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

Abstract

The Qaidam Basin (QB) in the northeastern Tibetan Plateau held a mega-lake system during the Pliocene. Today, the lower elevations in the basin are hyperarid. To understand to what extend the climate plays a role in the maintenance of the mega-lake system during the Pliocene, we applied the Weather Research and Forecasting model for dynamical downscaling of ECHAM5 global climate simulations for the present day and the mid-Pliocene.When imposing the mid-Pliocene climate on the QB with its modern land surface settings, the annual water balance (∆S), i.e., the change in terrestrial water storage within the QB, increases. This positive imbalance of ∆S induced solely by the changes in the large-scale climate state would lead to a readjustment of lake extent, until a new equilibrium state is reached, where loss due to evaporation over lake areas compensates for the feeding by runoff and precipitation. Atmospheric water transport (AWT) analysis at each border of the QB reveals that this imbalance of ∆S is caused by stronger moisture influx across the western border in winter, spring, and autumn and weaker moisture out-flux across the eastern border in summer. These changes in AWT are associated with the strengthening of the mid-latitude westerlies in all seasons, except for summer, and the intensification of the East Asian Summer Monsoon. Given that the mid-Pliocene climate is an analog to the projected warm climate of the near future, our study contributes to a better understanding of climate change impacts in Central Asia.

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

“…This finding has later been also demonstrated by Wang, Schmidt, et al. (2021) using dynamical downscaling techniques. They found that specific humidity, precipitation, and net precipitation were higher during the mid‐Pliocene, although air temperature was lower in the mid‐Pliocene over this region.…”

“…In regions with complex mountain topography, GCMs' predictions of orographic precipitation may be dry biased due to the GCM smoothing of regional topography (Tselioudis et al., 2012). Dynamic downscaling techniques in conjunction with paleoclimate GCM simulations could help improve precipitation prediction (e.g., Wang, Schmidt, et al., 2021). Furthermore, ECHAM5 tends to underestimate the moisture from the local recycling (Haese et al., 2013).…”

“…We assume that ECHAM5 is able to reproduce aspects of the regional hydroclimate over the TP and CA and the main dynamical features in the atmosphere. While ECHAM5 is able to reproduce modern and paleoclimate, including monsoonal Asian climate (e.g., Knorr et al., 2011; Li, Ehlers, Mutz, et al., 2016; Wang, Schmidt, et al., 2021), mesoscale and fine scale processes that are relevant for regional hydroclimate over land, such as local convection and soil evapotranspiration, are poorly resolved in ECHAM5 (e.g., Cheng et al., 2012).…”

“…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 (2021) further investigated the large-scale controls of water balance in the Qaidam Basin and revealed the role of mid-latitude westerlies and EASM in maintaining the Qaidam mega-lake under the mid-Pliocene climate. Our results are consistent with those of both Scherer (2020) and Wang, Schmidt, et al (2021), who predict higher mean annual precipitation (or long-term mean) in a mid-Pliocene-like climate across the TP and CA, as well as the possible formation and maintenance of mega-lake systems.…”

“…Moreover, past changes in regional hydroclimate over the northeastern TP are often interpreted as shifts in the Indo-Asian monsoons (e.g., Cheng et al, 2012). Wang, Schmidt, et al (2021) concluded that the difference in the moisture budget in the Qaidam Basin between the mid-Pliocene and the present is due to a combined effect of changes in the mid-latitude westerlies and the EASM. In general, regions influenced by the EASM have been shown to experience increased precipitation rates in the Pliocene, even in regions dominated by the mid-latitude storm tracks (Haywood et al, 2013).…”