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| Titel |
The biogeochemical structuring role of horizontal stirring: Lagrangian perspectives on iron delivery downstream of the Kerguelen Plateau |
| VerfasserIn |
F. d'Ovidio, A. Della Penna, T. W. Trull, F. Nencioli, M.-I. Pujol, M.-H. Rio, Y.-H. Park, C. Cotté, M. Zhou, S. Blain |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 19 ; Nr. 12, no. 19 (2015-10-01), S.5567-5581 |
| Datensatznummer |
250118107
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| Publikation (Nr.) |
 copernicus.org/bg-12-5567-2015.pdf |
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| Zusammenfassung |
| Field campaigns are instrumental in providing ground truth for understanding
and modeling global ocean biogeochemical budgets. A survey however can only
inspect a fraction of the global oceans, typically a region hundreds of kilometers wide for
a temporal window of the order of (at most) several weeks. This
spatiotemporal domain is also the one in which the mesoscale activity induces
through horizontal stirring a strong variability in the biogeochemical
tracers, with ephemeral, local contrasts which can easily mask the regional
and seasonal gradients. Therefore, whenever local in situ measures are used
to infer larger-scale budgets, one faces the challenge of identifying the
mesoscale structuring effect, if not simply to filter it out. In the case of
the KEOPS2 investigation of biogeochemical responses to natural iron
fertilization, this problem was tackled by designing an adaptive sampling
strategy based on regionally optimized multisatellite products analyzed in
real time by specifically designed Lagrangian diagnostics. This strategy
identified the different mesoscale and stirring structures present in the
region and tracked the dynamical frontiers among them. It also enabled
back trajectories for the ship-sampled stations to be estimated, providing
important insights into the timing and pathways of iron supply, which were
explored further using a model based on first-order iron removal. This context
was essential for the interpretation of the field results. The mesoscale
circulation-based strategy was also validated post-cruise by comparing the
Lagrangian maps derived from satellites with the patterns of more than one
hundred drifters, including some adaptively released during KEOPS2 and a
subsequent research voyage. The KEOPS2 strategy was adapted to the specific
biogeochemical characteristics of the region, but its principles are general
and will be useful for future in situ biogeochemical surveys. |
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