Erlangen 2018 – scientific programme
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UP: Fachverband Umweltphysik
UP 6: Oceanography
UP 6.2: Talk
Tuesday, March 6, 2018, 17:00–17:15, G 1.011
39Ar-dating with 5 litres ocean water samples — •Sven Ebser1, Arne Kersting2, Zhongyi Feng1, Lisa Ringena1, Maximilian Schmidt1, Stefan Beyersdorfer2, Emeline Mathouchanh2, Florian Ritterbusch2, Tim Stöven3, Toste Tanhua3, Werner Aeschbach2, and Markus K. Oberthaler1 — 1Kirchhoff-Institut für Physik, Universität Heidelberg, Germany — 2Institut für Umweltphysik, Universität Heidelberg, Germany — 3GEOMAR - Helmholtz-Zentrum für Ozeanforschung Kiel, Germany
With a half-life of 269 years, 39Ar is the only available dating tracer on the time scale of 50 to 1000 years, which makes it the perfect tool to investigate ocean ventilation. Up to now, Low-Level Counting was the only available technique for routine 39Ar measurements. Requiring water sample volumes around one cubic meter and 6 weeks of counting, its application was limited to overall 125 ocean samples so far.
We will report the first 39Ar measurements using only 5 litres of ocean water and taking only one day of analysis, based on the atom optical technique Argon Trap Trace Analysis. In 2015, three depth profiles at 8 samples each were taken during an east-west transect investigating the eastern tropical North Atlantic Oxygen Minimum Zone. The samples were further processed and analysed in Heidelberg. All three profiles show a rapid increase of the 39Ar-age with depth in the upper 1500 m followed by a more homogeneous 39Ar concentration down to 4000 m. The 39Ar results are used in combination with CFC-12 and SF6 data to constrain the Transit Time Distribution (TTD) method better, which is used to describe the ocean ventilation.