| Summary: | Alkenone sediment data from the Nordic seas and North Atlantic are compared to those from Sikes et al.[1997] for the Southern Ocean to evaluate further UK37 and UK37' as proxies to estimate cold temperatures (<10°C) and the effect of salinity and temperature in the relative abundance of 37∶4 to the total abundance of C37 alkenones (37∶4%). UK37 and UK37' are found to be equally viable as proxies, but there are significant regional differences in their cold temperature dependence. The measurement of 37∶4% in cores from the North Atlantic region can be used to identify situations when UK37' is not a reliable paleothermometer. Variations in salinity are probably responsible for changes in the sedimentary record of 37∶4%, and a preliminary calibration has been obtained for 37:4%=f(salinity). This new relationship should be further confirmed through field or laboratory experiments, but it paves the way to derive a molecular proxy to reconstruct paleosalinity in surface waters.
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