On the sensitivity of an ocean general circulation model to glacial boundary conditions

Several studies in the last two decades measuring stable isotope ratios #delta#"1"3C from foraminifera shells pointed out that during the last glacial maximum (LGM) the Atlantic thermohaline circulation was significantly different from the present day circulation, indicating a shallower and reduced North Atlantic deep water (NADW), while the compensating Antarctic bottom water (AABW) penetrated further northward. Here, we show a 3 D OGCM response to glacial wind stress and air temperature derived from an atmospheric GCM and salinity reconstructions adapted from #delta#"1"8O measurements in foraminifera shells. The OGCM includes a simplified biogeochemical cycle and reproduces the main features of the past #delta#"1"3C distribution with a reduction of the Atlantic ''conveyor belt'' by about the half at 30 S. Sensitivity experiments with respect to possible errors in the reconstructed salinity boundary fields show circulation patterns in the Atlantic ranging from an even stronger than the present day one to a nearly shut down of the ''conveyor belt'' circulation. Additionally, a sensitivity experiment with respect to uncertainties of the wind field in order of the glacial-interglacial amplitude shows that Atlantic overturning circulation is not severely affected. (orig.)SIGLEAvailable from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman