Seasonal and interannual variation in the hydrography of the Cariaco Basin: implications for basin ventilation

The hydrography of the Cariaco Basin (temperature, salinity, density, dissolved oxygen concentration) was studied using monthly observations collected between November 1995 and August 1998 at the CArbon Retention In A Colored Ocean (CARIACO) time-series station (10.5°N, 64.66°W). Satellite scatterometer wind estimates showed that changes in the wind preceded changes in hydrography by 1–2 weeks. Upward migration of isopleths within the upper 150 m was observed between November and May each year, when the Trade Wind was more intense. A seasonal deepening of the isopleths was observed when winds relaxed. A secondary upwelling event was observed every year between July and August, in response to an intensification of the southward component of the Trade Wind. Interannual variation in the upwelling cycle was driven in part by variations in wind intensity and in part by other events at time scales of 1–3 months. The latter were associated with 90–140 m deep intrusions of Caribbean Sea water that forced waters above them to the surface. Satellite-derived sea surface height anomaly maps demonstrated that these events were related to cyclonic and anticyclonic eddies moving along the continental shelf. Waters deeper than 1200 m showed small temperature and salinity increases of 0.0075°C yr−1 and 0.0016 yr−1, consistent with previous estimates.