Interhemispheric appraisal of the value of alkenone indices as temperature and salinity proxies in high‐latitude locations

Abstract

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 U K 37 and U K 37′ 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 C 37 alkenones (37∶4%). U K 37 and U K 37′ 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 U K 37′ 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.