Holocene Southern Ocean surface temperature variability west of the Antarctic Peninsula

The Antarctic Peninsula is currently one of the fastest-warming locations on Earth, but its long-term variability has remained unclear. Amelia Shevenell and colleagues now use the TEX86 proxy, a palaeothermometer that tracks membrane lipids of the marine picoplankton Crenarchaeota, to show that a long-term cooling of about 4 °C occurred in waters near the tip of Antarctic Peninsula over the past 12,000 years. This is consistent with orbitally controlled changes in insolation. Shorter-term variability in temperature seems to have been strongly influenced by the position of the westerly winds. This work suggests that the present influence of the El-Nino Southern Oscillation system on the Antarctic Peninsula is a relatively recent phenomenon, dating to the late Holocene. The Antarctic Peninsula is currently one of the fastest-warming locations on Earth, but its long-term variability has remained unclear. This study uses TEX86 sea surface temperature proxy evidence to show that a long-term cooling of about 3–4 °C occurred in waters near the tip of the Antarctic Peninsula over the past 12,000 years, consistent with orbitally controlled changes in insolation. Shorter-term variability in temperature at the Antarctic Peninsula appears to have been strongly influenced by the position of westerly winds. The present influence of the El Nino/Southern Oscillation system on the Antarctic Peninsula may have arisen only during the late Holocene. The disintegration of ice shelves, reduced sea-ice and glacier extent, and shifting ecological zones observed around Antarctica1,2 highlight the impact of recent atmospheric3 and oceanic warming4 on the cryosphere. Observations1,2 and models5,6 suggest that oceanic and atmospheric temperature variations at Antarctica's margins affect global cryosphere stability, ocean circulation, sea levels and carbon cycling. In particular, recent climate changes on the Antarctic Peninsula have been dramatic, yet the Holocene climate variability of this region is largely unknown, limiting our ability to evaluate ongoing changes within the context of historical variability and underlying forcing mechanisms. Here we show that surface ocean temperatures at the continental margin of the western Antarctic Peninsula cooled by 3–4 °C over the past 12,000 years, tracking the Holocene decline of local (65° S) spring insolation. Our results, based on TEX86 sea surface temperature (SST) proxy evidence from a marine sediment core, indicate the importance of regional summer duration as a driver of Antarctic seasonal sea-ice fluctuations7. On millennial timescales, abrupt SST fluctuations of 2–4 °C coincide with globally recognized climate variability8. Similarities between our SSTs, Southern Hemisphere westerly wind reconstructions9 and El Nino/Southern Oscillation variability10 indicate that present climate teleconnections between the tropical Pacific Ocean and the western Antarctic Peninsula11 strengthened late in the Holocene epoch. We conclude that during the Holocene, Southern Ocean temperatures at the western Antarctic Peninsula margin were tied to changes in the position of the westerlies, which have a critical role in global carbon cycling9,12.