Temperature estimation at the beginning of the last millennium in western Greenland: preliminary results from the application of a degree-day glaciological model on the Lyngmarksbrceen glacier

The last millennium is defined as a "stable" climatic period with anomalies such as the Little Ice Age (LIA:similar to 1450 AD to 1850 AD), a period marked by low temperatures and associated with a glacier advance. Also the Medieval Climate Anomaly (MCA:similar to 950 AD to 1250 AD), considered as a period at least as warm as nowadays and associated with glacier retreat in the northern hemisphere. However, several studies have shown that glacial advances have occurred during the MCA period in the Baffin Land and western Greenland, in contradiction with hemispheric-scale temperature reconstructions. In this study we propose temperature conditions for the last millennium determined from a recent study on the glacial fluctuations of the Lyngmarksbrceen glacier and the application of an empirical positive degree-day model (PDD) constrained by the outputs of the regional climate MAR atmospheric model. This simulation was conducted on the Lyngmarksbrceen glacier, which shows an original succession of nested moraines dated from the last millennium. The results show that the most likely scenarios are based on air temperatures in the range of -1.3 degrees C to -1.6 degrees C lower during the MCA than at the end of the 20th century if we consider a variation of about +/- 10% in precipitation. Sensitivity tests are then made on different parameters of the glaciological model to better constrain the uncertainty of the temperature estimations.