Impact of amplified evaporation due to lake expansion on the water budget across the inner Tibetan Plateau

Abstract

Over the past decades, changing climate has exerted pronounced influences on the cryo‐hydrological environment on the Tibetan Plateau. One major manifestation is the widespread lake expansions over Tibetan endorheic basins. The enlarged lake water surface areas are expected to significantly alter land‐atmosphere water fluxes, which in return may pose feedbacks to the climate system and hydrological processes. The goal of this study is to investigate the potential influences of the recent lake expansions on amplifying the evaporation flux over the basins of inner Tibetan Plateau (ITP). We detected that the ITP lakes have experienced a net inundation increase of 4,542.3 km2 during 2000–2015, about 95.6% of which was contributed by lakes larger than 1 km2. We further estimated the land and water evaporations based on multi‐source, available actual evapotranspiration (ETa) and potential evapotranspiration data sets, and in situ evaporation records. The differences between land ETa and lake water evaporation were employed to represent the evaporation alternation over newly inundated basin (named “land‐to‐lake” hereafter) areas. The land ETa was estimated based on the average of three commonly used gridded data sets while the over‐lake evaporation was calculated by the empirical correction of potential evaporation estimates by spatial interpolation of pan evaporation. A conservative estimate using the pan coefficient of 0.6 indicates that the newly inundated lake area may have led to a potential evaporation increase of 3.08 ± 1.08 Gt/year on the ITP. The increased evaporation flux is close to half of the recent annual growth rate of lake water storage in the ITP. Despite unneglectable uncertainties, our estimates initiate an important assessment of how the recent lake expansion across the ITP has influenced the local land‐atmosphere interactions and the water cycle. Accounting this evaporation amplification is crucial to reduce the uncertainty in estimating basin‐scale water budgets and projecting the regional water balance.

Limited Contribution of Glacier Mass Loss to the Recent Increase in Tibetan Plateau Lake Volume

“…Our study focuses on the water budget at basin scale, and consequently does not investigate individual lake responses. However, we find that at the scale of the plateau, the increased lake mass corresponds to a sustained water excess of 6.0 ± 1.6 mm/yr, reduced to approximately 4 mm/yr if we account for the additional evaporation losses due to lake expansion (Song et al, 2019). In a qualitative approach, we can compare this value to the annual variability of the series of P and ET ( Table 3).…”

“…Even for the endorheic basins considered here, Δ(P-ET) is not directly comparable to the water excess, because of the additional evaporation due to lake area increase is not taken into account by reanalysis products (Song et al, 2019). Consequently, we do a simple scaling with the lake area change.…”

The Dependence of Ecosystem Water Use Partitioning on Vegetation Productivity at the Inter‐Annual Time Scale

“…Estimated ET has been validated against field observations by Miralles et al (2010). Both E PML and E G-LEAM have been widely used previously to reveal the linkage role of terrestrial evaporation in hydrological and biogeochemical cycles (Schwingshackl et al, 2017;Song et al, 2020;Wei et al, 2017). In this study, monthly E PML was aggregated to annual values at 0.5° × 0.5° spatial resolution for 1982-2011.…”

Century‐Scale Reconstruction of Water Storage Changes of the Largest Lake in the Inner Mongolia Plateau Using a Machine Learning Approach

“…Lake plays a crucial role in the global water cycle and ecological balance (Verpoorter et al., 2014). Under ongoing climate change and intensified human activities in the recent several decades, the area, water level, and storage of numerous lakes have experienced significant changes (Pickens et al., 2020; C. Song et al., 2014, 2020; S. Tao et al., 2020). Owing to remote sensing techniques, numerous studies focus on large‐scale research, which substantially contributes to revealing the characteristics of lake changes in different global regions (Pekel et al., 2016; Pickens et al., 2020; J. Wang et al., 2018; J. Zhu et al., 2020).…”