Distinctive 13C isotopic signature distinguishes a novel sea ice biomarker in Arctic sediments and sediment traps

A C-25 highly branched isoprenoid (HBI) monoene hydrocarbon, designated IP25, has been proposed previously to originate from diatoms living in Arctic sea ice, while the presence of IP25 in sediments has been suggested to be a proxy for the occurrence of former Arctic sea ice. Here, we show that the C-13 isotopic composition of IP25 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 delta C-13 values for IP25 were -22.3 +/- 0.4 parts per thousand. (sea ice), -19.6 +/- 1.1 parts per thousand. (sediment traps) and -19.3 +/- 2.3 parts per thousand. (sediments). These measurements, therefore. support further the proposed use of IP25 as an Arctic sea ice proxy. (c) 2008 Elsevier B.V. All rights reserved.