Near-surface structure of the Antarctic Circumpolar Current derived from World Ocean Circulation Experiment drifter data

Abstract

In this work, the dynamics of the Antarctic Circumpolar Currrent (ACC) are investigated on the basis of near-surface Lagrangian observations carried out under the framework of the World Ocean Circulation Experiment (WOCE) and contained within the WOCE drifter data set. Approximately 440 drifters that were deployed in the Southern Ocean, between 1995 and 2002, were considered during the study. The mean surface current field was derived using natural bicubic splines, whose application yielded a high-resolution mean flow which allowed a detailed description for ACC meridional shear as well as its jets. ACC volume transport was estimated using a novel approach that was based upon the surface transport that was computed on the basis of drifter data and by assuming an exponential form for vertical current shear. The volume transport was determined to be 133 Sv for an e folding depth of 1000 m. Lagrangian diffusivities and integral parameters were derived by assuming a broadly homogenous eddy field. The zonal and meridional diffusivity components were determined to be 9 × 107 and 2 × 107 cm2 s-1, respectively. The eddy field is described in terms of the eddy kinetic energy distribution. Copyright 2011 by the American Geophysical Union.