Variation in upwelling intensity along the NorthWest Iberian Peninsula (Galicia)

Álvarez, I.; Gesteira, Moncho Gómez; deCastro, M.; Prego, Ricardo

doi:10.1080/17417530601127480

Cited by 8 publications

(8 citation statements)

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“…Upwelling did not reach the surface water, where high temperatures were observed, especially at the inshore stations. Both facts seems to be usual resulting a significant difference with respect to the rias located close (Varela et al, 2005) and south (Rosón et al, 1997;Prego et al, 2001) Cape Finisterre because upwelling penetrates inside them, raising up to surface layers (Alvarez-Salgado et al 1993;Alvarez et al, 2005a). Another difference is the origin of the upwelled water mass.…”

Section: Discussionmentioning

confidence: 97%

“…Galicia which is situated in the north-western corner of the Iberian Peninsula, has three different littoral orientations. This fact makes the effect of northerly prevailing wind conditions (Torres et al, 2003;Alvarez et al, 2005a;Gómez-Gesteira et al, 2006) on upwelling development to be different both in probability and intensity at north of Cape Ortegal, where are the Northern Rias, between Capes Ortegal and Finisterre, where are the Middle Rias, and south of Cape Finisterre, where are the Western Rias (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…•km -1 ; Alvarez et al, 2005a) and event time scale (10-15 days; Nogueira et al, 1997) are higher in the western shelf.…”

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confidence: 98%

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Oceanographical patterns during a summer upwelling–downwelling event in the Northern Galician Rias: Comparison with the whole Ria system (NW of Iberian Peninsula)

Ospina-Álvarez¹,

Prego²,

Álvarez

et al. 2010

Continental Shelf Research

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Summer upwelling and downwelling processes were characterized in the Northern Galician Rias during July and August 2008 by means of sampling carried out onboard R/V Mytilus (CSIC) and R/V Lura (IEO). Thermohaline variables, dissolved oxygen, nutrients, chlorophyll, phytoplankton, ciliates and zooplankton abundances were measured at sections located in the Rias of Viveiro, Barqueiro and Ortigueira and their adjacent shelves. Ekman transport was calculated from QuikSCAT satellite, upwelling intensity estimated with upwelling index from the average daily geostrophic winds, and SST maps obtained from NASA GHRSST satellite. Ekman transport and SST behaviour showed two different patterns: (i) offshore and upwelling favourable conditions on 13-22 nd of July; (ii) onshore and downwelling favourable conditions from 23 rd July to 19 th August). During upwelling, TS diagram showed an intrusion of Eastern North Atlantic Central Water affecting the continental shelf but not the rias. Nutrient salt concentrations increased with depth, reaching their maximum values near the mouth of Ortigueira Ria. During downwelling, coastal water increased its temperature (18.5-19.8ºC) and was retained inside rias; nutrients were nearly depleted, except for the innermost ria (estuarine zone) due to fluvial nutrient inputs. In this inner area, the maximum of chlorophyll-a (Barqueiro Ria) was observed. Low phytoplankton abundances were measured in both cases, even though a short increase in the plankton biomass was observed inside rias during upwelling, while under downwelling a small red tide of Lingulodinium polyedrum was detected. During the upwelling period Northern Rias tend to be mesotrophic systems as revealed by nutrient concentrations, chlorophyll levels and plankton abundances. On the contrary, in similar situations, the Western Rias behaves as eutrophics. In the Northern Galician shelf, the average of upwelling (downwelling) was 1.9±0.8 (2.1±1.0) events•yr-1 from May to September (1990-2008) considering at least one week with favourable wind conditions and UI averages out of the range of ±500 m 3 •s-1 •km-1. *Manuscript Click here to download Manuscript: MS_Ospina-Alvarez et al v3.docx Click here to view linked References

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Oceanographical patterns during a summer upwelling–downwelling event in the Northern Galician Rias: Comparison with the whole Ria system (NW of Iberian Peninsula)

Ospina-Álvarez¹,

Prego²,

Álvarez

et al. 2010

Continental Shelf Research

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“…The UPW intensity in this region has been shown to be strongly dependent on the wind pattern and spatially non-uniform, increasing from the north to the south along the coast [9]. The complexity of the wind field in Galicia is partially associated with the jagged shoreline where Cape Finisterre (CF, denoted in Figure 1b) marks an abrupt change between the zonal north and the meridional west coasts of Galicia.…”

Section: Introductionmentioning

confidence: 99%

Comparative Analysis of Summer Upwelling and Downwelling Events in NW Spain: A Model-Observations Approach

Lorente¹,

Piedracoba

Montero

et al. 2020

Remote Sensing

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Upwelling and downwelling processes play a critical role in the connectivity between offshore waters and coastal ecosystems, having relevant implications in terms of intense biogeochemical activity and global fisheries production. A variety of in situ and remote-sensing networks were used in concert with the Iberia–Biscay–Ireland (IBI) circulation forecast system, in order to investigate two persistent upwelling and downwelling events that occurred in the Northwestern (NW) Iberian coastal system during summer 2014. Special emphasis was placed on quality-controlled surface currents provided by a high-frequency radar (HFR), since this land-based technology can effectively monitor the upper layer flow over broad coastal areas in near-real time. The low-frequency spatiotemporal response of the ocean was explored in terms of wind-induced currents’ structures and immediacy of reaction. Mean kinetic energy, divergence and vorticity maps were also calculated for upwelling and downwelling favorable events, in order to verify HFR and IBI capabilities, to accurately resolve the prevailing surface circulation features, such as the locus of a persistent upwelling maximum in the vicinity of Cape Finisterre. This integrated approach proved to be well-founded to efficiently portray the three-dimensional characteristics of the NW Iberian coastal upwelling system regardless of few shortcomings detected in IBI performance, such as the misrepresentation of the most energetic surface dynamics or the overestimation of the cooling and warming associated with upwelling and downwelling conditions, respectively. Finally, the variability of the NW Iberian upwelling system was characterized by means of the development of a novel ocean-based coastal upwelling index (UI), constructed from HFR-derived hourly surface current observations (UIHFR). The proposed UIHFR was validated against two traditional UIs for 2014, to assess its credibility. Results suggest that UIHFR was able to adequately categorize and characterize a wealth of summer upwelling and downwelling events of diverse length and strength, paving the way for future investigations of the subsequent biophysical implications.

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“…As a result of bottom friction, the alongshore northwestward flow in the Northern Hemisphere drives a near-bottom Ekman transport in the opposite direction of the surface transport, which helps to transport cold deep water onshore. The alongshore wind stress has been identified as the most important dynamical forcing in most coastal upwelling events in the world [e.g., Allen, 1973;Andrews and Hutchings, 1980;Allen et al, 1995;Escribano et al, 2004;Alvarez et al, 2005;Gu et al, 2012]. Similarly, for a northeast-southwest-oriented coastline, when the northeastward current in the Northern Hemisphere flows along isobaths in the absence of favorable wind, the Ekman transport in the bottom boundary layer (BBL) will also tend to move cold water up the slope in a stratified and rotational fluid, resulting in current-induced upwelling [Hsueh and O'Brien, 1971;Janowitz and Pietrafesa, 1982].…”

Section: Introductionmentioning

confidence: 99%

Relative contributions of local wind and topography to the coastal upwelling intensity in the northern South China Sea

Wang

Shu

Xue

et al. 2014

J. Geophys. Res. Oceans

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Topographically induced upwelling caused by the interaction between large-scale currents and topography was observed during four cruises in the northern South China Sea (NSCS) when the upwelling favorable wind retreated. Using a high-resolution version of the Princeton Ocean Model, we investigate relative contributions of local wind and topography to the upwelling intensity in the NSCS. The results show that the topographically induced upwelling is sensitive to alongshore large-scale currents, which have an important contribution to the upwelling intensity. The topographically induced upwelling is comparable with the wind-driven upwelling at surface and has a stronger contribution to the upwelling intensity than the local wind does at bottom in the near-shore shelf region. The widened shelf to the southwest of Shanwei and west of the Taiwan Banks intensifies the bottom friction, especially off Shantou, which is a key factor for topographically induced upwelling in terms of bottom Ekman transport and Ekman pumping. The local upwelling favorable wind enhances the bottom friction as well as net onshore transport along the 50 m isobath, whereas it has less influence along the 30 m isobath. This implies the local wind is more important in upwelling intensity in the offshore region than in the nearshore region. The contribution of local upwelling favorable wind on upwelling intensity is comparable with that of topography along the 50 m isobath. The effects of local upwelling favorable wind on upwelling intensity are twofold: on one hand, the wind transports surface warm water offshore, and as a compensation of mass the bottom current transports cold water onshore; on the other hand, the wind enhances the coastal current, and the bottom friction in turn increases the topographically induced upwelling intensity.

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Variation in upwelling intensity along the NorthWest Iberian Peninsula (Galicia)

Cited by 8 publications

References 49 publications

Oceanographical patterns during a summer upwelling–downwelling event in the Northern Galician Rias: Comparison with the whole Ria system (NW of Iberian Peninsula)

Oceanographical patterns during a summer upwelling–downwelling event in the Northern Galician Rias: Comparison with the whole Ria system (NW of Iberian Peninsula)

Comparative Analysis of Summer Upwelling and Downwelling Events in NW Spain: A Model-Observations Approach

Relative contributions of local wind and topography to the coastal upwelling intensity in the northern South China Sea

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