Mid-Holocene Climate Variations Recorded by Palaeolake in Marginal Area of East Asian Monsoon: A Multi-proxy Study

Traditionally, the mid-Holocene in most parts of China was thought to be warmer with higher precipitation, resulting from a strong Asian summer monsoon. However, some recent researches have proposed a mid-Holocene drought interval of millennial-scale in East Asian monsoon margin areas. Thus whether mid-Holocene was dry or humid remains an open issue. Here, Zhuyeze palaeolake, the terminal lake of the Shiyang River Drainage lying in Asian monsoon marginal areas, was selected for reconstructing the details of climate variations during the Holocene, especially mid-Holocene, on the basis of a sedimentological analysis. Qingtu Lake (QTL) section of 6.92m depth was taken from Zhuyeze palaeolake. Multi-proxy analysis of QTL section, including grain size, carbonate, TOC, C/N and δ13C of organic matter, was used to document regional climatic changes during 9-3 cal ka B.P. The record shows a major environmental change at 9.0-7.8 cal ka B.P., attributed to a climate trend towards warmth and humidity. This event was followed by a typical regional drought event which occurred during 7.8-7.5 cal ka B.P. And a warm and humid climate prevailed from 7.5 to 5.0 cal ka B.P., attributed to the warm/humid Holocene Optimum in this region. After that, the climate gradually became drier. Moreover, comparison of the climate record from this paper with the summer insolation at 30°N indicates that the climate pattern reflecting the Asian monsoon changes was caused by insolation change.

Drought fluctuations based on dendrochronology since 1786 for the Lenglongling Mountains at the northwestern fringe of the East Asian summer monsoon region

The Lenglongling Mountains （LLM） located in northeastern part of the Tibet Plateau, belong to a marginal area of the East Asian summer monsoon （EASM） and are sensitive to monsoon dynamics. Two tree-ring width chronologies developed from six sites of Picea crassifolia in the LLM were employed to study the regional drought variability. Correlation and temporal correlation analyses showed that relationships between the two chronologies and self-calibrated Palmer Drought Severity Index （sc_PDSI） were significant and stable across time, demonstrating the strength of sc_PDSI in modeling drought conditions in this region. Based on the relationships, the mean sc_PDSI was reconstructed for the period from 1786 to 2013. Dry conditions prevailed during 1817-1819, 1829-1831, 1928-1931 and 1999-2001. Relatively wet periods were identified for 1792-1795 and 1954-1956. Spatial correlations with other fourteen precipitation/drought reconstructed series in previous studies revealed that in arid regions of Northwest China, long-term variability of moisture conditions was synchronous before the 1950s at a decadal scale （1791-1954）. In northwestern margin of the EASM, most of all selected reconstructions had better consistency in low-frequency variation, especially during dry periods, indicating similar regional moisture variations and analogous modes of climate forcing on tree growth in the region.

High-frequency climatic fluctuations over the past 30 ka in northwestern margin of the East Asian monsoon region, China

Whether millennial-to centennial-scale climate variations throughout the Holocene convey universal climate change is still widely debated.In this study,we aimed to obtain a set of high-resolution multi-proxy data(1343 particle size samples,893 total organic carbon samples,and 711 pollen samples)from an alluvial-lacustrine-aeolian sequence based on an improved age-depth model in the northwestern margin of the East Asian monsoon region to explore the dynamics of climate changes over the past 30 ka.Results revealed that the sequence not only documented the major climate events that corresponded well with those reported from the North Atlantic regions but also revealed many marked and high-frequency oscillations at the millennial-and centennial-scale.Specifically,the late stage of the last glacial lasting from 30.1 to 18.1 cal.ka BP was a dry and cold period.The deglacial(18.1-11.5 cal.ka BP)was a wetting(probably also warming)period,and three cold and dry excursions were found in the wetting trend,i.e.,the Oldest Dryas(18.1-15.8 cal.ka BP),the Older Dryas(14.6-13.7 cal.ka BP),and the Younger Dryas(12.5-11.5 cal.ka BP).The Holocene can be divided into three portions:the warmest and wettest early portion from 11.5 to 6.7 cal.ka BP,the dramatically cold and dry middle portion from 6.7 to 3.0 cal.ka BP,and the coldest and driest late portion since 3.0 cal.ka BP.Wavelet analysis results on the total pollen concentration revealed five substantially periodicities:c.5500,2200,900,380,and 210 a.With the exception of the c.5500 a quasi-cycle that was causally associated with the Atlantic meridional overturning circulation,the other four quasi-cycles(i.e.,c.2200,900,380,and 210 a)were found to be indirectly causally associated with solar activities.This study provides considerable insight into the dynamic mechanism of the Asian climate on a long-time scale and future climatic change.

Collating Historic Weather Observations for the East Asian Region： Challenges, Solutions, and Reanalyses

1. IntroductionHistoric instrumental weather observations, made on land or at sea from as early as the 17th century （e.g.,Camuffo et al.,2010）,are integral to extending our understanding of the decadal and centennial variations of Earth＇s climate and for comparison with paleo-proxy data.

Economic growth and unemployment in East Asia

Barro and Sala-i-Martin （2004） analyzed the empirical determinants of growth. The data used in this paper consists of panel data of several macroeconomic variables observed for 55 years 0950-2004） in six East Asian countries and regions. Following the implications of semi-endogenous growth theory, the author regressed output growth on the determinants of steady-state income. The estimation and test results suggest the existence of significant relationship between steady-state income and （trend weighted） R ＆ D input both in Japan and South Korea. In addition, following Cellini （1995）, the author also considers cointegration and error-correction methods as the growth regression of East Asian countries. Meanwhile, Chang, et al （2004） derived the conclusion that the decreases in reallocation shocks are main factor in a downward trend in natural rate of unemployment for South Korea. The author extends this analysis using structural VAR to other Asian countries and regions, Japan and Taiwan region. Impulse responses show that the growth of production in Korea and Taiwan reduce unemployment, but, in Japan, this raises unemployment.

East Asian Regional Cooperation Network and China’s Path Choice

The current East Asian regional cooperation framework is a complex system with multiple fields,levels,and players.In terms of social network theory and analysis,the East Asian regional cooperation framework can be defined as an affiliation network of cooperative mechanisms and players.Combing through the process of East Asian regional cooperation and constructing an East Asian regional cooperation network on the basis of the affiliation network model shows that the network has distinct characteristics in terms of cooperation mechanisms,cooperation entities,inter-entity relations,and the interaction of various fields of cooperation.These characteristics are apparent in concentrated form in the dynamics and limitations of East Asian regional cooperation networks.Describing and analyzing the structure and characteristics of the regional cooperation network of the Association of Southeast Asian Nations(ASEAN)can help us conduct a comprehensive examination of the current regional cooperation framework,grasp the developmental prospects of East Asian regional cooperation,and provide reference material for China's path choice in the process of future regional cooperation.