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. What is a Climate Coffee? #climatecoffees are short (circa 40 min: 20 min talk + 20 min Q&A), relaxed meetings for scientists to share ideas, discuss methods, and communicate new results. They are open to speakers of all seniority; we especially encourage early-career scientists to become speakers. The Coffees are an exciting opportunity for scientists to build a network and disseminate recent results peer-to-peer. We invite researchers from across the climate science community to join us for this series of regular online knowledge exchange events.