Calibration changes in the isotopic thermometer for snow according to different climatic states

Bore hole thermometry indicates that the estimated temperature shift at Sum mit (Greenland) from the Last Glacial to Holocene times was similar to 50% higher than the value obtained using the traditional isotopic delta (T) the rmometer calibrated with today's data. A mechanism offered by Boyle [1997] to explain the anomalous ice core delta shift is examined. The mechanism, c alled the Boyle Effect, is theoretically possible but if it operated at Sum mit, it appears to be only capable of accounting for slightly more than hal f of the Summit delta O-18 anomaly of similar to4.3%. A new semi-quantitati ve mechanism is proposed that could account for the remaining part of the a nomaly. Other mechanisms have been advanced but they are not so amenable to quantitative application and testing.