%0 Journal Article %J Nature Communications %D 2021 %T Group 2i Isochrysidales produce characteristic alkenones reflecting sea ice distribution %A Wang, Karen Jiaxi %A Huang, Yongsong %A Majaneva, Markus %A Belt, Simon T. %A Liao, Sian %A Novak, Joseph %A Kartzinel, Tyler R. %A Herbert, Timothy D. %A Richter, Nora %A Cabedo-Sanz, Patricia %K RCC107 %K RCC1195 %K RCC1334 %K RCC5486 %X Alkenones are biomarkers produced solely by algae in the order Isochrysidales that have been used to reconstruct sea surface temperature (SST) since the 1980s. However, alkenone-based SST reconstructions in the northern high latitude oceans show significant bias towards warmer temperatures in core-tops, diverge from other SST proxies in down core records, and are often accompanied by anomalously high relative abundance of the C 37 tetra-unsaturated methyl alkenone (%C 37:4 ). Elevated %C 37:4 is widely interpreted as an indicator of low sea surface salinity from polar water masses, but its biological source has thus far remained elusive. Here we identify a lineage of Isochrysidales that is responsible for elevated C 37:4 methyl alkenone in the northern high latitude oceans through next-generation sequencing and lab-culture experiments. This Isochrysidales lineage co-occurs widely with sea ice in marine environments and is distinct from other known marine alkenone-producers, namely Emiliania huxleyi and Gephyrocapsa oceanica . More importantly, the %C 37:4 in seawater filtered particulate organic matter and surface sediments is significantly correlated with annual mean sea ice concentrations. In sediment cores from the Svalbard region, the %C 37:4 concentration aligns with the Greenland temperature record and other qualitative regional sea ice records spanning the past 14 kyrs, reflecting sea ice concentrations quantitatively. Our findings imply that %C 37:4 is a powerful proxy for reconstructing sea ice conditions in the high latitude oceans on thousand- and, potentially, on million-year timescales. %B Nature Communications %V 12 %P 15 %8 dec %G eng %U http://dx.doi.org/10.1038/s41467-020-20187-z http://www.nature.com/articles/s41467-020-20187-z %R 10.1038/s41467-020-20187-z