Hydroclimate variations in central and monsoonal Asia over the past 700 years.

Keyan Fang,Jinbao Li,Fahu Chen,Asok K Sen,Wei Huang,Nicole Davi,Heikki Seppä,Eryuan Liang

doi:10.1371/journal.pone.0102751

Abstract

Hydroclimate variations since 1300 in central and monsoonal Asia and their interplay on interannual and interdecadal timescales are investigated using the tree-ring based Palmer Drought Severity Index (PDSI) reconstructions. Both the interannual and interdecadal variations in both regions are closely to the Pacific Decadal Oscillation (PDO). On interannual timescale, the most robust correlations are observed between PDO and hydroclimate in central Asia. Interannual hydroclimate variations in central Asia are more significant during the warm periods with high solar irradiance, which is likely due to the enhanced variability of the eastern tropical Pacific Ocean, the high-frequency component of PDO, during the warm periods. We observe that the periods with significant interdecadal hydroclimate changes in central Asia often correspond to periods without significant interdecadal variability in monsoonal Asia, particularly before the 19th century. The PDO-hydroclimate relationships appear to be bridged by the atmospheric circulation between central North Pacific Ocean and Tibetan Plateau, a key area of PDO. While, in some periods the atmospheric circulation between central North Pacific Ocean and monsoonal Asia may lead to significant interdecadal hydroclimate variations in monsoonal Asia.

Highlights

Hydroclimate changes in central and monsoonal Asia have generated much concern due to their close linkages with water resources, critical for increasing population and economical development [1,2]
Possible mechanisms related to this inverse relationship include the different responses of hydroclimate changes to external forcings, the boundary conditions, the internal ocean-atmospheric feedbacks (e.g. North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO)) and the regional topographic features (e.g. Tibetan Plateau), which can modulate the strength of the Asian summer monsoon and westerlies [3,4,5]
Analytical methods We investigate the percentage of areas affected by drought over the past 700 years, i.e. the Drought Area Index (DAI)

Summary

Introduction

Hydroclimate changes in central and monsoonal Asia have generated much concern due to their close linkages with water resources, critical for increasing population and economical development [1,2]. Central and monsoonal Asia are strongly influenced by the westerlies and Asian summer monsoon. Possible mechanisms related to this inverse relationship include the different responses of hydroclimate changes to external forcings (e.g. orbital changes and solar irradiance), the boundary conditions (e.g. ice volume), the internal ocean-atmospheric feedbacks (e.g. North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO)) and the regional topographic features (e.g. Tibetan Plateau), which can modulate the strength of the Asian summer monsoon and westerlies [3,4,5]. Hydroclimate variations in central and monsoonal Asia at the interannual and interdecadal timescales and their relationships remain unclear [6,7]. We used the MADA to provide a comprehensive investigation of the hydroclimate variability of central and monsoonal Asia and their relationships

Data and Methods

Conclusions

Author Contributions