HBIs and sterols in surface sediments across the East Siberian Sea: implications for palaeo sea‐ice reconstructions
Résumé
Highly branched isoprenoids (HBIs) in marine sediments have emerged as promising semi-quantitative proxies to reconstruct seasonal sea-ice in polar oceans. In this work, we examine the distribution of sympagic HBIs (IP25 and HBI II), pelagic phytoplankton biomarkers (brassicasterol, dinosterol and HBI-III) as well as terrestrial sterols (campesterol and β-sitosterol) in the surface sediments of the East Siberian Sea (ESS) to test their reliability as sea-ice proxies under continental runoff influence. Our data suggest that dinosterol performs better than brassicasterol to assess sea-ice across the ESS shelf, yet the correlation between PDIP25 and spring sea-ice is relatively weak but improves when removing sites with salinity <25. Strongest relationship is found between PIIIIP25 and summer sea-ice in regions remote from riverine influence. Overall, our results show that semi-quantitative estimates of sea-ice based on biomarkers can be problematic in Arctic Ocean margins because of biases induced by continental runoff on biological productivity and sea-ice production.
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