The Interdecadal Variation Of The East Asian Monsoon Event In The Middle And Late MIS3

Bipolar abrupt events punctuating climate variability of the Last Glacialperiod have been identified worldwide in highly resolved terrestrial,marine and ice core records.The intensive study includes structure,timing and frequency of millennial-scale events during the last glacial period at present,forcing mechanism and transmission mechanism of these abrupt events also has many different hypotheses.A large number of bipolar climate records use of millennial-scale events details characteristics during the last glacial periodestablished the possible teleconnections of the two hemispheres climate change.Asian monsoon is an important part of the global climate system,is the bridge of north and south hemisphere climate change,so the research for behaviors of millennial-scale monsoon events during the last glacial period has important scientific significance,such as through the details comparison ofmillennial-scaleabrupt events between Asian monsoon region and bipolar high latitude,the low latitude atmospheric circulation is closely associated with the north and south high latitudetemperature change,through the spectrum analysis of the Asian monsoon evolution sequence to exploreoccurrence regularity and forcing mechanism of monsoon abrupt events.Here a newly retrieved and improved stalagmite oxygen isotope(?18O)record from the Yongxing Cave in Hubei province,central China is presented to provide an Asian monsoon history spanning 52 to33 kyr BP with an average 7-yr-resolution,based on 8U/Th dates,about1950 pairs of stable isotope data.High-resolution calcit?18O profiles show six millennial-scale strong monsoon events and two weak monsoon events,correlate well in timing and durationwith Dansgaard/Oeschger(D/O)events 6-9,12,13 and Heinrich event 4?5(H4?H5)identified in high-latitude regions ofthe Northern Hemisphere.The interannual resolution stalagmite record characterizes in detail themillennial-scale monsoon abrupt events.Asian monsoon recorded D06-8 events is similar to the form of an isosceles trapezoid,the intensity of monsoon maintain at a high level fora long time after monsoonenhanced rapidly,and then the intensity of monsoon weakened quickly,the three eventsidentify many of century-scalesecondary oscillationandthe internalpresent for "twin peaks" or "three peaks" structure;D09 event only lasted for hundreds of years,it characterized by"isosceles triangle" form of unimodal,monsoon intensity increased rapidly to a peak value and then decreases quickly;While D012,13 eventsshowed irregular shape with severe internal fluctuation.H4 and H5 events internal structure are divided into three processes,the process ofmonsoonenhancedandweakened are extremely fast,the bottom of monsoon events change are relatively slow.Stalagmites H4 and H5 events to the internal structure is divided into three process,monsoons and enhanced process is very fast,events at the bottom of the monsoon changes relatively slowly.The power spectrum analysis of stalagmites?180 data identified intense solar activity cycle with 595a,371a,261a,219a,208a,86a,44a,the use of empirical mode decomposition(EMD)algorithm to analysis YX175 stalagmites ??18O shows that Centennial scale solar activity cycle with maximum contributionrate,The resultillustrate that Asian monsoonwith close connections tosolar activity during the last glacial period.After the summer insolationat 65°N was removed,the de-trended stalagIite?18O record(??18O)with a significant negative correlation to Antarctic ice core record after time scaleadjustrentmthe stalagmite ??18O record is perfectly anti-phasedwith Antarctic temperature variability and in-phased with Greenland temperature on sub-orbital timescales.This correlation helps to established bipolar temperature phase relationship by the monsoonal bridge,that is anti-phase synchronization relationship between the temperature changes over Greenland and Antarctica is found to support the classic bipolar see-saw mechanism.And in contrast tostalagmite record with Greenland ice core record,the north Atlantic sea surface temperature,Antarctic-Stackice core record,found in different regions of millennial scale events almost synchronous changes of event time consistent support of the thermohaline circulation hypothesis.The north Atlantic sea surface temperature,Greenland ice core recordand Antarctic-Stackice core recordhigher similarity in century-scale,it shows that Asian monsoon evolution is closely related toAntarctic temperature.North high latitude climate change could first affect the Antarctic climate,and thenthe climate mutation signal is transmitted to the tropical Pacific through Antarctic,eventually affect the evolution of the Asian monsoon.Greenland temperature change may have an important impact on the Asian monsoon boundary area,but for monsoon core area or near the water source area,the Antarctic and southern ocean may play a more important role.