Using Argo Float Data as a Tool to Investigate the Circulation of the Weddell Gyre

The Weddell Gyre plays a role in the climate system by advecting heat poleward to the Antarctic ice shelves and by regulating the density of water masses that feed the lowest limb of the global ocean overturning circulation. Warm Deep Water is the water mass that delivers heat to the Weddell Gyre, which is subject to complex modification processes to form Weddell Sea Deep and Bottom Water, providing an important sink for atmospheric heat and carbon dioxide. A fleet of Argo floats drifting in the currents of the upper 2000 m of the water column have recently provided data covering more or less the entire Weddell Gyre region in the horizontal, and Warm Deep Water in the vertical. Argo float data thus provide an opportunity to investigate surface to mid-depth ocean dynamics by providing both hydrographic and trajectory data. Here, Argo float profile and trajectory data are exploited in order to produce a full gyre scale view of the Weddell Gyre’s circulation from a purely observation-based dataset, whose pertinent features include the double-cell structure, with a stronger eastern core that intensifies with depth, and a weaker western core that remains invariant with depth. Considerable recirculation occurs within the gyre interior about the eastern core, before the water is able to fully traverse the zonal extent of the gyre, which causes considerable uncertainty when determining the gyre strength using single transects as is typical with ship-based surveys. Further investigation of the causes, temporal stability and the physical consequences of the recirculation cells along the central gyre axis, is required if we are to fully identify and understand the ways in which the Weddell Gyre may be changing in a rapidly changing climate