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Seasonality in currents of the Rockall Channel

Published online by Cambridge University Press:  05 December 2011

R. R. Dickson ,
W. J. Gould ,
C. Griffiths ,
K. J. Medler  and
E. M. Gmitrowicz
R. R. Dickson
Affiliation:
Ministry of Agriculture, Fisheries and Food, Directorate of Fisheries Research, Fisheries Laboratory, Lowestoft, Suffolk NR33 OHT, U.K.
W. J. Gould
Affiliation:
Institute of Oceanographic Sciences, Brook Road, Wormley, Godalming, Surrey GU8 5UB, U.K.
C. Griffiths
Affiliation:
Scottish Marine Biological Association, Dunstaffnage Marine Research Laboratory, P.O. Box 3, Oban, Argyll PA34 4AD, U.K.
K. J. Medler
Affiliation:
Ministry of Agriculture, Fisheries and Food, Directorate of Fisheries Research, Fisheries Laboratory, Lowestoft, Suffolk NR33 OHT, U.K.
E. M. Gmitrowicz
Affiliation:
Ministry of Agriculture, Fisheries and Food, Directorate of Fisheries Research, Fisheries Laboratory, Lowestoft, Suffolk NR33 OHT, U.K.
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Synopsis

Though our knowledge of the circulation in this complex region is still incomplete, recent direct current measurements have identified four separate elements of the circulation which appear to undergo a seasonal variation of some sort. These are: (i) a summer-autumn maximum in the deep overflow of Norwegian Sea Deep Water across the Wyville-Thomson Ridge; (ii) an autumn minimum in the upper-ocean circulation around Rockall Bank, ascribed to Taylor Column processes; (iii) an autumn-winter maximum in the strength and breadth of the slope current along the European continental margin; (iv) a winter-spring maximum in eddy kinetic energy in the open waters of the Rockall Channel, and over the full depth range, as a function of windstress and stratification. The first three of these elements are of localised occurrence along the northern, western and eastern margins of the Channel and are described only briefly. The fourth process, encountered at a range of sites in the northeast Atlantic, is described in detail using a total data set of 68 instrument-years of direct current measurements recovered from the Rockall Channel in 1977–84. In the seasonally-varying 3–27 day (d) band of periods, eddy kinetic energies (kE) are shown to be depth-dependent in amplitude, but with little evidence of any significant phase-lag with either depth or location between the individual timeseries of kE estimates. These time-series demonstrate clearly and for the first time that the winterspring peaks in eddy kinetic energy lag the winter peaks in windstress by between 1 and 3 months. This phase-lag is explained as the cumulative result of wind forcing and eddy dissipation.

Type
Research Article
Information
Proceedings of the Royal Society of Edinburgh, Section B: Biological Sciences , Volume 88: The Oceanography of the Rockall Channel , 1986 , pp. 103 - 125
Copyright
Copyright © Royal Society of Edinburgh 1986

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