Labrador Shelf Research Articles

Seasonal variations of the cold intermediate layer on the Newfoundland and Labrador Shelf

Across the Newfoundland and Labrador (NL) continental shelf, sub-surface temperatures remain below 0°C throughout the summer, when the surface is much warmer. This oceanographic feature is known as a cold intermediate layer (CIL), and its properties are assessed annually in the region to support ocean climate research and fisheries management. Monitoring in this region is either too infrequent or too sparse spatially to provide a detailed picture of sub-annual variations, so the GLORYS12 global ocean reanalysis is used for this purpose. GLORYS12 is shown to reproduce both the signs and magnitudes of inter-annual variations in CIL area on NL Shelf transects, although the magnitude of the seasonal cycle may be under-estimated.GLORYS12 indicates that sub-zero water volume is maximized across the region during March and decreases with time, beginning in the south and proceeding north. CIL minima are reached between November to December at most shelf locations, proceeding in the opposite direction. Stratification triggered by surface freshwater is an important contributor to CIL seasonal changes on all transects on the NL Shelf. While the CIL area tends to gradually erode throughout the summer, the downstream advection of CIL water from more northern transects leads to the development of secondary CIL area maxima during late August to early September on the Newfoundland component of the shelf. Onshore intrusions either at the shelf break or via cross-shelf troughs contribute to the erosion of CIL area from below at some transects, although this effect may be exaggerated in the model.

Autumn Warming of the Cold Intermediate Layer in the Labrador Shelf

Autumn Warming of the Cold Intermediate Layer in the Labrador Shelf

What Drives the Mean Along‐Shelf Flow in the Northwest Atlantic Coastal Ocean?

AbstractA long‐standing hypothesis is that the steady along‐shelf circulation in the Northwest Atlantic (NWA) coastal ocean is driven by buoyancy input from continental freshwater runoff. However, the forcing from the freshwater runoff has not been adequately evaluated and compared with other potential driving mechanisms. This study investigates the roles of both wind stress and freshwater runoff in driving the mean along‐shelf flow in the NWA coastal ocean and examines other potential drivers using a newly developed high‐resolution regional model with realistic forcing conditions. The results reveal that wind stress has a larger impact than freshwater runoff on the overall mean circulation and along‐shelf sea‐level gradient on the NWA shelf. While the continental freshwater input consistently contributes to the equatorward along‐shelf flow and higher sea level along the coast, wind stress is more effective for the setup of the broad‐scale circulation pattern by driving the along‐shelf flow on the Labrador Shelf and opposing the flow in the Mid‐Atlantic Bight and on the Scotian Shelf. In addition to the local wind and continental runoff, the sub‐Arctic inflow from higher latitude is an essential part of the NWA shelf circulation system. This remote driver directly contributes to the along‐shelf flow and insulates the shelf flow from the Gulf Stream on the southern shelves.

Labrador Coastal Current and productivity variations offshore Nain (Nunatsiavut) during the late Holocene

The Labrador Coastal Current (LCC) transports cold and fresh waters of Arctic origin towards the North Atlantic and has a strong influence on the coastal ecosystems and climate of eastern Canada. Here, we present a multi-decadally resolved record of changes in sea-surface and near-bottom conditions of the LCC during the last 3000 years based on the analysis of biogenic tracers (organic-walled dinoflagellate cysts, carbon, and nitrogen geochemistry) and sedimentary content (sortable silt, magnetic susceptibility, elemental ratios) in the upper 2 m of sediments in a core retrieved offshore Nain, Nunatsiavut. Our data reveal multi-centennial bottom flow strength variability in the LCC, with strong linkages to changes in regional ocean circulation patterns. At about 2100- and 550-years BP, the sedimentological and biogenic tracer data suggest changes in the LCC bottom current intensity (decline and strengthening, respectively) that coincide with shifts in the persistent mode of the North Atlantic Oscillation. Our proxy data suggests increased biological production during the last 500 years compared to the preceding 2500 years, possibly reflecting a gradual decrease length of the sea-ice season. The data show a decline in the LCC strength during periods of increased polar water influence identified in previous palaeoceanographic studies conducted further north, which may be attributed to the trapping of freshwater in sea ice during these periods. Our results highlight the dynamical oceanographic and atmospheric factors that influence the LCC and the coastal ecosystems along its path and confirm that the processes in Baffin Bay impact the Labrador Shelf oceanography.

Geomorphological analysis of grounding-zone wedges reveals glacial retreat processes on the Labrador Shelf

Newly acquired high-resolution geophysical data from four glacial cross-shelf troughs of the Labrador Shelf, namely the Okak, Hopedale, Makkovik and Cartwright troughs, are presented in this study. These cross-shelf troughs were repeatedly excavated by the former Laurentide Ice Sheet (LIS) during past glaciations. We map and describe three previously unknown grounding-zone wedges (GZWs) from an area where only sparse information about the retreat of the LIS is available. Based on our geomorphological analysis, we derive the dynamics and the direction of the ice retreat. For the Okak, Makkovik, and Cartwright troughs, the newly identified GZWs indicate fast-flowing ice streams with a high sediment load. We propose that a stable ice grounding-zone paralleled the present-day coastline in the Okak and Makkovik troughs, while in the Cartwright Trough, an ice-margin retreat towards the outlet of Lake Melville is more likely. We date available sediment samples of the deposits that onlap one of the GZWs to 14.5 ka cal BP and can show that the discovered GZWs must be older. This new information updates our understanding of the dynamics of the LIS, particularly at its eastern boundary, the Labrador Shelf and Sea, which is important to better reconstruct the effects of the LIS dynamics on global ocean currents and climate.

Protected and conserved coastal areas in Canada: insights with respect to Target 3 of the Kunming-Montreal Global Biodiversity Framework

Despite coastal area being recognised as an important subcomponent in protected and conserved areas targets for over a decade, it has been orphaned in both national and international reporting. In this paper, we provide the first progress report on protected and conserved coastal area in Canada. While 13.6 per cent of Canada’s coastal area is protected and conserved, there is substantial variation across Canada’s three oceans and Great Lakes, jurisdictional authorities, and marine/terrestrial ecosystems. Importantly, Manitoba (37.3 per cent) and the Yukon (45.1 per cent) have already achieved the 30 per cent coastal protection target of the Kunming-Montreal Global Biodiversity Framework (KM-GBF). However, Newfoundland and Labrador (7 per cent) and the Northwest Territories (8 per cent) currently fall significantly short. Very poor protection is evident in several marine bioregions and terrestrial ecozones, including across the Arctic, the Newfoundland and Labrador Shelves (0.7 per cent) and the Hudson Bay Complex (5.1 per cent). The Great Lakes require urgent and focused conservation attention, with lakes Ontario (3.6 per cent) and Erie (3.7 per cent) exhibiting a dismal amount of coastal protected and conserved area. Our results highlight the importance of explicitly reporting on the status of coastal area protection and we outline several considerations that can be used by the global conservation community to support more effective coastal protection, accounting and reporting vis-à-vis Target 3 of the KM-GBF

Trends in larval densities, spawning timing, and site quality of capelin (Mallotus villosus) across bays and habitats in Newfoundland, Canada

Abstract Capelin is a short-lived forage fish species that underwent a population collapse in 1991 on the Newfoundland and Labrador Shelf, Canada (Northwest Atlantic Fisheries Organization Divisions 2J3KL) and has not recovered. The collapsed stock is characterized by delayed spawning timing and low recruitment. As year-class strength is set early in life, long-term larval monitoring at an intertidal spawning site in Trinity Bay (TB) is used as a proxy for stock-wide recruitment. Capelin spawn at both intertidal and subtidal habitats; however, there is minimal larval information from bays with a high incidence of subtidal spawning. We aimed to (i) compare inter-annual trends in temperatures, timing of spawning, and annual larval densities between two northeastern bays [TB and Notre Dame Bay (NDB)] and (ii) compare habitat quality metrics and larval densities between subtidal and intertidal sites in NDB. The date of first spawning in TB and NDB was positively correlated, suggesting that years with delayed spawning are experienced shelf-wide. While larval density was lower in NDB compared to TB, inter-annual trends were similar. In NDB, larval densities at both intertidal and subtidal spawning habitats were similar within a year, but temperatures and the proportion of dead eggs were lower at subtidal sites. These habitat quality metrics, however, were not related to annual larval density. These findings improve our knowledge on sources of capelin productivity, including the potential importance of subtidal spawning to recruitment dynamics.

Biomarker Records of Environmental Shifts on the Labrador Shelf During the Holocene

AbstractThe ultimate demise of the Laurentide Ice Sheet (LIS) and the preceding and succeeding oceanographic changes along the western Labrador Sea offer insights critically important to improve climate predictions of expected future climate warming and further melting of the Greenland ice cap. However, while the final disappearance of the LIS during the Holocene is rather well constrained, the response of sea ice during the resulting meltwater events is not fully understood. Here, we present reconstructions of paleoceanographic changes over the past 9.3 Kyr BP on the northwestern Labrador Shelf, with a special focus on the interaction between the final meltwater event around 8.2 Kyr BP and sea ice and phytoplankton productivity (e.g., IP25, HBI III (Z), brassicasterol, dinosterol, biogenic opal, total organic carbon). Our records indicate low sea‐ice cover and high phytoplankton productivity on the Labrador Shelf prior to 8.9 Kyr BP, sea‐ice formation was favored by decreased surface salinities due to the meltwater events from Lake Agassiz‐Ojibway and the Hudson Bay Ice Saddle from 8.55 Kyr BP onwards. For the past ca. 7.5 Kyr BP sea ice is mainly transported to the study area by local ocean currents such as the inner Labrador and Baffin Current. Our findings provide new insights into the response of sea ice to increased meltwater discharge as well as shifts in atmospheric and oceanic circulation.

Physical controls and ecological implications of the timing of the spring phytoplankton bloom on the Newfoundland and Labrador shelf

AbstractThe timing of spring phytoplankton blooms is crucial to many species that have adapted their development to benefit from the enhanced feeding opportunity they offer. Any change to their timing may affect the productivity of an entire ecosystem. This study explores the relationship between the ocean climate, the timing of the spring bloom and the secondary production on the Newfoundland and Labrador shelf. It is found that over interannual cycles, the ocean climate is significantly correlated with the timing of the bloom and the abundance of Calanus finmarchicus, a key zooplankton species for the ecosystem. It also appears that the spring bloom is initiated by the onset of ocean re‐stratification following winter mixing. Understanding how annual variation in climate relates to the timing of the spring bloom and zooplankton abundance, that is, the base of the marine food web, can inform the development of ecosystem‐informed models for higher trophic levels.

Climatology of Transport in the Strait of Belle Isle

AbstractThe Strait of Belle Isle (SBI) is an important pathway for water mass exchanges between the Labrador Shelf and the Gulf of St. Lawrence (GSL), particularly for transport toward the GSL. Seasonal and inter‐annual variability of transport in the SBI are examined using 15 years of moored acoustic Doppler current profiler data. Tidal currents are largely along strait and homogeneous with depth. Transports are toward the GSL on average, lowest (−1.0 ± 0.8 dSv) from April to July, and highest (−4.0 ± 1.1 dSv) from September to January. Averaged seasonal transports are usually within one standard deviation of previously published modeled values. The volume of winter Labrador Shelf water (LShW) entering the GSL is computed by transport integration and compares well with integrated volumes that meet LShW temperature‐salinity criteria during an annual March survey of the GSL. Integrating over the whole year showed that on average 649 ± 397 km3 enters the GSL after the March surveys are conducted, independently of the volume that has entered up to March; this addition represents on average about a third of the total volume. Annual volumes of LShW calculated from transport suggest that flow through the SBI accounts for 12%–18% of the GSL winter surface mixed layer. Cross‐strait current shear may affect transport integration values, but sea surface temperature data suggests this bias is limited to the summer. Corrections are empirically derived to account for cross‐strait shear in our transport calculation. The corrected time series suggests that the average transport may be flowing toward the Labrador Shelf in July (0.6 ± 1.0 CI [0.1 1.1] dSv).

Behavioural flexibility in an Arctic seabird using two distinct marine habitats to survive the energetic constraints of winter

BackgroundHomeothermic marine animals in Polar Regions face an energetic bottleneck in winter. The challenges of short days and cold temperatures are exacerbated for flying seabirds with small body size and limited fat stores. We use biologging approaches to examine how habitat, weather, and moon illumination influence behaviour and energetics of a marine bird species, thick-billed murres (Uria lomvia).MethodsWe used temperature-depth-light recorders to examine strategies murres use to survive winter in the Northwest Atlantic, where contrasting currents create two distinct marine habitats: cold (−0.1 ± 1.2 °C), shallower water along the Labrador Shelf and warmer (3.1 ± 0.3 °C), deep water in the Labrador Basin.ResultsIn the cold shelf water, murres used a high-energy strategy, with more flying and less diving each day, resulting in high daily energy expenditure and also high apparent energy intake; this strategy was most evident in early winter when day lengths were shortest. By contrast, murres in warmer basin water employed a low-energy strategy, with less time flying and more time diving under low light conditions (nautical twilight and night). In warmer basin water, murres increased diving at night when the moon was more illuminated, likely taking advantage of diel vertically migrating prey. In warmer basin water, murres dove more at night and foraging efficiency increased under negative North Atlantic Oscillation (calmer ocean conditions).ConclusionsThe proximity of two distinct marine habitats in this region allows individuals from a single species to use dual (low-energy/high-energy) strategies to overcome winter energy bottlenecks.

Sea surface salinity variability in the western subpolar North Atlantic based on satellite observations

Sea surface salinity (SSS) variability during the recent decade in the western subpolar North Atlantic is investigated using three satellite salinity products, Aquarius, SMAP and SMOS, as well as in-situ observations. Satellite datasets successfully resolve the large scale SSS pattern but are significantly biased near the western boundary regions. Freshwater flux induced by sea ice formation/melting plays a dominant role in shaping the SSS annual cycle in the coastal regions of the western Labrador Sea, but data gaps and uncertainties prevent satellite products from accurately resolving the seasonality in the Labrador Shelf. On the other hand, seasonal fluctuations near the Grand Banks are reasonably captured in satellite data. They are essentially driven by both local freshwater flux associated with ice and advective signals from the north. The interannual variability of SSS is detectable in both in-situ observations and Aquarius. During the low salinity period in 2011–2012, interannual anomalies are no longer controlled by ice formation/melting. Instead, they are mostly determined by oceanic advection, which moves low salinity water around the Labrador Sea in a cyclonic direction. In addition, the Data Interpolating Empirical Orthogonal Function (DINEOF) is applied to satellite datasets to weed out noise and fill data gaps. The resulting reconstructed datasets show apparent bias reduction and better performances in depicting seasonal cycles in both coastal region and deep ocean. DINEOF does not improve the capability of SMAP and SMOS in resolving the interannual anomalies as their original fields do not include such signals.

Spatial variation in food web structure in a recovering marine ecosystem.

Spatial heterogeneity in food web structure and interactions may reconcile spatial variation in population and community dynamics in large marine ecosystems. In order to assess food web contributions to the different community recovery dynamics along the Newfoundland and Labrador shelf ecosystem, we quantified species interactions using stable isotope mixing models and food web metrics within three sub-regions. Representative samples of each species caught in trawls and plankton tows were analyzed for stomach contents and stable isotope ratios (δ15N and δ13C) to parameterize isotope mixing models. Regional variation, highlighted by the diets of three economically important species, was observed such that the southern region demonstrated a variety of trophic pathways of nutrient flow into the higher food web while the diets of fish in the northern regions were typically dominated by one or two pathways via dominant prey species, specifically shrimp (Pandalus sp.) and hyperiids. Food web metrics indicated that the low-diversity northern regions had higher connectance and shorter food chain lengths. This observed regional variation contributes to our understanding of the role of specific forage species to the ecosystem which is an essential contribution towards ecosystem-based management decisions.

A climate index for the Newfoundland and Labrador shelf

Abstract. This study presents in detail a new climate index for the Newfoundland and Labrador (NL) shelf. The NL climate index (NLCI) aims to describe the environmental conditions on the NL shelf and in the Northwest Atlantic as a whole. It consists of the average of 10 normalized anomalies, or subindices, derived annually: winter North Atlantic Oscillation, air temperature, sea ice season severity, iceberg count, seasonal sea surface temperature, vertically averaged temperature and salinity at the Atlantic Zone Monitoring Program (AZMP) Station 27, summer cold intermediate layer (CIL) core temperature at AZMP Station 27, summer CIL area on three AZMP hydrographic sections, and bottom temperature on the NL shelf. This index runs from 1951 to 2020 and will be updated annually. It provides continuity in the production of advice for fisheries management and ecosystem status on the NL shelf, for which a similar but recently abandoned index was used. The new climate index and its subindices are available at https://doi.org/10.20383/101.0301 (Cyr and Galbraith, 2020).

Climate‐Modulated Nutrient Conditions Along the Labrador Shelf: Evidence From Nitrogen Isotopes in a Six‐Hundred‐Year‐Old Crustose Coralline Alga

AbstractThe impacts of climate change on north Atlantic nutrient chemistry remain poorly understood, as there exist a multitude of rapidly changing biological and physical drivers of nutrient conditions throughout the region. Here, we present nitrogen isotope measurements derived from a six‐hundred‐year‐old crustose coralline alga (δ15Nalgal) to elucidate historical and contemporary trends in nitrate utilization and circulation patterns along the Labrador Shelf. Prior to the early 1900s, we argue that intervals during which utilization approached completion were controlled by reduced nitrate advection linked to an increased proportion of nitrate‐poor polar waters and subdued Atlantic influence, as expected from concurrent negative modes of the Atlantic multidecadal oscillation. While nitrate conditions should have recovered in recent years, our record suggests that high utilization persisted since ∼1870, which we also attribute to reduced Atlantic advection, likely associated with the twentieth‐century anthropogenic weakening of the Atlantic meridional overturning circulation. These results highlight the role of ongoing climate‐induced circulation changes in modulating nutrient distributions throughout the subpolar north Atlantic, which may have implications for other environmental phenomena such as fisheries and oceanic carbon storage.

Transport of fine-grained sediment in oceanic currents: Holocene supply to sediment drifts around Flemish Cap by the Labrador Current

Hemipelagic sediment on the upper continental slope is commonly transported from the adjacent continental shelf, but along-slope transport of sediment by thermohaline currents may be an important source of sediment. One such case is Flemish Cap, a promontory of the eastern Canadian continental shelf protected from direct continental sediment supply by the deep-water Flemish Pass. Pleistocene sediment drifts around Flemish Cap accumulated glacially derived sediment from the north, transported by the Labrador Current. This study determines the changing sources and controls on the accumulation of bioturbated hemipelagic sediment through the Holocene. From a set of >150 box cores in water depths of 600–1200 m, some 30 push cores, up to 55 cm long, were studied in detail for stratigraphic variation in grain size, bulk geochemistry (XRF) and detrital petrology (granule petrology and qXRD). Criteria were developed to identify trawling disturbance. Two Holocene stratigraphic units, A) almost lacking ice-rafted detritus and B) with some coarse IRD and higher detrital carbonate, correlate with similar units farther north on the Labrador Shelf and Slope. Sedimentation rates based on 26 radiocarbon dates were ~ 0.02–0.03 m/ka over much of the region below the 800 m isobath, locally reaching 0.1 m/ka in some sediment drifts, but as low as 0.01 m/ka on southeastern Flemish Cap. Where sedimentation rate was >0.03 m/ka, the record of flow vigor from the sortable silt proxy since 6 ka shows three different zones of Labrador Current flow with different timing of changes in flow vigor. The mid to early Holocene record shows that the meltwater-driven inner Labrador Current extended across the entire study area. Where sedimentation rates are lower, periods of sediment bypassing are inferred and the sortable silt record varies little. Correlation with external drivers is hampered by century-scale core resolution and sparse dating control. The distinctive abundance of dolomite rock flour in hemipelagic sediments around Flemish Cap indicates important supply from Baffin Bay icebergs during the entire Holocene, diluted prior to 6 ka by sediment from Hudson Strait and some Labrador ice streams. Baffin Bay icebergs melt preferentially in the southern Labrador Sea, dropping their load, with the fine grained component transported to the south by the Labrador Current. Similar partitioning of coarse- from fine-grained components of IRD may take place on other high-latitude outer continental margins.

Surface and subsurface Labrador Shelf water mass conditions during the last 6000 years

Abstract. The Labrador Sea is important for the modern global thermohaline circulation system through the formation of intermediate Labrador Sea Water (LSW) that has been hypothesized to stabilize the modern mode of North Atlantic deep-water circulation. The rate of LSW formation is controlled by the amount of winter heat loss to the atmosphere, the expanse of freshwater in the convection region and the inflow of saline waters from the Atlantic. The Labrador Sea, today, receives freshwater through the East and West Greenland currents (EGC, WGC) and the Labrador Current (LC). Several studies have suggested the WGC to be the main supplier of freshwater to the Labrador Sea, but the role of the southward flowing LC in Labrador Sea convection is still debated. At the same time, many paleoceanographic reconstructions from the Labrador Shelf focussed on late deglacial to early Holocene meltwater run-off from the Laurentide Ice Sheet (LIS), whereas little information exists about LC variability since the final melting of the LIS about 7000 years ago. In order to enable better assessment of the role of the LC in deep-water formation and its importance for Holocene climate variability in Atlantic Canada, this study presents high-resolution middle to late Holocene records of sea surface and bottom water temperatures, freshening, and sea ice cover on the Labrador Shelf during the last 6000 years. Our records reveal that the LC underwent three major oceanographic phases from the mid- to late Holocene. From 6.2 to 5.6 ka, the LC experienced a cold episode that was followed by warmer conditions between 5.6 and 2.1 ka, possibly associated with the late Holocene thermal maximum. While surface waters on the Labrador Shelf cooled gradually after 3 ka in response to the neoglaciation, Labrador Shelf subsurface or bottom waters show a shift to warmer temperatures after 2.1 ka. Although such an inverse stratification by cooling of surface and warming of subsurface waters on the Labrador Shelf would suggest a diminished convection during the last 2 millennia compared to the mid-Holocene, it remains difficult to assess whether hydrographic conditions in the LC have had a significant impact on Labrador Sea deep-water formation.

Arctic Ocean and Hudson Bay Freshwater Exports: New Estimates from Seven Decades of Hydrographic Surveys on the Labrador Shelf

AbstractWhile reasonable knowledge of multidecadal Arctic freshwater storage variability exists, we have little knowledge of Arctic freshwater exports on similar time scales. A hydrographic time series from the Labrador Shelf, spanning seven decades at annual resolution, is here used to quantify Arctic Ocean freshwater export variability west of Greenland. Output from a high-resolution coupled ice–ocean model is used to establish the representativeness of those hydrographic sections. Clear annual to decadal variability emerges, with high freshwater transports during the 1950s and 1970s–80s, and low transports in the 1960s and from the mid-1990s to 2016, with typical amplitudes of 30 mSv (1 Sv = 106m3s−1). The variability in both the transports and cumulative volumes correlates well both with Arctic and North Atlantic freshwater storage changes on the same time scale. We refer to the “inshore branch” of the Labrador Current as the Labrador Coastal Current, because it is a dynamically and geographically distinct feature. It originates as the Hudson Bay outflow, and preserves variability from river runoff into the Hudson Bay catchment. We find a need for parallel, long-term freshwater transport measurements from Fram and Davis Straits to better understand Arctic freshwater export control mechanisms and partitioning of variability between routes west and east of Greenland, and a need for better knowledge and understanding of year-round (solid and liquid) freshwater fluxes on the Labrador shelf. Our results have implications for wider, coherent atmospheric control on freshwater fluxes and content across the Arctic Ocean and northern North Atlantic Ocean.

Capelin (Mallotus villosus) availability influences the inshore summer diet of Atlantic cod (Gadus morhua) in coastal Newfoundland

In the early 1990s, the Atlantic cod (Gadusmorhua) population on the Newfoundland and Labrador shelf declined dramatically, leading to a fishing moratorium in 1992. The Northern cod population has not fully recovered, possibly due to the simultaneous population collapse of an important prey type, capelin (Mallotus villosus), which migrates from the continental shelf into coastal Newfoundland to spawn every summer. Our objective was to test whether capelin availability influenced short-term dietary shifts of cod while inshore on the northeast Newfoundland coast. We quantify the dietary composition and relative abundance and biomass of prey types in cod stomachs sampled weekly or bi-weekly throughout July-August 2017 and 2018. Survey-based acoustic estimates of capelin biomass and the timing of spawning in the study area revealed that peak capelin biomass was five times higher (0.239 g/m²) and two weeks earlier (July 28) during 2018 relative to 2017 (0.048 g/m², August 9). Cod stomachs were ~ 10 times more likely to contain capelin during 2018 relative to 2017. As capelin availability increased throughout each summer, cod shifted from a high diversity diet of lower-quality invertebrate prey (e.g., shrimp, crab) to a low diversity, capelin-dominated diet, whereby capelin presence, abundance and biomass increased. These findings indicate that capelin remains a primary prey type of cod in inshore waters during their summer growing season, but dietary proportions of capelin vary with their availability. As low dietary proportions of capelin are associated with reduced body condition and reproductive potential in cod, findings support the need for an integrated capelin-cod management approach.

Definition of the Churchill River Delta and its petroleum potential, offshore Labrador, Canada

Starting in 2011, a multiyear modern 2D long offset broadband seismic survey was acquired offshore Labrador, Canada, by TGS and PGS in partnership with Nalcor Energy. This regional survey covers the slope and deepwater portions of the margin. Three Mesozoic and Cenozoic-aged basins were informally defined from these data, the Chidley, Henley, and Holton; also, the poorly constrained Hawke Basin was remapped. The 2D data set imaged for the first time a very large Cenozoic-aged delta adjacent to the mouth of Lake Melville. We have mapped this delta on a [Formula: see text] 2D seismic grid. The delta is 5–8 km thick, and its aerial extent is [Formula: see text]. The age of this delta has been interpreted to be Eocene to Miocene. Adjacent to this Cenozoic delta on the Labrador shelf, there is a working petroleum system within the proximal Hopedale and Saglek Basins where there are five gas discoveries and one oil discovery. The modern long-offset 2D data set appears to indicate a working petroleum system within the newly mapped Cenozoic delta, and two phases of hydrocarbons may be present.