Inter-basin contrast in the Southern Ocean warming.

Area of Science:

• Oceanography
• Climate Science
• Earth System Science

Background:

• The Southern Ocean (SO) is critical for global ocean heat uptake.
• Deep-reaching warming trends are observed in the SO (35°S-55°S).
• Previous studies indicate significant heat uptake but lack detailed inter-basin comparisons.

Purpose of the Study:

• To investigate and quantify the inter-basin differences in Southern Ocean warming rates.
• To identify the driving mechanisms behind observed warming contrasts.
• To project future trends in Southern Ocean warming.

Main Methods:

• Analysis of historical oceanographic data (past six decades).
• Ocean-only and coupled climate model experiments.
• Comparison of warming rates between the Atlantic-Indian and Pacific sectors of the SO.

Main Results:

• The Atlantic-Indian sector warmed 40.0% ± 5.7% faster than the Pacific sector (0-700m depth).
• Warming rates nearly doubled in the Atlantic-Indian sector around 44°S.
• Wind-driven heat redistribution, not surface heating, is the primary cause of the contrast.
• Intensifying and poleward-migrating westerly winds enhance heat convergence in the Atlantic-Indian sector.

Conclusions:

• A significant and persistent inter-basin contrast in Southern Ocean warming exists.
• Altered wind patterns are the main driver of this regional warming disparity.
• This contrast is projected to intensify through the 21st century.
• Findings have implications for SO climate, ice mass balance, and marine ecosystems.