The impact of climatic conditions on Pb and Sr isotopic ratios found in Greenland ice, 7–150 ky BP
Résumé
We present here a time series of Pb and Sr isotopes in Greenland ice over the last glacial cycle. The data were obtained by analysing the dust contained in small (less than 10 g) aliquots of sections of the GRIP (European Greenland ice core project) ice core. The concentrations of Pb, Ba and Sr vary by large factors of 70, 140 and 75 respectively over this time period and show a significant correlation with δ18O, used as a proxy for temperature. Elemental ratios of Pb, Ba and Sr indicate the provenance of dust is mainly crustal with possible volcanic influences but the contribution from seawater is negligible. The Pb and Sr isotopic ratios change over time and form two distinct groups above and below a temperature corresponding to a δ18O value of − 39‰. While changing elemental concentrations may be explained by changes in wind strengths, the variation in isotopic composition appears to reflect climate induced changes in the source areas of dust deposited in the snow in Greenland. Available source data suggest that dust may originate from the Gobi Desert in central Asia in cooler periods and from glacial sediments adjacent to Greenland in warmer periods.