The Evolution of a Submesoscale Eddy from In Situ and Aerial Observations

Due to their short lifetimes and small spatial scales, it is a significant challenge to obtain high-resolution measurements of submesoscale features. However, high quality in situ and aerial observations are essential to advance our understanding of the role of submesoscale features in local energy cascades, the re-stratification and mixing of the upper ocean, and connections between enhanced vertical transport and phytoplankton production. Here, we present the results of a collaborative effort in the Southern California Bight to measure an approximately 1.5 km diameter submesoscale eddy. The Submesocale Experiment (SubEx) included aerial SST and ocean color, current profiles from a ship-mounted ADCP, and temperature profiles from a towed CTD chain. The combination of platforms produced very-high-resolution measurements on the order of 1 m in both the horizontal and the vertical, and the eddy was sampled repeatedly at approximately 15 minute intervals. Combining the resulting data set showed the general evolution of the eddy over a period of 5 hours, and provided quantitative insight into the eddy’s energy and transport characteristics. In general, the size of the eddy decreased, during which the surface signature changed from a circular vortex with a distinctive “tail”, to a distorted and elongated shape. During this period, there was a decrease in both the kinetic energy and available potential energy of the eddy, suggesting dissipation.