Preprints
https://doi.org/10.5194/egusphere-2023-21
https://doi.org/10.5194/egusphere-2023-21
 
10 Jan 2023
10 Jan 2023
Status: this preprint is open for discussion.

The Weddell Gyre heat budget associated with the Warm Deep Water circulation derived from Argo Floats

Krissy Anne Reeve1, Torsten Kanzow1,2, Olaf Boebel1, Myriel Vredenborg1, Volker Strass1, and Rüdiger Gerdes1,3 Krissy Anne Reeve et al.
  • 1Alfred Wegener Institute, Bremerhaven, Germany
  • 2Bremen University, Department of Physics and Electrical Engineering, Bremen, Germany
  • 3Jacobs University, Bremen, Germany

Abstract. 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.

Krissy Anne Reeve et al.

Status: open (until 07 Mar 2023)

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  • RC1: 'Comment on egusphere-2023-21', Anonymous Referee #1, 27 Jan 2023 reply

Krissy Anne Reeve et al.

Krissy Anne Reeve et al.

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Short summary
The Weddell Gyre is key for bottom water formation. Prior studies show warming of the whole water column, except the gyre’s heat source, Warm Deep Water (WDW). We use Argo floats to estimate a heat budget within WDW. Heat advects into the southern limb, and upwards from below throughout. Turbulent diffusion removes heat through the top, and transports heat from the southern limb into the interior, and southwards towards Antarctica. Turbulent diffusion imports heat across the northern boundary.