The Water Tower of India in a Long-term Perspective – A Way to Reconstruct Glaciers and Climate in Himachal Pradesh during the last 13,000 Years

Abstract

Here we present the first results from the project “Water Related Effects of Changes in Glacier Mass balance and River Runoff in Western Himalaya, India: Past, Present and Future” (GLACINDIA) project, aiming to reconstruct Holocene glacier variability as documented through physical sediment properties analysed on sediments from the former distal glacier-fed lake Chandra Tal (4300 m a.s.l.) combined with direct dating of marginal moraines using cosmogenic isotopes proximal to Chandra Tal and in front of the glaciers Batal and Chhota Shigri, located in Himachal Pradesh, western Himalaya, India. GLACINDIA is a multi-disciplinary project and unique, not only due to the participating institutions bringing together scientists from Norway and India, but also for the logistical challenges and the state-of-the-art science. In this particular case, we aim for detailed reconstructions of past glacier activity over the Holocene time scale (last ~11,700 years) emphasising different sediment parameters by means of statistical methods as well as integrating chronological uncertainties along with uncertainties of reconstructed glacier variability. We also aim to do oxygen isotope measurements on the pore water in addition to extracting lipids for leaf wax analysis in the sediment cores.

A multi-proxy data set of lake sediments consisting of sedimentological, physical and geochemical analyses reflects all types of processes in the lake catchment that delivers sediments to the lake. By means of principal component analysis (PCA), it is possible to extract the main process(es) driving the sediment variability in distal glacier-fed lakes. The common signal extracted from the sediment data is indicative of the main process in the catchment and is interpreted to vary in concert with the changing glacier equilibrium-line altitude over the region. Lake Chandra Tal has, based on earlier retrieved results from cosmogenic isotope dating, the potential to contain sediments deposited over the last 13,000 years, continuously deposited since the deglaciation after the glaciers retreated during the Late Glacial period. We, therefore, aim to do continuous reconstruction of climate with high temporal resolution for a better dynamical understanding of past climate. Understanding the controls of decadal, multi-decadal and century scale climate variability is crucial for many aspects of climate predictability. Climate reconstructions are important in order to validate Earth system modelling scenarios for the future; but there is at present a scarcity of consistent observational records from the Himalayas that can be used to understand and validate the existence of climate dynamics in this region.