Warming of circumpolar deep water in Antarctica A million-year perspective on recent changes around Antarctica.

Climate coffee with Dave Chandler (NORCE) on 16 April 2025

Recording of the talk: https://youtu.be/QIy7dqeaj1E

Abstract

Future climate and sea level projections depend sensitively on Antarctic Ice Sheet response to ocean-driven melting and the resulting freshwater fluxes into the Southern Ocean. Circumpolar Deep Water (CDW) in the Southern Ocean is increasingly recognised as a crucial heat source for ice shelf melt. Quantifying past changes in the temperature of CDW is therefore of great benefit for modelling ice sheet response to past warm climates, and for putting recent and projected CDW temperature changes into context. Here we use marine sedimentary evidence to estimate CDW temperature changes over the last eight glacial-interglacial cycles (800,000 years). Estimated interglacial warming reached 0.6 ± 0.4 °C relative to present, while glacial cooling was typically −1.5 to −2 °C. The peak warmth occurred in the last interglacial, when sea-levels were a few metres higher than present. For comparison, observations indicate CDW warming of around 0.1 °C/decade since the 1990s, while climate projections (CMIP6 SP585) suggest 0.6 °C warming could already be reached by 2100.

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