Catchment instability and Asian summer monsoon variability during the early Holocene in southwestern China

Abstract

A high-resolution palaeorecord (06SD) from Lake Shudu, Yunnan Province, southwestern China indicates a broad trend towards catchment stability, enhanced organic productivity and regional forest-cover expansion during the early to mid Holocene. These changes are congruent with a shift to warm, wet climatic conditions, probably driven by orbitally forced Asian summer monsoon strengthening. Intriguingly, however, during the very early Holocene (c. 10.7 to 10.1 cal. ka BP), there is a prominent reversal in this trend, suggesting a weakening Asian summer monsoon. The precise cause and extent of this event remain unclear but demonstrate the urgent need for more comprehensive dating of records from across the region to test for synchroneity and examine climatic forcing mechanisms.

Lake geochemistry reveals marked environmental change in Southwest China during the Mid Miocene Climatic Optimum

“…However, if the lower relative terrestrial input was due to an opening in vegetation cover, we should see an increase in the abundance of pioneer taxa, such as Alnus and Cupressacea/Taxodiaceae [21,56]. We did not observe such a pattern, implying that there is no evidence to support a retreat of the forest cover in Wenshan.…”

“…Lakes are environmentally sensitive and so are ideal to study past climatic fluctuations [18]. For example, lake sediment geochemistry has been widely used to explore environmental changes on the Tibetan Plateau during the Miocene [19,20] and in Yunnan during the Quaternary [21][22][23]. However, there is very limited research using terrestrial geochemistry to investigate environmental changes in Yunnan during the Miocene, and the MMCO in particular.…”

Hydrological and ecosystem response to abrupt changes in the Indian monsoon during the last glacial, as recorded by sediments from Xingyun Lake, Yunnan, China

“…In the past few decades, abrupt changes of the ISM have been inferred from marine sediments in the Arabian Sea (Schulz et al, 1998;Leuschner and Sirocko, 2000;Altabet et al, 2002;Govil and Naidu, 2010;Deplazes et al, 2013); the Bay of Bengal and the Andaman Sea (Colin et al, 1998) and speleothems from Socotra Island (Burns et al, 2003;Shakun et al, 2007), India (Sinha et al, 2005) and China (Cai et al, 2006). However, relatively few terrestrial paleoclimatic records of the ISM are from monsoon-dominated regions (Cook et al, 2013;Chabangborn et al, 2014;Dixit et al, 2014). In addition, the environmental significance of stable isotope records from stalagmites remains highly debated (Wang et al, 2001;Yuan et al, 2004;Maher, 2008;Clemens et al, 2010;Pausata et al, 2011;Liu et al, 2014;Tan, 2014).…”

“…Variability of the ISM, especially abrupt changes, can have significant environmental, social and economic effects within its region of influence (Turner and Slingo, 2011;Cook et al, 2013). For example, extreme variations of the ISM can cause crop failures and flooding that impact almost two-thirds of the world's population (Webster et al, 1998).…”

“…Yunnan, in southwestern China, is located in the heart of Monsoon Asia and is significantly influenced by the ISM Cook et al, 2013). The availability of sedimentary records from numerous lakes makes Yunnan very suitable for reconstructing the evolution history of the ISM (X.M.…”