scholarly journals First Evidence of Anoxia and Nitrogen Loss in the Southern Canary Upwelling System

2019 ◽  
Vol 46 (5) ◽  
pp. 2619-2627 ◽  
Author(s):  
E. Machu ◽  
X. Capet ◽  
P. A. Estrade ◽  
S. Ndoye ◽  
J. Brajard ◽  
...  
Keyword(s):  
Nitrogen Loss ◽  
Upwelling System ◽  
Canary Upwelling

scholarly journals On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

2017 ◽  
Vol 14 (13) ◽  
pp. 3337-3369 ◽  
Author(s):  
Elisa Lovecchio ◽  
Nicolas Gruber ◽  
Matthias Münnich ◽  
Zouhair Lachkar
Keyword(s):  
Organic Carbon ◽  
North Atlantic ◽  
Ecosystem Model ◽  
Ocean Modeling ◽  
Regional Ocean Modeling System ◽  
Net Community Production ◽  
Upwelling System ◽  
Canary Upwelling ◽  
Vertical Export ◽  
Offshore Transport

Abstract. A compilation of measurements of net community production (NCP) in the upper waters of the eastern subtropical North Atlantic had suggested net heterotrophic conditions, purportedly supported by the lateral export of organic carbon from the adjacent, highly productive Canary Upwelling System (CanUS). Here, we quantify and assess this lateral export using the Regional Ocean Modeling System (ROMS) coupled to a nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model. We employ a new Atlantic telescopic grid with a strong refinement towards the northwestern African shelf to combine an eddy-resolving resolution in the CanUS with a full Atlantic basin perspective. Our climatologically forced simulation reveals an intense offshore flux of organic carbon that transports about 19 Tg C yr−1 away from the nearshore 100 km over the whole CanUS, amounting to more than a third of the NCP in this region. The offshore transport extends beyond 1500 km into the subtropical North Atlantic, adding organic carbon along the way to the upper 100 m at rates of between 8 and 34 % of the alongshore average NCP as a function of offshore distance. Although the divergence of this lateral export of organic carbon enhances local respiration, the upper 100 m layer in our model remains net autotrophic in the entire eastern subtropical North Atlantic. However, the vertical export of this organic carbon and its subsequent remineralization at depth makes the vertically integrated NCP strongly negative throughout this region, with the exception of a narrow band along the northwestern African shelf. The magnitude and efficiency of the lateral export varies substantially between the different subregions. In particular, the central coast near Cape Blanc is particularly efficient in collecting organic carbon on the shelf and subsequently transporting it offshore. In this central subregion, the offshore transport adds as much organic carbon as nearly 60 % of the local NCP to the upper 100 m, giving rise to a sharp peak of offshore respiration that extends to the middle of the gyre. Our modeled offshore transport of organic carbon is likely a lower-bound estimate due to our lack of full consideration of the contribution of dissolved organic carbon and that of particulate organic carbon stemming from the resuspension of sediments. But even in the absence of these contributions, our results emphasize the fundamental role of the lateral redistribution of the organic carbon for the maintenance of the heterotrophic activity in the open sea.

scholarly journals A Shift in the Wind Regime of the Southern End of the Canary Upwelling System at the Turn of the 20th Century

2021 ◽  
Author(s):  
D. Gallego ◽  
R. García‐Herrera ◽  
T. Losada ◽  
E. Mohino ◽  
B. Rodríguez de Fonseca
Keyword(s):  
20Th Century ◽  
Wind Regime ◽  
Upwelling System ◽  
Canary Upwelling

scholarly journals Mesoscale contribution to the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic

2018 ◽  
Vol 15 (16) ◽  
pp. 5061-5091 ◽  
Author(s):  
Elisa Lovecchio ◽  
Nicolas Gruber ◽  
Matthias Münnich
Keyword(s):  
Organic Carbon ◽  
Long Range ◽  
North Atlantic ◽  
Turbulent Flux ◽  
Ecosystem Model ◽  
Structure Identification ◽  
Flux Divergence ◽  
Upwelling System ◽  
Canary Upwelling ◽  
Offshore Transport

Abstract. Several studies in upwelling regions have suggested that mesoscale structures, such as eddies and filaments, contribute substantially to the long-range transport of the organic carbon from the nearshore region of production to the offshore region of remineralization. Yet a comprehensive analysis of this mesoscale flux and of its impact across the Canary Upwelling System (CanUS) has not been provided. Here, we fill this gap using simulations with the Regional Oceanic Modeling System (ROMS) coupled to a Nutrient, Phytoplankton, Zooplankton and Detritus (NPZD) ecosystem model. We run climatological simulations on an Atlantic telescopic grid with an eddy-resolving resolution in the CanUS. Using both a Reynolds flux decomposition and structure-identification algorithms, we quantify and characterize the organic carbon fluxes driven by filaments and eddies within the upper 100 m and put them in relationship to the total offshore transport. Our analysis reveals that both coastal filaments and eddies enhance the offshore flux of organic carbon, but that their contribution is very different. Upwelling filaments, with their high speeds and high concentrations, transport the organic carbon offshore in a very intense, but coastally confined manner, contributing nearly 80 % to the total flux of organic carbon at 100 km offshore. The filament contribution tapers off quickly to near zero values at 1000 km off the coast, leading to a strong offshore flux divergence that is the main lateral source of organic carbon in the coastal waters up to 1000 km offshore. Some of this divergence is also due to the filaments inducing a substantial vertical subduction of the organic carbon below 100 m. Owing to the temporal persistence and spatial recurrence of filaments, the filament transport largely constitutes a time-mean flux, while the time-varying component, i.e., the turbulent flux, is comparatively small. At distances beyond 500 km from the coast, eddies dominate the mesoscale offshore transport. Although their contribution represents only 20 % of the total offshore flux and its divergence, eddies, especially cyclones, transport organic carbon offshore to distances as great as 2000 km from the coast. The eddy transport largely represents a turbulent flux, but striations in this transport highlight the existence of typical formation spots and recurrent offshore propagation pathways. While they propagate slowly, eddies are an important organic carbon reservoir for the open waters, as they contain, on average, a third of the organic carbon in this region, two thirds of which is found in cyclones. Our analysis confirms the importance of mesoscale processes for the offshore organic carbon transport and the fueling of the heterotrophic activity in the eastern subtropical North Atlantic, and highlights the need to consider the mesoscale flux in order to fully resolve the three-dimensionality of the marine organic carbon cycle.

scholarly journals From The Cover: Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation

2005 ◽  
Vol 102 (18) ◽  
pp. 6478-6483 ◽  
Author(s):  
M. M. M. Kuypers ◽  
G. Lavik ◽  
D. Woebken ◽  
M. Schmid ◽  
B. M. Fuchs ◽  
...  
Keyword(s):  
Nitrogen Loss ◽  
Anaerobic Ammonium Oxidation ◽  
Ammonium Oxidation ◽  
Upwelling System ◽  
Benguela Upwelling

Spatio-temporal Upwelling Trends along the Canary Upwelling System (1967-2006)

2008 ◽  
Vol 1146 (1) ◽  
pp. 320-337 ◽  
Author(s):  
M. Gómez-Gesteira ◽  
M. de Castro ◽  
I. Álvarez ◽  
M. N. Lorenzo ◽  
J. L. G. Gesteira ◽  
...  
Keyword(s):  
Upwelling System ◽  
Canary Upwelling ◽  
Spatio Temporal

Seasonality of coastal upwelling trends under future warming scenarios along the southern limit of the canary upwelling system

2017 ◽  
Vol 153 ◽  
pp. 16-23 ◽  
Author(s):  
Magda Catarina Sousa ◽  
Ines Alvarez ◽  
Maite deCastro ◽  
Moncho Gomez-Gesteira ◽  
João Miguel Dias
Keyword(s):  
Coastal Upwelling ◽  
Southern Limit ◽  
Upwelling System ◽  
Canary Upwelling ◽  
Future Warming

scholarly journals Drivers and impact of the seasonal variability of the organic carbon offshore transport in the Canary Upwelling System

2020 ◽  
Author(s):  
Giulia Bonino ◽  
Elisa Lovecchio ◽  
Nicolas Gruber ◽  
Matthias Münnich ◽  
Simona Masina ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Temporal Variability ◽  
Seasonal Variability ◽  
Coastal Upwelling ◽  
Ocean Modeling ◽  
Regional Ocean Modeling System ◽  
Nearshore Processes ◽  
Upwelling System ◽  
Canary Upwelling ◽  
Offshore Transport

Abstract. The Canary Upwelling System (CanUS) is a productive coastal region characterized by strong seasonality and an intense offshore transport of organic carbon (Corg) to the adjacent oligotrophic offshore waters. There, the respiration of this Corg substantially modifies net community production (NCP). While this transport and the resulting coupling of the biogeochemistry between the coastal and open ocean has been well studied in the annual mean, the temporal variability, and especially its seasonality has not yet been investigated. Here, we fill this gap, and determine the seasonal variability of the offshore transport of Corg, its mesoscale component, latitudinal differences, and the underlying physical and biological drivers. To this end, we employ the Regional Ocean Modeling System (ROMS) coupled to a nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecosystem model. Our results reveal the importance of the mesoscale fluxes and of the upwelling processes (coastal upwelling and Ekman pumping) in modulating the seasonal variation of the offshore Corg transport. We find that the region surrounding Cape Blanc (21° N) hosts the most intense Corg offshore flux in every season, linked to the persistent, and far reaching Cape Blanc filament. Coastal upwelling filaments dominate the seasonality of the total offshore flux up to 100 km from the coast, contributing in every season season at least 80 % to the total flux. The seasonality of the upwelling modulates the offshore Corg seasonality hundreds of km from the CanUS coast via lateral redistribution of nearshore production. North of 24.5° N, the sharp summer-fall peak of coastal upwelling results in an export of more than 30 % of the coastal Corg at the 100 km offshore due to a combination of intensified nearshore production and offshore fluxes. To the south, the less pronounced upwelling seasonality regulates an overall larger, but farther-reaching and less seasonally varying lateral flux, which exports between 60 and 90 % of the coastal production more than 100 km offshore. Overall, we show that the temporal variability of nearshore processes impacts the variability of Corg and NCP hundreds of km offshore from the CanUS coast via the offshore transport of the nearshore production.

Impact of intra-seasonal coastal Kelvin waves on SST in the Canary upwelling system: composite analysis in Spring

2021 ◽  
Author(s):  
Badara Sané ◽  
Alban Lazar ◽  
Malick Wade
Keyword(s):  
Ocean Waves ◽  
Meridional Wind ◽  
Kelvin Waves ◽  
Composite Analysis ◽  
Upwelling System ◽  
Sst Variability ◽  
Basin Scale ◽  
Canary Upwelling ◽  
The Impact ◽  
Coastal Kelvin Waves

<p>The impact of intra-seasonal coastally trapped waves on SST in the Canary upwelling system is studied in satellite estimates of sea surface height, wind, and temperature, using a composite analysis of propagating upwelling and downwelling events. We focus on Spring, the season of strongest SST variability at this frequency. The results obtained show that the average wave reaches an amplitude at sea level of +/- 2 cm and is associated with an SST signal of +/-0.4 °C in the vicinity of the upwelling front, located off Senegal. Strikingly, this composite wave is reinforced by a constructive meridional wind anomaly when it reaches the upwelling front, the wind signal is likely as important as the wave in terms of SST impacts. We discuss the possible cause of this synchronicity in terms of basin-scale atmosphere and ocean waves.<br>Keywords:<br>- Impact<br>- Coastal Kelvin waves<br>- Intra-seasonal<br>- Boundary upwelling systems<br>- Composite analysis of spring<br>- Tropical Atlantic</p>

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