Application and validation of Na/Ca as a proxy for seawater salinity in the Red Sea around Termination II

Abstract

In this study a novel approach to reconstruct salinity in the Red Sea on glacialinterglacial time scales is explored. This method combines Na/Ca, Mg/Ca and d18O (Calcite) ratios measured on planktonic foraminifera. Samples from a piston core from the Red Sea (KL09) are used. Core tops from the Mediterranean Sea are used to compare Laser Ablation Inductively Coupled Mass Spectrometry (LAICP- MS) to solution Inductively Coupled Mass Spectrometry (solution ICP-MS). We find that solution ICP-MS can only be used effectively for Na/Ca and Mg/Ca when a sufficiently large sample group is used. For large amounts of samples with sufficient foraminifera, LA-ICP-MS requires significantly more time and solution ICP-MS is preferable. The results show that foraminiferal calcite Na/Ca from the sediment cannot be compared directly to plankton pump data, as this would result in unrealistic values for the calibration of the salinity proxy. We find that different species result in different Na/Ca values: the Na/Ca record of Globogerinoides sacculifer shows a similar trend with global sea level, while the record of Globogerinoides ruber (white) shows no correlation. The records are not of sufficient length for statistical significance, but promising for future research.