Dansgaard was the first paleoclimatologist to demonstrate that measurements of the trace isotopes oxygen-18 and deuterium in accumulated glacier ice could be used as an indicator of past climate. Dansgaard was the first to note deuterium excess, or a water sample's deviation from the global meteoric water line (GMWL) in ice cores. He found that the kinetic differences between hydrogen-1 and deuterium related to the temperature of source water, and the absolute humidity.
He was the first scientist to extract palaeoclimatic information from the American Camp Century ice core from Greenland drilled by the US army Cold Regions Research and Engineering Laboratory (CRREL). Dansgaard also took a leading role in the drilling of the first ice core to bedrock for scientific reasons, the DYE-3 core from South Greenland, 1,400 kilometres (870 mi) from the Camp Century. Confirming findings from the analysis of the Camp Century ice core, the DYE-3 climate profile documented the existence of rapid climate change, during and at the end of the last glacial. The repeated events of abrupt climate change during the glacial are named after Willi Dansgaard and his Swiss colleague, Hans Oeschger, and are known as Dansgaard-Oeschger events.
http://isis.ku.dk/kurser/blob.aspx?feltid=60066 - Professor Willi Dansgaard, 'Frozen Annals, Greenland Ice Sheet Research' free pdf download of this inspiring 2005 autobiography by the pioneer of Greenland Ice Core drilling. Hard copies of the book were only printed in limited numbers and are not generally for sale.