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

虽然对整个(南亚)东亚的夏季风系统进行了相对较好的研究和了解，但目前对冬季风的了解非常有限--特别是在没有仪器记录的数据的情况下，对它们如何变化的了解。然而，主要是亚洲冬季季风将大部分降水带到了越南的一些沿海地区和中部高地，从而在农业和水资源以及与洪水和山体滑坡有关的自然灾害风险方面发挥了关键作用。近年来，东南亚各地不同档案馆公布了一些古气候记录，但这些记录在很大程度上集中在不同时间尺度上亚洲夏季风系统的变异性、位置和强度。更重要的是，到目前为止，越南的可比古气候记录基本上是缺乏的。越南的现代气候一般分为温带北部和热带南部，其中海文关(“海洋云口”)形成了气候分水岭。温带和热带气候带之间的这种紧密联系使中央高地区域对水文气候变化特别敏感。同样重要的是，中央高地拥有许多天然湖泊，这些湖泊构成了记录古气候变异性的合适地理档案。鉴于越南覆盖整个全新世的低密度古气候记录，以及中部高地地区对不同季风系统相互作用的微小变化的敏感性，我们旨在对中南部高地的湖泊，特别是Ea Sno湖进行比较调查，以追求以下中央研究目标：(1)分析自全新世以来人类活动对环境造成重大影响之前，中南部高地的自然/初始(古)环境状况。(2)中南部高地气候扰动的量化影响，特别是在夏季风与冬季风变化的背景下。根据这些一般研究目标，该项目拟就该区域针对全新世季风变化的古气候和古水文条件提出下列工作假设：(1)我们的目标是确定并甚至量化不同时间尺度上气候变化对季风强度的影响，利用(A)从中央高地湖泊沉积物中提取的有机替代物中应可追踪到的同位素位移，以及(B)来自湖泊沉积物的对降水量和降水时间变化敏感的无机替代数据，这应反映出ITCZ位置的变化，特别是在推断出大变化的时期。以及(2)我们的目标是重建水文极端事件(干旱/洪水)。

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).