Multi-sensor satellite and in situ measurements of a warm core ocean eddy south of the Brazil–Malvinas Confluence region

Abstract

A warm core eddy was detected south of the Brazil–Malvinas (Falkland) Confluence (BMC) region in satellite images of the southwestern Atlantic Ocean in late 2002. The structure was also sampled by in situ instruments deployed by a ship in 2 days of November 2002. An analysis of satellite data was performed to account for the lifecycle, dimension, surface temperature, surface chlorophyll concentration, surface height anomaly and displacement of the eddy since it was detached from the Brazil Current in September 2002. Satellite data were derived from several sources such as the AMSR-E, MODIS and radar altimeter. The structure lasted 64 days at south of the Brazil–Malvinas Confluence region later being re-assimilated by the Brazil Current return flow. In situ data collected during 2 days showed that the eddy was about 150 m deep, 5.5 °C warmer and 1 practical salinity unit saltier than adjacent waters. The salt anomaly associated to the eddy was estimated as 1.37 × 10 12 kg while its heat content was 4.24 × 10 18 J. These are typical estimates for eddies present at the BMC region. Sea surface temperature (SST), chlorophyll concentration, and sea surface height anomaly time series were analyzed for the eddy's center along its trajectory path throughout its lifetime. Mean translational velocities for the eddy during its lifetime were computed from visual interpretation and by using an adaptation of the Maximum Cross-Correlation (MCC) method on AMSR-E SST images. The overall deviation between the two methods was 26%. This suggests that the MCC method has a potential to be applied in monitoring programs to automatically account for the translational velocities of eddies in the BMC region.