Abstract
Two atmospheric circulation patterns, the Indian Summer Monsoon (ISM) and mid-latitude Westerlies control precipitation and thus glacier variability in the Himalaya. However, the role of the ISM and westerlies in controlling climate and thus past glacier variability in the Himalaya is poorly understood because of the paucity of the ice core records. In this article, we present a new Holocene paleorecord disentangling the presence of the ISM and mid-latitude westerlies and their effect on glacier fluctuations during the Holocene. Our new record is based on high-resolution multi-proxy analyses (δ18Oporewater, deuterium-excess, grain size analysis, permeability, and environmental magnetism) of lake sediments retrieved from Chandratal Lake, Western Himalaya. Our study provides new evidence that improves the current understanding of the forcing factor behind glacier advances and retreat in the Western Himalaya and identifies the 8.2 ka cold event using the aforementioned proxies. The results indicate that the ISM dominated precipitation ~ 21% of the time, whereas the mid-latitude westerlies dominated precipitation ~ 79% of the time during the last 11 ka cal BP. This is the first study that portrays the moisture sources by using the above proxies from the Himalayan region as an alternative of ice core records.
Highlights
Two atmospheric circulation patterns, the Indian Summer Monsoon (ISM) and mid-latitude Westerlies control precipitation and glacier variability in the Himalaya
Our interpretation is that the dominance of ISM may be interpreted as leading to an increased supply of total organic carbon (TOC), which is anti-correlated with magnetic susceptibility (MS)
The porewater isotopic composition of the studied lake core is similar to the bottom water isotopic effect during the time of deposition[26].The pore water extracted from clay-rich glacial till marine and lacustrine sediments have been used to understand paleoclimate and paleoenvironmental c onditions[27,28,29]
Summary
The Indian Summer Monsoon (ISM) and mid-latitude Westerlies control precipitation and glacier variability in the Himalaya. The results indicate that the ISM dominated precipitation ~ 21% of the time, whereas the mid-latitude westerlies dominated precipitation ~ 79% of the time during the last 11 ka cal BP This is the first study that portrays the moisture sources by using the above proxies from the Himalayan region as an alternative of ice core records. Since the d-excess values reflect westerly precipitation during winters in the Western H imalaya[16], reconstruction of moisture sources during the Holocene from sediment records provides a new avenue for understanding past climate and glacier variability in the Himalaya. We attempted to answer the following questions; (1) is the ice mass stored in the glaciers in the Western Himalaya formed by precipitation transported by mid-latitude Westerlies or the ISM and, (2) can pore water stable isotope records be trusted as a proxy to disentangle different Holocene climatic phases, including the 8.2 ka BP event?. We extracted porewater samples at every 5 cm interval and analyzed for triple
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