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| Titel |
Numerical analysis of the primary processes controlling oxygen dynamics on the Louisiana shelf |
| VerfasserIn |
L. Yu, K. Fennel, A. Laurent, M. C. Murrell, J. C. Lehrter |
| 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. 7 ; Nr. 12, no. 7 (2015-04-02), S.2063-2076 |
| Datensatznummer |
250117887
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| Publikation (Nr.) |
 copernicus.org/bg-12-2063-2015.pdf |
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| Zusammenfassung |
| The Louisiana shelf, in the northern Gulf of Mexico, receives large amounts of
freshwater and nutrients from the Mississippi–Atchafalaya river system.
These river inputs contribute to widespread bottom-water hypoxia every
summer. In this study, we use a physical–biogeochemical model that
explicitly simulates oxygen sources and sinks on the Louisiana shelf to
identify the key mechanisms controlling hypoxia development. First, we
validate the model simulation against observed dissolved oxygen
concentrations, primary production, water column respiration, and sediment
oxygen consumption. In the model simulation, heterotrophy is prevalent in
shelf waters throughout the year, except near the mouths of the Mississippi
and Atchafalaya rivers, where primary production exceeds respiratory oxygen
consumption during June and July. During this time, efflux of oxygen to the
atmosphere, driven by photosynthesis and surface warming, becomes a
significant oxygen sink. A substantial fraction of primary production occurs
below the pycnocline in summer. We investigate whether this primary
production below the pycnocline is mitigating the development of hypoxic
conditions with the help of a sensitivity experiment where we disable
biological processes in the water column (i.e., primary production and water
column respiration). With this experiment we show that below-pycnocline
primary production reduces the spatial extent of hypoxic bottom waters only
slightly. Our results suggest that the combination of physical processes
(advection and vertical diffusion) and sediment oxygen consumption largely
determine the spatial extent and dynamics of hypoxia on the Louisiana shelf. |
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