干旱区生态环境知识资源中心

[1] Terrestrial records of loess-paleosol sequences from across the Asian interior (Chinese Loess Plateau) have been used to reconstruct climatic conditions through the Quaternary and they correlate, in general, with oxygen isotope records from deep sea cores (e. g., the grain-size maxima from Chinese loess with ages that match well those of the last six Heinrich events evidenced in the North Atlantic marine sediments during the last glacial period). Possible reasons for this teleconnection of the similar climate signal of the North Atlantic and China are investigated by using an Earth system model of intermediate complexity (CLIMBER-2) for the typical period of last glacial age (during 60 20 kyr BP). By using the CLIMBER- 2 model, we have studied the response of East Asian climate during the typical glacial age (60-20 kyr BP) to Dansgaard/Oeschger (D/O) and Heinrich events. TotriggerD/O and Heinrich events in the model, transient forcings in addition to changes in insolation caused by variations in the Earth orbit are prescribed in the modeling experiment. These additional forcings include changes in inland-ice volume over North America, in freshwater flux into the northern North Atlantic. The modeling results show that the variations of the annual-mean near-surface air temperature over Eurasia closely follow climate changes in North Atlantic. The stronger intensity of westerly wind in the midlatitude of northern hemisphere versus the weaker Asian summer monsoon as well as the slightly weaker Asian winter monsoon (north easterly flow near surface) corresponds well with the (prescribed) Heinrich events during 60-20 kyr BP. This suggests that the climate signals found in Chinese loess (grain-size maxima with ages that match those of the last six Heinrich events) during the last glaciation are likely related to the relatively stronger westerly winds over Eurasia in boreal winter and a relatively weaker Asian summer monsoon that intensified the aridity of northern China which lead to expansion of the northern deserts during the Heinrich events.