Water Changes and Sources of Siling Co Using Landsat and GRACE Data since 1972

The inland lakes on the Tibetan Plateau (TP) are undergoing significant changes due to their sensitivity to climate. The largest lake in Tibet, Siling Co, has expanded most dramatically during recent decades. Using Landsat, GRACE and meteorological data, the expansion of Siling Co was detailed in four stages and the process was further explained. The results show that the lake area increased from 1 647.30 km2 in 1972 to 2 438.99 km2 in 2020. It experienced a slow growth at a rate 6.03 km2/yr from 1972 to 1988, while fluctuating at 1.44 km2/yr during 1989–1997, then accelerated at 60.28 km2/yr between 1998 and 2005, and expanded slowly again at 11.40 km2/yr since 2006. The continued expansion led to its merger with nearby Yagain Co in 2003. Terrestrial water storage (TWS) increase was also observed from GRACE (0.65 cm/yr), with about 0.75 coefficient of determination between the TWS and lake area during 2002–2020. The long-term expansion of Siling Co is related to the increasing trends of temperature and precipitation, but their contributions vary with time span. Specifically, the accelerated stage between 1998 and 2005 can be explained by the increased temperature and precipitation accompanied by a drop in evaporation, while the slow expansion since 2006 was due to the decrease in precipitation and temperature and the rise in evaporation. There is no obvious mass loss of glaciers revealed by GRACE during 2002–2020, which may be related to the negative trend of the temperature. Furthermore, the precipitation may still make a major contribution in this phase, as its average is about 93.9 mm higher than that in 1988–1997.