Seasonal and interannual variations in geostrophic velocity in the Middle Atlantic Bight

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Abstract
More than 6 years of measurements from the TOPEX/POSEIDON (T/P) altimeter are used to study the seasonal and interannual variations of the geostrophic velocity anomalies in the Middle Atlantic Bight region. Geostrophic velocities from T/P data are compared with the simultaneous low‐pass filtered current meter data. The correlations are all above 95% significance for the three current meter observations at the 1000‐m, 2210‐m, and 2990‐m isobaths. The seasonal mean geostrophic currents from 63°–75°W show coherent variations along isobaths, with seasonal reversals: toward the southwest during the winter and toward the northeast during the summer. The EOF analysis indicates that the seasonal reversals disappeared during 1996. This disruption is part of the intensification of the slope sea gyre and is related to the southward shift of the Gulf Stream, which acts as the boundary between the subpolar and subtropical gyres. The Gulf Stream moved farther south during 1996–1998. The variations in the Gulf Stream position may be caused by the wind stress/wind stress curl change.

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