Paleo-climate reconstruction on sediment core M72/5_628-1 (25-GC-1), Black Sea

The Marine Isotope Stage (MIS) 3 stands out due to its abrupt changes from cold and dry stadials to warm and humid interstadials, the so-called Dansgaard-Oeschger cycles that also affected temperature and rainfall in the Black Sea region. This study is based on a gravity core from the southeastern (SE) Black Sea that covers the last glacial lake stage from 64 to 20 ka BP. By using the composition of major and trace elements in the sediments, terrestrial plant-derived n-alkane flux, and Sr/Ca from benthic ostracods, we reconstruct the variability of riverine and aeolian input, salinity, and productivity in the SE Black Sea region in response to the Northern Hemisphere climate oscillations. During colder and drier stadials, the aeolian input increased relative to the riverine discharge, potentially due to southward shifted and/or stronger westerly winds and due to changes in the vegetation cover. An evaporation exceeding freshwater supply by rainfall and rivers possibly caused higher salinity and a lower lake level. The environmental status during MIS 4 and 2 is very much comparable with the stadial conditions during MIS 3. During warmer and more humid interstadials, lower salinity and presumably positive lake level changes most likely resulted from increased precipitation and river discharge. This likely increased primary productivity through an augmented nutrient supply. Lowest average salinities are suggested for the middle part of MIS 3 in response to enhanced meltwater from the disintegrating Fennoscandian Ice Sheet and/or by generally more humid conditions.

海洋同位素阶段（Marine Isotope Stage, MIS）3以其从寒冷干旱的冰阶向温暖湿润的间冰阶的急剧转变为显著特征，即所谓的丹斯果-奥什格尔旋回（Dansgaard-Oeschger cycles），该旋回同样对黑海区域的气温与降水产生影响。本研究依托采自黑海东南部（SE）的一根重力岩心（gravity core），其覆盖了64~20 ka BP（距今千年）的末次冰期湖泊阶段。研究人员通过分析沉积物中的常量与微量元素组成、陆生植物源正构烷烃通量（n-alkane flux），以及底栖介形虫（benthic ostracods）的锶钙比（Sr/Ca），重建了黑海东南部区域响应北半球气候振荡过程中，河流输入、风成输入（aeolian input）、盐度及初级生产力的变化特征。在寒冷干旱的冰阶（stadials）阶段，风成输入相对河流径流量有所增加，这可能与西风带南移且强度增强、以及植被覆盖变化有关。此时蒸发量超过降雨与河流带来的淡水补给，或导致盐度升高与湖泊水位下降。MIS 4与MIS 2时期的环境状态与MIS 3的冰阶条件高度相似。在温暖湿润的间冰阶（interstadials）阶段，盐度降低且湖泊水位大概率上升，这主要源于降水增加与河流径流量提升。这一过程或通过增强的营养盐补给提升了区域初级生产力。研究认为，MIS 3中期的平均盐度最低，这一方面是由于芬诺斯堪的亚冰盖（Fennoscandian Ice Sheet）解体产生的融水补给增强，另一方面也与区域整体更为湿润的气候条件有关。