High precipitation and low evaporation resulted in high lake levels of the Juyanze paleolake, northwest China, during 34-26 cal kyr BP

摘要

ABSTRACT: This study addressed the lake evolution of the Juyanze paleolake with the goal of calculating precipitation and evaporation during 34-26 cal kyr BP, which will aid evaluation of the reliability of using lake level changes to assess past changes in climate. Fourteen paleoshorelines were recognized at the Juyanze paleolake, and 14C dating results showed that the highest 8 formed during 34-26 cal kyr BP. A unified Juyanze paleolake with an area of 7601 km2 reached 932 m above sea level (a.s.l.) at 34 cal kyr BP. The paleolake then decreased to an area of 6104 km2 and an elevation of 930 m a.s.l. at 32 cal kyr BP, and to 5589 km2 and 926 m a.s.l. at 26 cal kyr BP. Using water and energy balance equations, catchment paleo-precipitation and paleo-runoff were calculated for 3 previous periods. The results revealed that the catchment of the Heihe River required approximately 177 ± 29 mm yr-1 of precipitation to sustain the maximum lake area, which is a 32% increase compared with the modern value. Runoff from rivers to the lake was 61.9 × 108 m3 at 34 cal kyr BP, with a calculation error of ±22.3 × 108 to 29.7 × 108 m3. The humid climate and high lake levels of Juyanze paleolake that occurred during 34-26 cal kyr BP might have resulted from an enhanced monsoon. Moreover, low levels of evaporation may also have affected moisture changes.