The Weddell Gyre heat budget associated with the Warm Deep Water circulationderived from Argo floats

The Weddell Gyre plays an important role in the global climatesystem by supplying heat to underneath the ice shelves and in the formation of deep and bottom water masses, which have been subject to widespreadwarming over past decades. In this study, we investigate the re-distributionof heat throughout the Weddell Gyre by diagnosing the terms of the heatconservation equation for a 1000 m thick layer of water encompassing thecore of Warm Deep Water. The spatial distributions of the different advectiveand diffusive terms in terms of heat tendencies are estimated using griddedclimatologies of temperature and velocity, obtained from Argo floats in theWeddell Gyre from 2002 to 2016. While the results are somewhat noisy on thegrid scale and the representation of the effects of eddy mixing is highlyuncertain due to the need to parameterise them by means of turbulent diffusion,the heat budget (i.e. the sum of all terms) closes (within the uncertaintyrange) when integrated over the open inflow region in the southern limb,whereas the interior circulation cell remains unbalanced. There is anoverall balance in the southern limb between the mean horizontal advectionand horizontal turbulent diffusion of heat, whereas the vertical termscontribute comparatively little to the heat budget throughout the WeddellGyre. Heat convergence due to mean horizontal advection balances withdivergence due to horizontal turbulent diffusion in the open southern limbof the Weddell Gyre. In contrast, heat divergence due to mean horizontaladvection is much weaker than convergence due to horizontal turbulentdiffusion in the interior circulation cell of the Weddell Gyre, due to largevalues in the latter along the northern boundary due to large meridionaltemperature gradients. Heat is advected into the Weddell Gyre along thesouthern limb, some of which is turbulently diffused northwards into theinterior circulation cell, while some is likely turbulently diffusedsouthwards towards the shelf seas. This suggests that horizontal turbulentdiffusion plays a role in transporting heat both towards the gyre interiorwhere upwelling occurs and towards the ice shelves. Horizontal turbulent diffusion is also a mechanism by which heat can be transportedinto the Weddell Gyre across the open northern boundary. Temporal deviationsfrom the mean terms are not included due to study limitations. In order toappreciate the role of transient eddying processes, a continued effort toincrease the spatial and temporal coverage of observations in the easternWeddell Sea is required.