The Cr-isotope signature of surface seawater - A global perspective

This study presents chromium-isotope data (expressed as delta Cr-53) and chromium concentrations (Cr) of surface seawater (0-2 m depth) from a variety of locations worldwide. In addition to samples from the open ocean (Arctic, Southern, Pacific, and Atlantic Oceans), samples were analysed from areas with more restricted water exchange rates (the Mediterranean Sea, Oresund, and Baltic Sea). The data indicate a heterogeneous distribution of delta Cr-53 in seawater with a total range from +0.13%o to +1.24 parts per thousand. The data are in agreement with a previous study, which focused on depth profiles, suggesting that seawater heterogeneity in delta Cr-53 and Cr concentration can be explained using a single fractionation factor for Cr-reduction (epsilon = -0.79 +/- 0.06 parts per thousand 2SD). In basins with limited water exchange with the open ocean, however, local factors seem to control the Cr-isotope composition. (C) 2016 Elsevier B.V. All rights reserved.