Tipping elements and thresholds for extreme climate events in the Indian Summer Monsoon (ISM) realm (TISUR) IP3: Ecological regime shifts in response to monsoon dynamics and anthropogenic activities

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The Indian Summer Monsoon (ISM) affects the lives of over a billion strong population, yet remains one of the least understood components of the global climate system. While the mid- and late-Holocene weakening of the ISM in response to decreasing solar insolation is well established, the spatiotemporal influence of tipping elements (e.g. ENSO, THC) in triggering extreme climate events and ecological regime shifts in the ISM realm is not well understood. Reconstructing major ISM shifts preserved in palaeoenvironmental archives is essential to advance our understanding of its interaction with known tipping elements and contribute towards identifying the mechanistic principles underlying climate shifts and extremes. In this coordinated effort we aim to develop a comprehensive picture of mid- to late Holocene climate variability over the ISM realm using a multiproxy approach on three lakes (sediment cores) from climatically sensitive regions. Four closely interrelated proposals aim to (i) reconstruct palaeoenvironmental changes, identify tipping points and regime shifts at each site; (ii) provide information on ecosystem response in different climate settings; and (iii) undertake transregional comparison using modern numerical methods to disentangle tipping elements driving ISM shifts and extreme events. The results of these studies can potentially help in predicting and mitigating the ecological and economic impact of future climate change in vulnerable regions.This proposed project addresses mid to late Holocene dynamics of vegetation, climate and human activity based on detailed pollen analyses on lacustrine sediments of the Manasbal Lake (N India) and the Khecheopalri Lake (NE India). We especially focus on the identification of threshold responses and regime shifts in the studied terrestrial and aquatic ecosystems. Furthermore, investigations on modern surface pollen spectra will be carried out in order to capture the relationship between the modern pollen assemblages, vegetation, climate and human pressure and thus to improve the interpretation of the fossil pollen record.