Biomarker Records of Phytoplankton Productivity and Community Structure Changes in the Central Yellow Sea Mud Area During the Mid-Late Holocene

The Yellow Sea （YS） environmental and ecological changes during the Holocene are driven by the interactions between the Yellow Sea Warm Current （YSWC）, the East Asian Winter Monsoon （EAWM） and the Kuroshio Current （KC）. We report marine biomarker records of brassicasterol, dinosterol and C37 alkenones in core ZY1 and core ZY2 from the South Yellow Sea （SYS） to reconstruct the spatial/temporal variations and possible mechanisms of phytoplankton primary productivity and community structure changes during the Mid-late Holocene. The contents of the corresponding biomarkers in the two cores are similar, and they also reveal broadly similar temporal trends. From 6kyr to 3kyr, the biomarker contents in the two cores were relatively low with small oscillations, followed by a distinct increase at about 3 kyr indicating productivity increases caused by a stronger EAWM. The alkenone/brassicasterol ratio （A/B） is used as a community structure proxy, which also showed higher values in both cores since 3 kyr, indicating increased haptophyte contribution to total productivity. It is proposed that the YS community structure has been mainly influenced by the YSWC, with stronger YSWC influences causing an increase in haptophyte contribution since 3 kyr. Some differences of the biomarker records between ZY2 and ZYI suggest spatial variations in response to YSWC and KC forcing. When the KC was intensified during the periods of 6-4.2kyr and 1.7-0kyr, the YSWC extended eastward, exerting more influence on core ZY1. On the other hand, when the KC weakened during 4.2-1.7 kyr, the YSWC extended westward, exerting more influence on the ZY2.

Effects of Intraseasonal Oscillation on the Anomalous East Asian Summer Monsoon During 1999

The 1999 East Asian summer monsoon was very unusual for its weak northward advance and remarkably anomalous climate conditions. The monsoonal southwesterly airflow and related rain belt in East Asia were blocked south of the Yangtze River Valley. The monsoonal airflow and major moisture transport conduct shifted eastward and turned northward to Japan from the tropical western Pacific rather than to East China from the South China Sea （SCS） as in normal years. Severe and prolonged drought occurred over extensive areas of North China and heavy precipitation in South China and Japan. The investigation on the possible intrinsic mechanisms related to such an anomalous monsoon year has shown that the unique behavior of intraseasonal oscillation may play an essential role during this process. During this year, the northward propagation of 30-60-day anomalous low-level cyclone/anticyclone collapsed in the region around 20°N and did not extend beyond the latitudes of the Yangtze River basin due to the barrier of strong cold air intrusion from the mid-latitudes. The southwesterly moisture flux on the northwestern flank of the anticyclonic moisture transport system in the western North Pacific, which was regulated by the northward shift of 30-60-day cyclonic/anticyclonic moisture transport, also did not reach the region north of 30°N as well. Under this circumstance, the weak northward advance of the monsoon westerlies and associated northward moisture transport could not arrive in North China and led to the severe droughts there in 1999. The SCS and South China were mostly affected by the airflow in the southern and northern flanks of the same 30-60-day cyclones or anticyclones, respectively, and thus controlled by the nearly reverse zonal wind and moisture convergent/divergent conditions. The rainfall in the SCS and South China showed out-of-phase oscillation through the transient local Hadley circulation, with the rainfall maximum occurring in the SCS （South China） when the 30-60-day anticyclone （cyclone） reached its peak phase.

Heinrich events recorded in a loess-paleosol sequence from Hexigten,Inner Mongolia

We describe the last glaciation climatic history Marine Isotope Stage(MIS, 2-4) from 66.7 ka to 14.5 ka in Hexigten, northeast Inner Mongolia, North China. The climate of the region experienced frequent and significant fluctuations between dry-cold and less dry-cold during the late MIS4. The climate was generally warm and humid during early MIS3(MIS3 c) and late MIS3(MIS3 a), whereas it was cold and dry in middle MIS3(MIS3 b) and during MIS2. In this study, the cold and dry conditions were correlated with a stronger East Asian winter monsoon and strong dune activity; whereas, warm and humid conditions were related to a stronger East Asian summer monsoon(EASM) and weak dune activity. This study establishes six distinct dry and cold intervals during the last glacial period(66.7-14.5 ka) based on optically stimulated luminescence data, multi-proxies record(magnetic susceptibility, grain size analysis, Rb/Sr, SiO2/TiO2) and chemical index of alteration(CIA). The last glacial period may be correlated with Heinrich events 1 to 6 which were further confirmed by comparison with the Hulu cave stalagmites and Greenland ice core records. It is concluded that the study area was substantially affected by the EASM, as compared with the loess-desert transition zone of the Chinese Loess Plateau, especially in MIS3 c and suggested that the East Asian monsoon played a pivotal role in the last glacial period climate and dune activity.

A Critical Inquiry into the Concept of East Asia （China, Japan, Korea） of the Past Centuries： In the Context of Asia＇s Image

In East Asia---China, Japan and Korea^there has always existed both a desire and hope for regional integration. Europe has been, and remains, a symbolic model of regional integration at political, economic, social and cultural levels. The hope to achieve a similar regional community has provided the momentum and impetus to think about a more general idea of East Asia： An idea that might substantiate the entire region＇s future prospects. Previously, East Asia has not been overly successful at generating any knowledge or understanding of its own identity. It is therefore necessary to conduct an inquiry into the concept of East Asia. The complexity of knowledge about East Asia should be clarified. This paper interprets the concept of East Asia in past centuries, explains how people conceptualized East Asia in the broader context of the continent and evaluates its characteristic features.

Evaluation of East Asian Summer Climate Prediction from the CESM Large-Ensemble Initialized Decadal Prediction Project

Based on surface air temperature and precipitation observation data and NCEP/NCAR atmospheric reanalysis data,this study evaluates the prediction of East Asian summer climate during 1959–2016 undertaken by the CESM(Community Earth System Model)large-ensemble initialized decadal prediction(CESM-DPLE)project.The results demonstrate that CESM-DPLE can reasonably capture the basic features of the East Asian summer climate and associated main atmospheric circulation patterns.In general,the prediction skill is quite high for surface air temperature,but less so for precipitation,on the interannual timescale.CESM-DPLE reproduces the anomalies of mid-and highlatitude atmospheric circulation and the East Asian monsoon and climate reasonably well,all of which are attributed to the teleconnection wave train driven by the Atlantic Multidecadal Oscillation(AMO).A transition into the warm phase of the AMO after the late 1990s decreased the geopotential height and enhanced the strength of the monsoon in East Asia via the teleconnection wave train during summer,leading to excessive precipitation and warming over East Asia.Altogether,CESM-DPLE is capable of predicting the summer temperature in East Asia on the interannual timescale,as well as the interdecadal variations of East Asian summer climate associated with the transition of AMO phases in the late 1990s,albeit with certain inadequacies remaining.The CESM-DPLE project provides an important resource for investigating and predicting the East Asian climate on the interannual and decadal timescales.

VALIDATION STUDY ON THE EAST ASIAN CLIMATE SIMULATED BY CCM2

The NCAR community climate model was run for 20 years and the simulated East Asian climate was analyzed and checked against the observation data.It is found that the large-scale features of the East Asia climate were simulated pretty well by the model,though there are still some discrepancies between the model output and the observation.The simulated geopotential height,wind and temperature fields are very close to the observations.The large scale systems such as subtropical high.Mongolia high,Indian low which have important influence on the East Asia monsoon also simulated pretty well.It is also found that the moisture field is not simulated so well as those fields mentioned above.The simulated precipitation is rather different from the observations.These suggest that some physical processes in the CCM2 need to be improved.