Mesoscale variability of the Caribbean Sea from GEOSAT

Two years of GEOSAT Exact Repeat Mission (ERM) altimetry and wind speed measurements in the Caribbean Sea are used to determine the sea surface height mesoscale variability and to characterize the wind stress field during 1987-88. The alongtrack sea surface anomalies are determined using alongtrack derivatives for the estimation of the mean sea surface height and a least square fit is used to remove the orbital error. Biased points near land were removed and high frequency noise was filtered by using a 70 km spatial running mean. Contours of sea surface height anomalies made by every ERM period detected the formation and evolution of two anticyclonic eddies formed during the "non-windy" tropical season, one each year, with a height signature that reached + 30 cm. No eddies related to the Caribbean Current were apparent during the other seasons. A quasi-permanent cyclonic eddy was detected near the San Andreas Archipelago, confirming model predictions. Seasonal wind speed derived from GEOSAT data agrees with previous studies in the area. The relaxation of the wind after the windy season and the strong meridional wind gradient in the center of the Caribbean coincide with the formation of the anticyclones. This suggests that the wind field influences eddy formation. Anomalies in the averaged wind field were produced by strong synoptic events (hurricanes) which are biased due to the 17 day sampling character of the GEOSAT data.