Evidence for the non-influence of salinity variability on the &amp;lt;i&amp;gt;Porites&amp;lt;/i&amp;gt; coral Sr/Ca palaeothermometer

M Moreau,T Corrège,E P Dassié,F Le Cornec

doi:10.5194/cp-11-523-2015

Abstract

Abstract. Porites coral-based sea surface temperature (SST) reconstructions are obtained from the measurement of skeleton Sr/Ca ratio. However, the influence of salinity in the incorporation of these trace elements in the Porites aragonitic skeleton is still poorly documented. Laboratory experiments indicate that in three different coral species (not including the widely used Porites genus), salinity does not influence the Sr/Ca thermometer. In this study, we test the salinity effect on Porites Sr/Ca-based SST reconstructions at monthly and interannual timescales in open-ocean environmental conditions. We use a large spatial compilation of published Porites data from the Red Sea and Pacific and Indian oceans. Additionally to those published records, we add a new eastern Pacific coral Sr/Ca record from Clipperton Atoll. Using two different salinity products (Simple Ocean Data Assimilation (SODA) SSS reanalyses version 2.2.4, Carton and Giese, 2008; and instrumental SSS from the Institut de Recherche pour le Développement, France (IRD) Delcroix et al., 2011), we find no evidence of salinity bias on the Sr/Ca SST proxy at monthly and interannual timescales. We conclude that Porites Sr/Ca is a reliable palaeothermometer that is not influenced by salinity variability.

Highlights

Massive scleractinian corals have been extensively used in the past 3 decades as a source of environmental information for the tropical belt at different timescales (Cole et al, 1993; Gagan et al, 1998; Cobb et al, 2003; Corrège, 2006; Linsley et al, 2006; Jones, 2009; Delong et al, 2012 and therein)
Using two different salinity products (Simple Ocean Data Assimilation (SODA) sea surface salinity variability (SSS) reanalyses version 2.2.4, Carton and Giese, 2008; and instrumental SSS from the Institut de Recherche pour le Développement, France (IRD) Delcroix et al, 2011), we find no evidence of salinity bias on the Sr / Ca sea surface temperature (SST) proxy at monthly and interannual timescales
We observe no relationship between SST and SODA SSS/IRD SSS at seasonal resolution except for the Ogasawara location (r = 0.42 (SODA); p < 0.01; Table 2)

Summary

Introduction

Massive scleractinian corals have been extensively used in the past 3 decades as a source of environmental information for the tropical belt at different timescales (from weekly to multi-annual) (Cole et al, 1993; Gagan et al, 1998; Cobb et al, 2003; Corrège, 2006; Linsley et al, 2006; Jones, 2009; Delong et al, 2012 and therein). Among the different geochemical tracers used in coralbased palaeoclimatology, the Sr / Ca ratio has been shown to be the most robust and straightforward coral geochemical proxy for reconstructing past SST changes (Smith et al, 1979; Beck et al, 1992; Alibert et McCulloch, 1997; Corrège, 2006; Nurhati et al, 2009; Delong et al, 2012; 2013). Several sources of noise and error can interfere when generat-

Methods

Results

Conclusion