Strong quasi-stationary wintertime atmospheric surface pressure anomalies drive a dipole pattern in the Subantarctic Mode Water formation

Cerovečki, Ivana; Meijers, Andrew J.S. ORCID: https://orcid.org/0000-0003-3876-7736. 2021 Strong quasi-stationary wintertime atmospheric surface pressure anomalies drive a dipole pattern in the Subantarctic Mode Water formation. Journal of Climate, 34 (17). 6989-7004. 10.1175/JCLI-D-20-0593.1

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Text © 2021 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses) [15200442 - Journal of Climate] Strong Quasi-Stationary Wintertime Atmospheric Surface Pressure Anomalies Drive a Dipole Pattern in the Subantarctic Mode Water Formation.pdf - Published Version Download (5MB) | Preview

Abstract/Summary

The deepest wintertime (Jul-Sep) mixed layers associated with Subantarctic Mode Water (SAMW) formation develop in the Indian and Pacific sectors of the Southern Ocean. In these two sectors the dominant interannual variability of both deep wintertime mixed layers and SAMW volume is a east-west dipole pattern in each basin. The variability of these dipoles are strongly correlated with the interannual variability of overlying winter quasi-stationary mean sea level pressure (MSLP) anomalies. Anomalously strong positive MSLP anomalies are found to result in the deepening of the wintertime mixed layers and an increase in the SAMW formation in the eastern parts of the dipoles in the Pacific and Indian sectors. These effects are due to enhanced cold southerly meridional winds, strengthened zonal winds and increased surface ocean heat loss. The opposite occurs in the western parts of the dipoles in these sectors. Conversely, strong negative MSLP anomalies result in shoaling (deepening) of the wintertime mixed layers and a decrease (increase) in SAMW formation in the eastern (western) regions. The MSLP variability of the Pacific and Indian basin anomalies are not always in phase, especially in years with a strong El Niño, resulting in different patterns of SAMW formation in the western vs. eastern parts of the Indian and Pacific sectors. Strong isopycnal depth and thickness anomalies develop in the SAMW density range in years with strong MSLP anomalies. When advected eastward, they act to precondition downstream SAMW formation in the subsequent winter.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1175/JCLI-D-20-0593.1
ISSN:	0894-8755
Additional Keywords:	Atmosphere-ocean interaction; Oceanic mixed layer; Interannual variability; Oceanic variability
Date made live:	26 Jan 2021 11:52 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/529489

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