Ice Service. The results showed that the proposed workflow was able to segment Sentinel-1 images in to appropriate number of classes, and the potential water identification rate reached 95%.

Mercury distribution and transport in the North Atlantic Ocean along the GEOTRACES-GA01 transect

Abstract. We report here the results of total mercury (HgT) determinations along the 2014 Geotraces Geovide cruise (GA01 transect) in the North Atlantic Ocean (NA) from Lisbon (Portugal) to the coast of Labrador (Canada). HgT concentrations in unfiltered samples (HgTUNF) were log-normally distributed and ranged between 0.16 and 1.54 pmol L−1, with a geometric mean of 0.51 pmol L−1 for the 535 samples analysed. The dissolved fraction (&lt; 0.45 µm) of HgT (HgTF), determined on 141 samples, averaged 78 % of the HgTUNF for the entire data set, 84 % for open seawaters (below 100 m) and 91 % if the Labrador Sea data are excluded, where the primary production was high (with a winter convection down to 1400 m). HgTUNF concentrations increased eastwards and with depth from Greenland to Europe and from subsurface to bottom waters. The HgTUNF concentrations were similarly low in the subpolar gyre waters ( ∼ 0.45 pmol L−1), whereas they exceeded 0.60 pmol L−1 in the subtropical gyre waters. The HgTUNF distribution mirrored that of dissolved oxygen concentration, with highest concentration levels associated with oxygen-depleted zones. The relationship between HgTF and the apparent oxygen utilization confirms the nutrient-like behaviour of Hg in the NA. An extended optimum multiparameter analysis allowed us to characterize HgTUNF concentrations in the different source water types (SWTs) present along the transect. The distribution pattern of HgTUNF, modelled by the mixing of SWTs, show Hg enrichment in Mediterranean waters and North East Atlantic Deep Water and low concentrations in young waters formed in the subpolar gyre and Nordic seas. The change in anthropogenic Hg concentrations in the Labrador Sea Water during its eastward journey suggests a continuous decrease in Hg content in this water mass over the last decades. Calculation of the water transport driven by the Atlantic Meridional Overturning Circulation across the Portugal–Greenland transect indicates northward Hg transport within the upper limb and southward Hg transport within the lower limb, with resulting net northward transport of about 97.2 kmol yr−1.

Mechanisms of interannual- to decadal-scale winter Labrador Sea ice variability

The variability of the winter sea ice cover of the Labrador Sea region and its links to atmospheric and oceanic forcing are investigated using observational data, a coupled ocean–sea ice model and a fully-coupled model simulation drawn from the CMIP5 archive. A consistent series of mechanisms associated with high sea ice cover are found amongst the various data sets. The highest values of sea ice area occur when the northern Labrador Sea is ice covered. This region is found to be primarily thermodynamically forced, contrasting with the dominance of mechanical forcing along the eastern coast of Baffin Island and Labrador, and the growth of sea ice is associated with anomalously fresh local ocean surface conditions. Positive fresh water anomalies are found to propagate to the region from a source area off the southeast Greenland coast with a 1 month transit time. These anomalies are associated with sea ice melt, driven by the enhanced offshore transport of sea ice in the source region, and its subsequent westward transport in the Irminger Current system. By combining sea ice transport through the Denmark Strait in the preceding autumn with the Greenland Blocking Index and the Atlantic Multidecadal Oscillation Index, strong correlation with the Labrador Sea ice area of the following winter is obtained. This relationship represents a dependence on the availability of sea ice to be melted in the source region, the necessary atmospheric forcing to transport this offshore, and a further multidecadal-scale link with the large-scale sea surface temperature conditions.

Comparison of Three Methods for Aging the Iceland Scallop Chlamys islandica

The Gilbert Bay (GB) Marine Protected Area (MPA) on the southeastern coast of Labrador was established in 2005 to protect a resident population of Atlantic cod (Gadus morhua). Commercial dredging for Iceland scallops (Chlamys islandica) in the bay was permitted to continue under MPA regulations, but was excluded from areas of cod spawning. The average size of Iceland scallops harvested in GB is smaller than in the Strait of Belle Isle approximately 150 km to the south. Local fishermen have suggested this is due to slow growth, and this prompted the present study to test the hypothesis that Iceland scallops grow more slowly in GB than in the Strait of Belle Isle. Scallop growth was parameterized as change in shell height with age. Three methods of aging individual scallops were used: interpreting external growth rings on the shell, counting growth increments on the calcareous portion of the shell hinge ligament, and counting internal shell layer growth zones. Counting ligament growth increments and internal shell layer growth zones gave similar estimates of age. In comparison, interpreting external growth rings on the shell underestimated the age of individual scallops. If the ligament method and the internal shell layer method of aging are accurate (scallops of known-age were not examined), scallops in GB require eleven years of growth to recruit to the fishery (attain a shell height of 60 mm). This is substantially longer than the 6-y period estimated using the external growth rings method of aging. Growth rate parameters of Iceland scallops in GB, the Strait of Belle, and in the Nuuk area of West Greenland were found to be similar. The relatively small shell size of scallops presently harvested in GB is not due to anomalous growth, but more likely attributable to repeated dredging of scallop beds in the past and removal of the larger individuals.

Sources, cycling and transfer of mercury in the Labrador Sea (Geotraces-Geovide cruise)

Abstract The Labrador Sea links the Arctic and North Atlantic oceans and constitutes one of the main entrances of atmospheric inputs into the Ocean's interior. We report here the first high-resolution Hg distribution pattern along a transect from Greenland to Labrador coasts sampled after the 2014 winter convection. Total Hg concentrations in unfiltered (HgT UNF ) samples ranged from 0.25 pmol L − 1 to 0.67 pmol L − 1 averaging 0.44 ± 0.10 pmol L − 1 (n = 113, 1σ). Concentrations in filtered samples (HgT F , UNF and exhibited a similar distribution. High HgT UNF concentrations were found (i) in the waters of the Labrador Current, which receive desalted waters from the Canadian Arctic Archipelago, and (ii) in the waters over the Labrador shelf and rise. In the Labrador Sea Waters formed during the 2014 winter convection, HgT UNF concentrations were low (0.38 ± 0.05 pmol L − 1 , n = 23), and increased gradually with depth (up to > 0.5 pmol L − 1 ) in the Northeast Atlantic Deep Waters. HgT F correlates with apparent oxygen utilization implying that atmospheric deposition, biological uptake, and microbial respiration control the Hg distribution in the Labrador Sea. Subtracting the amount of Hg released during organic matter remineralization allows us to identify a Hg and organic matter enriched fraction, which originates from fluvial sources in the Canadian Arctic Archipelago waters. This fraction is transferred southward, in surface waters with the Labrador Current, and at depth with the lower limb of the Atlantic Meridional Overturning Circulation. Climate warming, which will increase the mobilization of Hg from thawing permafrost, would consequently increase the Arctic export of Hg initially associated with organic matter.