Climate and Groundwater Recharge During the Last Glaciation in an Ice-Covered Region

A multitracer study of a small aquifer in northern Switzerland indicates that the atmosphere in central Europe cooled by at least 5°C during the last glacial period. The relation between oxygen isotope ratios ($\delta^{18}$O) and recharge temperatures reconstructed for this period is similar to the present-day one if a shift in the $\delta^{18}$O value of the oceans during the ice age is taken into account. This similarity suggests that the present-day $\delta^{18}$O-temperature relation can be used to reconstruct paleoclimate conditions in northern Switzerland. A gap in calculated groundwater age between about 17,000 and 25,000 years before the present indicates that during the last glacial maximum, local groundwater recharge was prevented by overlying glaciers.