Late Holocene Asian summer monsoon dynamics from small but complex networks of paleoclimate data
- PDF / 1,382,454 Bytes
- 17 Pages / 595.276 x 790.866 pts Page_size
- 28 Downloads / 184 Views
Late Holocene Asian summer monsoon dynamics from small but complex networks of paleoclimate data Kira Rehfeld • Norbert Marwan • Sebastian F. M. Breitenbach Ju¨rgen Kurths
•
Received: 30 April 2012 / Accepted: 5 July 2012 / Published online: 4 September 2012 Springer-Verlag 2012
Abstract Internal variability of the Asian monsoon system and the relationship amongst its sub-systems, the Indian and East Asian Summer Monsoon, are not sufficiently understood to predict its responses to a future warming climate. Past environmental variability is recorded in Palaeoclimate proxy data. In the Asian monsoon domain many records are available, e.g. from stalagmites, tree-rings or sediment cores. They have to be interpreted in the context of each other, but visual comparison is insufficient. Heterogeneous growth rates lead to uneven temporal sampling. Therefore, computing correlation values is difficult because standard methods require co-eval observation times, and sampling-dependent bias effects may occur. Climate networks are tools to extract system dynamics from observed time series, and to investigate Earth system dynamics in a spatio-temporal context. We establish paleoclimate networks to compare paleoclimate records within a spatially extended domain. Our approach is based on adapted linear and nonlinear association measures that are more efficient than interpolation-based measures in the presence of inter-sampling time variability. Based on this new method we investigate Asian Summer Monsoon dynamics for the late Holocene, focusing on the Medieval Warm Period (MWP), the Little Ice Age (LIA), and the recent period of warming in East Asia. We find a strong Indian Summer Monsoon (ISM) influence on the East Asian Summer Monsoon during the MWP. During the K. Rehfeld (&) N. Marwan J. Kurths Potsdam Institute for Climate Impact Research, P.O. Box 60 12 03, 14412 Potsdam, Germany e-mail: [email protected] S. F. M. Breitenbach ETHZ Geologisches Institut, Climate Geology, Sonneggstrasse 5, CH-8092 Zurich, Switzerland
cold LIA, the ISM circulation was weaker and did not extend as far east. The most recent period of warming yields network results that could indicate a currently ongoing transition phase towards a stronger ISM penetration into China. We find that we could not have come to these conclusions using visual comparison of the data and conclude that paleoclimate networks have great potential to study the variability of climate subsystems in space and time. Keywords Asian summer monsoon Complex networks Irregular sampling Little ice age Medieval warm period
1 Introduction Monsoonal precipitation dynamics and their possible change due to global warming are a matter of political and public concern in most of South-East Asia, and especially in India and China, as lives and prosperity depend critically on the monsoons’ rainfall delivery (Cook et al. 2010; Kumar et al. 2010; Zhang et al. 2011). The Asian (Summer) Monsoon has shown abrupt changes in the past and its intensification (weakening) was likely conc
Data Loading...
