Utility of dissolved barium in distinguishing North American from Eurasian runoff in the Arctic Ocean

• Published in: Marine Chemistry
• Main Authors: Roeske, T., Bauch, Dorothea, Rutgers V.D. Loeff, M., Rabe, B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2012
• Subjects: Arctic; Arctic Ocean; Barents Sea; Laptev Sea; Makarov Basin; Mendeleyev; Pacific; The Ark; Fram Strait; Kara-Laptev; laptev; makarov basin; Sea ice
• Online Access: https://oceanrep.geomar.de/id/eprint/14072/; https://oceanrep.geomar.de/id/eprint/14072/1/Roeske.pdf; https://doi.org/10.1016/j.marchem.2012.01.007

Dissolved barium has been shown to have the potential to distinguish Eurasian from North American (NA) river runoff. As part of the ARK-XXII/2 Polarstern expedition in summer 2007, Ba was analyzed in the Barents, Kara, Laptev seas, and the Eurasian Basins as well as the Makarov Basin up to the Alpha and Mendeleyev Ridges. By combining salinity, δ18O and initial phosphate corrected for mineralization with oxygen (PO4*) or N/P ratios we identified the water mass fractions of meteoric water, sea ice meltwater, and marine waters of Atlantic as well as Pacific origin in the upper water column. In all basins inside the lower halocline layer and the Arctic intermediate waters we find Ba concentrations close to those of the Fram Strait branch of the lower halocline (41–45 nM), reflecting the composition of the incoming Atlantic water. A layer of upper halocline water (UHW) with higher Ba concentrations (45–55 nM) is identified in the Makarov Basin. Atop of the UHW, the Surface Mixed Layer (SML), including the summer and winter mixed layers, has high concentrations of Ba (58–67 nM). In the SML of the investigated area of the central Arctic the meteoric fraction can be identified by assuming a conservative behavior of Ba to be primarily of Eurasian river origin. However, in productive coastal regions biological removal compromises the use of Ba to distinguish between Eurasian and NA rivers. As a consequence, the NA river water fraction is underestimated in productive surface waters or waters that have passed a productive region, whereas this fraction is overestimated in subsurface waters containing remineralised Ba, particularly when these waters have passed productive shelf regions. Especially in the Laptev Sea and small regions in the Barents Sea, Ba concentrations are low in surface waters. In the Laptev Sea exceptionally high Ba concentrations in shelf bottom waters indicate that Ba is removed from surface waters to deep waters by biological activity enhanced by increasing ice-free conditions as well as by scavenging ...