Changes in water balance of the Qaidam Basin from Pliocene to present day

In the Pliocene, the Qaidam Basin in the northeastern Tibetan Plateau contained a freshwater mega-lake system. The lake system disappeared and the lower parts of the basin now feature hyperarid conditions. What led to the collapse of the lake system and could it appear again in the future? Understanding the sensitivity of the basin’s water balance to changes in atmospheric conditions is crucial for answering this question. We employed the Weather Research and Forecasting model for the dynamical downscaling of two time slices. These were simulated by ECHAM5-wiso atmospheric general circulation model under different boundary conditions, representing present day and Pliocene climate. We present a comparison study analyzing how the basin‘s water balance changes, when we put the Qaidam basin catchment area with its modern geographical features into the Pliocene climate environment. Furthermore, we investigate large scale controls of the basin’s water balance. We find that (1) the Basin’s water balance is more positive or less negative under Pliocene climate; (2) the atmospheric water transport from the west into the basin to be stronger under Pliocene than under present day conditions except for the summer months, while at the same time the influence of the Indian Summer Monsoon is weaker. The analysis suggests that minor changes in atmospheric boundary conditions can have substantial effects on the basin’s water balance.