Upper Quaternary Sea Levels, Coral Terraces, Oxygen Isotopes and Deep-sea Temperatures

Abstract

There are two widely used sea level curves for the last glacial cycle, one based on coral terraces at Huon Peninsula (HP) in Papua New Guinea, the other on oxygen isotope data from deep sea cores. Previous sea level estimates from HP are 20-40 m higher than isotopic sea levels for the interval 30-75 ka but new sea level data from HP support the isotopic sea levels. Computer simulations of coral terraces are more similar to observed HP terraces when the computer model is driven by the isotopic sea level curve than by the previous HP sea level curve. HP sea levels and benthic isotope records were used previously to calculate deep sea temperatures through the last glacial cycle the new HP results lead to a sharper indication that deep sea temperatures were up to 1.8°C cooler during the last glacial cycle than in the interglacials. The temperature estimates depend on the isotopic composition of Pleistocene ice sheets. However, if deep sea temperatures did not change, the HP sea levels require unrealistically low oxygen isotope values for the Pleistocene ice sheets. The model of cooler deep sea temperatures during glacial cycles is adopted here and was used to derive isotopic sea level changes using the V19-30 record over the last 330 ka. The isotopic sea levels before the last interglacial are consistent with the limited data available but need to be tested by high quality data from older coral terrace sequences.