Here, we present a low-resolution biomarker sea-ice 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 diatomspecific highly branched isoprenoid (HBI) with 25 carbon atoms ("IP25"), in combi nation 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 pro ductivity. During the Early Holocene Climate Optimum, brassicasterol reach ed its maximum, interpreted as signal for elevated phytoplankton productivi ty due to a significantly reduced sea-ice cover. During the mid-late Holocene, IP 25increased and brassicasterol decreased, indicating extended sea-ice cover and reduced phytoplankton productivity, respectively. The HBI diene/IP25ratios probably reached maximum values during the Bølling-Allerød warm period and decreased during the Holocene, suggesting a correlation with sea-surface temperature.