Seasonal and abrupt changes in the water level of closed lakes on the Tibetan Plateau and implications for climate impacts

• Examine the spatial patterns of alpine lake water-level variability.
• Analyze abrupt lake-level changes and possible climate causes.
• Link the lake level variations to the GRACE-observed TWS changes.

SummaryUsing ICESat laser altimetry data, we examine seasonal and abrupt changes in the water level of 105 closed lakes on the Tibetan Plateau (TP) from 2003 to 2009. The cluster analysis method is applied to categorize different temporal evolution patterns of lake level, and the links between abrupt lake-level variations of the different clusters in specific seasons and key climatic variables during 2003–2009 based on 12 weather stations are further analyzed. The results show that seasonal lake-level variations were featured by strong spatio-temporal heterogeneity. Most lakes, especially in south Tibet, the central and northeastern Tibetan Plateau, showed large water-level increases (0.307 ± 0.301 m/year) in warm seasons (March–October), while showed declines or minor fluctuations (−0.091 ± 0.202 m/year) in cold seasons (November–February). Many small lakes in the Changtang Plateau and northern TP showed negative water budgets in warm seasons due to low precipitation and strong evaporation, but positive water budgets depending on seasonal snow meltwater supply in cold seasons. These lakes can be partitioned into eight clusters according to the common characteristics of seasonal and consistent abrupt lake-level variations. Lakes of Clusters 4 and 5 are not analyzed in detail because of their scattered distributions. The abrupt lake-level rises or declines for Clusters 1, 2, 3, 7 were inferred to be closely associated with dramatic changes in precipitation and evaporation. For example, most lakes in Cluster 1 experienced the substantial water-level rises (∼0.99 m on average) in the warm season of 2005, which were largely attributable to the high precipitation and low evaporation in this season. The abrupt changes of water level for lakes in Clusters 6 and 8 (in the Changtang Plateau and northern TP) were probably associated with more snow meltwater supply. Time series of GRACE-observed terrestrial water storage changes confirm that the abrupt lake-level changes in specific seasons are associated with abnormal hydro-climatological conditions. Besides, the limitations of spatial pattern analysis of lake variations classification based on cluster analysis and the possible primary causes of lake level fluctuations are discussed.