39Ar dating with small samples resolves ocean ventilation

Sven Ebser, Arne Kersting, Tim Stöven, Zhongyi Feng, Lisa Ringena, Maximilian Schmidt, Toste Tanhua, Werner Aeschbach and Markus K. Oberthaler

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Aug 09, 2018
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Received: 11th July 18

Ocean ventilation is the integrated effect of various processes that propagate surface properties to the ocean interior. Its precise understanding is the prerequisite for addressing essential questions such as oxygen supply, the storage of anthropogenic carbon and the heat budget of the ocean. Currently employed observational methods to infer ventilation utilise transient tracers, i.e. tritium, SF6, CFCs and the radioisotope 14C. However, their dating ranges are not suitable to resolve the dynamics of the deep ocean. The noble gas isotope 39Ar with a half-life of 269 years fills this gap. Its broad application has previously been hindered by its very low abundance, requiring at least 1000 litres of water for dating. Here we report on successful 39Ar dating with only 5 litres of water based on the atom-optical technique Atom Trap Trace Analysis. Our data reveal previously not quantifiable ventilation patterns in the Eastern Tropical North Atlantic, where we find that advection is more important for the ventilation of the intermediate depth range than previously assumed. This result implies faster ventilation than estimated in other studies and thus a significantly higher anthropogenic CO2-storage. The demonstrated analytical capabilities now allow for a global collection of 39Ar data, which will have significant impact on our understanding of ocean ventilation.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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