Wind-induced upwelling in the Kerguelen Plateau region
In contrast to most of the Southern Ocean, the Kerguelen Plateau supports an unusually strong spring chlorophyll (Chl <i>a</i>) bloom, likely because the euphotic zone in the region is supplied with higher iron concentrations. This study uses satellite wind, sea surface temperature (SST)...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2014-11-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/11/6389/2014/bg-11-6389-2014.pdf |
| _version_ | 1819262132758249472 |
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| author | S. T. Gille M. M. Carranza R. Cambra R. Morrow |
| author_facet | S. T. Gille M. M. Carranza R. Cambra R. Morrow |
| author_sort | S. T. Gille |
| collection | DOAJ |
| description | In contrast to most of the Southern Ocean, the Kerguelen Plateau supports an
unusually strong spring chlorophyll (Chl <i>a</i>) bloom, likely because the
euphotic zone in the region is supplied with higher iron concentrations. This
study uses satellite wind, sea surface temperature (SST), and ocean color
data to explore the impact of wind-driven processes on upwelling of cold
(presumably iron-rich) water to the euphotic zone. Results show that, in the
Kerguelen region, cold SSTs correlate with high wind speeds, implying that
wind-mixing leads to enhanced vertical mixing. Cold SSTs also correlate with
negative wind-stress curl, implying that Ekman pumping can further enhance
upwelling. In the moderate to high eddy kinetic energy (EKE) regions surrounding Kerguelen, we find
evidence of coupling between winds and SST gradients associated with
mesoscale eddies, which can locally modulate the wind-stress curl. This
coupling introduces persistent wind-stress curl patterns and Ekman pumping
around these long-lived eddies, which may modulate the evolution of Chl <i>a</i> in
the downstream plume far offshore. Close to the plateau, this eddy coupling
breaks down. Kerguelen has a significant wind shadow on its downwind side,
which changes position depending on the prevailing wind and which generates a
wind-stress curl dipole that shifts location depending on wind direction.
This leads to locally enhanced Ekman pumping for a few hundred kilometers
downstream from the Kerguelen Plateau; Chl <i>a</i> values tend to be more elevated in
places where wind-stress curl induces Ekman upwelling than in locations of
downwelling, although the estimated upwelling rates are too small for this
relationship to derive from direct effects on upward iron supply, and thus
other processes, which remain to be determined, must also be involved in the
establishment of these correlations. During the October and November (2011) KErguelen Ocean and Plateau compared Study
(KEOPS-2) field program, wind conditions were fairly typical for the region, with
enhanced Ekman upwelling expected to the north of the Kerguelen Islands. |
| first_indexed | 2024-12-23T19:52:50Z |
| format | Article |
| id | doaj.art-02b12e9d61584788a898f7d9e1375c5f |
| institution | Directory Open Access Journal |
| issn | 1726-4170 1726-4189 |
| language | English |
| last_indexed | 2024-12-23T19:52:50Z |
| publishDate | 2014-11-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Biogeosciences |
| spelling | doaj.art-02b12e9d61584788a898f7d9e1375c5f2022-12-21T17:33:19ZengCopernicus PublicationsBiogeosciences1726-41701726-41892014-11-0111226389640010.5194/bg-11-6389-2014Wind-induced upwelling in the Kerguelen Plateau regionS. T. Gille0M. M. Carranza1R. Cambra2R. Morrow3Scripps Institution of Oceanography, University of California, San Diego, USAScripps Institution of Oceanography, University of California, San Diego, USALaboratoire d'Etudes en Géophysique et Océanographie Spatiale, Observatoire Midi-Pyrénées, 31400 Toulouse, FranceLaboratoire d'Etudes en Géophysique et Océanographie Spatiale, Observatoire Midi-Pyrénées, 31400 Toulouse, FranceIn contrast to most of the Southern Ocean, the Kerguelen Plateau supports an unusually strong spring chlorophyll (Chl <i>a</i>) bloom, likely because the euphotic zone in the region is supplied with higher iron concentrations. This study uses satellite wind, sea surface temperature (SST), and ocean color data to explore the impact of wind-driven processes on upwelling of cold (presumably iron-rich) water to the euphotic zone. Results show that, in the Kerguelen region, cold SSTs correlate with high wind speeds, implying that wind-mixing leads to enhanced vertical mixing. Cold SSTs also correlate with negative wind-stress curl, implying that Ekman pumping can further enhance upwelling. In the moderate to high eddy kinetic energy (EKE) regions surrounding Kerguelen, we find evidence of coupling between winds and SST gradients associated with mesoscale eddies, which can locally modulate the wind-stress curl. This coupling introduces persistent wind-stress curl patterns and Ekman pumping around these long-lived eddies, which may modulate the evolution of Chl <i>a</i> in the downstream plume far offshore. Close to the plateau, this eddy coupling breaks down. Kerguelen has a significant wind shadow on its downwind side, which changes position depending on the prevailing wind and which generates a wind-stress curl dipole that shifts location depending on wind direction. This leads to locally enhanced Ekman pumping for a few hundred kilometers downstream from the Kerguelen Plateau; Chl <i>a</i> values tend to be more elevated in places where wind-stress curl induces Ekman upwelling than in locations of downwelling, although the estimated upwelling rates are too small for this relationship to derive from direct effects on upward iron supply, and thus other processes, which remain to be determined, must also be involved in the establishment of these correlations. During the October and November (2011) KErguelen Ocean and Plateau compared Study (KEOPS-2) field program, wind conditions were fairly typical for the region, with enhanced Ekman upwelling expected to the north of the Kerguelen Islands.http://www.biogeosciences.net/11/6389/2014/bg-11-6389-2014.pdf |
| spellingShingle | S. T. Gille M. M. Carranza R. Cambra R. Morrow Wind-induced upwelling in the Kerguelen Plateau region Biogeosciences |
| title | Wind-induced upwelling in the Kerguelen Plateau region |
| title_full | Wind-induced upwelling in the Kerguelen Plateau region |
| title_fullStr | Wind-induced upwelling in the Kerguelen Plateau region |
| title_full_unstemmed | Wind-induced upwelling in the Kerguelen Plateau region |
| title_short | Wind-induced upwelling in the Kerguelen Plateau region |
| title_sort | wind induced upwelling in the kerguelen plateau region |
| url | http://www.biogeosciences.net/11/6389/2014/bg-11-6389-2014.pdf |
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