In the last decades, changing climate conditions have had a severe impact on sea ice at the western Antarctic Peninsula (WAP), an area rapidly transforming under global warming. To study the development of spring sea ice and environmental conditions in the pre-satellite era we investigated three short marine sediment cores for their biomarker inventory with a particular focus on the sea ice proxy IPSO₂₅ and micropaleontological proxies. The core sites are located in the Bransfield Strait in shelf to deep basin areas characterized by a complex oceanographic frontal system, coastal influence and sensitivity to large-scale atmospheric circulation patterns. We analyzed geochemical bulk parameters, biomarkers (highly branched isoprenoids, glycerol dialkyl glycerol tetraethers, sterols), and diatom abundances and diversity over the past 240 years and compared them to observational data, sedimentary and ice core climate archives, and results from numerical models. Based on biomarker results we identified four different environmental units characterized by (A) low sea ice cover and high ocean temperatures, (B) moderate sea ice cover with decreasing ocean temperatures, (C) high but variable sea ice cover during intervals of lower ocean temperatures, and (D) extended sea ice cover coincident with a rapid ocean warming. While IPSO₂₅ concentrations correspond quite well to satellite sea ice observations for the past 40 years, we note discrepancies between the biomarker-based sea ice estimates, the long-term model output for the past 240 years, ice core records, and reconstructed atmospheric circulation patterns such as the El Niño–Southern Oscillation (ENSO) and Southern Annular Mode (SAM). We propose that the sea ice biomarker proxies IPSO₂₅ and PIPSO₂₅ are not linearly related to sea ice cover, and, additionally, each core site reflects specific local environmental conditions. High IPSO₂₅ and PIPSO₂₅ values may not be directly interpreted as referring to high spring sea ice cover because variable sea ice conditions and enhanced nutrient supply may affect the production of both the sea-ice-associated and phytoplankton-derived (open marine, pelagic) biomarker lipids. For future interpretations we recommend carefully considering individual biomarker records to distinguish between cold sea-ice-favoring and warm sea-ice-diminishing environmental conditions.

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过去240年中南极半岛布兰斯菲尔德海峡的海冰动力学：一项多代理比对研究

在过去的几十年中，不断变化的气候条件对南极半岛西部（WAP）的海冰造成了严重影响，该地区在全球变暖下正在迅速转变。为了研究卫星前时代春季海冰的发展和环境条件，我们研究了三个短的海洋沉积物核的生物标记物清单，特别侧重于海冰代理IPSO ₂₅和微古生物学的代理。核心站点位于布兰斯菲尔德海峡的陆架至深海盆地地区，其特征是复杂的海洋额叶系统，沿海影响和对大规模大气环流模式的敏感性。我们分析了过去240年间的地球化学总体参数，生物标志物（高度分支的类异戊二烯，甘油二烷基甘油四醚，固醇）以及硅藻的丰度和多样性，并将其与观测数据，沉积和冰芯气候档案以及数值模型的结果进行了比较。根据生物标志物的结果，我们确定了四个不同的环境单位，其特征是（A）低海冰覆盖和高海洋温度；（B）中海冰覆盖，海洋温度降低；（C）高海平面但在低海间隔期间海冰覆盖率可变温度，（D）扩大的海冰覆盖范围伴随着海洋的迅速变暖。而IPSO_25种 浓度与过去40年的卫星海冰观测非常吻合，我们注意到基于生物标记物的海冰估算值，过去240年的长期模型输出，冰芯记录以及重构的大气环流模式之间存在差异。如厄尔尼诺-南方涛动（ENSO）和南方环形模式（SAM）。我们建议海冰生物标志物代理IPSO ₂₅和PIPSO ₂₅与海冰覆盖率不成线性关系，此外，每个核心站点都反映特定的当地环境条件。高IPSO ₂₅和PIPSO ₂₅该值可能不能直接解释为春季春季海冰覆盖率较高，因为变化的海冰条件和增加的养分供应可能会影响与海冰相关的和浮游植物衍生的（开放海洋，中上层）生物标志物脂质的产生。对于将来的解释，我们建议仔细考虑各个生物标记物记录，以区分有利于冷海和不利于暖海的环境条件。