Removal of bias in C37 alkenone-based sea surface temperature measurements by high-performance liquid chromatography fractionation

Abstract

Sea surface temperature determinations based on marine sedimentary C37 alkenone distributions have provided a wealth of data for paleoclimatic studies, including those performed at high resolution. The success of this approach results from several characteristics of alkenone compounds, e.g. their geochemical properties (such as unequivocal synthesis by certain widespread haptophyte algae, plus chemical stability/preservation of the original alkenone distributions during sedimentation), and their analytical properties (such as fast clean up procedures using alkaline hydrolysis of sediment extracts, followed by robust instrumental methods allowing large scale sample processing). Here we show that, in sediments under the influence of continental inputs, coelution of these compounds with cholest-5-enyl 3β-undecenyl ether and 24-methylcholesta-5,22-dienyl 3β-undecenyl ether deviate the SST measurements despite alkaline hydrolysis. Here, we report a new high performance liquid chromatrography fractionation method which eliminates these interfering compounds and gathers all the alkenones into a single fraction. These fractions can then be analysed by gas chromatography as in the initial approach, providing large amounts of data as required in high resolution studies.