Subpolar gyres

Collaborators: Andrew Thompson, Andrew Stewart, Shantong Sun

A schematic illustrating the discharge of subglacial meltwater into the ocean.
Figure 1: Contour map of annual mean temperature between 200-1000 m derived from available shipboard and Argo float data. Green lines represent select contours of dynamic ocean topography from Armitage et al. (2018) for the Weddell and Ross Gyres. Dark contours show the approximate position of the ACC. Annotated areas: Weddell Sea (WS), Bellingshausen Sea (BS), Amundsen Sea (AS) and Ross Sea (RS).

The Southern Ocean is arguably the central cog in the global ocean overturning circulation. In addition to connecting all the major ocean basins, the Southern Ocean facilitates the upwelling of deep, carbon-rich waters as well as the production of the dense bottom water that fills most of the abyssal ocean. While much of the deep water upwelling occurs within Antarctic Circumpolar Current (ACC), the production of bottom water occurs almost exclusively along the continental margins of Antarctica. In between the regions of deep water upwelling and the key sites of bottom water export lie the subpolar gyres—the most prominent of which are located in the Ross and Weddell Seas.

gyre schematic.
Figure 2: Schematic illustrating the transport of deep ocean heat across the polar gyres of the Southern Ocean. Circles with dots indicate eastward flow (out of the screen) while circles with crosses indicate westward flow (into the screen). Squiggly arrows denote vertical flux of heat and other deep ocean traces. Straighter arrows represent the mean flow of selected water masses: Circumpolar Deep Water (CDW), modified Circumpolar Deep Water (mCDW), Antarctic Bottom Water (AABW). In the gyre region, the tau symbol represents the wind stress curl.

Though many studies have examined the subpolar gyres in isolation, we still lack a firm understanding of the mechanisms that control their circulation and stratification. Perhaps more importantly, the role of these gyres as a bridge between the Antarctic Circumpolar Current and the continental shelf is not well comprehended. As a result, we lack clear intuition for how anomalies in the northern part of the Southern Ocean may be communicated across theses gyres to the Antarctic margin.

This project aims to address these gaps in our understanding and our main approach will be to carryout a series of idealized numerical simulations that reduce these gyres to their fundamental dynamics. In doing so, we hope to develop and sharpen our mechanistic understanding of these subpolar gyres and their role in shaping the broader, regional circulation.

Publications: This is a work in progress, so stay tuned!

Earle Wilson
Postdoctoral Scholar