Abstract
A C 25 highly branched isoprenoid (HBI) monoene hydrocarbon, designated IP 25, has been proposed previously to originate from diatoms living in Arctic sea ice, while the presence of IP 25 in sediments has been suggested to be a proxy for the occurrence of former Arctic sea ice. Here, we show that the 13C isotopic composition of IP 25 in sea ice, in sediment trap material collected under sea ice, and in high latitude northern sediments, is distinctive (isotopically ‘heavy’) and distinguishable from that of organic matter of planktonic or terrigenous origin. Mean δ 13C values for IP 25 were − 22.3 ± 0.4‰ (sea ice), − 19.6 ± 1.1‰ (sediment traps) and − 19.3 ± 2.3‰ (sediments). These measurements, therefore, support further the proposed use of IP 25 as an Arctic sea ice proxy.
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