Inter-Hemispheric Appraisal of the Role of the C37:4 Alkenone as a Climate Proxy: A New Molecular Index to Determine the Position of the Arctic Front and Sea Surface Temperature?

Abstract

The U3K7 and U~7' index are used as proxies to reconstruct absolute sea surface temperature (SST) variations in the photic zone (Brassell et al. , 1986; Prahl et al., 1988). These indices are derived from the relative abundance of methyl alkenones with 37 carbon atoms and 2, 3 or 4 double bonds (e.g. C37:4 stands for C37 alkenone with 4 double bonds). Alkenones are biosynthesized by some algae of the Class Prymnesiophyceae, such as E m i l i a n i a hux ley i which is the most abundant and widespread coccolithophorid in the oceans, and most likely, the main producer of alkenones found in recent sediments. In comparison to other sedimentary organic components (i.e. biomarkers), alkenones are more resilient to degradation, abundant in sediments, and their presence is widespread in all oceans. The purpose of this paper is to provide new insights into the value of uK7/u3K7 ' tO estimate SST at low temperatures (<10C), and to examine the information contained in C37:4 for palaeoceanographic reconstruction. Alkenone sediment data from the Nordic Seas are compared to data for the Southern Ocean (Sikcs et al. , 1997), to appraise the global significance of regional data from the North and South hemispheres.