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The role of variable wind forcing in generating eddy energy in the North Atlantic

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Stammer, D. , Böning, C. and Dieterich, C. (2001): The role of variable wind forcing in generating eddy energy in the North Atlantic , Progress in Oceanography, 48 (2), pp. 289-311 .
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Seasonal changes in eddy energy are used to investigate the role of high-frequency wind forcingin generating eddy kinetic energy in the oceans. To this end, we analyze two experiments of aneddy-permitting model of the North Atlantic driven by daily and monthly mean wind stress fields,and compare results with corresponding changes in the variance of the wind fields, and relatedresults from previous studies using altimeter and current meter data.With daily wind-stress forcing the model is found to be in general agreement with altimetricobservations and reveal a complex pattern of temporal changes in variability over the NorthAtlantic. Observations and the model indicate enhanced levels of eddy energy during wintermonths over several areas of the northern and, particularly northeastern North Atlantic. Since thewind-generated variability is primarily barotropic, its signal can be detected mostly in thelow-energy regions of the northern and north-eastern North Atlantic, which are remote frombaroclinically unstable currents. There the winter-to-summer difference in simulated eddy kineticenergy caused by the variable wind forcing is <0.5cm2 s2 between 30° and 55°N, and is 1-3cm2 s2north of 55°N. Seasonal changes in kinetic energy are insignificant along the path of the NorthAtlantic current and south of about 30°N.The weak depth dependence of the seasonal changes in eddy energy implies that the relativeimportance of wind-generated eddy energy is maximum at depth where the general (baroclinic)variability level is low. Accordingly, a significant correlation is found between the seasonal cycle inthe variance of wind stress and the seasonal cycle in eddy energy over a substantially wider areathan near the surface, notably across the entire eastern North Atlantic between the North AtlanticCurrent and the North Equatorial Current.

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