Reconnaissance field survey at Ea Sno Lake in the South-Central Highlands of Vietnam – assessment of the lake as palaeoclimate archive

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While the summer monsoon systems across (South) East Asia are relatively well researched and understood, there is currently very limited understanding of winter monsoons – especially of how they have changed during periods when there is no data from instrumental records. However, it is mainly the Asian winter monsoon that brings the majority of precipitation to some coastal areas of Vietnam and the Central Highlands, thus playing a critical role in agriculture and water resources, as well as natural hazard risks related to flooding and landslides. In recent years, several palaeoclimatic records from different archives around South-East Asia have been published, yet all these records focus to a large extent on the variability, position, and strength of the Asian Summer monsoon systems at different timescales. The more, comparable palaeoclimatic records from Vietnam have been largely lacking so far. Vietnam’s modern climate is generally divided into a temperate North and a tropical South with the Hai Van Pass (“Ocean Cloud Pass”) forming a climatic divide. This close proximity between temperate and tropical climate zones makes the region of the Central Highlands particularly sensitive to hydrological climate changes. Equally important, the Central Highlands host a number of natural lakes, which constitute suitable geoarchives for recording palaeoclimate variability. Given the low density of palaeoclimatic records from Vietnam covering the entire Holocene and given the sensitivity of the Central Highland region to small changes in the interplay of different monsoon systems, we aim at comparatively investigating lakes of the Southern Central Highlands, specifically Ea Sno Lake, pursuing the following central research goals: (1) Analysing the natural/initial (palaeo-)environmental conditions in the Southern Central Highlands prior to significant impact of human on the environment, since the onset of the Holocene. (2) Quantifying effects of climate perturbations in the Southern Central Highlands, specifically in the context of summer versus winter monsoon variability. Based on these general research goals, the project addresses the following working hypotheses on the palaeoclimatic and palaeohydrological conditions in the region in response to the monsoon variability during the Holocene: (1) We aim on identifying and potentially even quantifying the impact of climate variability on different timescales on the monsoon intensity, using (a) isotopic shifts that should be traceable in organic proxies from lake sediments in the Central Highlands, and using (b) inorganic proxy data derived from lake sediments, which is sensitive to changes in amount and timing of precipitation, which should reflect variations in the position of the ITCZ, especially during periods where large changes have been inferred. And (2) we aim on reconstructing hydrological extreme events (droughts/floods).