Historical droughts in East Asia and their reflection in a 1000-year long record from Ea Tyn Lake (Vietnam)

Abstract

The South-East Asian tropics remain severely under-represented in paleoenvironmental and paleoclimatic reconstructions, although a few recent paleoclimate studies evaluated the variability, position and strength of the main Asian monsoon systems at different timescales from modern records to the Late Pleistocene. Comparable data from Vietnam, however, are scarce although Vietnam and its Central Highlands are critically located at the intersection of the East Asian Summer Monsoon and the Indian Summer Monsoon with highly important socio-ecological consequences from changes in the climate system. We here present a high-resolution sedimentary climate record from Ea Tyn Lake in the Vietnam’s Central Highlands covering the last 1,250 years. Using geochemical and sedimentological proxies and principal component analysis, we reconstructed at least 12 drought events, some of which appear to be of supraregional significance as they coincide with historically documented droughts in India, China, and Cambodia. Especially the summarizing XRF-based PC2 values are in very good agreement with the Palmer Drought Severity Index (PDSI) of the region so far based on tree rings. Beyond tracking short-term climate events, the Rb/Sr elemental ratio along our lake sediment sequence reflects long-term monsoon variability throughout the last millennium, which was previously only reconstructed via δ18O speleothem records from China and India. Our record shows that the East Asian Summer Monsoon was relatively strong between ~1000 and 1350 cal CE and weaker between 1350 and 1850 cal CE, followed by renewed intensification after ~1850 cal CE. Our study may provide the basis for more profound studies in human-climate-interaction and interdependence on historical timescales. It also provides insight to potential recurrence rates of drought events, thus helping to assess natural variability and anthropogenically altered (enhanced) monsoon variability.