Investigating Grain Size and Precipitation Relationships in the Context of Past Monsoon Variability

Changes in the strength of the Indian Summer Monsoon (ISM) can lead to an increased threat of drought and reduction of crop yield or conversely, a threat of flooding and damage to infrastructure. Sediment cores taken from lakes can provide many valuable details about past environmental and climatic conditions. In this study we examine a sediment core taken from Loktak Lake in India which is affected by the ISM. Loktak is a very shallow and wide lake, with a considerable amount of evaporation; consequently, lake level is very sensitive to hydroclimate changes. In the last 70 years, historical and meteorological records document a weakening of the ISM. Our hypothesis is that this led to a decreasing lake level and increases in mean sediment grain size. Results support our hypothesis; thus, our interpretation may be applied to the rest of the core in order to reconstruct the last 3,000 years of ISM strength. This research is part of a larger, multi-proxy, multi-millennial, multi-institutional project that looks to examine connections between lake level, climate, and drivers of the ISM.