Ice-shelf and sea-ice dynamics: the biomarker perspective

Evaluating the impact of sea ice and ocean temperature changes on ice-shelf stability is a crucial aspect for the identification of ocean-cryosphere interactions and the response of Antarctic ice-sheets to climate variability. The role of sea ice in ice-sheet proximal environments, however, remains poorly constrained as the application of diatom assemblages in heavily (summer) sea ice covered coastal areas is often hampered by silica dissolution. Highly branched isoprenoids (HBIs) provide a promising tool to overcome this gap. Biomarker analyses focusing on the di-unsaturated HBI termed IPSO25 (Ice Proxy for the Southern Ocean with 25 carbon atoms; Belt et al., 2016), related tri-unsaturated HBIs and phytosterols as well as the application of GDGTs as paleothermometer provide a valuable toolbox for assessing paleoenvironmental conditions in ice-proximal areas. Here, we present preliminary biomarker data obtained from sediment cores collected in the Bransfield Strait, the Amundsen Sea and the Weddell Sea. The data reveal distinct fluctuations in sea ice coverage and primary productivity during the last deglacial(s), which, through consideration of sedimentological data alongside these biomarker records, can be linked to phases of retreating and advancing glacial ice.