Water isotopologues as a quantitative paleosalinity proxy

Abstract

Paleosalinity reconstructions are a goal of paleoceanographic study because of their potential to provide insight into past ocean circulation. While temperature reconstructions have been assessed by using multiple independent proxies, the skill of existing salinity reconstructions remains poorly quantified. We examine the applicability of two different approaches using a set of coupled water isotope-enabled general circulation model experiments as a numerical analog for the real climate system. These simulations for the Holocene, at roughly 1000 year time steps, explicitly track variability in both the water isotopologues and salinity. Our simulations suggest that quantitative reconstructions of past salinity variability based solely on inferred δ 18 O sw variability have very large errors and uncertainties. However, we find that paired δ 18 O sw and δD variability (from combining biomarker and calcite proxies) holds promise for providing better quantitative estimates of salinity variability. Copyright 2011 by the American Geophysical Union.