Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Open Access Clim. Past Discuss., 10, 895–975, 2014 Climate www.clim-past-discuss.net/10/895/2014/ doi:10.5194/cpd-10-895-2014 of the Past CPD © Author(s) 2014. CC Attribution 3.0 License. Discussions 10, 895–975, 2014 This discussion paper is/has been under review for the journal Climate of the Past (CP). Nonlinear regime Please refer to the corresponding final paper in CP if available. shifts in Holocene Asian monsoon Nonlinear regime shifts in Holocene Asian variability monsoon variability: potential impacts on J. F. Donges et al. cultural change and migratory patterns Title Page 1,2 1,3 1 4 1,5 J. F. Donges , R. V. Donner , N. Marwan , S. F. M. Breitenbach , K. Rehfeld , Abstract Introduction and J. Kurths1,6,7 Conclusions References 1Potsdam Institute for Climate Impact Research, Telegrafenberg A31, 14473 Potsdam, Germany Tables Figures 2Stockholm Resilience Centre, Stockholm University, Kräftriket 2B, 114 19 Stockholm, Sweden 3 Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, J I Hans-Knöll-Straße 10, 07745 Jena, Germany 4Geological Institute, Department of Earth Sciences, ETH Zurich, 8092 Zurich, Switzerland J I 5Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A43, Back Close 14473 Potsdam, Germany 6 Department of Physics, Humboldt University, Newtonstr. 15, 12489 Berlin, Germany Full Screen / Esc 7Institute for Complex Systems and Mathematical Biology, University of Aberdeen, Aberdeen, AB24 3FX, UK Printer-friendly Version Interactive Discussion 895 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Received: 10 February 2014 – Accepted: 10 February 2014 – Published: 6 March 2014 Correspondence to: J. F. Donges ([email protected]) CPD Published by Copernicus Publications on behalf of the European Geosciences Union. 10, 895–975, 2014 Nonlinear regime shifts in Holocene Asian monsoon variability J. F. Donges et al. Title Page Abstract Introduction Conclusions References Tables Figures J I J I Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion 896 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract CPD The Asian monsoon system has been recognised as an important tipping element in Earth’s climate. In this work, we apply recurrence networks, a recently devel- 10, 895–975, 2014 oped technique for nonlinear time series analysis of palaeoclimate data, for detect- 5 ing episodes with pronounced changes in Asian monsoon dynamics during the last Nonlinear regime 10 ka in speleothem records from 10 caves covering the major branches of the Asian shifts in Holocene monsoon system. Our methodology includes multiple archives, explicit consideration of Asian monsoon dating uncertainties with the COPRA approach and rigorous significance testing for the variability coexistence of monsoonal regime shifts at multiple locations to ensure a robust detec- 10 tion of continental-scale changes in monsoonal dynamics. This approach enables us J. F. Donges et al. to identify several epochs characterised by nonlinear regime shifts in Asian monsoon variability (8.5–8.0, 5.7–5.4, 4.1–3.6 and 2.8–2.2 ka BP), the timing of which suggests a connection to high-latitude Bond events and other episodes of Holocene rapid cli- Title Page mate change (RCC). Interestingly, we also observe a previously unnoticed episode of Abstract Introduction 15 significantly increased regularity of monsoonal variations around 7.3 ka BP, a timing that is consistent with the typical 1.0–1.5 ka return intervals of Bond events. A possi- Conclusions References ble solar forcing of the detected nonlinear regime shifts in Asian monsoon dynamics is Tables Figures suggested by their co-occurence with pronounced minima and strong variability in solar activity. Drawing on a comprehensive review of the Holocene archeological record in J I 20 the Asian monsoon realm, we find that these regime shifts partly coincide with known major periods of migration, pronounced cultural changes, and the collapse of ancient J I human societies. These findings indicate that also future transitions in monsoonal dy- namics could induce potentially severe socio-economic impacts of climate change. Back Close Full Screen / Esc Printer-friendly Version Interactive Discussion 897 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 Introduction CPD Relationships between past climate change and societal responses in the historical and archeological record have frequently been reported, e.g. increased war frequencies 10, 895–975, 2014 (Zhang et al., 2007), societal conflicts and crises (Hsiang et al., 2011, 2013; Zhang 5 et al., 2011), migrations (Büntgen et al., 2011), and collapse of complex societies such Nonlinear regime as the Akkadian empire (Gibbons, 1993; Cullen et al., 2000), the Egyptian Old Kingdom shifts in Holocene (Stanley et al., 2003), Mayan urban centres (Haug et al., 2003; Kennett et al., 2012) Asian monsoon and Chinese dynasties (Yancheva et al., 2007). While those societal responses are variability generally acknowledged to be driven by multiple factors and societies differ in their 10 vulnerability to changing environmental conditions (Tainter, 1990), investigating climate J. F. Donges et al. as one possible key driver is of large interest in the face of recent anthropogenic climate change (Stocker et al., 2014). In this contribution, we focus on regime shifts in Asian Summer Monsoon dynam- Title Page ics during the last 10 ka and discuss their potential societal impacts such as cultural Abstract Introduction 15 change or migratory patterns. Investigating the Asian monsoon domain is relevant for three reasons: (i) the Asian monsoon is a highly dynamic, vulnerable and multistable Conclusions References system (Zickfeld et al., 2005; Levermann et al., 2009) that has been identified as a po- Tables Figures tential climatic tipping element (Lenton et al., 2008). (ii) Ca. 60 % of the world’s popu- lation are directly affected by the Asian monsoon with monsoon failures having large J I 20 potential consequences for food supply in these regions (Wu et al., 2012). (iii) There are multiple known examples for the collapse of early complex societies in the Asian mon- J I soon realm such as the Harappan culture in the Indus valley (Staubwasser and Weiss, 2006), as well as for the impact of climate change on socio-political developments, Back Close e.g. war frequencies or dynastic changes in China (Zhang et al., 2007; Yancheva et al., Full Screen / Esc 25 2007). Thus, a deeper understanding of past changes in Asian monsoon dynamics and their impact on societies will contribute to being able to better anticipate potential Printer-friendly Version consequences of future climate change in the region. Interactive Discussion 898 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | The Asian Summer Monsoon system is a seasonally recurring wind pattern related to the migration of the Intertropical Convergence Zone and is active from June to Oc- CPD tober. It is nominally separated into the Indian Summer Monsoon (ISM) and the East 10, 895–975, 2014 Asian Summer Monsoon (EASM). The ISM is divided into the Arabian Sea (AS) branch 5 and the Bay of Bengal (BB) branch, which transport moisture from the Indian Ocean towards Arabia and the Indian Peninsula during the summer wet season (Fig. 1). The Nonlinear regime AS branch reaches NE Africa and the Arabian Peninsula before turning east towards shifts in Holocene the west coast of India. The BB branch of the ISM receives much of its moisture from Asian monsoon the Arabian Sea, crosses India and reloads over the Bay of Bengal before moving variability 10 northward until it reaches the Himalaya mountain range. Unable to cross this barrier, it splits into two branches, one moving NW-ward along the Himalaya, the other extending J. F. Donges et al. NE-ward into Tibet and China, where it contributes greatly to the summer rainfall. The EASM transports moisture from the adjacent seas into China and also onto the Tibetan Title Page Plateau. Complex and time-varying interdependencies have been demonstrated to ex- 15 ist between the different branches of the Asian Summer Monsoon system during the Abstract Introduction late Holocene (Feldhoff et al., 2012; Rehfeld et al., 2013) as well as at present (Baker et al., 2014). Conclusions References Our approach is to integrate information on decadal to centennial Asian palaeomon- Tables Figures soonal variability during the Holocene from high-resolution oxygen isotope records 20 from multiple caves, since speleothems are recognised as high-quality palaeoclimate J I archives for the considered time scales and geographical region. Of special importance for the present study is a robust chronology of the included archives, a requirement J I that is met by speleothem records. Focussing on one type of archive and proxy, this Back Close work extends upon and complements several related re-assessment studies (Morrill 25 et al., 2003; Hu et al., 2008; Maher, 2008; Rehfeld et al., 2013). In contrast to earlier Full Screen / Esc work, we focus not only on the intensity of monsoonal rainfall per se, but aim at iden- tifying changes in the complexity of monsoonal variations as important higher-order Printer-friendly Version information contained in the available records. The rationale behind this approach is that regular and, thus, predictable monsoonal variations are crucial for sustained