How is the surface Atlantic water inflow through the Gibraltar Strait forecasted? A lagrangian validation of operational oceanographic services in the Alboran Sea and the Western Mediterranean

Sotillo, Marcos García; Amo-Baladrón, Arancha; Padorno, Elena; Garcı́a-Ladona, Emilio; Orfila, Alejandro; Rodríguez-Rubio, Pablo; Conti, Daniel; Madrid, José; Santos, Francisco J. de los; Fanjul, Enrique Álvarez

doi:10.1016/j.dsr2.2016.05.020

Cited by 20 publications

(15 citation statements)

References 41 publications

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“…The seasonal variability and occasional interruptions of the Atlantic inflow due to meteorological forcing have been previously investigated with in situ data from fixed moorings [10,11]. More recently, a considerable number of satellite tracked drifters were released on both sides of the SoG within the framework of MEDESS-4MS project, thus providing a complete Lagrangian view of the Atlantic waters inflow into the Alboran Sea [16,17].…”

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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“…Complementarily, opportunistic inter-comparisons are conducted in the frame of diverse EU-funded projects such as MEDESS-4MS (Sotillo et al, 2016a): 35 satellite-tracked drifters were released on both sides of the Strait of Gibraltar and the quality-controlled in situ data of sea surface temperature and currents were collected to build the MEDESS-GIB database (Sotillo et al, 2016b), hence providing a complete Lagrangian view of the surface inflow of Atlantic waters through the GIBST and the Alboran Sea. Such valuable oceanographic information was subsequently used to compare IBI and SAMPA forecast products to identify strengths (realistic simulation of the Atlantic Jet and the Algerian Current) and shortcomings (position and intensity of the Alboran gyres, especially the western one) in both model performances.…”

Section: Frameworkmentioning

confidence: 99%

“…Previous research has unequivocally proved the ability of PdE-SAMPA to accurately capture basic circulation features of the GIBST area and Algeciras Bay (Sanchez-Garrido et al, 2014;Sammartino et al, 2014;Soto-Navarro et al, 2016). A preliminary model skill assessment was conducted within the framework of the MEDESS-4MS project (Sotillo et al, 2016a). However, the added value of this coastal OOFS with respect to the regional IBI system was only quantified from a Lagrangian perspective by using a wealth of drifters.…”

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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“…The REG model has been already validated at tidal (Sammartino et al ) and subinertial timescales (Sánchez Garrido et al ). The operational system SAMPA (http://sampa-apba.puertos.es/) maintained by the Spanish National and Bay of Algeciras Port Authorities uses REG as the hydrodynamic model and, within this frame, its outputs have been further validated against different sources of observations (Soto‐Navarro et al ; Jordà et al ), including a validation of the surface fields using the Lagrangian trajectories of a set of surface drifters released in the Strait area (Sotillo et al ).…”

Section: The Hydrodynamic Modelmentioning

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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How is the surface Atlantic water inflow through the Gibraltar Strait forecasted? A lagrangian validation of operational oceanographic services in the Alboran Sea and the Western Mediterranean

Cited by 20 publications

References 41 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

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

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

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