Non-linear regime shifts in Holocene Asian monsoon variability: potential impacts on cultural change and migratory patterns

J F Donges,N Marwan,R V Donner,K Rehfeld,S F M Breitenbach,J Kurths

doi:10.5194/cp-11-709-2015

Abstract

Abstract. The Asian monsoon system is an important tipping element in Earth's climate with a large impact on human societies in the past and present. In light of the potentially severe impacts of present and future anthropogenic climate change on Asian hydrology, it is vital to understand the forcing mechanisms of past climatic regime shifts in the Asian monsoon domain. Here we use novel recurrence network analysis techniques for detecting episodes with pronounced non-linear changes in Holocene Asian monsoon dynamics recorded in speleothems from caves distributed throughout the major branches of the Asian monsoon system. A newly developed multi-proxy methodology explicitly considers dating uncertainties with the COPRA (COnstructing Proxy Records from Age models) approach and allows for detection of continental-scale regime shifts in the complexity of monsoon dynamics. Several epochs are characterised by non-linear regime shifts in Asian monsoon variability, including the periods around 8.5–7.9, 5.7–5.0, 4.1–3.7, and 3.0–2.4 ka BP. The timing of these regime shifts is consistent with known episodes of Holocene rapid climate change (RCC) and high-latitude Bond events. Additionally, we observe a previously rarely reported non-linear regime shift around 7.3 ka BP, a timing that matches the typical 1.0–1.5 ky return intervals of Bond events. A detailed review of previously suggested links between Holocene climatic changes in the Asian monsoon domain and the archaeological record indicates that, in addition to previously considered longer-term changes in mean monsoon intensity and other climatic parameters, regime shifts in monsoon complexity might have played an important role as drivers of migration, pronounced cultural changes, and the collapse of ancient human societies.

Highlights

This work presents the first application of recurrence network (RN) analysis, a novel technique of non-linear time series analysis, to a consistent set of spatially distributed palaeoclimatic archives from the Asian monsoon domain
RN analysis has earlier demonstrated the ability to detect relevant nonlinear dynamic changes such as shifts from regular to more-erratic variability that cannot be readily revealed by linear statistics such as windowed mean or variance
After combining the results from multiple proxy records, statistical significance testing enables the identification of epochs where an unexpected fraction of all considered sites displays unusual dynamics, pointing towards pronounced non-linear regime shifts in monsoon dynamics on a continental scale

Summary

Introduction

Relationships between past climate change and societal responses in the historical and archaeological record have frequently been reported, e.g. increased frequencies of war (Zhang et al, 2007), societal conflicts and crises (Hsiang et al, 2011, 2013; Zhang et al, 2011), migrations (Büntgen et al, 2011), and collapse of complex societies such as the Akkadian empire (Gibbons, 1993; Cullen et al, 2000), the Egyptian Old Kingdom (Stanley et al, 2003), Mayan urban centres (Haug et al, 2003; Kennett et al, 2012), and Chinese dynasties (Yancheva et al, 2007). Donges et al.: Non-linear regime shifts in Holocene Asian monsoon variability vironmental change within the co-evolving planetary socioenvironmental system (Schellnhuber, 1998, 1999)

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