8.15 – Alkenone Paleotemperature Determinations

The alkenone paleotemperature (‘U k 37 ’) method, which relies on determining the unsaturation index of biomarker compounds produced by one group of closely related haptophyte algae, is now widely used to reconstruct near-surface ocean temperatures on timescales ranging from a few centuries to millions of years. In comparison with other methods of paleotemperature estimation, the alkenone method is rapid and extremely precise and appears to obey a global relationship to sea surface temperature (SST). This does not mean that the ecological and physiological complexities of the alkenone-producing organisms may not intrude in some cases on the application of U k 37 to derive past SST or that the results of alkenone paleotemperature reconstructions agree to the stated uncertainties with other paleotemperature proxies. Nevertheless, the alkenone method has proven remarkably successful at generating regionally consistent, physically plausible pictures of past SST change at all timescales and appears to have a reliable place in the toolkit of paleoclimatologists.