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Deep ocean exchange with west-European shelf seas

Huthnance, J.M.; Holt, J.T.; Wakelin, S.L.. 2009 Deep ocean exchange with west-European shelf seas. Ocean Science, 5. 621-634. 10.5194/os-5-621-2009

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Abstract/Summary

We review mechanisms and studies of exchange between the north-east Atlantic and the adjacent shelf sea. Well-developed summer upwelling and associated filaments off Portugal and north-west Spain give exchange O(3 m**2/s per unit length of shelf). Prevailing westerly winds further north drive exchange O(1 m**2/s). Poleward flow along most of the upper slope has associated secondary circulation O(1 m**2/s), meanders and eddies. Eddies are shed from slope waters into the Bay of Biscay, and local exchanges occur at shelf spurs and depressions or canyons (e.g. dense-water cascading of order 1 m**2/s). Tidal transports are larger, but their reversal every six hours makes exchange largely ineffective except where internal tides are large and non-linear, as in the Celtic Sea where solitons carry water with exchange O(1 m**2/s). These various physical exchanges amount to an estimated 2-3 m**2/s per unit length of shelf, between ocean and shelf. A numerical model estimate is comparable: 2.5 x 106 m**3/s onto and off the shelf from Brittany to Norway. Mixing controls the seasonal thermocline, affecting primary production and hence fluxes and fate of organic matter. Specifically, CO2 take-up by primary production, settling below the thermocline before respiration, and then off-shelf transport, make an effective shelf-sea “pump” (for CO2 from the atmosphere to the deep ocean). However, knowledge of biogeochemical fluxes is generally sparse, giving scope for more measurements, model validation and estimates from models.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.5194/os-5-621-2009
Programmes: Oceans 2025 > Shelf and coastal processes
Oceans 2025 > Continental margins and deep oceans
ISSN: 1812-0784
Additional Keywords: deep ocean, shelf sea, exchange, Europe
NORA Subject Terms: Marine Sciences
Date made live: 14 Dec 2009 12:17
URI: http://nora.nerc.ac.uk/id/eprint/8719

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