DONALD J. EASTERBROOK DISTINGUISHED SCIENTIST AWARD: Pleistocene Glaciation in the Gobi Desert

The Gobi Desert is in the arid core of Asia, with mean annual precipitation ranging from 50 to 120 mm/yr and temperatures from -35 to 40 °C. Elevations in the Gobi range from 400 m to 2600 m, and the desert floor is cut by E-W trending massifs of the Gobi-Altai range with elevations up to 3950 m. Modern icings are preserved year-round in favorable locations above ~2400 m; Pleistocene cryoturbation has been demonstrated at ~1700 m. Previous studies posed the question: were the massifs glaciated during the Pleistocene, or was the Gobi then so arid that the ELA was above the peaks? The answer has been equivocal. The Gobi is a large gap in the paleo-ELA map of Asia, and filling that gap is important for paleoclimatic studies there. Now it appears that the massifs were indeed glaciated, with their plateaus above ~2900 m covered by firn fields. The firn locally fell into canyons, contributing ice to glaciers that left behind sequences of moraines. This apparently happened repeatedly, as suggested by the eroded U-shaped form of the upper valleys. The combination of U-shaped valleys and high plateaus is seen widely in Central Asia, from the Kyrgyz Tien Shan to the southern border of Siberia. Modern analogs are present in the Altai range of western Mongolia. Although the estimation of the paleo-ELAs is inaccurate because of the avalanche nature of the glaciers, it appears to be ~3350 m in the Gichgeniy Nuruu, one of the Gobi massifs. The Gobi paleo-ELA is close to the value interpolated from larger glaciers to the north (Sayan) and south (Tibet). This finding is significant because it suggests that MIS-2 precipitation in the Gobi was sufficient that melting controlled ablation, as in southern Siberia, and not sublimation as in Kyrgyzstan.