Hannover 2013 – wissenschaftliches Programm

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MS: Fachverband Massenspektrometrie

MS 10: Accelerator Mass Spectrometry and Applications III

MS 10.2: Vortrag

Donnerstag, 21. März 2013, 14:15–14:30, F 442

The first transect of U-236 in the North Atlantic Ocean — •Núria Casacuberta¹, Marcus Christl¹, Johannes Lachner¹, Michiel Rutgers van der Loeff², Viena Puigcorbé³, Pere Masqué³, and Hans-Arno Synal¹ — ¹Laboratory of Ion Beam Physics, ETH Zurich, Switzerland — ²AWI-Geochemistry, Bremerhaven, Germany — ³ICTA & Departament de Física, UAB, Barcelona, Spain

New developments in accelerator mass spectrometry (AMS) allow determining very low-levels of anthropogenic ²³⁶U in Ocean waters. As a result, the potential of using the ²³⁶U/²³⁸U ratio as a new conservative and transient tracer in oceanography is now being tested. In this study ²³⁶U/²³⁸U ratios and ²³⁶U concentrations were determined in 90 3L seawater samples, collected from 9 depth profiles during the Dutch GEOTRACES cruise GA02 in 2010 along the Northwest Atlantic Ocean (from equator to 64^∘N). The ²³⁶U/²³⁸U ratios ranged from (44±15)·10⁻¹² to (1477±91)·10⁻¹². Higher values correspond to North Atlantic water masses (i.e. Labrador Sea Water (LSW) and North East Atlantic Deep Water (NEADW)), which have higher input from global fallout and possibly an additional contribution from the European nuclear reprocessing plants. In contrast, lower ²³⁶U values are representative of southern water masses such as Antarctic Bottom Water (AABW) and Antarctic Intermediate Water (AAIW). To explore the potential of this new tracer in oceanography it is compared to other transient tracers (e.g. CFCs) used so far to quantify oceanic processes such as water mass mixing and deep water formation rates.