Pb and Sr isotopic evidence of Saharan dust during the Last Glacial Maximum in the NEEM ice core, Greenland

초록

Pb and Sr isotopes were analyzed in the core sections from the NEEM (North Greenland Eemian Ice Drilling) ice core (~8?30.8 kyr b2k)? to identify the potential sources of dust transported to northwestern Greenland during the glacial period using a thermal ionization mass spectrometer (TIMS; TRITON, Thermo Scientific). Our data are the first high-resolution record of Pb and Sr isotopic composition obtained from the Greenland deep ice core, providing the characteristics of climate-related changes in concentrations and isotopic compositions. Previous isotopic studies suggested that the source of dust deposited in Greenland originated from Chinese deserts during the cooler periods and/or from glacial sediments adjacent to Greenland in warmer periods of the glacial period. However, the isotopic compositions of Sr determined in NEEM ice core show that dust in Greenland could have originated from the Sahara and Taklamakan deserts during the cold Greenland Stadial (GS). During the GS-2, the Last Glacial maximum (LGM), the isotopic ratios of the insoluble fractions are observed to be less radiogenic than the values in the silicate fractions. Sr isotopic composition coupled with Pb isotopic ratios suggests that the Sahara was the dominant source area of glacial dust in the NEEM ice core. Our high-resolution isotopic results provides the first evidence that the Saharan dust can’t be ruled out as a potential sources of Greenland dust during glacial periods.