A series of cyclonic eddies in the Antarctic Divergence off Adélie Coast

Abstract

The spatial and temporal characteristics of cyclonic eddies in the Antarctic Divergence off Adélie Coast are described using repeated in situ observations between 2001 and 2003, satellite observations, and results of a high‐resolution ocean general circulation model. Satellite ocean color images and altimetry clearly revealed a series of cyclonic eddies, with diameters of about 100–150 km that were separated by about 150 km in the zonal direction. The eddies are found at almost the same locations and can be traced for at least two months in the spring‐summer period. Cold and fresh anomalies were found throughout the water column in the cores of the cyclonic eddies. The water properties in the core of the eddies are similar to water found over the continental slope, 150–200 km to the south. The geopotential anomaly of the cold features was smaller than the sea level anomaly detected with satellite altimetry, indicating that significant barotropic flow is associated with the eddies. The Ocean general circulation model for the Earth Simulator (OFES) reproduces a series of cyclonic eddies similar to those observed, including a significant barotropic component. In the model, the series of eddies appear to originate further west over the continental slope region with no consistent phase propagation. The combination of repeat in situ observations, remote sensing and high‐resolution model results confirms the existence of persistent cyclonic eddies near 140°E and suggests the eddies play an important role in the exchange of water across the Antarctic Divergence.