Loktak Lake Highstand in NE India During a Wet LIA Following Megadrought conditions

Abstract:

There are several terrestrial Holocene-scale records of the Indian Summer Monsoon (ISM) from the Indian mainland, but few records from northeastern India, which has previously been noted as displaying a precipitation dipole with mainland. We summarize a 2500-year record from Loktak Lake in northeastern India with the objective of characterizing hydroclimate during the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). On the basis of percent organic matter and carbon isotopes, we find strong evidence for a megadrought during the MCA followed by an extreme wet period during the LIA. These trends confirm the existence of a precipitation dipole with the mainland that cannot be explained by the Indian Ocean Dipole or El Niño Southern Oscillation enacting changes on the ISM. Since this region of India is in the transition zone of being impacted by both the ISM and the East Asian Summer Monsoon (EASM), one possibility to explain these trends is a shift in moisture sources. Alternatively, increased snow on the Himalayas may have induced changes in ISM northward penetration. In the case of either mechanism, additional records from this region will be necessary to test hypotheses and understand what drives the substantial spatiotemporal variability in ISM hydroclimate.