Bahamian speleothem reveals temperature decrease associated with Heinrich stadials

Abstract

Temperature reconstructions across Heinrich stadials 1-3 are presented from an absolute-dated speleothem from Abaco Island in the Bahamas to understand the nature of climate change across these intervals in the subtropical Atlantic. The stalagmite carbonate record, dated by the U-Th geochronometry technique, includes higher δ18O and δ13C values within Heinrich stadials 1, 2, and 3 followed by rapid declines at the end of the stadials. To aid in the interpretation of these results, the δ18O of fluid inclusions associated with the Heinrich stadials were also analyzed. These measurements, which allowed for the relative influence of temperature and δ18O of precipitation to be distinguished, demonstrate minimal changes in the δ18O of fluid inclusions, suggesting that changes in the δ18O values of the speleothem carbonate associated with Heinrich stadials 1-3 are principally driven by an average ~4°C temperature decrease, rather than a change in the δ18O of the rainfall (hence rainfall amount). These findings support previous work in the North Atlantic and are consistent with the climate response to a weakening of the Atlantic meridional overturning circulation.