An upwelling filament off southwest Iberia: Effect on the chlorophyll a and nutrient export

Cravo, Alexandra; Relvas, Paulo; Cardeira, Sara; Rita, Filomena; Madureira, Miguel; Sánchez, Ricardo

doi:10.1016/j.csr.2010.06.007

Cited by 44 publications

(44 citation statements)

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“…This reach is larger than previous observations, which indicated about 700 km of maximum offshore extension for the giant Cape Blanc filament, as seen from satellite coastal zone color scanner (CZCS) radiometer images (Ohde et al, 2015). However, our analysis shows that the filament offshore transport reaches the largest offshore extension at a depth of 20 m to 30 m. A few filament transects from in-situ measurement also show that the filament lateral transport of biogeochemical tracers deepens below the surface at a depth of a few tens of meters moving away from the continental shelf (Cravo et al, 2010). This implies that the whole offshore range of reach of a filament may not be easily visible from surface chlorophyll images, with a likely underestimation of its range.…”

Section: Comparison With Previous Workmentioning

confidence: 80%

“…Exceptions are found in the surroundings of the incoming Azores and North Equatorial Counter Currents. The cross-product of SSH and C org is 25 particularly negative in the nearshore northern and central CanUS subregions (Figure 9b), where we find the most intense and recurrent upwelling filaments, by definition characterized by strongly negative SSH (Cravo et al, 2010).…”

mentioning

confidence: 92%

“…The laterally exported C org , part of it in the form of particulate organic carbon (POC) and part of it in the form of dissolved organic carbon (DOC) (García-Muñoz et al, 2005), may accumulate then in the 20 oligotrophic open ocean regions (Álvarez-Salgado, 2007), eventually fueling heterotrophic activity there. In addition to C org , filaments are also responsible for the lateral export of chlorophyll, nutrients (Cravo et al, 2010) and living organisms (Brochier et al, 2014) to the open sea.…”

Section: Introductionmentioning

confidence: 99%

“…Even though these structures have a typical thickness of about 100 meters or less (Cravo et al, 2010), filament subduction well below their depths has been documented in observations Brink, 1992;Barth et al, 2002;Peliz et al, 2004) and numerical studies (Nagai et al, 2015;Bettencourt 10 et al, 2017). Differing from the zonal flux, the pattern of the vertical downwelling associated with filaments clearly resembles the turbulent component of the vertical Reynolds fluxes.…”

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confidence: 99%

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

Lovecchio¹,

Gruber²,

Münnich³

2018

Preprint

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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 this has not been demonstrated in a quantitative manner for the entire Canary Upwelling System (CanUS). Here, we fill this gap using 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 5 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 analyses reveal 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 organic carbon concentrations, transport this carbon offshore in a very intense, but coastally-confined, manner, contributing nearly 10 80% to the total flux at 100 km offshore distance. The filament contribution tapers off quickly to near zero values at 1000 km distance, leading to a strong offshore flux divergence that is the main lateral source of organic carbon in the first 500 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 and only to a limited degree represents a turbulent flux. At distances beyond 500 km from the coast, eddies 15 dominate the mesoscale offshore transport. Although their contribution represents only 20 % of the total offshore flux and of 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, since they contain on average a third of the offshore organic carbon, two third of which is found 20 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 account for the three-dimensionality of the marine biological pump.

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Section: Comparison With Previous Workmentioning

confidence: 80%

mentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

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

Lovecchio¹,

Gruber²,

Münnich³

2018

Preprint

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“…Castro et al, 2000;Cravo et al, 2010;Queiroga et al, 2007;Santos et al, 2007). For example, the shelf--ocean exchange of biogenic materials is thought to be strongly influenced by such mesoscale events, the off-shelf export being favored through filaments developed during the spring--summer upwelling (Álvarez-Salgado et al, 2001(Álvarez-Salgado et al, , 2007Cravo et al, 2010) in opposition to in situ mineralization favored by autumn--winter termohaline fronts developed under downwelling conditions/slope poleward flow (Álvarez-Salgado et al, 2003).…”

mentioning

confidence: 99%

Seasonal cycle of plankton production in the Iberian margin based on a high resolution ocean model

Reboreda

Nolasco

Castro

et al. 2014

Journal of Marine Systems

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Filaments on the Western Iberian Margin: A modeling study

et al. 2015

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Coastal upwelling filaments off the Western Iberian Margin, detected in AVHRR satellite imagery and in a realistic ROMS simulation of sea surface temperature, were studied in the upwelling seasons (May-October) of [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010]. Sea surface temperature data were retrieved from AVHRR satellite imagery and from a realistic ROMS numerical simulation. The development and variability of the observed filaments were characterized and analyzed during each upwelling season of the 10 year period. Filaments were generally found anchored to the main bathymetric and coastal features but off the more regular northern coast of the Western Iberian Margin their locations were more variable. The results from the modeling analysis reproduced well the general features of filament development. Moreover results of model and observation showed very similar characteristics as those found in the earlier study of Haynes et al. (1993). The model output was used to relate filament patterns, eddy activity, and wind forcing. There was a clear relation between upwelling-favorable wind strength and number and length of filaments, although the relation was weaker in the north of the region. Model filaments were clearly related to eddies only during periods of weak winds. The filament detection method was also applied to a climatologically forced ROMS simulation, which reproduced only gross features of the observed and interannually forced model filament development. This suggests that direct wind forcing and its spatial structure are highly important.

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An upwelling filament off southwest Iberia: Effect on the chlorophyll a and nutrient export

Cited by 44 publications

References 45 publications

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

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

Seasonal cycle of plankton production in the Iberian margin based on a high resolution ocean model

Filaments on the Western Iberian Margin: A modeling study

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