The chemical forms of water-soluble microparticles preserved in the Antarctic ice sheet during Termination I

摘要

This study clarifies changes in the chemical forms of microparticles during Termination I, the period of drastic climate change between the Last Glacial Maximum (LGM) and the Holocene. We determine the chemical forms of individual water-soluble microparticles through micro-Raman spectroscopy and compare the relative frequencies of different types with the ion concentrations in melted ice. Micro-Raman spectroscopy shows that Na2SO4・10H2O and MgSO4・11H2O are abundant in Holocene ice, while CaSO4・2H2O and other salts are abundant in LGM ice. Further, the number of CaSO4・2H2O particles is strongly correlated with the concentration of Ca2+ during Termination I. Taken together, the evidence strongly suggests that most of the Ca2+ exists as CaSO4・2H2O. The different compositions of microparticles from the Holocene and LGM can be explained by ion balance arguments.