Continuous profiles of deuterium excess in Holocene snow and ice in Greenland and Antarctica will be examined and correlated with currently available profiles of deuterium excess values in polar ice. These include two profiles of surface snow, one near Crete, Greenland, and one at DYE-3, Greenland, a section of Wisconsin ice at DYE-3, Greenland, and the Holocene last glacial maximum transition at Dome C, Antarctica. All of these profiles show clear, systematic changes in deuterium excess values accompanying changes in the isotope values. This project will determine the causes of changes in the deuterium excess values of polar snow and will examine changes in deuterium excess during the glacial to interglacial transition in Greenland, surface snow along coastal to inland transects in East Antarctica, seasonal cycles in East Antarctica, and modern vapor evaporating in the North Atlantic Ocean.