Numerical study on the response of the largest lake in China to climate change

Lakes are sensitive indicators of climate change. There are thousands of lakes on the Tibetan Plateau (TP), more than 1200 of them having an area larger than 1 km2, but few observation data of lakes are available. Therefore, the thermal condition of the plateau lakes under the background of climate warming remain poorly understood. In this study, the China Meteorological Forcing Dataset developed by Institute of Tibetan Plateau Research, Chinese Academy of Sciences (ITPCAS), MODIS Land Surface Temperature (LST) data and buoy observation data were used to reveal the response of thermal conditions of Qinghai Lake to the recent climate change and to analyze the applicability of Freshwater Lake Model (FLake) to Qinghai Lake. Despite some deviations caused by model simplifications and uncertain forcing data, FLake demonstrated a good ability in capturing the seasonal variations of the lake surface temperature and the internal thermal structure of Qinghai Lake. The simulated lake surface temperature demonstrated a positive trend from 1979 to 2012, positively correlated with the air temperature and the downward longwave radiation, while negatively correlated with the wind speed and with the solar radiation but failing to pass the significance test. The simulated internal thermodynamic structure revealed that, if the impact of salinity is not considered, the Qinghai Lake is a dimictic lake with two overturn periods occurring in late spring and late autumn respectively. The surface and mean water temperatures significantly increased from 1979 to 2012, while the bottom temperatures showed no significant trend, even decreasing slightly from 1989 to 2012. The warming was the strongest in winter for both LST and air temperature. With the warming of the climate, the earlier ice break-up and later ice-on were simulated, having a strong effect on lake-air temperature differences in January and May.