Abstract
Abstract. Frequently occurring mega-droughts under current global climate change have attracted broad social attention. A paleoclimatic perspective is needed to increase our understanding of the causes and effects of droughts. South-western (SW) China has been threatened by severe seasonal droughts. Our current knowledge of millennial-scale dry and wet phases in this region is primarily based on the variability of the Indian summer monsoon. However, water availability over land does not always follow patterns of monsoonal precipitation but also depends on water loss from evaporation and transpiration. Here, we reconstructed precipitation intensity, lake hydrological balance and the soil water stress index (SWSI) for the last 27 000 years. Grain size, geochemical and pollen records from Yilong Lake reveal the long-term relationships and inconsistencies of dry–wet patterns in meteorological, hydrological and soil systems in the central Yunnan region, SW China. Our results show that the long-term trends among precipitation, hydrological balance and soil moisture varied through time. The hydrological balance and soil moisture were primarily controlled by temperature-induced evaporation change during periods of low precipitation such as the Last Glacial Maximum and Younger Dryas. During periods of high precipitation (the early to late Holocene), intensified evaporation from the lake surface offset the effects of increased precipitation on the hydrological balance. However, abundant rainfall and the dense vegetation canopy circumvented a soil moisture deficit that might have resulted from rising temperature. In conclusion, the hydrological balance in the central Yunnan region was more sensitive to temperature change while soil moisture could be further regulated by vegetation changes over millennial timescales. Therefore, under future climate warming, the surface water shortage in the central Yunnan region may become even more serious. Our study suggests that reforestation efforts may provide some relief to soil moisture deficits in this region.
Highlights
The global land area experiencing extreme-to-exceptional terrestrial water storage drought could more than double by the late twenty-first century (Pokhrel et al, 2021)
It is generally thought that longterm dry and wet phases in SW China are primarily regulated by the intensity of monsoonal precipitation associated with the evolution of atmospheric circulation systems (Chen et al, 2014; Hillman et al, 2017; Sun et al, 2019; Wang et al, 2019)
The results show that the reconstructed precipitation is generally consistent with the regional pattern, with low precipitation during the Last Glacial Maximum (LGM) and the YD event and high precipitation during the B/A event and the early to middle Holocene
Summary
The global land area experiencing extreme-to-exceptional terrestrial water storage drought could more than double by the late twenty-first century (Pokhrel et al, 2021). Drought refers to the amount of water available in both the soil and hydrological systems, which are dependent on precipitation and a range of other factors. These include how much water is able to infiltrate to deeper ground layers or is lost as runoff, and how much is evaporated directly from water and soil surfaces, or transpired by plants (Breshears et al, 2005; Dai et al, 2018; Feng and Liu, 2015; Mishra and Singh, 2010; Trenberth et al, 2014).
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