Fresh water balance of the Gulf Stream system in a regional model study |
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Authors: | R Gerdes A Biastoch R Redler |
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Institution: | (1) Alfred Wegener Institute for Polar and Marine Research, Bussestr. 24, 23568 Bremerhaven, Germany E-mail: rgerdes@awi-bremerhaven.de, DE;(2) Scripps Institution of Oceanography, 8605 La Jolla Shores Dr., La Jolla, CA 92093-0230, USA, US;(3) SCAI Institute for Algorithms and Scientific Computing, GMD – German National Research Center for Information Technology, Schloss Birlinghoven, 53754 Sankt Augustin, Germany, DE |
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Abstract: | We investigate the dependence of surface fresh water fluxes in the Gulf Stream and North Atlantic Current (NAC) area on the
position of the stream axis which is not well represented in most ocean models. To correct this shortcoming, strong unrealistic
surface fresh water fluxes have to be applied that lead to an incorrect salt balance of the current system. The unrealistic
surface fluxes required by the oceanic component may force flux adjustments and may cause fictitious long-term variability
in coupled climate models. To identify the important points in the correct representation of the salt balance of the Gulf
Stream a regional model of the northwestern part of the subtropical gyre has been set up. Sensitivity studies are made where
the westward flow north of the Gulf Stream and its properties are varied. Increasing westward volume transport leads to a
southward migration of the Gulf Stream separation point along the American coast. The salinity of the inflow is essential
for realistic surface fresh water fluxes and the water mass distribution. The subpolar–subtropical connection is important
in two ways: The deep dense flow from the deep water mass formation areas sets up the cyclonic circulation cell north of the
Gulf Stream. The surface and mid depth flow of fresh water collected at high northern latitudes is mixed into the Gulf Stream
and compensates for the net evaporation at the surface.
Received: 19 September 2000 / Accepted: 5 February 2001 |
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