998 resultados para Baffin Bay


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"CG 373-37."

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"Oceanographic data collected from 28 July to 4 August 1963 during the U.S. Coast Guard cutter Evergreen's special survey."

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The Horwood Peninsula - Gander Bay area is located at NE Newfoundland in the Botwood Zone (Williams et a1., 1974) or in the Dunnage Zone (Williams, 1979) of the Central Mobile Belt of the Newfoundland Appalachians. The area is underlain by Middle Ordovician to possible Lower Silurian rocks of the Davidsville and Indian Islands Groups, respectively. Three conformable formations named informally : the Mafic Volcanic Formation, the Greywacke and Siltstone Formation and the Black Slate Formation, have been recognized in the Davidsville Group. The Greywacke and the Black Slate Formations pass locally into a Melange Formation. From consideration of regional structure and abundant locally-derived mafic volcanic olisto- 1iths in the melange, it is considered to have originated by gravity sliding rather than thrusting. Four formations have been recognized in the Indian Islands Group. They mainly contain silty slate and phyllite, grey cherty siltstone, green to red micaceous siltstone and limestone horizons. Repetition of lithological units by F1 folding are well-demonstrated in one of formations in this Group. The major structure in this Group on the Horwood Peninsula is interpreted to be a synclinal complex. The lithology of this Group is different from the Botwood Group to the west and is probably Late Ordovician and/or Early Silurian in age. The effects of soft-sediment deformation can be seen from the lower part of the Davidsville Group to the middle part of the Indian Islands Group indicating continuous and/or episodic slumping and sliding activities throughout the whole area. However, no siginificant depOSitional and tectonic break that could be assigned to the Taconian Orogeny has been recognized in this study. Three periods of tectonic deformation were produced by the Acadian Orogeny. Double boudinage in thin dikes indicates a southeast-northwest sub-horizontal compression and main northeast-southwest sub-horizontal extension during the D1 deformation. A penetrative, axial planar slaty cleavage (Sl) and tight to isocJ.ina1 F1 folds are products of this deformation. The D2 and D3 deformations formed S2 and S3 fabrics associated with crenulations and kink bands which are well-shown in the slates and phyllites of the Indian Islands Group. The D2 and D3 deformations are the products of vertical and northeast-southwest horizontal shortening respectively. The inferred fault between the Ordovician slates (Davidsville Group) and the siltstones (Indian Islands Group) suggested by Williams (1963, 1964b, 1972, 1978) is absent. Formations can be followed without displacement across this inferred fault. Chemically, the pillow lavas, mafic agglomerates, tuff beds and diabase dikes are subdivided into three rock suites : (a) basaltic komatiite (Beaver Cove Assemblage), (b) tholeiitic basalt (diabase dikes), (c) alkaline basalt (Shoal Bay Assemblage). The high Ti02 , MgO, Ni contents and bimodal characteristic of the basaltic komatiite in the area are comparable to the Svartenhuk Peninsula at Baffin Bay and are interpreted to be the result of an abortive volcano-tectonic rift-zone in a rear-arc basin. Modal and chemical analyses of greywackes and siltstones show the trend of maturity of these rocks increasing from poorly sorted Ordovician greywackes to fairly well-sorted Silurian siltstones. Rock fragments in greywackes indicate source areas consisting of plagiogranite, low grade metamorphic rocks and ultramafic rocks. Rare sedimentary structures in both Groups indicate a southeasterly provenance. Trace element analyses of greywackes also reveal a possible island-arc affinity.

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Twenty-one narwhals tagged in 2003 and 2004 in Admiralty Inlet showed a different summer distributional pattern than previous narwhal-tracking studies from Somerset Island, Eclipse Sound and Melville Bay. The migration of the narwhals tracked from Admiralty Inlet moved out through Lancaster Sound 15 days earlier (P <0.0001) than the narwhals summering around Eclipse Sound, whereas the Admiralty Inlet narwhals reached the mouths of Eclipse Sound 18 days later (P <0.0001) than the Eclipse Sound summering population. The winter range of the Admiralty Inlet narwhals overlapped with the winter range of narwhals from Melville Bay and Eclipse Sound in central southern Baffin Bay and Northern Davis Strait, but not with the winter range of narwhals from Somerset Island that wintered further north. Distribution size of range, and population size did not appear to be related. An example of considerable year to year variation between area of summer and winter distribution in the 2 years was believed to be related to the sample size and number of pods of whales tagged, rather than to differences in sex or age classes.

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Trigger weight (TWC) and piston (PC) cores obtained from surveys of the three sites drilled during Ocean Drilling Program (ODP) Leg 105 were studied in detail for benthic foraminiferal assemblages, total carbonate (all sites), planktonic foraminiferal abundances (Sites 645 and 647), and stable isotopes (Sites 646 and 647). These high-resolution data provide the link between modern environmental conditions represented by the sediment in the TWC and the uppermost cores of the ODP holes. This link provides essential control data for interpretating late Pleistocene paleoceanographic records from these core holes. At Site 645 in Baffin Bay, local correlation is difficult because the area is dominated by ice-rafted deposits and by debris flows and/or turbidite sedimentation. At the two Labrador Sea sites (646 and 647), the survey cores and uppermost ODP cores can be correlated. High-resolution data from the site survey cores also provide biostratigraphic data that refine the interpretations compiled from core-catcher samples at each ODP site.

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We report on wintertime data collected from Baffin Bay and northern Davis Strait, a major gateway linking the Arctic with the subpolar North Atlantic, using narwhals (Monodon monoceros) as an oceanographic sampling platform. Fourteen narwhals were instrumented with satellite-linked time-depth-temperature recorders between 2005 and 2007. Transmitters collected and transmitted water column temperature profiles from each dive between December and April, where >90% of maximum daily dive depths reached the bottom. Temperature measurements were combined with 15 helicopter-based conductivity-temperature-depth (CTD) casts taken in April 2007 across central Baffin Bay and compared with hydrographic climatology values used for the region in Arctic climate models. Winter temperature maxima for whale and CTD data were in good agreement, ranging between 4.0°C and 4.6°C in inshore and offshore Baffin Bay and in Davis Strait. The warm Irminger Water was identified between 57°W and 59°W (at 68°N) between 200 and 400 m depths. Whale data correlated well with climatological temperature maxima; however, they were on average 0.9°C warmer ±0.6°C (P < 0.001). Furthermore, climatology data overestimated the winter surface isothermal layer thickness by 50-80 m. Our results suggest the previously documented warming in Baffin Bay has continued through 2007 and is associated with a warmer West Greenland Current in both of its constituent water masses. This research demonstrates the feasibility of using narwhals as ocean observation platforms in inaccessible Arctic areas where dense sea ice prevents regular oceanographic measurements and where innate site fidelity, affinity for winter pack ice, and multiple daily dives to >1700 m offer a useful opportunity to sample the area.

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There is a paucity of information on abundance, densities, and habitat selection of narwhals Monodon monoceros in the offshore pack ice of Baffin Bay, West Greenland, despite the critical importance of winter foraging regions and considerable sea ice declines in the past decades. We conducted a double-platform visual aerial survey over a narwhal wintering ground to obtain pack ice densities and develop the first fully corrected abundance estimate using point conditional mark-recapture distance sampling. Continuous video recording and digital images taken along the trackline allowed for in situ quantification of winter narwhal habitat and for the estimation of fine-scale narwhal habitat selection and habitat-specific sighting probabilities. Abundance at the surface was estimated at 3484 (coefficient of variation [CV] = 0.46) including whales missed by observers. The fully corrected abundance of narwhals was 18 044 (CV = 0.46), or approximately one-quarter of the entire Baffin Bay population. The narwhal wintering ground surveyed (~9500 km**2) had 2.4 to 3.2% open water based on estimates from satellite imagery (NASA Moderate Resolution Imaging Spectroradiometer) and 1565 digital photographic images collected on the trackline. Thus, the ~18 000 narwhals had access to 233 km**2 of open water, resulting in an average density of ~77 narwhals/km**2 open water. Narwhal sighting probability near habitats with <10% or 10 to 50% open water was significantly higher than sighting probability in habitats with >50% open water, suggesting narwhals select optimal foraging areas in dense pack ice regardless of open water availability. This study provides the first quantitative ecological data on densities and habitat selection of narwhals in pack ice foraging regions that are rapidly being altered with climate change.

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This thesis presents the discovery of eight submerged deltas (-19 to -45m), the first documented submerged boulder barricade, a submerged sill platform and spits off the coast of Cumberland Peninsula, eastern Baffin Island, NU. The geomorphic characteristics of these features in relation to contemporaneous sea-level are presented and compared with the modern shore-zone. The submerged boulder barricade at Qikiqtarjuaq in the west indicates a -16 m sea level that isolated Broughton Channel from Baffin Bay to the north, changing the coastal dynamics from those observed at present. A shoreline deeper than -50 m planed off the fiord-mouth sill in Akpait Fiord and formed spits at -50 m and -30 m present depth. These features define a submerged shoreline gradient of 0.35 m/km to the east across northeastern Cumberland Peninsula. The linear gradient sediment supply requirements for delta formation suggest a synchronous lowstand, bracketed by ice margins and sourced from glacial outwash between 11.8-8.5 ka. This confirms the submergence trend hypothesized for eastern Cumberland Peninsula (Dyke, 1979).