caa a22 4500 528787667 20190104030322.0 cr unu---uuuuu 180924s2011 xx s 000 0 eng 10.3929/ethz-b-000041095 doi 10.5194/bg-8-2961-2011 doi (ETHRESEARCH)oai:www.research-collection.ethz.ch:20.500.11850/41095 Lachkar Zouhair What controls biological production in coastal upwelling systems? Insights from a comparative modeling study [Elektronische Daten] [Zouhair Lachkar, Nicolas; id_orcid 0000-0002-2085-2310 Gruber] Open access ethresearch 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. Creative Commons Attribution 3.0 Unported http://creativecommons.org/licenses/by/3.0 ethresearch Gruber Nicolas; id_orcid 0000-0002-2085-2310 joint author Biogeosciences Göttingen : Copernicus 8 (10), pp. 2961-2976 http://hdl.handle.net/20.500.11850/41095 text/html WWW-Backlink auf das Repository (Open access) 1 Journal Article ethresearch ETHRESEARCH 856 40 http://hdl.handle.net/20.500.11850/41095 text/html WWW-Backlink auf das Repository (Open access) ETHRESEARCH 100 1- Lachkar Zouhair ETHRESEARCH 700 1- Gruber Nicolas; id_orcid 0000-0002-2085-2310 joint author ETHRESEARCH 773 0- Biogeosciences Göttingen : Copernicus 8 (10), pp. 2961-2976 BK010053 XK010053 XK010000 ETHRESEARCH ETHRESEARCH ETHRESEARCH Journal Article Open access