Cross-shelf variability in the Iberian Peninsula Upwelling System: Impact of a mesoscale filament

Rossi, Vincent; Garçon, Véronique; Tassel, Joëlle; Romagnan, Jean‐Baptiste; Stemmann, Lars; Jourdin, Frédéric; Morin, Pascal; Morel, Yves

doi:10.1016/j.csr.2013.04.008

Cited by 29 publications

(64 citation statements)

References 51 publications

(81 reference statements)

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“…Similar to the winter conditions off Sydney (Figure a), this resulted in low nitrate levels on the shelf in the top 70 m (<2 µmol L −1 ). Note that submesoscale processes superimposed their signatures on the shelf‐scale downwelling signal (see section 5), resulting in finer‐scale (∼km) variability in these fields [ Rossi et al ., ].…”

Section: Resultsmentioning

confidence: 99%

“…Such small-scale factors were also invoked by Malcolm et al [2011] to explain the contrast in high-frequency variability of coastal temperature measured at several sites situated within a 50 km radius. They include the cross-shelf location of the observation, the local topography, and the numerous submesoscale processes such as eddies, filaments and fronts [Rossi et al, 2013a].…”

Section: Postvalidation and Nonresolved Processesmentioning

confidence: 99%

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Seasonality of sporadic physical processes driving temperature and nutrient high‐frequency variability in the coastal ocean off southeast Australia

et al. 2014

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[1] Physical processes forced by alongshore winds and currents are known to strongly influence the biogeochemistry of coastal waters. Combining in situ observations (moored platforms, hydrographic surveys) and satellite data (sea surface wind and sea surface height), we investigate the transient occurrence of wind-driven upwelling/downwelling and current-driven upwelling events off southeast Australia. Remote-sensed indices are developed and calibrated with multiannual time series of in situ temperature and current measurements at two shelf locations. Based on archives up to 10 years long, climatological analyses of these indices reveal various latitudinal regimes with respect to seasonality, magnitude, duration of events, and their driving mechanisms (wind or current). Generally, downwelling-favorable winds prevail in this region; however, we demonstrate that up to 10 wind-driven upwelling days per month occur during spring/summer at 28-33.5 S and up to 5 days in summer further south. Current-driven upwelling upstream of the East Australian Current separation zone (32 S) occurs twice as often as downstream. Using independent in situ data sets, we show that the response of the coastal ocean is consistent with our climatology of shelf processes: upwelling leads to a large range of temperatures and elevated nutrient concentrations on the shelf, maximized in the wind-driven case, while downwelling results in destratified nutrient-poor waters. The combination of these sporadic wind-and current-driven processes may drive an important part of the high-frequency variability of coastal temperature and nutrient content. Our results suggest that localized nutrient enrichment events of variable magnitude are favored at specific latitudes and seasons, potentially impacting coastal ecosystems.Citation: Rossi, V., A. Schaeffer, J. Wood, G. Galibert, B. Morris, J. Sudre, M. Roughan, and A. M. Waite (2014), Seasonality of sporadic physical processes driving temperature and nutrient high-frequency variability in the coastal ocean off southeast Australia,

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Section: Resultsmentioning

confidence: 99%

Section: Postvalidation and Nonresolved Processesmentioning

confidence: 99%

Seasonality of sporadic physical processes driving temperature and nutrient high‐frequency variability in the coastal ocean off southeast Australia

et al. 2014

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“…Upwelling off the WIC is highly seasonal, with higher intensity during the boreal summer (Wooster et al, 1976;Fiúza et al, 1982;Lemos and Pires, 2004), particularly off upwelling centers (e.g., off Galiza and Sagres). The influence of the nutrient input driven by upwelling on the marine phytoplankton off the WIC has been thoroughly studied for several regions within the WIC (e.g., Tilstone et al, 2003;Ribeiro et al, 2005;Rossi et al, 2013;Goela et al, 2014). Other significant agents in this region include several large river basins along the coast (e.g., Tagus, Douro, Guadiana, Guadalquivir), which deliver valuable nutrient inputs for coastal phytoplankton communities.…”

Section: Study Areamentioning

confidence: 99%

Disentangling Environmental Drivers of Phytoplankton Biomass off Western Iberia

2019

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“…Filaments, with their high concentration of organic carbon (C org ), have been shown to export laterally about half of the coastal production from their region of origin (Gabric et al, 1993;Pelegrí et al, 2005;Arístegui et al, 2003). Locally, this transport can exceed the mean Ekman transport in the nearshore several times (Rossi et al, 2013;Álvarez-Salgado, 2007). 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.…”

Section: Introductionmentioning

confidence: 99%

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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Cross-shelf variability in the Iberian Peninsula Upwelling System: Impact of a mesoscale filament

Cited by 29 publications

References 51 publications

Seasonality of sporadic physical processes driving temperature and nutrient high‐frequency variability in the coastal ocean off southeast Australia

Seasonality of sporadic physical processes driving temperature and nutrient high‐frequency variability in the coastal ocean off southeast Australia

Disentangling Environmental Drivers of Phytoplankton Biomass off Western Iberia

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

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