Decadal Thermal Variability of the Upper Southern Ocean: Zonal Asymmetry
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clim-JCLI-D-23-0649.1.pdf
Description
Published version
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35.22 MB
Format
Adobe PDF
Checksum (MD5)
230f00a06cf00773d88822059bd93793
Author(s)
Song, Yuanyuan
Li, Yuanlong
Hu, Aixue
Cheng, Lijing
Forget, Gaël
Chen, Xiaodan
Duan, Jing
Wang, Fan
Date Issued
May 17, 2024
Journal
Journal of Climate
Publisher
American Meteorological Society
Citation
Song, Y., Y. Li, A. Hu, L. Cheng, G. Forget, X. Chen, J. Duan, and F. Wang, 2024: Decadal Thermal Variability of the Upper Southern Ocean: Zonal Asymmetry. J. Climate, 37, 3117–3132.
Version
Final published version
Abstract
As the major sink of anthropogenic heat, the Southern Ocean has shown quasi-symmetric, deep-reaching warming since the mid-twentieth century. In comparison, the shorter-term heat storage pattern of the Southern Ocean is more complex and has notable impacts on regional climate and marine ecosystems. By analyzing observational datasets and climate model simulations, this study reveals that the Southern Ocean exhibits prominent decadal (>8 years) variability extending to ∼700-m depth and is characterized by out-of-phase changes in the Pacific and Atlantic–Indian Ocean sectors. Changes in the Pacific sector are larger in magnitude than those in the Atlantic–Indian Ocean sectors and dominate the total heat storage of the Southern Ocean on decadal time scales. Instead of heat uptake through surface heat fluxes, these asymmetric variations arise primarily from wind-driven heat redistribution. Pacemaker and preindustrial simulations of the Community Earth System Model version 1 (CESM1) suggest that these variations in Southern Ocean winds arise primarily from natural variability of the tropical Pacific, as represented by the interdecadal Pacific oscillation (IPO). Through atmospheric teleconnection, the positive phase of the IPO gives rise to higher-than-normal sea level pressure and anticyclonic wind anomalies in the 50°–70°S band of the Pacific sector. These winds lead to warming of 0–700 m by driving the convergence of warm water. The opposite processes, involving cyclonic winds and upper-layer divergence, occur in the Atlantic–Indian Ocean sector. These findings aid our understanding of the time-varying heat storage of the Southern Ocean and provide useful implications on initialized decadal climate prediction.
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DOI of Published Version
https://doi.org/10.1175/JCLI-D-23-0649.1
