|
Titel |
Deep ocean exchange with west-European shelf seas |
VerfasserIn |
John M. Huthnance, Jason T. Holt, Sarah L. Wakelin |
Konferenz |
EGU General Assembly 2010
|
Medientyp |
Artikel
|
Sprache |
Englisch
|
Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 12 (2010) |
Datensatznummer |
250032606
|
|
|
|
Zusammenfassung |
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 m2/s per unit length of shelf). Prevailing westerly
winds further north drive exchange O(1 m2/s). Poleward flow along most of the upper slope
has associated secondary circulation O(1 m2/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 m2/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 m2/s). These various physical exchanges amount to an
estimated 2-3 m2/s per unit length of shelf, between ocean and shelf. A numerical
model estimate is comparable: 2.5 x 106 m3/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. |
|
|
|
|
|