Sensitivity of Water Balance in the Qaidam Basin to the Mid-Pliocene Climate

Abstract

The Qaidam Basin (QB) is an intermontane endorheic drainage basin located in the northeastern Tibetan Plateau (TP) (Figure 1). The central and lower elevation part of the QB is hyperarid today, but paleogeographic studies revealed that the QB contained a freshwater megalake system during the Pliocene (Chen & Bowler, 1986;Mischke et al., 2010;J. Wang et al., 2012) even though the basin and surrounding mountain areas experienced general aridification throughout the Pliocene (Y. F. Miao et al., 2013;Rieser et al., 2009). With the beginning of the Pleistocene, the megalake system began to shrink. This process continued throughout the Pleistocene until today when only a few playas and saline lakes remain (J. Wang et al., 2012). In the mid-Pliocene (3 Ma), the global climate was warmer and wetter (Ravelo et al., 2004), while paleogeographic features were similar to those of today (Dowsett et al., 2010). The principal objective of this study is to investigate to what extent climate plays a role in the maintenance of the Qaidam megalake system during the mid-Pliocene.In an endorheic basin, the steady-state water balance (S) is zero (Broecker, 2010;Ibarra et al., 2018). S is defined as the total change in terrestrial water storage (TWS) within all the reservoirs inside the basin. However, changes in climate state can alter the TWS and lead to an imbalanced S (e.g.,