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| Titel |
Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements |
| VerfasserIn |
T. Stöven, T. Tanhua |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 10, no. 3 ; Nr. 10, no. 3 (2014-06-05), S.439-457 |
| Datensatznummer |
250117001
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| Publikation (Nr.) |
 copernicus.org/os-10-439-2014.pdf |
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| Zusammenfassung |
Ventilation is the primary pathway for atmosphere–ocean boundary
perturbations, such as temperature anomalies, to be relayed to the ocean
interior. It is also a conduit for gas exchange between the interface of
atmosphere and ocean. Thus it is a mechanism whereby, for instance, the ocean
interior is oxygenated and enriched in anthropogenic carbon. The ventilation
of the Mediterranean Sea is fast in comparison to the world ocean and has
large temporal variability. Here we present transient tracer data from a
field campaign in April 2011 that sampled a unique suite of transient tracers
(SF6, CFC-12, 3H and 3He) in all major basins of the
Mediterranean. We apply the transit time distribution (TTD) model to the data
in order to constrain the mean age, the ratio of the advective / diffusive
transport and the number of water masses significant for ventilation.
We found that the eastern part of the eastern Mediterranean can be reasonably
described with a one-dimensional inverse Gaussian TTD (IG-TTD), and thus
constrained with two independent tracers. The ventilation of the Ionian Sea
and the western Mediterranean can only be constrained by a linear combination
of IG-TTDs. We approximate the ventilation with a one-dimensional, two
inverse Gaussian TTD (2IG-TTD) for these areas and demonstrate a possibility
of constraining a 2IG-TTD from the available transient tracer data. The deep
water in the Ionian Sea has a mean age between 120 and 160 years and is
therefore substantially older than the mean age of the Levantine Basin deep
water (60–80 years). These results are in contrast to those expected by the
higher transient tracer concentrations in the Ionian Sea deep water. This is
partly due to deep water of Adriatic origin having more diffusive properties
in transport and formation (i.e., a high ratio of diffusion over
advection), compared to the deep water of Aegean Sea origin that still
dominates the deep Levantine Basin deep water after the Eastern Mediterranean
Transient (EMT) in the early 1990s. The tracer minimum zone (TMZ) in the
intermediate of the Levantine Basin is the oldest water mass with a mean age
up to 290 years. We also show that the deep western Mediterranean has
contributed approximately 40% of recently ventilated deep water from the
Western Mediterranean Transition (WMT) event of the mid-2000s. The deep water
has higher transient tracer concentrations than the mid-depth water, but the
mean age is similar with values between 180 and 220 years. |
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