Evidence of Recent Climatic Changes Shown by Tibetan Highland Lakes

Abstract

IN I905 Ellsworth HuntingtonI observed that the Pangong Tso in Ladakh shows a set of benches and beach-lines which lie lower than any of the older terraces surrounding the lake. The latter, of which Godwin Austen in I866 said that they must be witnesses of the Ice Age, have unduly diverted the attention of explorers from a less conspicuous but equally important feature: the erosive and bathymetric evidence of recent climatic oscillations on the Tibetan highland lakes. During the summer of 1932 we 2 had occasion to spend several weeks in the immediate neighbourhood of the lakes Pangong, Pongur, Mirpa, Morari, and Kar in eastern Ladakh along the Kashmir-Tibetan boundary. Our geological and biological work provided, amongst other results, new information regarding changes of depth, of shore features, and related phenomena which bear witness to regional climatic oscillations of Post-Quaternary age. It may encourage those who visit lake shores to gather more data. The evidence for recent changes of lake-levels is topographic, physiographic, and hydrographic. Data gathered by former explorers most fortunately record changes in level and in local precipitation in Ladakh reaching back over one hundred years, which had made it possible to compare these oscillations and to trace their origin. The Pangong Tso, being the largest mountain lake north of the Himalaya (I3,9I5 feet above sea-level), gave the first evidence of recent topographic changes. When our pony caravan attempted to use an old path along the northern shore between Churtse and Lukung we found it impossible to proceed round the base of the cliffs as the path had become flooded. On the promontory which flanks the north-western part of Churtse bay the old path was found well constructed with large slabs of rock, and the road, which first follows a higher beach terrace, could be seen to lead into the lake, where the path continued 5 feet below the water and around the cliff. We noticed two drowned beaches at 3 and 5 feet which may also be recognized on Plate I. Natives from the hamlet of Lukung corroborated the recent rise of the lake. At some previous date a path had been constructed through the rocks above the cliff, but this road had long been out of use, for we were warned that it had been impassable for years. Sven Hedin3 however had been able to use it in I90I, from which we may conclude that the natives had since then con-