Hydroclimatic variations in the Tianshan Mountains based on grain size and geochemistry of core sediments since~1490 CE

Numerous studies have focused on modern hydroclimate and the modulated mechanisms in the Tianshan Mountains(TMs),arid central Asia.However,the detailed information of hydroclimatic processes beyond the instrumental period is still scarce.This paper reconstructed a hydrology history from core sediments of the Dalongchi Lake in the Tianshan Mountains.The comparability between endmembers(EMs)of grain size and ICP-AES based geochemical elements in the lake sediments highlighted their availability for hydrological reconstructions.Hydrodynamic forces(EM1,EM4,Ti/Al and Li/Al),chemical weathering intensity[(Mg+Ca+K)/Al],salinity proxy(Mg/Ca)and redoxsensitive proxy(Fe/Mn)highly correlated with the first principal component(P<0.01),whereas paleoproductivity proxies(TN,TOC,Ba/Al,Zn/Al and Cu/Al)and C/N showed high loadings on the second principal component(P<0.05).The inferred hydrology progress was nonlinearly responded to temperature,precipitation and climate-dictated glaciers.Specifically,the water level didn’t always covary with the humidity because of glaciers.The maximum water level was the comprehensive result of glaciers melting and high humidity around 1830 CE.Thereafter,water level continually decreased with declining moisture at high temperature,implying a limited buffering capacity of glaciers in the Dalongchi Lake basin.EM3-indicated eolian activity intensity was caused by the behaviors of Siberian High because the latter intensified surface wind and the dust transportation.The hydrothermal patterns were characterized by warm/dry and cold/wet alternations in a long run although warm/wet pattern was identified from a short-term view.

Toward understanding Cretaceous climate An updated review

New data and ideas are changing our view of conditions during the Cretaceous.Paleotopography of the continents was lower than originally thought,eliminating the'cold continental interior paradox'of fossils of plants that could not tolerate freezing occurring in regions indicated by climate models to be well below freezing in winter.The controversy over the height of Cretaceous sea levels has been resolved by knowledge of the effects of passage of the subducted slab of the Farallon Plate beneath the North American crust.The cause of shorter term sea level changes of the order of 30 to 50 meters is not because of growth and decay of ice sheets,but more likely the filling and release of water from groundwater reservoirs and lakes although there may have been some ice in the Early and latest Cretaceous.Carbon dioxide was not the only significant greenhouse gas;methane contributed significantly to the warmer climate.Suggestions of very warm tropical ocean temperatures(>40℃)have implications for the nature of plant life on land limited by Rubisco activase.The land surfaces were much wetter than has been thought,with meandering rivers and many oxbow lakes providing habitat for large dinosaurs.A major rethinking of the nature of conditions on a warmer Earth is underway,and a new suite of paleoclimate simulations for the Cretaceous is needed.