Berlin 2014 – wissenschaftliches Programm
MS 11.5: Vortrag
Freitag, 21. März 2014, 11:45–12:00, DO24 1.205
236U and 129I as tracers of water masses in the Arctic Ocean — •Núria Casacuberta1, Marcus Christl1, Christof Vockenhuber1, Clemens Walther2, Michiel Van-der-Loeff3, Pere Masqué4, and Hans-Arno Synal1 — 1Laboratory of Ion Beam Physics, ETH-Zurich, Switzerland — 2Institut für Radioökologie und Strahlenschutz, Leibniz Universität Hannover, Germany — 3AWI-Geochemistry, Alfred Wegener Institut Für Polar und Meeresforshung, Bremerhaven, Germany. — 4Institut de Ciència i Tecnologia Ambientals, Universitat Autònoma de Barcelona, Bellaterra, Spain
Recently 236U attested to be a new transient oceanographic tracer: it is conservative in seawater and far from having reached steady state in the oceans. Its main sources in the North Atlantic are global fallout and European reprocessing plants. In this study, concentrations of 236U and 129I of eight deep profiles in the Arctic Ocean collected in 2011-2012 were determined with a compact ETH Zurich AMS system (TANDY). Results on 236U/238U show a steep gradient, from the lowest ever-reported 236U/238U atomic ratio in open ocean water (5±5) x 10−12 up to (3700±80) x 10−12. Whereas the very low ratios are indicative for deep old waters, high ratios in shallow and surface waters show a clear signature of Atlantic Waters (AW) penetrating to the Arctic Ocean. The combination of 236U with 129I, both being released by the nuclear reprocessing plants of Sellafield and La Hague, with a distinct temporal input function, is used to estimate transit time of AW distributions in the Arctic Ocean.