Subtropical North Atlantic Temperatures 60,000 to 30,000 Years Ago.

A reconstruction of sea surface temperature based on alkenone unsaturation ratios in sediments of the Bermuda Rise provides a detailed record of subtropical climate from 60,000 to 30,000 years ago. Northern Sargasso Sea temperatures changed repeatedly by 2 degrees to 5 degrees C, covarying with high-latitude temperatures that were previously inferred from Greenland ice cores. The largest temperature increases were comparable in magnitude to the full glacial-Holocene warming at the site. Abrupt cold reversals of 3 degrees to 5 degrees C, lasting less than 250 years, occurred during the onset of two such events (Greenland interstadials 8 and 12), suggesting that the largest, most rapid warmings were especially unstable.