Continuous Lake Recession of Siling Co, Central Tibet, Since the Middle Holocene
Thursday, 18 December 2014
Lake level changes and the associated water budget of closed lake basins are sensitive to climatic change. Although paleoshorelines around large lakes in Tibet were previously studied, reliable dating and surveying of these sequences of shorelines to reconstruct a detailed lake history in this region remain sparse. The rate of lake recession in response to paleoclimate changes remains poorly constrained. We have utilized flights of shoreline features with heights of up to 64 m above modern lake level within the Siling Co (lake) drainage basin to evaluate the history of the lake recession. Our results show that Siling Co underwent a continuous recession since ~ 4 ka from the Lingtong lake highstand (at ~ 4594 m in elevation). Simple calculations based on the history of these shorelines and the geometry of Siling Co lake basin suggest a systematic decrease in lake volume and surface area over the last 4 ka. Calculation of a ‘hydrologic index’ for closed lake basins (Mifflin and Wheat, 1979) suggests that historic lake levels reflect a decrease in effective moisture by a factor of 3 relative to the Middle Holocene lake highstand. The systematic recession of the lake likely reflects a progressive change in the water balance through time (rather than a protracted response to a step-function change). This is consistent with a weakening of the Indian Summer Monsoon. Our study shows how lacustrine shoreline archives can be used to quantify long-held inferences about the strength of the Indian Summer Monsoon.