Meeting Documents

Detections of Submesoscale Coherent Vortices in the Seasonally Sea Ice-Covered Southern Ocean

Abstract

Coherent vortices are long-lived eddies that advect and mix heat, salt, and biogeochemical tracers throughout the ocean. The presence of coherent vortices in sea ice-covered regions may be especially important as the ice limits air-sea exchanges. Observations point to an abundance of subsurface-intensified eddies in the Arctic, generated by surface buoyancy fluxes from leads, polynyas, and ice-shelf processes; baroclinic instabilities of the interior flow; and flow above coastal topography. However, while various regional observational and modeling studies have indicated that eddies may be abundant beneath Antarctic sea ice, a comprehensive pan-Antarctic survey of sub-ice eddies has not previously been conducted. Additionally, the influence of these sub-ice eddies on regional ocean dynamics is presently not well accounted for.

In this study, we present the discovery of eddies in the Southern Ocean's seasonally sea ice-covered region using the Marine Mammals Exploring the Oceans Pole to Pole (MEOP) data set. These eddies were identified with an automated eddy-detection algorithm, which utilizes a time-series analysis of the data collected by individual swimming seals to locate anomalous water masses based on criteria such as anomalies in spice, isopycnal separation, and dynamic height, and their statistical significance relative to the background field. This algorithm was tested and optimized using output from the MITgcm LLC4320, a high-resolution global ocean simulation. We discuss the distribution and statistics of detected eddies and compare these findings with simulated eddies from the MITgcm LLC4320. Our findings provide a first observational characterization of eddies in the seasonally ice-covered Southern Ocean, which will serve as a basis for future investigation of their role in near-Antarctic circulation and tracer transport.