Water exchange between Algeciras Bay and the Strait of Gibraltar: A study based on HF coastal radar

Chioua, Jamal; Dastis, C.; González, Carlos J.; Reyes, Emma; Mañanes, Rafael; Ruiz, María Ángeles Martínez; Alvarez, Enrique; Yanguas, F.; Romero, Javier; Álvarez, O.; Bruno, Miguel

doi:10.1016/j.ecss.2017.06.030

Cited by 17 publications

(12 citation statements)

References 45 publications

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“…Skill metrics improved when calibrated antenna patterns were used to process radial data. Recent research with this HFR network successfully investigated the water exchange between Algeciras Bay (Figure 1a) and the SoG [19], the impact of the atmospheric pressure fluctuations on the mesoscale water dynamics of the SoG and the Alboran Sea [20], or the dominant modes of spatio-temporal variability of the surface circulation [21].…”

Section: Introductionmentioning

confidence: 99%

Long-Term Monitoring of the Atlantic Jet through the Strait of Gibraltar with HF Radar Observations

Lorente

Piedracoba

Sotillo

et al. 2019

JMSE

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The present work focuses on the long-term coastal monitoring of the Atlantic surface inflow into the Mediterranean basin through the Strait of Gibraltar. Hourly current maps provided during 2016–2017 by a High Frequency radar (HFR) system were used to characterize the Atlantic Jet (AJ) since changes in its speed and direction modulate the upper-layer circulation of the Western Alboran Gyre (WAG). The AJ pattern was observed to follow a marked seasonal cycle. A stronger AJ flowed north-eastwards during autumn and winter, while a weaker AJ was directed more southwardly during the middle of the year, reaching a minimum of intensity during summertime. A strong relationship between AJ speeds and angles was evidenced: the AJ appeared to be frequently locked at an angle around 63°, measured clockwise from the North. The AJ speed usually fluctuated between 50 cm·s−1 and 170 cm·s−1, with occasional drops below 50 cm·s−1 which were coincident with abrupt modifications in AJ orientation. Peaks of current speed clearly reached values up to 250 cm·s−1, regardless of the season. A number of persistent full reversal episodes of the surface inflow were analyzed in terms of triggering synoptic conditions and the related wind-driven circulation patterns. High sea level pressures and intense (above 10 m·s−1), permanent and spatially-uniform easterlies prevailed over the study domain during the AJ collapse events analyzed. By contrast, tides seemed to play a secondary role by partially speeding up or slowing down the westward currents, depending on the phase of the tide. A detailed characterization of this unusual phenomenon in the Strait of Gibraltar is relevant from diverse aspects, encompassing search and rescue operations, the management of accidental marine pollution episodes or efficient ship routing.

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Section: Introductionmentioning

confidence: 99%

Long-Term Monitoring of the Atlantic Jet through the Strait of Gibraltar with HF Radar Observations

Lorente

Piedracoba

Sotillo

et al. 2019

JMSE

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“…The AJ is known to be modulated in amplitude and direction at different time scales (Garrett et al ; García Lafuente et al ; Sarhan et al ; Vargas‐Yáñez et al ). Although the atmospheric pressure gradient between the western Mediterranean and the Gulf of Cádiz is the main source of subinertial modulation of the inflow and of the own Jet (García Lafuente et al 2002 b ; Sánchez Garrido et al ), local wind has also been proven to determine marked deflections of the very surface current, especially ahead of the Bay entrance (García Lafuente et al 2002 a ; Sánchez Garrido et al ; Chioua et al ): westerly (easterlies) winds seem to favor an intensification (weakening) of the AJ and its deflection southward (northward). Whatever the cause of the AJ fluctuations, it is clear that the intensity and especially the position of this swift current flowing close to the entrance of the Bay has to influence its renewal efficiency.…”

Section: Resultsmentioning

confidence: 99%

“…After the pioneer study by de Buen (), the interest of the scientific community turned to the Strait of Gibraltar itself, displacing the Bay to the background. During the last decade of the 20 th century, it attracted the interest of physicists (e.g., Watson and Robinson ) and biologists (e.g., Naranjo et al and references therein), but it is only recently that more extensive multidisciplinary studies have been published (Álvarez et al ; Periáñez ; González et al ; Sammartino et al ; Sánchez Garrido et al ; Chioua et al ). A recurrent concern about the Bay is the chronic degree of pollution caused by the intense activities of the local Port and industries, which has been assessed even higher than the one found in the coast of Galicia in the northwest of the Iberian Peninsula after the Prestige oil spill (Morales‐Caselles et al ).…”

mentioning

confidence: 99%

Water renewal in semi‐enclosed basins: A high resolution Lagrangian approach with application to the Bay of Algeciras, Strait of Gibraltar

Sammartino

Garrido

Naranjo

et al. 2017

Limnology & Ocean Methods

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Lagrangian experiments of particle tracking were carried out in the semi-enclosed Bay of Algeciras attached to the Strait of Gibraltar in order to investigate the flushing patterns. A high resolution three-domain-nested hydrodynamic model provided the velocity fields from a 61-d hindcast, with the aim of analyzing the flushing efficiency of eight different docks under a variety of external conditions, namely, tide phase and strength, and winds. The tracking algorithm was specifically developed to exploit the high spatial resolution of the model that reproduces the local dynamics accurately. Winds are the dominant agent, with westerlies featuring e-folding times one order of magnitude lower than easterlies. Fortnightly tidal modulation causes a counter-intuitive effect, with spring tides promoting higher accumulation of particles inside the docks and higher e-folding times than neap tides. Additionally to high resolution details on the flushing patterns of the Algeciras Port, the model also confirms the Bay as a potential feeder of floating tracers for the nearby Alboran Sea. The proposed approach is easily scalable and exportable to other similar locations worldwide.

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“…Recent work relying on this HFR system has successfully investigated the water exchange between Algeciras Bay and the Strait of Gibraltar (Chioua et al, 2017), the impact of the atmospheric pressure fluctuations on the mesoscale water dynamics of the Strait of Gibraltar and the Alboran Sea (Dastis et al, 2018), the dominant modes of spatio-temporal variability in the surface circulation (Soto-Navarro et al, 2016), or the characterization of the Atlantic surface inflow into the Mediterranean Sea (Lorente et al, 2018).…”

Section: Hfr-derived Observationsmentioning

confidence: 99%

“…Over the last three decades, significant progress has been made in the discipline of operational oceanography thanks to the substantial increase in high-performance computational resources that have fostered seamless evolution in ocean modelling techniques and numerical efficiency (Cotelo et al, 2018) and given rise to an inventory of operational ocean forecasting systems (OOFSs) running in overlapping regions 968 P. Lorente et al: Skill assessment of global, regional, and coastal circulation forecast models in order to reliably portray and predict the ocean state and its variability at diverse spatio-temporal scales.…”

Section: Introductionmentioning

confidence: 99%

Skill assessment of global, regional, and coastal circulation forecast models: evaluating the benefits of dynamical downscaling in IBI (Iberia–Biscay–Ireland) surface waters

et al. 2019

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Abstract. In this work, a multi-parameter inter-comparison of diverse ocean forecast models was conducted at the sea surface ranging from global to local scales in a two-phase stepwise strategy. Firstly, a comparison of CMEMS GLOBAL and the nested CMEMS IBI regional system was performed against satellite-derived and in situ observations. Results highlighted the overall benefits of both the GLOBAL direct data assimilation in open water and the increased horizontal resolution of IBI in coastal areas. Besides, IBI (Iberia–Biscay–Ireland) proved to capture shelf dynamics by better representing the horizontal extent and strength of a river freshwater plume, according to the results derived from the validation against in situ observations from a buoy moored in NW Spain. Secondly, a multi-model inter-comparison exercise for 2017 was performed in the Strait of Gibraltar among GLOBAL, IBI, and SAMPA (Sánchez-Garrido et al., 2013) high-resolution coastal forecast systems (partially nested to IBI) in order to elucidate the accuracy of each system to characterize the Atlantic Jet (AJ) inflow dynamics. A quantitative validation against hourly currents from high-frequency radar (HFR) highlighted both the steady improvement in AJ representation in terms of speed and direction when zooming from global to coastal scales through a multi-nesting model approach and also the relevance of a variety of factors at local scale such as a refined horizontal resolution, a tailored bathymetry, and a higher spatio-temporal resolution of the atmospheric forcing. The ability of each model to reproduce a 2 d quasi-permanent full reversal of the AJ surface inflow was examined in terms of wind-induced circulation patterns. SAMPA appeared to better reproduce the reversal events detected with HFR estimations, demonstrating the added value of imposing accurate meteorologically driven barotropic velocities in the open boundaries (imported from the NIVMAR (Álvarez-Fanjul et al., 2001) storm surge model) to take into account the remote effect of the atmospheric forcing over the entire Mediterranean basin, which was only partially included in IBI and GLOBAL systems. Finally, SAMPA coastal model outputs were also qualitatively analysed in the western Alboran Sea to put in a broader perspective the context of the onset, development, and end of such flow reversal episodes.

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Water exchange between Algeciras Bay and the Strait of Gibraltar: A study based on HF coastal radar

Cited by 17 publications

References 45 publications

Long-Term Monitoring of the Atlantic Jet through the Strait of Gibraltar with HF Radar Observations

Long-Term Monitoring of the Atlantic Jet through the Strait of Gibraltar with HF Radar Observations

Water renewal in semi‐enclosed basins: A high resolution Lagrangian approach with application to the Bay of Algeciras, Strait of Gibraltar

Skill assessment of global, regional, and coastal circulation forecast models: evaluating the benefits of dynamical downscaling in IBI (Iberia–Biscay–Ireland) surface waters

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