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January 10, 2023 Krissy Anne Reeve; Torsten Kanzow; Olaf Boebel; Myriel Vredenborg; Volker Strass; Rüdiger Gerdes

The Weddell Gyre plays an important role in the global climate system by supplying heat to underneath the ice shelves, and to the formation of deep and bottom water masses, which have been subject to widespread warming over past decades. In this study, we investigate the redistribution of heat throughout the Weddell Gyre by diagnosing the terms of the heat conservation equation for a 1000 m thick layer of water encompassing the core of Warm Deep Water. The spatial distribution of the different advective and diffusive terms in terms of heat tendencies are estimated using gridded climatologies of temperature and velocity, obtained from Argo floats in the Weddell Gyre from 2002 to 2016. While the results are somewhat noisy on the grid scale, the heat budget (i.e., the sum of all terms) nearly closes when integrated over the southern limb and the interior circulation cell of the Weddell Gyre. There is an overall balance between the mean horizontal advection and horizontal turbulent diffusion of heat, whereas the vertical terms contribute comparatively little to the heat budget. Heat convergence due to mean horizontal advection balances with divergence due to horizontal turbulent diffusion in the southern limb of the Weddell Gyre. In contrast, heat divergence due to mean horizontal advection nearly balances with convergence due to horizontal turbulent diffusion in the interior circulation cell of the Weddell Gyre. Heat is advected into the Weddell Gyre along the southern limb, some of which is turbulently diffused northwards into the interior circulation cell, while some is turbulently diffused southwards towards the shelf seas. This suggests that horizontal turbulent diffusion plays a role in transporting heat both towards the gyre interior where upwelling occurs, as well as towards the ice shelves. Horizontal turbulent diffusion is also a mechanism by which heat can be transported into the Weddell Gyre across the open northern boundary.

Publication DOI: https://doi.org/10.5194/egusphere-2023-21