Climate changes in the Qaidam Basin in NW China over the past 40 kyr

Little is known about the climate and environmental changes that have occurred in the extremely arid regions of China since MIS (Marine Isotope Stage) 3 (59-29 cal kyr BP), when most regions in northwestern China and the Tibetan Plateau featured warm and humid conditions. In this paper, we present a record of the climate changes in the Qaidam Basin in arid northwestern China over the past 40 kyr based on the mineralogy of a 35-m-long sediment core recovered from Qarhan Salt Lake. Our results show that the lake was a saline or hyper-saline lake saturated with respect to gypsum between 40 and 33 cal kyr BP. Beginning at 33 cal kyr BP, evaporite formation was dominated by halite precipitation, indicating that the lake salinity had increased extensively and that the climate became drier during 33-24.5 cal kyr BP. The lake salinity then increased continuously, resulting in the appearance of bischofite between 24.5 and 14.6 cal kyr BP. The disappearance of bischofite and the increase in gypsum indicate that the salinity of the water decreased slightly between 14.6 and 8.3cal kyr BP. However, during the last 8300 years, the lake has dried up and is now a playa. Generally, the climate was wet in late MIS 3, arid in MIS 2 (29-11.7 cal kyr BP), and hyperarid in the Holocene. The relatively humid conditions may have resulted from weak evaporation caused by the relatively low insolation and intense ice-albedo feedback in late MIS 3. The decreased insolation and dramatically increased Eurasian ice volume in MIS 2 may have led to limited precipitation, which resulted in persistent dry climate conditions in the Qaidam Basin. In the Holocene, the reduction in ice volume reduced the albedo, and this change, in conjunction with increased insolation, may have led to evaporation exceeding local precipitation, resulting in hyperarid climate conditions in the Qaidam Basin.