A new model for the role of the oceans in determining atmospheric PCO2

Recent ice-core measurements have revealed that the atmospheric CO2 level increased comparatively rapidly by about 70 ppm at the end of the last ice age. An ocean-atmosphere model is presented in which changes in the productivity of high latitude surface waters (from which deep water is formed and circulated around the world's ocean) and/or in the thermohaline overturning rate can lead to substantial change in atmospheric partial pressure of carbon dioxide (PCO2), over a concentration range 163-425 ppm. A major contribution to the low PCO2 of the last ice age may have been an increase in the net high latitude productivity, possibly coupled with a decrease in the thermohaline overturning.