Reconstruction of sea ice variability in the Chukchi Sea during the last three centuries based on biomarker proxies

Abstract In this study, we reconstruct three-century of sea ice cover history in the Chukchi Sea from the downcore profile of total organic carbon (TOC) and biomarker proxies, namely the Ice Proxy with 25 carbon atoms (IP25), the di- and tri-unsaturated highly branched isoprenoid (HBI II and HBI III) and two phytosterols (brassicasterol and dinosterol) in three sediment cores from the northern, eastern and southern Chukchi Sea reflecting different sea ice conditions. Our data indicate higher IP25 values in the eastern site and lowest ones in the northern Chukchi Sea site that are consistent with the modern sea ice distribution. They also underline the predominance of sympagic over pelagic production except at the southern site where pelagic production depicts a sharp increased over the last decades. We present a new approach improving the linear relationship between PIIIIP25 (PBIP25) and satellite-derived spring (summer) sea ice concentrations (SIC) to advance sea ice reconstructions across the Arctic Ocean. This method results in better assessment of PIP25 derived SIC and reconstruction of past seasonal sea ice conditions. They indicate marginal sea ice conditions at the three sites until 1950s-1960s followed by a reduction of seasonal sea ice as captured by PBIP25 index.