Lake Evolution Simulations In Global Closed Basins Since The Last Glacial Maximum Based On Water Balance Models

As an important part of global change research,paleoclimate change has always been a research hotspot in the field of international geoscience.Among many geological materials for paleoclimate research,lakes have become one of the core research fields in the international Past Global Changes(PAGES)project due to their high sensitivity to climate change.With the implementation of the Future Earth project,the primary mission of PAGES has shifted from paleoclimate research to predicting future environmental change based on paleoclimate data,therefore,conducting studies on paleolake evolution and climate change is crucial for assessing climate patterns in the context of future global warming.Previous studies have mostly used lacustrine sediment proxies to reconstruct sedimentary environments and climate conditions,or used numerical paleoclimate simulations to infer the driving mechanisms of climate change,however,lacustrine sediment proxies are often complicated,multiple and uncertain,and paleoclimate models have diverse versions due to the differences in resolution and parameterization schemes of different submodels.The effective combination of proxy reconstruction and numerical simulation has become a research trend to explore lake evolution and environmental change and their driving mechanisms.Meanwhile,the current researches on paleolake and climate simulation are mainly focused on the characteristic periods,while the continuous simulation researches on long time scale are relatively scarce.Accordingly,it is of great significance to perform continuous simulation experiments of lake evolution and climate change on long time scale for deeply understanding the paleoclimatological mechanisms of lake evolution,and scientifically assessing the future hydroclimatic pattern change.Covering about one-fifth of the terrestrial surface,the global closed basins with the relatively closed geographical environment,relatively independent water cycle and widespread lakes,are an ideal region for studying lake evolution and climate change on long time scale.Using paleoclimate models,paleoclimate proxies,virtual lake water balance model and basin water balance model,according to the principle of water balance,this study first conducted the continuous simulation of lake evolution since the Last Glacial Maximum,and the time-slice simulation of lake evolution during three characteristic periods in the global closed basins.Meanwhile,six typical closed basins were further selected to perform quantitative reconstruction of paleolake area and paleohydrological conditions of the basins.Then,combining the simulation and reconstruction results,the paleoclimatological mechanism of lake evolution is comprehensively discussed from three aspects of lake water balance components,atmospheric circulation system and climate forcing mechanism.On this basis,this paper attempts to assess the future hydroclimatic pattern of closed basins from the perspective of paleoclimatology.This study aims to deeply understand the lake evolution process and its paleoclimatological mechanisms in the global closed basins since the Last Glacial Maximum,with the purpose of providing a scientific basis for assessing the future development direction of water resources change.The main conclusions of this paper are as follows:(1)In global closed basins,the time-slice simulation of lake evolution during the Last Glacial Maximum(LGM),Mid-Holocene(MH)and Preindustrial(PI),and the continuous simulation of lake evolution since the LGM show that:the lake evolution since the LGM presents inverse variation in the mid-and low-latitude closed basins.And the overall performance is that the lake level in the mid-latitude closed basins of Western North America,Dry Andes and Patagonia,South Africa,and western Central Eurasia during the LGM is generally higher than that in the Holocene,while higher level lakes are widely developed in the low-latitude closed basins of Sahara and Arabia,Great Rift Valley,eastern Central Eurasia,and Australia during the early-to-mid Holocene when the lake level is generally higher than that in the LGM.In addition,most of the lakes in closed basins experience significant fluctuations in water level during the last deglaciation under the influence of abrupt warm and cold events.(2)In six typical closed basins,the reconstructions of paleolake area and paleohydrological condition show that:during the LGM,the area of Lahontan Lake in North America is about 13854 km~2,and the restored watershed precipitation is about417 mm;in Titicaca Lake Basin of South America,the lake area during the MH is about3873 km~2,and the watershed precipitation is about 466 mm;while the area of Chad Lake in Africa is about 301787 km~2 during the MH,and the reconstructed watershed precipitation is about 568 mm;in the eastern part of Asia,the area of Qinghai Lake during the MH and PI is about 5071 km~2 and 4814 km~2 respectively,and the watershed precipitation during the MH and PI is about 525 mm and 338 mm respectively;in the western part of Asia,the area of Van Lake during the LGM and MH is about 4383 km~2and 3813 km~2 respectively,and the watershed precipitation during the LGM and MH is about 511 mm and 650 mm respectively;besides,the area of Eyre Lake in Oceania during the LGM,MH and PI is about 0 km~2,6258 km~2and 790 km~2 respectively,and the watershed precipitation in the corresponding periods is about 138 mm,428 mm and233 mm respectively.(3)The combined results of lake evolution simulation and hydrological condition reconstruction indicate that:the high water level of Lahontan Lake during the LGM is caused by high precipitation and low evaporation;high precipitation and low evaporation also contribute to the occurrence of high water level in Titicaca Lake during the LGM,while high evaporation and low precipitation are the main factors leading to the sudden drop of water level in Titicaca Lake during the MH;low precipitation and high evaporation jointly result in the low water level of Chad Lake during the LGM and late Holocene,while high precipitation and low evaporation maintain the high water level of Chad Lake in the early-to-mid Holocene;precipitation change on long time scale is the decisive factor controlling the evolution direction of Qinghai Lake since the LGM;the occurrence of high water level in Van Lake during the LGM is mainly induced by low evaporation;the combination of low precipitation and high evaporation triggers the low water level of Eyre Lake during the LGM.The different responses to the monsoon-dominated climate and the westerly-wind-dominated climate are the reasons for the great differences in lake evolution and controlled factors in each closed basin since the LGM.More specifically,the general higher precipitation and lake level in the low-latitude closed basins during the early-to-mid Holocene are closely related to the strengthened summer monsoon circulation system in the low-latitudes,while the general higher precipitation and lake level in the mid-latitude closed basins during the LGM are in response to the changes in the intensity and position of the westerly wind circulation system in the mid-latitudes.Solar insolation change driven by the Earth’s orbit is the main forcing factor affecting the lake evolution pattern in the monsoon-dominated closed basins since the LGM,and greenhouse gases and continental ice sheets are the significant forcing factors controlling the lake evolution pattern in the westerly-wind-dominated closed basins since the LGM.Besides,meltwater injection regulates the lake evolution of most closed basins through influencing the change of Atlantic Meridional Overturning Circulation(AMOC)during the last deglaciation.(4)Over the last few decades,the declining trend of water resource in Western North America,Sahara and Arabia,and Central Eurasia possibly has inherited the decreased water volume conditions across the millennial-scale under the natural state,while the decreasing water resource in Dry Andes and Patagonia,and the increasing water resource in Great Rift Valley and Southern Africa may be temporary.Under the continued global warming in the future,the water volume in parts of Western North America,northern Dry Andes and Patagonia,northern Sahara and Arabia,and southwestern Central Eurasia will continue to decline,while in parts of southern Sahara and Arabia,southern Great Rift Valley,southeastern Central Eurasia,and eastern Australia it will continue to rise.