Long‐term sea surface temperature and climate change in the Australian–New Zealand region

Abstract

We compile and compare data for the last 150,000 years from four deep‐sea cores in the midlatitude zone of the Southern Hemisphere. We recalculate sea surface temperature estimates derived from foraminifera and compare these with estimates derived from alkenones and magnesium/calcium ratios in foraminiferal carbonate and with accompanying sedimentological and pollen records on a common absolute timescale. Using a stack of the highest‐resolution records, we find that first‐order climate change occurs in concert with changes in insolation in the Northern Hemisphere. Glacier extent and inferred vegetation changes in Australia and New Zealand vary in tandem with sea surface temperatures, signifying close links between oceanic and terrestrial temperature. In the Southern Ocean, rapid temperature change of the order of 6°C occurs within a few centuries and appears to have played an important role in midlatitude climate change. Sea surface temperature changes over longer periods closely match proxy temperature records from Antarctic ice cores. Warm events correlate with Antarctic events A1–A4 and appear to occur just before Dansgaard‐Oeschger events 8, 12, 14, and 17 in Greenland.