Sea level changes forced ice breakouts in the Last Glacial cycle: new results from coral terraces

Abstract

Sea level cycles recorded by coral terraces at Huon Peninsula (HP) in Papua New Guinea match rapid climate changes that occurred between 30,000 and 65,000 years ago, seen in Greenland ice cores and marine sediments. Each cycle of 6000–7000 years ended with a sea level rise of 10–15 m lasting 1000–2000 years, following a longer period of falling sea level. Precise dating shows that each rise corresponds to a “Heinrich” episode of ice-rafted detritus in north Atlantic, signalling massive ice outbreak from north America. Sea level may be the trigger that forced near-synchronous breakouts of ice from north America and eastern Greenland. The HP sea level changes also correspond to similar cycles in benthic oxygen isotopes reported from the north Atlantic, which are too large to be explained entirely in terms of ice volumes. Jointly, the sea level and isotope records suggest that the north Atlantic deep ocean cooled as sea level fell and warmed as sea level rose, in each 6000-year cycle.