Major Migration Channels of Mesoscale Eddies in the Southern Ocean Derived From Satellite Altimetry

Abstract

The propagation pathways of mesoscale eddies have an essential impact on the meridional transport of freshwater, carbon, nutrients, and other tracers. However, existing methods have limitations in exactly expressing their major propagation pathways. To tackle this problem, a direction‐based spatial clustering algorithm for the trajectory is proposed according to the partition‐and‐group framework. The idea is to extract the major eddy channels quantitatively, thus effectively representing the eddy trajectories with similar propagation pathways in a given spatial distance and direction, from the eddy identification and tracking datasets obtained by satellite altimetry spanning nearly 20 years in the Southern Ocean. The major eddy channels of the Southern Ocean are more geographically correlated rather than determined by polarity (anticyclonic eddies (AEs) and cyclonic eddies (CEs)). Importantly, the main axes of zonal propagation for eddy channels are extracted in this study. In the area north of 45°S (30°S–45°S), the zonal propagation (both for AEs and CEs) is intrinsically westward along ∼42°S ± 2° (main axes). While in those south of 45°S (45°S–80°S), it is reversed to eastward, propagating zonally along ∼56°S ± 2° (main axes) and obviously showing a gyre pattern. The bottom topography significantly effects on the propagation pathways of eddy channels in the Southern Ocean. Mainly, their meridional propagation pathways are pronouncedly steered by the shape of oceanic ridges around isobath −3900m (AEs for −3,877 m, CEs for −3,922 m).