The Warming of Large Lakes on the Tibetan Plateau: Evidence From a Lake Model Simulation of Nam Co, China, During 1979-2012

Lakes are considered as indicators of climate change on the Tibetan Plateau (TP). In the present study, we use the General Lake Model to simulate water temperature changes in Nam Co, the second largest lake on the central TP, for the period 1979-2012. The calibration and validation results demonstrate that this model is well suited for thermal simulation of Nam Co. The simulation results indicate that Nam Co has responded to the recent warming climate. The average summer surface water temperature fluctuated yearly, but its trend is positive at a rate of 0.52 +/- 0.25 degrees C per decade. At the same time, the onset of summer stratification advanced by 4.20 +/- 2.02d per decade, and the duration increased at a rate of 6.00 +/- 3.54d per decade. To explore the roles of air temperature and longwave radiation in lake warming, three sensitivity experiments are conducted by removing long-term trends from time series of air temperature and longwave radiation in the forcing data. These experiments prove that both increased air temperature and downward longwave radiation are two driving factors responsible for the warming of Nam Co.