What controls biological production in coastal upwelling systems? Insights from a comparative modeling study

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Author(s) Lachkar, Z., Gruber, N.
Publication Type Journal Items, Publication Status: Published
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Title What controls biological production in coastal upwelling systems? Insights from a comparative modeling study
Author(s) Lachkar, Z.
Gruber, N.
Journal or Series Title Biogeosciences
Volume Number 8
Issue Number 10
Start Page 2961
End Page 2976
ISSN 1726-4170
1726-4189
Publisher Copernicus
Publication Date 2011-10
Abstract 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.
DOI 10.5194/bg-8-2961-2011
Additional Notes Received 29 May 2011, Revised 1 October 2011, Accepted 9 October 2011
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
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NEBIS System Number 006289717
Source Database ID WOS-000296747000012
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@article{Lchkr2011,
  author = "Lachkar, Z. and Gruber, N.",
  title = "{W}hat controls biological production in coastal upwelling systems? {I}nsights from a comparative modeling study",
  journal = "Biogeosciences",
  year = 2011,
  volume = "8",
  number = "10",
  pages = "2961--2976",
  month = oct,
}


E-Citations record created: Mon, 19 Dec 2011, 11:25:39 CET