Interpretation of glaciochemical records from an array of Greenland ice cores.

摘要

Ice cores provide very high resolution, well preserved records of paleoclimate conditions. Previous studies have shown that snowpack chemical concentrations are representative of atmosphere conditions at the time of deposition. Hence, glaciochemical records have been used to infer paleoclimate conditions of sea salt and dust aerosols, volcanism, industrial pollution, as well as to estimate changes in the elevation and mass balance of the Greenland ice sheet. Using a novel methodology called Continuous Flow Analysis - Trace Element Dual (CFA-TED), very high resolution, exactly co-registered glaciochemical records were developed for a broad range of species from an array of seven Greenland ice cores. These glaciochemical records were used to identify regional annual accumulation rates for the Greenland ice sheet and examine the impacts of both small and medium-scale spatial variability on accumulation records, thereby allowing for more meaningful comparisons with atmospheric processes. The glaciochemical records were also evaluated with Positive Matrix Factorization (PMF) to assess source apportionment and composition of bulk impurities. PMF results indicated the glaciochemical records are best characterized by three sources, interpreted as sea salts, carbonate dust, and crustal dust. The PMF source factors agreed well with literature, and represent the first time that carbonate and crustal dust sources have been quantifiably differentiated using high resolution glaciochemistry. The three PMF factors varied on seasonal, annual and multi-annual scales, and correlated closely with atmospheric circulation processes, such as the Arctic Oscillation. These results demonstrate that high resolution trace element glaciochemical records are useful tools for examining atmospheric and hydrologic conditions on the Greenland ice sheet over recent centuries.