Origin of the 100,000-year timescale in Antarctic temperatures and atmospheric CO2

Abstract

Anew mechanism is proposed to explain the 100,000-year timescale for variations in Antarctic temperatures and atmospheric CO2 over the last 650,000 years. It starts with fluctuations in the oceanic overturning around Antarctica that release CO2 up to the atmosphere or trap it in the deep ocean. Every 50,000 years one of these fluctuations coincides with a changeover in the burial of CaCO3 in the deep ocean. The changeover alters the atmospheric pCO2 in a way that augments the tendency of the overturning. The augmented overturning then enhances the tendency of the CaCO3 burial, which augments the overturning, etc. In this way, an individual random fluctuation becomes one of the big transitions seen in the Antarctic ice cores. Alternating transitions toward the warm and cold states every 50,000 years produce the 100,000-year timescale. The 50,000-year time interval is set by the turnover time for CO3= ions in the ocean with respect to the CO2-induced weathering of silicate rocks and the burial of CaCO3 on the seafloor. Copyright 2008 by the American Geophysical Union.