Biomarker distributions in sediment core PS2767-4@en

Here, we present a first (low-resolution) biomarker sea-ice proxy record from the High Arctic (southern Lomonosov Ridge), going back in time to about 60 ka (MIS 3 to MIS 1). Variable concentrations of the sea-ice diatom specific highly branched isoprenoid (HBI) with 25 carbon atoms (\"IP25\"), in combination with the phytoplankton biomarker brassicasterol, suggest variable seasonal sea-ice coverage and open-water productivity during MIS 3. During most of MIS 2, the spring to summer sea-ice margin significantly extended towards the south, resulting in a drastic decrease in phytoplankton productivity. During the Early Holocene Climate Optimum, brassicasterol reached its maximum, interpreted as signal for elevated phytoplankton productivity due to a significantly reduced sea-ice cover. During the mid-late Holocene, IP25 increased and brassicasterol decreased, indicating extended sea-ice cover and reduced phytoplankton productivity, respectively. The HBI diene/IP25 ratios probably reached maximum values during the Bølling-Allerød warm period and decreased during the Holocene, suggesting a correlation with sea-surface temperature.本研究首次报道了来自高北极地区（High Arctic，罗蒙诺索夫海岭南部）的首套低分辨率海冰生物标志物替代记录，其时间跨度可追溯至约6万年前，涵盖海洋同位素阶段3（MIS 3）至海洋同位素阶段1（MIS 1）。针对海冰硅藻特异性25碳高支链类异戊二烯（highly branched isoprenoid, HBI，即IP25）的浓度变化，结合浮游植物生物标志物菜籽甾醇（brassicasterol）的含量特征，表明MIS 3时期存在季节性海冰覆盖范围的波动与开阔水域生产力的变化。在MIS 2的大部分时段，春季至夏季的海冰边缘显著向南扩张，导致浮游植物生产力大幅下降。在早全新世气候适宜期，菜籽甾醇浓度达到峰值，这被解释为海冰覆盖显著减少后浮游植物生产力提升的信号。在全新世中晚期，IP25浓度上升而菜籽甾醇浓度下降，分别对应海冰覆盖范围扩大与浮游植物生产力降低。高支链类异戊二烯二烯/IP25比值可能在博林-阿勒罗德暖期达到峰值，并在全新世期间逐渐下降，表明该比值与海表温度存在相关性。