Climate information imprinted in oxygen-isotopic composition of precipitation in Europe

Abstract

In this study we analyze the interannual variability of the oxygen-isotopic composition of winter precipitation ( δ 18 O prec ) over Europe and investigate its related climate information. For this purpose we compare winter temperature, precipitation and δ 18O prec modeled by the atmospheric general circulation model ECHAM5-wiso with different observational datasets over Europe. In general the model and data results are very similar for the present-day climate and the modeled δ 18 O prec is matching the Global Network of Isotopes in Precipitation station data. ECHAM5-wiso only slightly underestimates the temperatures over Europe (mean difference ~ 0.4 °C). The mean European precipitation amount is very similar (~ 85 mm/month), however in central western Europe the modeled precipitation is overestimated by up to 30 mm/month. We also evaluate the large-scale circulation associated with the regional δ 18 O prec values. By correlating the North Atlantic Oscillation (NAO) index to modeled δ 18 O prec fields, we show that the NAO pattern is most pronouncedly imprinted in δ 18 O prec over central western Europe, consistent with observations. We demonstrate for an example location near a stalagmite site in central Germany, how local isotope-related climate variables are related to large-scale European climate variability. We find that, in both the model results and the data, present-day winter variability of local δ 18 O prec is strongly related to atmospheric circulation (remote sea-level pressure fields) and much less to the local and remote temperature or precipitation fields. The simulated correlation pattern resembles the NAO pattern, but is tilted to the east due to the combined effect of temperature and precipitation.