The Antarctic ice sheet and the triggering of deglaciations

A new physical mechanism involving the Antarctic ice-sheet extent is able to link climatic and CO2 glacial-interglacial changes. It is furthermore able to explain many features of the glacial cycles, like the 100 kyr oscillations or the peculiarities of stage I I (about 400 kyr BP). Indeed, from recent results, the glacial ocean bottom waters were possibly much more saline and consequently, may have an unsuspected large density. This glacial deep stratification could account for a significant part of the glacial-interglacial CO2 difference. The formation of these waters around Antarctica involves brine rejection over the continental shelves and is directly linked to changes in sea ice formation and Antarctic ice-sheet extent. Using this new scenario, we formulate a conceptual model that reproduce the succession and the amplitude of glaciations over the last few million years. This new mechanism furthermore provides the clue to understanding the changes in the main climatic frequency from 23 to 41 ka about 3 Myr ago and from 41 to 100 ka about I Myr ago. The Antarctic ice-sheet influence on bottom water formation could provide the "missing piece" to complete the astronomical theory of Quaternary climates. (C) 2004 Elsevier B.V. All rights reserved.