A 2000 Year Multi-Proxy Evidence of Natural/Anthropogenic Influence on Climate from the Southwest Coast of India
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ISSN 1674-487X
A 2000 Year Multi-Proxy Evidence of Natural/Anthropogenic Influence on Climate from the Southwest Coast of India M. C. Manoj *1, Jyoti Srivastava1, Prem Raj Uddandam1, 2, Biswajeet Thakur1 1. Birbal Sahni Institute of Paleosciences, 53 University Road, Lucknow, Uttar Pradesh 226007, India 2. Banaras Hindu University, Varanasi, Uttar Pradesh, India M. C. Manoj: https://orcid.org/0000-0001-8112-6315 ABSTRACT: The last millennium climate reconstructions are complex and limit our understanding of the mechanisms behind environmental and climate variability. We present multi-proxy centennial-scale records from the Cherai, southwest India. The last 2000 cal yr AD record suggests a complex environmental condition that prevailed at the depositional site augmenting the role of natural as well as anthropogenic agents. Increased elemental variations and indices values indicate stronger weathering, presumably wetter conditions and intense precipitation. Provenance studies suggest diverse sources and the main composition fall close to the Charnockite and Gneissic composition. Multi-proxy data suggests that a shift towards wetter climatic conditions, which occurred from 910 to 1230 cal yr AD. The core also records a shift towards the drier conditions that started around 1230 cal yr AD with a loss in vegetation diversity. The pollution load index values suggest that the overall study area falls in moderate contamination levels, which are also substantiated with the diatom data indicating human influence in the natural habitat during the deposition time. The present study reveals that the enhanced Cd and As concentration is due to strong anthropogenic influence. We compared the multi-proxy record with other continental and marine palaeoclimatic records to explore global and/or regional trends in climate variability during the last 2000 years. KEY WORDS: estuaries, monsoon, provenance, vegetation, clmate, contamination. 0
INTRODUCTION Many paleoclimatic studies have been carried out to understand the climate of the last millennium for predicting future climate changes and its impact on societies. The last millennium is a crucial period in understanding the Earth’s climate response to external forcing and its internal variability on decadal-tocentennial timescales (Kamae et al., 2017; PAGES 2k Consortium, 2013). Global climate variability during the past 2000 years is generally characterized by multi-century episodes of distinct temperature and precipitation anomalies such as the Roman Warm Period (RWP; 0–500 cal yr AD), Dark Age Cold Period (DACP; 500–900 cal yr AD), Medieval Climate Anomaly (MCA, 900–1300 cal yr AD), Little Ice Age (LIA, 1300–1850 cal yr AD), and subsequent Current Warm Period (CWP) beginning in the 19th century (Graham et al., 2011; Mann et al., 2009; Keigwin 1996). The concept of Medieval Warm Period (MWP), centered at around 1100–1200 cal yr AD, was first reported by Lamb (1965). These studies also attracted much attention because it is the most recent example of long-term, naturally generated glo
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