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| Titel |
Mesoscale Eddies and the Coastal Carbon Cycling in the California Upwelling System |
| VerfasserIn |
Giuliana Turi, Zouhair Lachkar, Nicolas Gruber |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055071
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| Zusammenfassung |
| Eastern Boundary Upwelling Systems (EBUS) are sites of intense biogeochemical cycling
and among the most productive marine ecosystems in the world, and thus one of the hotspots
of the global carbon cycle. Upwelling brings carbon-enriched deep water to the surface,
which is subsequently warmed, leading to recently upwelled waters having very high surface
pCO2. At the same time, the upwelled nutrients stimulate phytoplankton growth which in
turn creates organic matter that can be exported laterally and vertically and also reduces
surface ocean pCO2. This interplay of upwelling and biological consumption together with
offshore transport and strong mesoscale turbulence leads to a highly variable mosaic of the
oceanic carbon system, which makes the quantification of the net carbon budget
in EBUS challenging. Here we investigate the coastal ocean carbon budget for
one of the four major EBUS, namely the California Upwelling System (CUS),
with a particular focus on the role of mesoscale eddies and their contribution to
the lateral, vertical and air-sea fluxes of carbon. To this end, we made an eddying
and a non-eddying CUS simulation based on a 5km horizontal resolution version
of the Regional Ocean Modeling System (ROMS), coupled to a nitrogen-based
nutrient-phytoplankton-zooplankton-detritus (NPZD) model, including a formulation of the
ocean carbon cycle. We first evaluate our model by comparing surface pCO2 from the
control simulation to a seasonal climatology based on the Lamont-Doherty Earth
Observatory (LDEO) and the Monterey Bay Aquarium Research Institute (MBARI)
databases. We then analyze the lateral, vertical and air-sea exchange fluxes of carbon in
both CUS simulations. Overall, our results show a small net air-sea CO2 flux in
the central CUS compared to the net community production and the lateral and
vertical export carbon fluxes. This suggests that the air-sea flux of CO2 in the CUS
represents only a small component of a very dynamic carbon cycle dominated by large
lateral and vertical carbon exports. The comparison of the eddying and non-eddying
CUS simulations reveals that eddies substantially reduce the CO2 outgassing in the
nearshore area due to eddy-driven leaking of DIC. Further offshore, the CO2 uptake is
slightly decreased as eddies tend to reduce productivity. Finally, we examine the
impact of mesoscale eddies on the lateral transport of carbon in the central CUS and
we document their contribution to the temporal variability of the surface pCO2. |
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