Flemish Cap Research Articles

Variability of Labrador Sea Water transported through Flemish Pass during 1993–2013

AbstractFlemish Pass, located at the western subpolar margin, is a passage (sill depth 1200 m) that is constrained by the Grand Banks and the underwater plateau Flemish Cap. In addition to the Deep Western Boundary Current (DWBC) pathway offshore of Flemish Cap, Flemish Pass represents another southward transport pathway for two modes of Labrador Sea Water (LSW), the lightest component of North Atlantic Deep Water carried with the DWBC. This pathway avoids potential stirring regions east of Flemish Cap and deflection into the interior North Atlantic. Ship‐based velocity measurements between 2009 and 2013 at 47°N in Flemish Pass and in the DWBC east of Flemish Cap revealed a considerable southward transport of Upper LSW through Flemish Pass (15–27%, −1.0 to −1.5 Sv). About 98% of the denser Deep LSW were carried around Flemish Cap as Flemish Pass is too shallow for considerable transport of Deep LSW. Hydrographic time series from ship‐based measurements show a significant warming of 0.3°C/decade and a salinification of 0.03/decade of the Upper LSW in Flemish Pass between 1993 and 2013. Almost identical trends were found for the evolution in the Labrador Sea and in the DWBC east of Flemish Cap. This indicates that the long‐term hydrographic variability of Upper LSW in Flemish Pass as well as in the DWBC at 47°N is dominated by changes in the Labrador Sea, which are advected southward. Fifty years of numerical ocean model simulations in Flemish Pass suggest that these trends are part of a multidecadal cycle.

Structure of thinned continental crust across the Orphan Basin from a dense wide-angle seismic profile and gravity data

We present a 500-km long, 2-D P-wave velocity model across the Orphan Basin, offshore NE Newfoundland, Canada, from Flemish Cap to the Bonavista Platform, formed using refraction and wide-angle reflection data from 89 ocean-bottom seismometers. This layered model builds on a recent traveltime tomography result using additional constraints from coincident multichannel seismic reflection and gravity data plus borehole logs from three wells. The model shows (i) post-rift Tertiary (velocities ∼1.7–3.5 km s−1) and (ii) both post-rift and syn-rift, Cretaceous and Jurassic sediments (∼4–5 km s−1), deposited within an eastern and a western sub-basin that are separated by a major basement block. The existence of Jurassic sediments indicates a pre-Cretaceous rifting phase in the eastern sub-basin, and possibly in the western sub-basin. However, there is no evidence that Triassic sediments are widespread across the Orphan Basin. Two upper crustal sublayers and one lower crustal layer are defined by differences in velocities (5.4–6.1, 6.1–6.5 and 6.3–7.1 km s−1, respectively) and vertical velocity gradients (mean = 0.14, 0.10 and 0.05 s−1, respectively). Crustal thinning is asymmetric across the Orphan Basin. Within the eastern sub-basin, continental crust beneath Flemish Cap (∼32 km thick; β ∼ 1.1) thins westward into a 35-km-wide zone of hyperextended crust (<10 km thick; β > 3.4) beneath an 11-km-deep sedimentary basin. Within the western sub-basin, the Bonavista Platform crust (∼32 km thick) thins eastward into a 116-km-wide zone of hyperextended crust. Two zones of thicker crust (β = 2–3.5) exist within the central section, with muted topography within the eastern part and large basement highs in the western part, separated by the eastward dipping White Sail Fault (WSF). The zone to the east of the WSF displays higher velocities in the lower crust than to the west. This can only be explained by a lateral ductile flow across the zone boundary. By combining the two upper crustal sublayers into one, we define the full crustal thicknesses of the upper and lower crusts as 12 and 22 km, respectively. The extension and thinning factors of these two layers are calculated across the basin. Discrepancies between upper crustal thinning and lower crustal thinning are common but only produce a small mass deficit (∼7 per cent or 1.5 km) in the lower crust. Structural connections are shown between the Rockall Trough and the West Orphan Basin and between the Porcupine Basin and the East Orphan Basin in that a wider hyperextended western basin is paired with a narrower eastern basin by a middle zone of thicker crust. In contrast to the Rockall Trough and the Porcupine Basin, serpentinized mantle is not observed in the East Orphan Basin where hyperextended crust is observed (βmax ∼ 8.5). One possible cause is that the restricted size of the basin and its location adjacent to Flemish Cap may have permitted a heavier supply of sediment to cover the basement early during its extension. Such a cover would inhibit the flow of water into the crust and thus leave the mantle unchanged.

Detrital zircon geochronology of the Cretaceous succession from the Iberian Atlantic Margin: palaeogeographic implications

Detrital zircon U–Pb data performed on eight Cretaceous sandstone samples (819 age isotopic results) from the Lusitanian basin (west Portugal) constrain the history of uplift and palaeodrainage of western Iberia following break-up of Pangaea and opening of the North Atlantic Ocean. We examined the links between shifts in provenance and known basinwide unconformities dated to the late Berriasian, Barremian, late Aptian and Cenomanian–Turonian. The detrital zircon record of sedimentary rocks with wider supplying areas is relatively homogenous, being characterized by a clear predominance of late Palaeozoic ages (c. 375–275 Ma) together with variable proportions of ages in the range c. 800–460 Ma. These two groups of ages are diagnostic of sources within the Variscan Iberian Massif. A few samples also reveal significant amounts of middle Palaeozoic (c. 420–385 Ma) and late Mesoproterozoic to early Neoproterozoic (c. 1.2–0.9 Ga) zircon, which are almost absent in the basement to the east of the Lusitanian basin, but are common in terranes with a Laurussia affinity found in NW Iberia and the conjugate margin (Newfoundland). The Barremian unconformity marks a sudden rise in the proportion of c. 375–275 Ma zircon ages accompanied by a decrease in the abundance of the c. 420–385 Ma and c. 1.2–0.9 Ga ages. This shift in the zircon signature, which is contemporaneous with the separation of the Galicia Bank from Flemish Cap, reflects increased denudation of Variscan crystalline rocks and a reduction in source material from NW Iberia and adjoining areas. The late Aptian unconformity, which represents the largest hiatus in the sedimentary record, is reflected by a shift in late Palaeozoic peak ages from c. 330–310 Ma (widespread in Iberia) to c. 310–290 Ma (more frequent in N Iberia). It is considered that this shift in the age spectra resulted from a westward migration of catchment areas following major uplift in northern Iberia and some transport southward from the Bay of Biscay under the influence of a well-established Atlantic circulation.

Interannual transport variability of Upper Labrador Sea Water at Flemish Cap

The transport of Upper Labrador Sea Water (ULSW) at Flemish Cap (47°N/45°W) is investigated in the period 1960–2009 using the output from an 8 km resolution numerical ocean model. The average model transport of ULSW decreases southward from 6.7 Sv at 53°N to 4.5 Sv at 45°N due to interior pathways. The largest fraction of the total ULSW volume transport goes around Flemish Cap within the Deep Western Boundary Current (DWBC, 72%) but a significant part goes through Flemish Pass (20%). At interannual timescales, the variability at Flemish Pass shows a distinct behavior when compared to the variability in the DWBC and to the upstream fluctuations. A running correlation method is applied to obtain the connection of the transport variability at Flemish Pass with several quantities, representative for different physical mechanisms: (1) the North Atlantic Oscillation index, (2) the Ekman transport, (3) the rate of ULSW formation in the Labrador Sea, (4) the position of the North Atlantic Current (NAC) relative to the slope and (5) the averaged transport in the subpolar gyre. Weakened or strengthened transport of ULSW through Flemish Pass coincides with changes of the atmospheric forcing or with changes of the NAC‘s position. Strong meandering of the NAC close to the DWBC reduces the transport off Flemish Cap, and the ULSW flow is “redirected” into the Flemish Pass, enhancing the transport there. In contrast, the transport variability in the DWBC is mainly caused by upstream fluctuations and changes according to the rate of ULSW formation.

Statistical Projections of Ocean Climate Indices off Newfoundland and Labrador

ABSTRACTPresent global climate models (GCMs) are unable to provide reliable projections of physical oceanographic properties on the continental shelf off Newfoundland and Labrador. Here we first establish linear statistical relationships between oceanographic properties and coastal air temperature based on historical observations. We then use these relationships to project future states of oceanographic conditions under different emission scenarios, based on projected coastal air temperatures from global (Canadian Earth System Model, version 2 (CanESM2), Geophysical Fluid Dynamics Laboratory's Earth System Model, version 2M (GFDL-ESM2M)) and regional (Canadian Regional Climate Model (CRCM)) climate models. Estimates based on CanESM2 agree reasonably well with observed trends, but the trends based on two other models result in substantial underestimates. Projected trends are closer to observations under a high emission scenario than under median-level emission scenarios. Over the next 50 years, the increases in projected sea surface temperature off eastern Newfoundland (Station 27) range from 0.4° to 2.2°C. The increases in bottom ocean temperature over the Newfoundland and Labrador Shelves range from 0.4° to 2.1°C. The area of the cold intermediate layer (<0°C) on the Flemish Cap (47°N) section is projected to decrease by 9–35% of the 1981–2010 average. The decline in sea-ice extent off Newfoundland and Labrador ranges from 20 to 77% of the average (0.4–1.5 × 105 km2), and the reduction in the number of icebergs at 48°N off Newfoundland ranges from 30% to nearly 100% of the norm at this latitude. Despite differences among the models and scenarios, statistical projections indicate that conditions in this region will reach or exceed their maxima (sea surface temperature, bottom ocean temperature) and reach or fall below their minima (sea-ice extent, number of icebergs) that were observed during the course of monitoring activities over the past 30–60 years, possibly as early as 2040. We note, however, that the statistical relationships based on historical data may not hold in the future because of the changing influence of input from Arctic waters and because of large uncertainties in projected air temperatures from GCMs.

Microstructure of the otoliths of the glacier lanternfish, Benthosema glaciale

Ageing using otolith microstructure is based on the assumption that growth increments are deposited daily. Individuals of the glacier lanternfish (Benthosema glaciale) were collected in the Flemish Cap (north-west Atlantic) during June–July 2010. A total of 44 individuals (ranging from 28 to 49mm standard length; &lt;2 years old) were selected to analyse otolith microstructure using light microscopy in order to assess the reliability of the use of microincrements to infer the true age of this species. Three distinct zones were distinguished: the larval zone, the postlarval zone and the postmetamorphic zone. The otolith core was, on average, 8±0.7μm. The mean microincrement number in the larval zone was 42±7.5 within a radius of 0.095±0.010mm whereas in the postlarval zone it was 25±3.0 within a segment of 0.104±0.015mm. SEM examinations in a subsample of otoliths showed that the resolution power of the light microscope was sufficient to study both the larval and the postlarval zones. Back-calculation from the time of capture suggests a hatching period from mid-June to mid-December with a peak in September. The spawning time and daily deposition of the microincrements in B. glaciale are discussed.

Circulation and transports in the Newfoundland Basin, western subpolar North Atlantic

The southwestern part of the subpolar North Atlantic east of the Grand Banks of Newfoundland and Flemish Cap is a crucial area for the Atlantic Meridional Overturning Circulation. Here the exchange between subpolar and subtropical gyre takes place, southward flowing cold and fresh water is replaced by northward flowing warm and salty water within the North Atlantic Current (NAC). As part of a long-term experiment, the circulation east of Flemish Cap has been studied by seven repeat hydrographic sections along 47 degrees N (2003-2011), a 2 year time series of current velocities at the continental slope (2009-2011), 19 years of sea surface height, and 47 years of output from an eddy resolving ocean circulation model. The structure of the flow field in the measurements and the model shows a deep reaching NAC with adjacent recirculation and two distinct cores of southward flow in the Deep Western Boundary Current (DWBC): one core above the continental slope with maximum velocities at mid-depth and the second farther east with bottom-intensified velocities. The western core of the DWBC is rather stable, while the offshore core shows high temporal variability that in the model is correlated with the NAC strength. About 30 Sv of deep water flow southward below a density of sigma=27.68 kg m(-3) in the DWBC. The NAC transports about 110 Sv northward, approximately 15 Sv originating from the DWBC, and 75 Sv recirculating locally east of the NAC, leaving 20 Sv to be supplied by the NAC from the south.

Age-based demography of the glacier lanternfish (Benthosema glaciale) in the Flemish Cap

It is important to understand the population dynamics of myctophids for a better understanding of the functioning of the ecosystem. In this work, age-based demography parameters of glacier lanternfish (Benthosema glaciale (Reinhardt, 1837)) were calculated. This study was based on 1213 individuals collected in the Flemish Cap during June–July 2008 and 2010. Ages were estimated from counts of annuli in the whole otolith. A strong relationship was found between both diameters of the otolith and fish length, and between otolith weight and increment number. Males predominated in 2008 (37.6% were females) whereas no differences from the expected sex ratio of 1:1 were observed in 2010. The somatic growth of B. glaciale is quite fast for the first three years and decreasing thereafter. The von Bertalanffy growth curves revealed interannual differences and no sexual dimorphism in growth. The instantaneous natural mortality coefficient, M, was 0.65 year–1 for the overall population. The maximum age recorded was 7. Our results were compared with age-based demographic parameters from previous studies in the Flemish Cap and in other regions. Because myctophids are considered opportunistic strategists, changes in their demographic features may reflect shifts in the ecosystem.

Provenance of sediment in the Labrador Current: a record of hinterland glaciation over the past 125 ka

ABSTRACTThe Labrador Current flows southward along the continental margin off eastern Canada and is the principal source of sediment to the outer continental margin areas where ice sheets did not cross the continental shelf. We present multi‐proxy mineralogical and geochemical records based principally on X‐ray diffraction and X‐ray fluorescence for core 2011031‐059 from northern Flemish Cap to determine changes in supply and hence to reconstruct provenance evolution during the last glacial cycle. The calcite to dolomite ratios in Heinrich layers ranged from 2 to 4, suggesting carbonate layers derived from Hudson Strait as early as Marine Isotope Stage (MIS) 5a–d. Mineral abundance shows three time‐dependent predominant sediment sources other than in Heinrich layers: (i) Baffin Bay shelves and adjacent land in MIS 5 and 1, with high Ca, Sr, kaolinite and feldspars and low clay minerals and calcite/dolomite ratios; (ii) Labrador in MIS 3, with low clays and grey color; and (iii) north‐east Newfoundland Shelf in MIS 2 and 4, with higher concentrations of clay minerals, red sandstones and transition elements. These results allow a reconstruction of principal ice streams supplying the north‐west Atlantic over the last full glacial cycle.

Protocols of the EU bottom trawl survey of Flemish Cap

Methods and procedures used in the EU bottom trawl survey of Flemish Cap (NAFO Division 3M) are described in detail. The objectives of publicizing these protocols are to achieve a better understanding of its results, and to contribute to the routines being unaltered.

Intra-seasonal variability of the DWBC in the western subpolar North Atlantic

The Deep Western Boundary Current (DWBC) along the western margin of the subpolar North Atlantic is an important component of the deep limb of the Meridional Overturning near its northern origins. A network of moored arrays from Denmark Strait to the tail of the Grand Banks has been installed for almost two decades to observe the boundary currents and transports of North Atlantic Deep Water as part of an internationally coordinated observatory for the Atlantic Meridional Overturning Circulation.The dominant variability in all of the moored velocity time series is in the week-to-month period range. While the temporal characteristics of this variability change only gradually between Denmark Strait and Flemish Cap, a broad band of longer term variability is present farther along the path of the DWBC at the Grand Banks and in the interior basins (Labrador and Irminger Seas). The vigorous intra-seasonal variability may well mask possible interannual to decadal variability that is typically an order of magnitude smaller than the high-frequency fluctuations. Here, the intra-seasonal variability is quantified at key positions along the DWBC path using both, observations and high resolution model data. The results are used to evaluate the model circulation, and in turn the model is used to relate the discrete measurements to the overall pattern of the subpolar circulation. Topographic waves are found to be trapped by the steep topography all around the western basins, the Labrador and Irminger Seas. In the Labrador Sea, the high intra-seasonal variability of the boundary current regime is separated by a region of extremely low variability in narrow recirculation cells from the basin interior. There, the variability is also on intra-seasonal time scales, but at much longer periods around 50days.

Improvements of simulated Western North Atlantic current system and impacts on the AMOC

Previous studies have shown that low horizontal resolution (of the order of 1°) ocean models, hence climate models, are not able to adequately represent boundary currents nor mesoscale processes which affect the dynamics and thermohaline circulation of the ocean. While the effect of mesoscale eddies can be parameterized in low resolution models, boundary currents require relatively high horizontal resolution. We clarify the impact of increasing the resolution on the North Atlantic circulation, with emphasis on the Atlantic Meridional Overturning Circulation (AMOC), by embedding a 1/8° nest covering the North Atlantic into a global 1/2° model.Increasing the resolution in the nest leads to regional improvements of the circulation and thermohaline properties in the Gulf Stream area, for the North Atlantic Current, in the subpolar gyre and the Nordic Seas, consistent with those of previous studies. In addition, we show that the Deep Western Boundary Current dense water transport increases with the nest, from the overflows down to Flemish Cap, due to an increase in the Denmark Strait overflow as well as dense water formation in the subpolar gyre. This increases the Atlantic Meridional Overturning Circulation in density space by about 8Sv in the subpolar gyre in the nested configuration. When exiting the Labrador Sea around 53°N we illustrate that the Deep Western Boundary Current successively interacts with the upper ocean circulation composed with the North Atlantic Current in the intergyre region, the Northern Recirculation Gyre, and the Gulf Stream near Cape Hatteras. This surface/deep current interaction seems to induce an increase of the AMOC intensity in depth-space, giving rise to an AMOC maximum near 35°N. This process is missing in the configuration without nesting. At 26.5°N, the AMOC is 4Sv larger in the nested configuration and is in good agreement with observations. Finally, beyond the nest imprint (i.e. in the low resolution area) in the South Atlantic the AMOC maximum at 40°S is 3Sv larger at the end of the simulation meaning that information is able to propagate outside the nest without being fully damped. This underlines the benefit of using the nest for a reasonable computing time compared to a fully global higher resolution configuration.

Reproductive ecology of the glacier lanternfish Benthosema glaciale

Myctophids play a key role in the transfer of energy in pelagic food webs, linking zooplankton to higher trophic levels. Data are presented, for the first time for the glacier lanternfish (Benthosema glaciale), on maturity ogives, size-at-maturity and reproductive strategy in terms of ovarian organization and fecundity type in two contrasting environments: North Atlantic and Mediterranean. We analysed 292 females collected in Flemish Cap during early summer 2009 and 2011 and off the Balearic Islands during late autumn 2009 and early summer 2010. The spawning season differed between areas. Size at 50% maturity in Flemish Cap was 47.6 and 49.1 mm in 2009 and 2011, respectively, but significantly smaller, 24.5 mm, in the Balearic sea. B. glaciale is a batch spawner with asynchronous ovarian development and indeterminate fecundity. Batch fecundity showed significant relationships with length and weight, although average relative batch fecundity was low (1031 ± 396 oocytes/gram). We compared two staining techniques: Hematoxylin–eosin and PAS–hematoxylin–metanil yellow with the latter being more useful to detect mature females and spawning indicators in regressing and regenerating females. Our results contribute to a better understanding of the reproductive potential and ecological role of this species, the most abundant myctophid in the northern Atlantic.

Aglaopheniid hydroids (Cnidaria: Hydrozoa: Aglaopheniidae) from bathyal waters of the Flemish Cap, Flemish Pass, and Grand Banks of Newfoundland (NW Atlantic).

Five species of aglaopheniid hydroids (Aglaophenopsis cornuta, Cladocarpus diana, C. formosus, C. integer, and Nematocarpus ramuliferus) were collected from the Flemish Cap, Flemish Pass, and Grand Banks of Newfoundland during surveys with bottom trawls, rock dredges, and scallop gear. All are infrequently reported species, with C. diana being discovered for the first time since its original description from Iceland. We document here the southernmost collections of C. diana and N. ramuliferus, both previously unknown in the western Atlantic. Each of the five species is described and illustrated based on fertile material, a key is provided for their identification, and bathymetric distributions are noted. Known depth ranges are extended for A. cornuta, C. diana, and C. integer. Aglaophenopsis and Nematocarpus are recognized as genera distinct from the polyphyletic Cladocarpus, based on the unique structure of the phylactocarp in the former, and the existence of appendages with nematothecae (ramuli) on almost all thecate internodes of hydrocladia in the latter. These appendages occur even in the absence of gonothecae, and are here considered defensive structures that protect the hydranths. In differing from typical phylactocarps, we accept the contention that they are characters of generic value.

Deep-sea sponge grounds enhance diversity and abundance of epibenthic megafauna in the Northwest Atlantic

AbstractBeazley, L. I., Kenchington E. L., Murillo, F. J., and Sacau, M. 2013. Deep-sea sponge grounds enhance diversity and abundance of epibenthic megafauna in the Northwest Atlantic. – ICES Journal of Marine Science, 70: . The influence of structure-forming deep-water sponge grounds on the composition, diversity, and abundance of the local epibenthic megafaunal community of the Flemish Pass area, Northwest Atlantic was statistically assessed. These habitats are considered vulnerable marine ecosystems and, therefore, warrant conservation measures to protect them from bottom fishing activities. The epibenthic megafauna were quantified from four photographic transects, three of which were located on the western slope of the Flemish Cap with an overall depth range of 444–940 m, and the fourth in the southern Flemish Pass between 1328 and 1411 m. We observed a diverse megafaunal community dominated by large numbers of ophiuroids and sponges. On the slope of the Flemish Cap, sponge grounds were dominated by axinellid and polymastid sponges, while the deeper sponge ground in the southern Flemish Pass was formed mainly by geodiids and Asconema sp. The presence of structure-forming sponges was associated with a higher biodiversity and abundance of associated megafauna compared with non-sponge habitat. The composition of megafauna significantly differed between sponge grounds and non-sponge grounds and also between different sponge morphologies. Surface chlorophyll a and near-bottom salinity were important environmental determinants in generalized linear models of megafaunal species richness and abundance.

Population-specific ranges of oceanic migration for adult Atlantic salmon (Salmo salar) documented using pop-up satellite archival tags

Pop-up satellite archival tags identified differences in oceanic migration of Atlantic salmon (Salmo salar) kelts from three distinct Canadian populations. Kelts from two endangered populations were restricted to coastal areas near home rivers, whereas kelts from a persisting nearby population migrated to the Labrador Sea and towards the Flemish Cap. Kelts spent most time near the surface (0–5 m), but coastal migrants undertook repeated daytime dives (10–40 m), associated with feeding, upon marine entry and progress was slow (8–23 km·day−1). Distant migrants moved rapidly along the continental shelf (10–50 km·day−1) against prevailing ocean currents, remaining near the surface, except for deep dives (100–1000 m) when crossing ocean channels and at the shelf edge. Home range water temperatures (0–15 °C) indicated that kelts avoided warmer adjacent areas in summer. Kelts did not avoid cold coastal habitat (0–5 °C) in winter, but avoided the surface layers. Kelt migration mimicked that of postsmolts of similar origins, with water temperature acting as a directive or controlling factor. Containment of kelts from endangered populations in coastal habitat was probably responsible for the disappearance of repeat spawners.

Feeding ecology of the glacier lanternfish Benthosema glaciale (Actinopterygii, Myctophidae) in the Flemish Cap (North Atlantic Ocean)

The feeding dynamics of the glacier lanternfish Benthosema glaciale were studied during the summer of 2010 in the Flemish Cap. B. glaciale constituted a majority of the deep scattering layer (DSL), which was located between 300 and 650 m during daylight hours; at night, a part of the DSL migrated to the surface. B. glaciale is a zooplanktivore, feeding primarily on copepods (Calanushyperboreus, Pareuchaeta norvegica, Metridia longa and Calanus finmarchicus), followed by amphipods (Themisto compressa) and krill (primarily Nematoscelis spp.). Although crustaceans dominated the diet, other invertebrates, such as chaetognaths, gastropods, polychaetes, ostracods and appendicularians, also contributed. The geographical differences in the composition of the diet resulted from the association of prey with distinct water masses. In the colder water at the north of the bank, Arctic species represented a higher proportion of the diet, but this situation was reversed in areas influenced by the warmer water from the south. B. glaciale fed more intensively towards the centre of the Flemish Cap. The diet of B. glaciale shifted ontogenetically, showing increasing prey size and prey diversity with increasing predator size.

Glass Sponges off the Newfoundland (Northwest Atlantic): Description of a New Species ofDictyaulus(Porifera: Hexactinellida: Euplectellidae)

Three species of hexactinellid sponges:Aphrocallistes beatrix beatrixGray,Asconema foliata(Fristedt), andDictyaulus romanisp. n. were collected off the Flemish Cap in the Flemish Pass and from the Grand Banks off the Newfoundland (northwest Atlantic) during different surveys on board of Spanish RVVizconde de Ezaand RVMiguel Oliver.

Plate tectonic reconstructions and paleogeographic maps of the central and North Atlantic oceans1This article is one of a series of papers published in this CJES Special Issue on the theme ofMesozoic–Cenozoic geology of the Scotian Basin.2Earth Sciences Sector Contribution 20120172.

We have established a new plate kinematic model of the central and North Atlantic oceans between North America, Africa, Meseta, Iberia, Flemish Cap, and Galicia Bank from Late Triassic to Late Cretaceous to better understand the nature and timing of rifting of Nova Scotia and Morocco conjugate continental margins since Late Triassic. The maps of salt distributions at the Sinemurian–Pliensbachian limit (190 Ma; after salt deposition) and in middle Bajocian (170 Ma) show that an area of the Nova Scotia margin is devoid of allochthonous salt and that an area of similar size located oceanward of the West African Coast Magnetic Anomaly shows salt deposits, suggesting that a portion of the Nova Scotia margin with its overlying salt deposits could have been transferred onto the Moroccan side right after the formation of the conjugate East Coast Magnetic Anomaly and West African Coast Magnetic Anomaly. Seven paleogeographic maps, from Late Triassic to Late Cretaceous, are presented with structural elements and magnetic lineations. They show that the connection between the Central Atlantic and the Tethys, with an aborted rift between Iberia and North America ending in the north against the Flemish Cap – Galicia Bank dam, started to deepen at the end of the first rifting phase (190 Ma ago) after the rupture of the thinned continental crust. It is only during the Early Cretaceous, after the rupture of the Flemish Cap – Galicia Bank dam, that the deep connection around Iberia was finally established between the Central and North Atlantic, the Tethys, and the Bay of Biscay.

Changes in distribution of Greenland halibut in a varying environment

AbstractMorgan, M. J., Garabana, D., Rideout, R. M., Román, E., Pérez-Rodriguez, A. and Saborido-Rey, F. 2013. Changes in distribution of Greenland halibut in a varying environment. – ICES Journal of Marine Science, 70: 352–361. Fish are expected to respond to changing oceanographic temperature by altering their distribution. Off the coast of Newfoundland, Canada, there have been major changes in oceanographic temperature over the last several decades, with both record cold and record warm years being observed. Greenland halibut is an important flatfish species in the area, and is distributed in deep waters over a very wide geographic range. Thus, it might be buffered from temperature change in the overall area by reduced temperature variation at depth, and the diverse temperature conditions over its wide range. We examined intrapopulation variation in temperature and depth distribution, and the biological changes in relation to changes in available temperature. On the Flemish Cap, variation in available temperature was limited, and changes in depth were related to changing age composition and the differential depth distribution with age/size. In other areas there was a larger decline in available temperature, and associated with this, Greenland halibut moved to deeper waters and occupied warmer temperatures than they had previously. Concurrently, growth declined and condition increased. This study shows that shifts in distribution may not result in maintenance of homogeneous environmental conditions, and that resulting biological changes will be difficult to predict.