Preprints
https://doi.org/10.5194/tc-2022-133
https://doi.org/10.5194/tc-2022-133
 
17 Aug 2022
17 Aug 2022
Status: this preprint is currently under review for the journal TC.

Southern Ocean polynyas and dense water formation in a high-resolution, coupled Earth System Model

Hyein Jeong1,2, Adrian K. Turner3, Andrew F. Roberts3, Milena Veneziani3, Stephen P. Price3, Xylar S. Asay-Davis3, Luke P. Van Roekel3, Wuyin Lin4, Peter M. Caldwell5, Jonathan D. Wolfe3, and Azamat Mametjanov6 Hyein Jeong et al.
  • 1Institute of Ocean and Atmospheric Sciences (IOAS), Hanyang University, Ansan, South Korea
  • 2Department of Ocean Science and Technology, Hanyang University, Ansan, South Korea
  • 3Los Alamos National Laboratory, Los Alamos, New Mexico, USA
  • 4Brookhaven National Laboratory, Upton, New York, USA
  • 5Lawrence Livermore National Laboratory, Livermore, California, USA
  • 6Argonne National Laboratory, Lemont, Illinois, USA

Abstract. Antarctic Bottom Water is an important component of Earth's climate system. Its formation occurs through ocean-atmosphere-sea ice flux interactions in coastal and open ocean polynyas around Antarctica. In this paper, we investigate Antarctic dense water formation in the high-resolution version of the Energy Exascale Earth System Model (E3SM-HR). The model is able to reproduce the major Antarctic coastal polynyas, though they are smaller in area compared to observations. E3SM-HR also simulates several occurrences of open-ocean polynyas (OOPs) in the Weddell Sea, at a higher rate than what the last 50 years of satellite sea ice observational record suggests, but similarly to other high-resolution Earth System Model simulations. Furthermore, the densest water masses in the model are formed within the OOPs, rather than on the continental shelf, as is typically observed. Biases related to the lack of dense water formation on the continental shelf are associated with overly strong atmospheric polar easterlies, which lead to a strong Antarctic Slope Front and hence too little communication between on and off continental shelf water masses. Strong polar easterlies also produce excessive southward Ekman transport, causing a build-up of sea ice over the continental shelf and enhanced ice melting in the summer season. This in turn produces water masses on the continental shelf that are overly fresh and less dense relative to observations. Our results indicate that the large-scale polar atmospheric circulation around Antarctica must be accurately simulated in models to properly reproduce Antarctic dense water formation.

Hyein Jeong et al.

Status: open (until 12 Oct 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on tc-2022-133', Anonymous Referee #1, 08 Sep 2022 reply
  • RC2: 'Comment on tc-2022-133', Anonymous Referee #2, 12 Sep 2022 reply
  • RC3: 'Comment on tc-2022-133', Anonymous Referee #3, 20 Sep 2022 reply

Hyein Jeong et al.

Hyein Jeong et al.

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Short summary
We find that E3SM-HR reproduces the main features of the Antarctic coastal polynyas. Despite the high amount of coastal sea ice production, densest water masses are formed in the open ocean. Biases related to the lack of dense water formation are associated with overly strong atmospheric polar easterlies. Our results indicate that the large-scale polar atmospheric circulation must be accurately simulated in models to properly reproduce Antarctic dense water formation.