Search

This paper provides another look at the response of the Asian summer monsoon (ASM) to insolation forcing and oceanic feedback during the Holocene, using a fully coupled general circulation ocean–atmosphere model forced by Earth’s orbital variations. The model results revealed a recurrent circumglobal teleconnection (CGT) pattern in the summertime (June–July–August) mid-latitude circulation of the Northern Hemisphere during the Holocene. The CGT index showed a decreasing trend before ~5 ka BP and a slight increasing trend afterwards, affected by the combined effects of summer insolation, Indian summer monsoon (ISM), North Atlantic and Indian Ocean–western Pacific Ocean sea surface temperature (SST). The CGT showed a close relationship with ASM precipitation and surface air temperature during the Holocene and, therefore, could act as a bridge linking the ASM to insolation, high-latitude forcing (North Atlantic SST), and low-latitude forcing (tropical Ocean SST). We emphasize that the mid-latitude atmospheric circulation has been a key factor for the evolution of the ASM during the Holocene. In addition, the CGT provides a viable explanation for the out-of-phase relationship in the moisture evolution but an in-phase relationship in the speleothem δ18O between arid central Asia and the ISM region during the Holocene. [ABSTRACT FROM AUTHOR]

A comprehensive and integrative view of East Asian monsoon evolution during the Holocene is still under debate, and additional high-resolution proxy records from climatically sensitive locations are requisite to solve this complex issue. In this paper, we present three well-dated mud/peat cores from a paleo-pingo depression in the Sanjiang Plain, a climatically sensitive region to monsoon variation, to reveal the paleoenvironmental history of the wetland and discuss the regional impacts from monsoon evolution. A paleolake developed in the study area before 5.5 ka BP, and a peatland initiated thereafter consequent upon the gradual shrinking of the paleolake. This transition lasted until 4.5 ka BP, when the paleolake changed entirely to a wetland. Considering the prevalent monsoon climate in the Sanjiang Plain, we suggest that the lake-to-wetland transition from 5.5 to 4.5 ka BP indicates a rapid decline of the East Asian summer monsoon in addition to autogenic basin infilling processes. Such a remarkable monsoon weakening event has been documented across northern China, and we associate this with ocean–atmosphere interactions throughout low-latitude regions. [ABSTRACT FROM AUTHOR]

The moisture history in arid central Asia (ACA) differs from that in the Asian monsoon region during the Holocene. Much less is known about causes of Holocene moisture changes in ACA than Asian monsoon precipitation changes, hampering our understanding of their spatiotemporal differences. In this study, orbital-scale evolution of winter rainfall in northwestern China (a part of the core zone in ACA) during the Holocene and possible driving mechanisms are investigated using results from a long-term transient simulation performed by an atmosphere–ocean–sea-ice coupled general circulation model, the Kiel Climate Model, forced by orbital variations. Our results reveal a persistent wetting trend in northwestern China in winter throughout the Holocene, which is in response to winter insolation at mid-northern latitudes. Winter insolation can influence the rainfall via three ways. First, increasing latitudinal gradient of the incoming solar insolation at mid-latitudes strengthens the westerly intensity. Second, the evaporation is enhanced because of insolation-induced winter temperature rising, resulting in an increase in the air humidity. Intensified westerly winds and the increased water vapour together are conductive to enhance moisture transport towards northwestern China and thus increase winter precipitation in this area. Third, the increasing trend of winter insolation weakens the East Asian winter monsoon, which is favourable for the formation of rainfall via crippling the Siberian High that is beneficial for atmospheric lifting motion. [ABSTRACT FROM AUTHOR]