Drinkwater Ken F.

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Drinkwater
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Ken F.
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Frontal dynamics of a buoyancy‐driven coastal current : quantifying buoyancy, wind, and isopycnal tilting influence on the Nova Scotia Current

2018-07-28 , Dever, Mathieu , Skagseth, Øystein , Drinkwater, Ken F. , Hebert, David

The focus of this study is on the relative roles of winds and buoyancy in driving the Nova Scotia Current (NSC) utilizing detailed hydrographic glider transects along the Halifax Line. We define a Hydrographic Wind Index (HWI) using a simplistic two‐layer model to represent the NSC and its frontal system. The HWI is based on local characteristics of the density front extracted from the glider data (e.g., frontal slope). The impact of wind‐driven isopycnal tilting on the frontal slope is estimated and corrected for to accurately scale the buoyancy‐driven component of the NSC. Observations from independent current profilers deployed across the NSC confirm that the HWI captures the low‐frequency variability of the NSC. The monthly wind‐driven flow is estimated to represent between 1.0% (±0.1%) and 48% (±1%) of the total alongshore currents, with a yearly mean of about 36% (±1%). We demonstrate that using local conditions is more appropriate to the study of buoyancy‐driven currents ranging over distances on the order of urn:x-wiley:jgrc:media:jgrc22972:jgrc22972-math-0001(100 km), compared to the traditional approach based on upstream conditions. Contrary to the traditional approach, the HWI is not affected by the advective time lag associated with the downshelf propagation of the buoyant water coming from the upstream source. However, the HWI approach requires high‐resolution data sets, as errors on the estimates of the buoyancy‐ and wind‐driven flows become large as the sampling resolution decreases. Despite being data intensive, we argue that the HWI is also applicable to multisource currents, where upstream conditions are difficult to define.

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Introduction to variability of the North Atlantic and its marine ecosystems, 2000–2009, the proceedings of an ICES/NAFO symposium held in Santander, Spain, 10–12 May 2011

2012-04-15 , Wiebe, Peter H. , Rudels, Bert , Cadrin, Steven X. , Drinkwater, Ken F. , Lavin, Alicia

An international symposium on decadal changes in the International Council for the Exploration of the Sea (ICES) and North Atlantic Fisheries Organization (NAFO) regions of the North Atlantic from 2001 to 2009, jointly sponsored by ICES and NAFO, took place in Santander, Spain, from 10 to 12 May 2011. During the period covered by the symposium, the upper ocean warmed, particularly in temperate and Arctic–boreal regions, and there were major biogeographic shifts and changes in the phenology of the biota that appear to be related to the physical changes.

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Article

Structure and functioning of four North Atlantic ecosystems - a comparative study

2020-09-11 , Melle, Webjørn , Klevjer, Thor A. , Drinkwater, Ken F. , Strand, Espen , Naustvoll, Lars Johan , Wiebe, Peter , Aksnes, Dag L. , Knutsen, Tor , Sundby, Svein , Slotte, Aril , Dupont, Nicolas , Vea Salvanes, Anne Gro , Korneliussen, Rolf J. , Huse, Geir

The epi- and mesopelagic ecosystems of four sub-polar ocean basins, the Labrador, Irminger, Iceland and Norwegian seas, were surveyed during two legs from Bergen, Norway, to Nuuk, Greenland, and back to Bergen. The survey was conducted from 1 May to 14 June, and major results were published in five papers (Drinkwater et al., Naustvoll et al., Strand et al., Melle et al., this issue, and Klevjer et al., this issue a, this issue b). In the present paper, the structures of the ecosystem are reviewed, and aspects of the functioning of the ecosystems examined, focusing on a comparison of trophic relationships in the four basins. In many ways, the ecosystems are similar, which is not surprising since they are located at similar latitudes and share many hydrographic characteristics, like input of both warm and saline Atlantic water, as well as cold and less saline Arctic water. Literature review suggests that total annual primary production is intermediate in the eastern basins and peaks in the Labrador Sea, while the Irminger Sea is the most oligotrophic sea. This was not reflected in the measurements of different trophic levels taken during the cruise. The potential new production was estimated to be higher in the Irminger Sea than in the eastern basins, and while the biomass of mesozooplankton was similar across basins, the biomass of mesopelagic micronekton was about one order of magnitude higher in the western basins, and peaked in the Irminger Sea, where literature suggests annual primary production is at its lowest. The eastern basins hold huge stocks of pelagic planktivore fish stocks like herring, mackerel and blue whiting, none of which are abundant in the western seas. As both epipelagic nekton and mesopelagic micronekton primarily feed on the mesozooplankton, there is likely competitive interactions between the epipelagic and mesopelagic, but we're currently unable to explain the estimated ~1 order of magnitude difference in micronekton standing stock. The results obtained during the survey highlight that even if some aspects of pelagic ecosystems are well understood, we currently do not understand overall pelagic energy flow in the North Atlantic.

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