study of Arctic Ocean surface sediments (Fig. 2; Xiao et al., 2015 ). During the last years, a large number of IP 25 /PIP 25 studies have been carried out to reconstruct the late Quaternary Arctic sea-ice [...] Polar sea ice variability - Arctic Our ability to quantitatively reconstruct Arctic paleo-sea-ice distributions has been greatly improved by a novel biomarker approach which is based on the determination [...] SeaIce4). In order to fully establish the IP 25 approach as key proxy for the reconstruction of past Arctic Ocean sea-ice conditions, however, more ground-truth data related to the synthesis, diagenesis, and