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| Titel |
The shape of the oceanic nitracline |
| VerfasserIn |
M. M. Omand, A. Mahadevan |
| 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. 11 ; Nr. 12, no. 11 (2015-06-03), S.3273-3287 |
| Datensatznummer |
250117961
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| Publikation (Nr.) |
 copernicus.org/bg-12-3273-2015.pdf |
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| Zusammenfassung |
| In most regions of the ocean, nitrate is depleted near the surface by
phytoplankton consumption and increases with depth, exhibiting a strong
vertical gradient in the pycnocline (here referred to as the nitracline). The
vertical supply of nutrients to the surface euphotic zone is influenced by
the vertical gradient (slope) of the nitracline and by the vertical
separation (depth) of the nitracline from the sunlit surface layer. Hence it
is important to understand the shape (slope and curvature) and depth of the
oceanic nitracline. By using density coordinates to analyze nitrate profiles
from autonomous Autonomous Profiling EXplorer floats with In-Situ Ultraviolet Spectrophotometers (APEX-ISUS) and ship-based platforms (World Ocean Atlas – WOA09; Hawaii Ocean
Time-series – HOT; Bermuda Atlantic Time-series Study – BATS; and
California Cooperative Oceanic Fisheries Investigations – CalCOFI), we are
able to eliminate much of the spatial and temporal variability in the
profiles and derive robust relationships between nitrate and density. This
allows us to characterize the depth, slope and curvature of the nitracline in
different regions of the world's oceans. The analysis reveals distinguishing
patterns in the nitracline between subtropical gyres, upwelling regions and
subpolar gyres. We propose a one-dimensional, mechanistic model that relates
the shape of the nitracline to the relative depths of the surface mixed layer
and euphotic layer. Though heuristic, the model accounts for some of the
seasonal patterns and regional differences in the nitrate–density
relationships seen in the data. |
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