ISOTOPIC EVIDENCE FOR REDUCED PRODUCTIVITY IN THE GLACIAL SOUTHERN-OCEAN

Records of carbon and nitrogen isotopes in biogenic silica and carbon isotopes in planktonic foraminifera from deep-sea sediment cores from the Southern Ocean reveal that the primary production during the last glacial maximum was lower than Holocene productivity. These observatio ns conflict with the hypothesis that the low atmospheric carbon dioxid e concentrations were introduced by an increase in the efficiency of t he high-latitude biological pump. Instead, different oceanic sectors m ay have had high glacial productivity, or alternative mechanisms that do not involve the biological pump must be considered as the primary c ause of the low glacial atmospheric carbon dioxide concentrations.