Survival of the Qaidam mega-lake system under mid-Pliocene climates and its restoration under future climates

Abstract

Abstract. The Qaidam Basin in the north of the Tibetan Plateau has undergone drastic environmental changes during the last millions of years. During the Pliocene, the Qaidam Basin contained a freshwater mega-lake system although the surrounding regions showed increasingly arid climates. With the onset of the Pleistocene glaciations, lakes began to shrink and finally disappeared almost completely. Today, hyperarid climate conditions prevail in the low-altitude parts of the Qaidam Basin. The question of how the mega-lake system was able to withstand the regional trend of aridification for millions of years has remained enigmatic so far. This study reveals that the mean annual water balance, i.e. the mean annual change in terrestrial water storage in the Qaidam Basin, is nearly zero under present climate conditions due to positive values of net precipitation in the high mountain ranges and shows positive annual values during warmer, less dry years. This finding provides a physically based explanation for how mid-Pliocene climates could have sustained the mega-lake system and that near-future climates not much different from present conditions could cause water storage in reservoirs, raising lake levels and expanding lake areas, and may even result in restoration of the mega-lake system over geological timescales. The study reveals that a region discussed as being an analogue to Mars due to its hyperarid environments is at a threshold under present climate conditions and may switch from negative values of long-term mean annual water balance that have prevailed during the last 2.6 million years to positive ones in the near future.

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

“…However, changes in climate state can alter the TWS and lead to an imbalanced (e.g., Jiao et al., 2015; Y. Li et al., 2019; J. Wang et al., 2018). A recent study by Scherer (2020) revealed that under the present climate conditions, the in the QB is close to zero, and specific humidity is the main climate driver of the annual . He found that the annual positively correlates with the annual specific humidity.…”

“…Wang et al, 2018;. A recent study by Scherer (2020) revealed that under the present climate conditions, the ∆S in the QB is close to zero, and specific humidity is the main climate driver of the annual ∆S. He found that the annual ∆S positively correlates with the annual specific humidity.…”

“…Scherer (2020) revealed the regional‐scale climate driver of the . However, the large‐scale controlling mechanisms of in the QB are still not fully understood.…”

Influence of Large‐Scale Atmospheric Dynamics on Precipitation Seasonality of the Tibetan Plateau and Central Asia in Cold and Warm Climates During the Late Cenozoic

“…Another issue is the regional water balance that includes evaporation, precipitation, surface runoff, groundwater storage, and atmospheric humidity influx and loss. Scherer (2020) studied the local climatic driver of net water balance of the Qaidam Basin region in the CA, the mechanism of drying of the Qaidam mega‐lake and its possible restoration under warmer and wetter climate. Wang, Schmidt, et al.…”

Late Quaternary landscape evolution and paleoenvironmental implications from multiple geomorphic dryland systems, Orog Nuur Basin, Mongolia

“…However, detailed temperature reconstructions are lacking for this area. Based on a climate model, Scherer (2020) showed similar mechanisms for the Qaidam Basin, for example, slight changes in water balance allow growth and sustainability of the lakes on longer timescales.…”