Sensitivity of near-surface marine winds and wind stress in coastal Antarctica to regional atmospheric model configuration

Caton Harrison, Thomas ORCID: https://orcid.org/0000-0001-7870-7039; Lock, Adrian; Bracegirdle, Thomas J. ORCID: https://orcid.org/0000-0002-8868-4739; King, John C. ORCID: https://orcid.org/0000-0003-3315-7568; Lu, Hua ORCID: https://orcid.org/0000-0001-9485-5082; Silvano, Alessandro. 2025 Sensitivity of near-surface marine winds and wind stress in coastal Antarctica to regional atmospheric model configuration. Quarterly Journal of the Royal Meteorological Society, e5019. 10.1002/qj.5019

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Abstract/Summary

Near-surface marine winds in coastal Antarctica have global importance, as they affect ocean circulation and sea-ice variability. We test the sensitivities of simulated near-surface winds and wind stress in coastal Antarctica to uncertain aspects of regional atmospheric model configuration. The UK Met Office Unified Model (MetUM) is run in a limited-area setup over 10 months, evenly split between austral summer and winter. Tests include varying horizontal grid spacing, stable boundary-layer representation, surface exchange of momentum, and subgrid orographic drag. We focus especially on winds over the Cape Darnley polynya, which is important for Antarctic Bottom Water formation. Output from the MetUM correlates well with low-level winds from sonde, station, and satellite observations, especially in the summer months. However, the shape of the vertical profile of wind speed depends strongly on model configuration. Enabling the subgrid orography scheme and enhancing the scale of subgrid mountains leads to major reductions in near-surface wind speed over the steep coastal slopes and over the Cape Darnley polynya, which we attribute to an upslope shift in the extent of katabatic flow. Near-surface winds and wind stress over near-shore ocean regions are also highly sensitive to the configuration of sea-ice roughness, which disproportionately affects strong winds, again leading to especially large impacts over Cape Darnley. Stable boundary-layer representation has a moderate impact on boundary-layer winds but a relatively small effect at the surface. Varying horizontal grid spacing between 4, 12, and 40 km has a relatively minor impact on winds, even though the steepness of the coastal terrain is greatly affected. The results underscore the sensitivity of Antarctic marine coastal winds to some highly model-dependent aspects of atmospheric model physics, with implications for simulation of atmosphere–ocean coupling, sea-ice dynamics, and Antarctic Bottom Water production.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1002/qj.5019
Additional Keywords:	coastal winds, Antarctica, physics, resolution, simulations, polynya, sea ice
Date made live:	04 Jun 2025 13:08 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/539373

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