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| Titel |
What controls biological production in coastal upwelling systems? Insights from a comparative modeling study |
| VerfasserIn |
Z. Lachkar, N. Gruber |
| 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 ; 8, no. 10 ; Nr. 8, no. 10 (2011-10-21), S.2961-2976 |
| Datensatznummer |
250006166
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| Publikation (Nr.) |
 copernicus.org/bg-8-2961-2011.pdf |
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| Zusammenfassung |
| The magnitude of net primary production (NPP) in Eastern Boundary Upwelling
Systems (EBUS) is traditionally viewed as directly reflecting the wind-driven
upwelling intensity. Yet, different EBUS show different sensitivities of NPP
to upwelling-favorable winds (Carr and
Kearns, 2003). Here, using a comparative
modeling study of the California Current System (California CS) and Canary
Current System (Canary CS), we show how physical and environmental factors,
such as light, temperature and cross-shore circulation modulate the response
of NPP to upwelling strength. To this end, we made a series of eddy-resolving
simulations of the two upwelling systems using the Regional Oceanic Modeling
System (ROMS), coupled to a nitrogen-based
Nutrient-Phytoplankton-Zooplankton-Detritus (NPZD) ecosystem model. Using
identical ecological/biogeochemical parameters, our coupled model simulates a
level of NPP in the California CS that is 50 % smaller than that in the
Canary CS, in agreement with observationally based estimates. We find this
much lower NPP in the California CS despite phytoplankton in this system
having nearly 20 % higher nutrient concentrations available to fuel their
growth. This conundrum can be explained by: (1) phytoplankton having a faster
nutrient-replete growth in the Canary CS relative to the California CS; a
consequence of more favorable light and temperature conditions in the Canary
CS, and (2) the longer nearshore water residence times in the Canary CS,
which permit a larger buildup of biomass in the upwelling zone, thereby
enhancing NPP. The longer residence times in the Canary CS appear to be a
result of the wider continental shelves and the lower mesoscale activity
characterizing this upwelling system. This results in a weaker offshore
export of nutrients and organic matter, thereby increasing local nutrient
recycling and reducing the spatial decoupling between new and export
production in the Canary CS. Our results suggest that climate change-induced
perturbations such as upwelling favorable wind intensification might lead to
contrasting biological responses in the California CS and the Canary CS, with
major implications for the biogeochemical cycles and fisheries in these two
ecosystems. |
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