Constraining the application of hydrogen isotopic composition of alkenones as a salinity proxy using marine surface sediments

Gabriella M Weiss,Jaap S Sinninghe Damsté,Marcel T.J Van Der Meer,Stefan Schouten

doi:10.1016/j.gca.2019.01.038

Gabriella M Weiss, Jaap S Sinninghe Damsté + Show 2 more

Open Access

https://doi.org/10.1016/j.gca.2019.01.038

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Abstract

Abstract Sea surface salinity is an essential environmental parameter necessary to understand past changes in global climate. However, reconstructing absolute salinity of the surface ocean with high enough accuracy and precision remains a complicated task. Hydrogen isotope ratios of long-chain alkenones (δ2HC37) have been shown to reflect salinity in culture studies and have been proposed as a tool to reconstruct sea surface salinity in the geologic record. The correlation between δ2HC37 – salinity in culture is prominently caused by the relationship between δ2HH2O and salinity, as well as the increase in fractionation factor α with increasing salinity. The δ2HC37 – salinity relationship in the natural environment is poorly understood. Here, surface sediments from a variety of environments covering a wide range of salinities were analyzed to constrain the environmental relationship between salinity and hydrogen isotopes of alkenones. δ2HC37 correlates significantly (r = 0.75, p

Highlights

Understanding changes in surface ocean salinity in the past would greatly increase knowledge about ocean circulation and heat transport around the globe with respect to global climate changes
Based on the compilation of surface sediments from a range of environmental settings, we have shown that d2HC37 ratios have a strong positive linear correlation with annual mean sea surface salinity
AC37 values do not correlate with sea surface salinity, in contrast to previous findings from culture experiments

Summary

Introduction

Understanding changes in surface ocean salinity in the past would greatly increase knowledge about ocean circulation and heat transport around the globe with respect to global climate changes. A reliable tool to reconstruct sea surface salinity has long been sought after by the paleoceanographic community. A number of possibilities have been explored, but the reconstruction of sea surface salinity changes can be quite complicated (Rohling, 2007 and references therein). Attempts to understand past salinity changes have employed dinoflagellate (dinocysts) (Wall and Dale, 1968) and diatom assemblages in combination with transfer functions

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