Abstract

Identifying the cause of the dramatic correlation between atmospheric CO₂ concentrations and climate variability during recent glacial cycles has been one of the principal goals of paleoclimate research over the past quarter century. New evidence from equatorial Pacific sediment cores indicates that increased strength of the ocean's biological pump was primarily responsible for drawdown of atmospheric CO₂ during the early stages of glaciation, and that increased ocean alkalinity (or, more specifically, an increase in the ocean carbonate ion concentration) led to a further reduction of atmospheric CO₂ during maximum glaciation. Increased strength of the biological pump is manifest as increasing differences between the carbon isotope composition of planktonic and benthic foraminifera during early stages of glaciation. Increased carbonate ion concentration is manifest by increased preservation and burial of calcium carbonate in deep equatorial Pacific sediments. New data show that these patterns were repeated systematically over at least the last three glacial cycles. There is still substantial uncertainty in the sensitivity of atmospheric CO₂ to each of these factors, but the records suggest roughly equal CO₂ drawdown by each process (biological pump and change in ocean alkalinity).

Light refreshments are served in the Interaction Area (4th floor of the Oceanography/Physics Building) at 4:00 p.m.

All seminars begin at 3:00 p.m. and are held in room 200 of the Oceanography/Physics building.