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 C37 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 U37(K)' 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.