AbstractThe causes for the rise of atmospheric CO2 during the last deglaciation are complex and remain a matter of controversial scientific discussion. One hypothesis explains this phenomenon with CO2 release from the deep ocean. A change in atmosphere-ocean interaction induced by a shift or intensification of Southern Hemisphere Westerlies (SHW) could have stimulated this process. Here this hypothesis is tested using oxygen isotope ratios of aquatic cellulose from Patagonian lacustrine sediments as west-wind proxy. Our record indicates maximum SHW strength at 52°S between 13.4 and 11.3 calibrated kyr B.P. This is in agreement with an increase in zonal wind strength extending to the southern mid-latitudes during the Younger Dryas chronozone triggering the final CO2 increase. Comparison with other Southern Hemisphere records implies southward migration of strengthened SHW at that time, leading to interglacial CO2 levels and hence terminating the Last Glacial.