Diatom lipids open window to past ocean temperatures in the polar regions

Sea surface temperature is a key indicator of climate change on Earth and is central to all related modelling endeavours. However, sea surface temperature is notoriously difficult to reconstruct accurately in the geological record, especially for the low temperatures of the polar regions, which occupy one-third of the world's oceans. Here we show that a sea surface temperature proxy based on two isomeric diatom lipid biomarkers can be applied to marine sediment archives to reconstruct temperatures in the range -1 to 14 °C for the Arctic and Antarctic using a single calibration. For both regions, our datasets span timeframes from recent decades to the Younger Dryas/Holocene, and we also showcase a 750 kyr record from the Fram Strait, the major gateway between the North Atlantic and the Arctic Ocean. We anticipate that this lipid biomarker-based proxy may become a standard component of the palaeoclimate toolkit, especially for the polar regions.