Publication Date:
2017-09-20
Description:
Artificial radionuclides have been introduced to the
oceans from nuclear weapons tests (1950’s-1960’s), nuclear
accidents (e.g. Chernobyl, 1986) and nuclear reprocessing
plants (Sellafield, and La Hague, from 1960s until today) and
since then they are used as transient tracers for ocean
circulation. Among these radionuclides, 129I and 236U have
become of special interest in the last decade and the
combination of 129I/236U to 236U/238U atom ratios has been
suggested as a tool to determine transit times in the Arctic
Ocean [1] and to constrain the source of the anthropogenic
contamination [2]. The performance of this new dual tracer
has now been tested as data from samples collected during
several cruises performed in the North Atlantic and Arctic
oceans.
Here we present the results of a number of expeditions to
the Arctic Ocean (2011, 2012 and 2015) and the North
Atlantic Ocean (2010, 2014). Atlantic waters entering the
Arctic Ocean are tagged with high 129I/236U ratios (〉100) and
236U/238U ratios (〉1000 x10-12), originating from more recent
(〈15 years) releases from reprocessing plants. Deep and
bottom waters in the Arctic Ocean have much lower 129I/236U
and 236U/238U ratios (supported by low 14C concentrations),
representing the isolation of these waters from anthropogenic
signals. New data from Barents Sea Branch Waters indicate
the presence of a stronger signal from waters tagged by La
Hague while Fram Strait Branch Waters, show a mixture of
both Sellafield and La Hague endmembers.
In order to better disentangle the sources and fate of 129I
and 236U to the North Atlantic and Arctic oceans, results from
a global ocean model will be presented and discussed in the
context of the experimental data.
[1] Christl et al. (2015) J. Geophys. Res. Oceans, 120.
[2] Casacuberta et al. (2016) Earth Planet. Sc. Lett. 440.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Conference
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notRev