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<p>The meridional overturning circulation makes a dominant contribution to the transport and budgets of heat, carbon and nutrients in the global ocean, with broad consequences for climate affecting terrestrial, oceanic and human ecosystems. Evidence is growing that the overturning circulation in both the Atlantic and Southern Oceans has slowed in recent decades and is projected to slow further as the planet warms. However, the significance of trends based on short instrumental records is debated, and models vary widely in the projected response of the circulation to changes in forcing. Here we use proxy records in deep-sea corals from the southwest Pacific to reconstruct Southern Ocean circulation over the past 1,300 years. We show that the Southern Ocean overturning circulation has declined irregularly over the past millennium and correlates on decadal to millennial timescales with a meridional overturning of the North Atlantic. Our results indicate that variability in Southern Ocean overturning historically precedes changes in the Atlantic, that overturning in both hemispheres is the weakest it has been over the past millennium and that local (North Atlantic) forcing since the mid-1900s has exacerbated an Atlantic overturning already preconditioned by Southern Ocean dynamics to remain weak.</p>

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Millennial-scale Atlantic overturning circulation led by the Southern Ocean

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年4月2日

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  • Ronald E. Thresher,
  • Stephen R. Rintoul,
  • Stewart J. Fallon,
  • Sylvain Richer de Forges,
  • Helen Neil,
  • Julie A. Trotter,
  • Craig Proctor,
  • Dianne M. Tracey

摘要

The meridional overturning circulation makes a dominant contribution to the transport and budgets of heat, carbon and nutrients in the global ocean, with broad consequences for climate affecting terrestrial, oceanic and human ecosystems. Evidence is growing that the overturning circulation in both the Atlantic and Southern Oceans has slowed in recent decades and is projected to slow further as the planet warms. However, the significance of trends based on short instrumental records is debated, and models vary widely in the projected response of the circulation to changes in forcing. Here we use proxy records in deep-sea corals from the southwest Pacific to reconstruct Southern Ocean circulation over the past 1,300 years. We show that the Southern Ocean overturning circulation has declined irregularly over the past millennium and correlates on decadal to millennial timescales with a meridional overturning of the North Atlantic. Our results indicate that variability in Southern Ocean overturning historically precedes changes in the Atlantic, that overturning in both hemispheres is the weakest it has been over the past millennium and that local (North Atlantic) forcing since the mid-1900s has exacerbated an Atlantic overturning already preconditioned by Southern Ocean dynamics to remain weak.