Kohfeld, Karen E.¹, Zanna Chase² and Robert F. Anderson³

¹Max Planck Institute for Biogeochemistry, Winzerlaer Strasse 10, 07745 Jena, Germany, Tel: +49 3641 57-6265, E-mail: kek@bgc-jena.mpg.de, ²Monterey Bay Aquarium Research Institute, 7700 Sandholdt Rd., Moss Landing CA 95039-0628, USA and ³Lamont-Doherty Earth Observatory, P.O. Box 1000, Palisades, NY 10964, USA

Glacial-interglacial changes in export production of the Southern Ocean

Increased biological utilization of surface-water nutrients in the Southern Ocean, via increased phytoplankton growth efficiency and export of biogenic material to the deep sea (export production), has been suggested to be an important factor contributing to the glacial lowering of atmospheric carbon dioxide concentrations. Here we show a compilation of nine different export production indicators from 65 deep-sea cores that highlights distinct regional changes in export production at the Last Glacial Maximum (LGM). Export production during the LGM was generally less than today at sites south of the Antarctic Polar Front (APF), but greater than today in the zone between the APF and the Subtropical Front, effectively creating a northward shift during the LGM in the zone of maximum export production. Overall, export production in the Southern Ocean during the LGM appears not to have been significantly greater than today. However, unlike today, when similar maximum levels of export production are found in all sectors of the Southern Ocean, substantial zonal gradients existed during the LGM. This feature is best illustrated by the burial rate of biogenic opal, which was greatest in the Atlantic sector of the glacial Southern Ocean and smallest in the Pacific sector. A similar pattern (Atlantic > Indian > Pacific) is seen in the accumulation rate of lithogenic material, suggesting that regional variability in the supply of iron may have contributed to regional variability in export production.