Paleo-biogeochemistry of the Central Himalayan region during late MIS 3 using stable isotopic composition of organic matter occluded in diatoms and lake sediments

Abstract:

Marine Isotope Stage (MIS) 3 was an interstadial stage in the climate history of the Earth where the last phase (40 to 30 ka) showed relatively warmer climate over the northwest China, Tibetan Plateau, and northwestern India compared to other regions of the world. However, not many studies are reported for the climate variability during this period from the Himalaya. Here, an attempt has been made to understand the paleoenvironment and carbon dynamics of the Central Himalaya lake during 45 - 29 ka using an emerging robust prxoy, i.e., δ ¹³C_Diatom (carbon isotope of occluded organic matter within diatom) with stable isotopic compositions of carbon (δ¹³C_TOC) and nitrogen (δ¹⁵N_TN) along with their elemental ratios (TOC/TN) of a paleolake sequence. Variabilities in δ¹³C_Diatom indicated intermittent change in lake carbon dynamics i.e., bicarbonate and carbon dioxide availability. This change in lacustrine carbon cycling corroborated δ¹³C_TOC, δ¹⁵N_TN and TOC/TN ratio results and suggested evidence for existence of sporadic dry events in the Central Himalaya during 45 - 29 ka. In agreement with the records from the northwest China, Tibetan Plateau, and northwestern India, our results also confirmed the existence of a relatively wetter period during 40 to 32 ka in the Central Himalaya. Therefore, it appeared that despite relatively cooler climate in other parts of the world, relatively warmer climate existed throughout this region. The possible mechanism behind this relative warming could be temperature pressure graddient between Mediterrenean Sea and Himalaya/TP.