Long-term changes in evaporation over Siling Co Lake on the Tibetan Plateau and its impact on recent rapid lake expansion

Most lakes on the inner Tibetan Plateau (TP) have undergone significant expansion during recent decades. This is particularly true for the largest lake in Tibet, Siling Co Lake, which has expanded approximately 45% in area since the 1970s. However, the reason for such a substantial lake expansion remains unclear. As a closed lake, evaporation is the only output component as there is no outlet runoff. Therefore, precisely quantifying lake evaporation is crucial to elucidate the mechanism of lake expansion on the TP. In this study, long-term evaporation over Lake Siling Co was simulated using a single-layer Lake Evaporation model and the simulated result was verified by observation from an eddy covariance system in the lake. The results show that the single-layer Lake Evaporation model is capable of accurately simulating lake evaporation on a daily scale. The multiyear (1961-2015) mean annual evaporation over Siling Co Lake was 1066.9 mm and ranged from 826.8 mm to 1349.2 mm. The temporal variations in lake evaporation can be divided into three periods as follows: a significant increasing trend (12.3 mm yr(-1), P < .01) during the period 1961-1984, a significant decreasing trend (-10.2 mm yr(-1), P < .01) during the period 1985-2006, and a slightly increasing trend (4.3 mm yr(-1)) during the period 2007-2015. The main factors that controlled the changes in evaporation were wind speed for the period 1961-2006. According to previous reports, Siling Co Lake significantly expanded from 1972 to 2010. We found that the lake evaporation presented a significant decreasing trend (-4.7 mm yr(-1), P < .01) during this period, accelerating the rapid expansion of Siling Co Lake to some extent.