Although the permanently to seasonally ice-covered Arctic Ocean is a unique and sensitive component in the Earth's climate system, the knowledge of its long-term climate history remains very limited due to the restricted number of pre-Quaternary sedimentary records. During Polarstern Expedition PS87/2014, we discovered multiple submarine landslides along Lomonosov Ridge. Removal of younger sediments from steep headwalls has led to exhumation of Miocene sediments close to the seafloor. Here we document the presence of IP25 as a proxy for spring sea-ice cover and alkenone-based summer sea-surface temperatures >4 °C that support a seasonal sea-ice cover with an ice-free summer season being predominant during the late Miocene in the central Arctic Ocean. A comparison of our proxy data with Miocene climate simulations seems to favour either relatively high late Miocene atmospheric CO2 concentrations and/or a weak sensitivity of the model to simulate the magnitude of high-latitude warming in a warmer than modern climate.

中文翻译：

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中新世中部北冰洋末期夏季无冰的证据。

尽管永久到季节性冰雪覆盖的北冰洋是地球气候系统中独特而敏感的组成部分，但由于第四纪前的沉积记录数量有限，其长期气候历史的知识仍然非常有限。在Polarstern探险队PS87 / 2014中，我们在罗蒙诺索夫山脊发现了多个海底滑坡。从陡峭的顶壁去除较年轻的沉积物已导致挖掘出靠近海床的中新世沉积物。在这里，我们记录了IP25的存在，可作为春季海冰覆盖和基于烯酮的夏季海表温度> 4°C的替代物，支持季节性海冰覆盖，中新世晚期主要是无冰的夏季在北冰洋中部。