The Impact of Parameterized Lateral Mixing on the Antarctic Circumpolar Current in a Coupled Climate Model

Journal Article · Wed Apr 01 00:00:00 EDT 2020 · Journal of Physical Oceanography

DOI:https://doi.org/10.1175/JPO-D-19-0249.1· OSTI ID:1607828

Ragen, Sarah  ^[1]; Pradal, Marie-Aude ^[2]; Gnanadesikan, Anand ^[2]

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1. School of Oceanography, University of Washington, Seattle, Washington
2. Department of Earth and Planetary Sciences, The Johns Hopkins University, Baltimore, Maryland

This study examines the impact of changing the lateral diffusion coefficient A _Redi on the transport of the Antarctic Circumpolar Current (ACC). The lateral diffusion coefficient A _Redi is poorly constrained, with values ranging across an order of magnitude in climate models. The ACC is difficult to accurately simulate, and there is a large spread in eastward transport in the Southern Ocean (SO) in these models. This paper examines how much of that spread can be attributed to different eddy parameterization coefficients. A coarse-resolution, fully coupled model suite was run with A _Redi = 400, 800, 1200, and 2400 m ² s ⁻¹ . Additionally, two simulations were run with two-dimensional representations of the mixing coefficient based on satellite altimetry. Relative to the 400 m ² s ⁻¹ case, the 2400 m ² s ⁻¹ case exhibits 1) an 11% decrease in average wind stress from 50° to 65°S, 2) a 20% decrease in zonally averaged eastward transport in the SO, and 3) a 14% weaker transport through the Drake Passage. The decrease in transport is well explained by changes in the thermal current shear, largely due to increases in ocean density occurring on the northern side of the ACC. In intermediate waters these increases are associated with changes in the formation of intermediate waters in the North Pacific. We hypothesize that the deep increases are associated with changes in the wind stress curl allowing Antarctic Bottom Water to escape and flow northward.

• Research Organization: Johns Hopkins Univ., Baltimore, MD (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• Grant/Contract Number: SC0019344
• OSTI ID: 1607828
• Alternate ID(s): OSTI ID: 1803713
• Journal Information: Journal of Physical Oceanography, Journal Name: Journal of Physical Oceanography Vol. 50 Journal Issue: 4; ISSN 0022-3670
• Publisher: American Meteorological Society
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Oceanography
Eddies
Isopycnal mixing
Mesoscale processes
Climate models
Parameterization
Subgrid-scale processes