Mass exchange at the Strait of Gibraltar in response to tidal and lower
                        frequency forcing as simulated by a Mediterranean Sea model

Harzallah, Ali; Alioua, Mohamed; Li, Laurent

doi:10.3402/tellusa.v66.23871

Cited by 12 publications

(15 citation statements)

References 53 publications

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“…Dynamical downscaling of reanalyses have therefore been used to force long-term hindcast simulations (Beuvier et al, , 2012Herrmann et al, 2010;Solé et al, 2012;Vervatis et al, 2013;Auger et al, 2014;Harzallah et al, 2014). The wind channeling at 12 km leads locally to increased wind speed, changes in wind direction and increased vorticity inputs for the ocean due to strong horizontal gradients.…”

Section: Illustration Of the Small-scale Features In The Aldera Forcingmentioning

confidence: 99%

“…This data set (called hereafter ALDERA) is based on a dynamical downscaling of the ERA-Interim reanalysis (Dee et al, 2011) over the period 1979-2013 by the RCM ALADIN-Climate (Radu et al, 2008;Colin et al, 2010;Herrmann et al, 2011). The dynamical downscaling technique is commonly used to overcome the lack of atmospheric regional reanalysis over sea and to improve locally the resolution of the air-sea forcing in areas dominated by small-scale atmospheric patterns such as the Mediterranean Sea (Sotillo et al, 2005;Herrmann and Somot, 2008;Beuvier et al, 2010;Herrmann et al, , 2011Josey et al, 2011;Beuvier et al, 2012a;Lebeaupin-Brossier et al, 2012;Solé et al, 2012;Vervatis et al, 2013;Auger et al, 2014;Harzallah et al, 2014). In ALDERA, we use the version 5 of ALADIN-Climate, first described in Colin et al (2010).…”

Section: Atmospheric Forcing: Alderamentioning

confidence: 99%

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Design and validation of MEDRYS, a Mediterranean Sea reanalysis over the period 1992–2013

Hamon

Beuvier

Somot³

et al. 2016

Ocean Sci.

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Abstract. The French research community in the Mediterranean Sea modeling and the French operational ocean forecasting center Mercator Océan have gathered their skill and expertise in physical oceanography, ocean modeling, atmospheric forcings and data assimilation to carry out a MEDiterranean sea ReanalYsiS (MEDRYS) at high resolution for the period 1992-2013. The ocean model used is NEMOMED12, a Mediterranean configuration of NEMO with a 1/12 • (∼ 7 km) horizontal resolution and 75 vertical z levels with partial steps. At the surface, it is forced by a new atmospheric-forcing data set (ALDERA), coming from a dynamical downscaling of the ERA-Interim atmospheric reanalysis by the regional climate model ALADIN-Climate with a 12 km horizontal and 3 h temporal resolutions. This configuration is used to carry a 34-year hindcast simulation over the period 1979, which is the initial state of the reanalysis in October 1992. MEDRYS uses the existing Mercator Océan data assimilation system SAM2 that is based on a reduced-order Kalman filter with a threedimensional (3-D) multivariate modal decomposition of the forecast error. Altimeter data, satellite sea surface temperature (SST) and temperature and salinity vertical profiles are jointly assimilated. This paper describes the configuration we used to perform MEDRYS. We then validate the skills of the data assimilation system. It is shown that the data assimilation restores a good average temperature and salinity at intermediate layers compared to the hindcast. No particular biases are identified in the bottom layers. However, the reanalysis shows slight positive biases of 0.02 psu and 0.15 • C above 150 m depth. In the validation stage, it is also shown that the assimilation allows one to better reproduce water, heat and salt transports through the Strait of Gibraltar. Finally, the ability of the reanalysis to represent the sea surface high-frequency variability is shown.

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Section: Illustration Of the Small-scale Features In The Aldera Forcingmentioning

confidence: 99%

Section: Atmospheric Forcing: Alderamentioning

confidence: 99%

Design and validation of MEDRYS, a Mediterranean Sea reanalysis over the period 1992–2013

Hamon

Beuvier

Somot³

et al. 2016

Ocean Sci.

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“…The tidally induced cooler and saltier AW crossing the Alboran section reaches almost the entire Mediterranean filling the upper 250 m in the western part of the western basin and deeper layers further east. Harzallah et al (2014) investigated the impact of tidal oscillations on the thermohaline circulation of the Mediterranean Sea from two parallel multi-decadal numerical experiments conducted with and without tides. They reported a Mediterranean 0.08 • C cooler and 0.012 salinity units saltier after the simulation period (spanning from 1957 to 2007) for the tidal run.…”

Section: Consequences Of the Water Mass Transformations Along The Strmentioning

confidence: 99%

Modelling study of transformations of the exchange flows along the Strait of Gibraltar

Sánchez-Román¹,

Jordà²,

Sannino³

et al. 2018

Ocean Sci.

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Abstract. Vertical transfers of heat, salt and mass between the inflowing and outflowing layers at the Strait of Gibraltar are explored basing on the outputs of a three-dimensional fully nonlinear numerical model. The model covers the entire Mediterranean basin and has a very high spatial resolution around the strait (1/200∘). Another distinctive feature of the model is that it includes a realistic barotropic tidal forcing (diurnal and semi-diurnal), in addition to atmospheric pressure and heat and water surface fluxes. The results show a significant transformation of the properties of the inflowing and outflowing water masses along their path through the strait. This transformation is mainly induced by the recirculation of water, and therefore of heat and salt, between the inflowing and outflowing layers. The underlying process seems to be the hydraulic control acting at the Espartel section, Camarinal Sill and Tarifa Narrows, which limits the amount of water that can cross the sections and forces a vertical recirculation. This results in a complex spatio-temporal pattern of vertical transfers, with the sign of the net vertical transfer being opposite in each side of the Camarinal Sill. Conversely, the mixing seems to have little influence on the heat and salt exchanged between layers (∼2 %–10 % of advected heat and salt). Therefore, the main point of our work is that most of the transformation of water properties along the strait is induced by the vertical advection of heat and salt and not by vertical mixing. A simple relationship between the net flux and the vertical transfers of water, heat and salt is also proposed. This relationship could be used for the fine-tuning of coarse-resolution model parameterizations in the strait.

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“…The same configuration was used to study the long-term changes in the Mediterranean Sea (Gualdi et al 2013b) and to investigate the impact of tide on the thermohaline circulation of the Mediterranean basin (Harzallah et al 2014). The model grid is curvilinear and extends westward over the Atlantic Ocean to nearly 7.88° W. The vertical resolution uses 27 σ layers.…”

Section: Appendix: Description Of Models and Simulations Usedmentioning

confidence: 99%

“…In addition the added heat loss is almost completely recovered by surface relaxation that restores the net heat flux at the sea surface to more realistic values. Details of such a correction are shown in Harzallah et al (2014).…”

Section: Appendix: Description Of Models and Simulations Usedmentioning

confidence: 99%

Long term evolution of heat budget in the Mediterranean Sea from Med-CORDEX forced and coupled simulations

et al. 2016

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temperature and is found to be significantly correlated for most models with the net heat flux at the sea surface (average correlation ~0.5) but not with the net heat flux through the Strait of Gibraltar (average correlation ~0.2), suggesting that in the considered RCSMs the interannual variability of the heat content rate is mainly driven by the surface heat fluxes. The resemblance between the simulated and observed heat content rates is stronger in the forced models than in the coupled ones. This is explained by the stronger constraint applied to the forced models by the use of the surface temperature relaxation to observations. The temperature of the outflowing water through the Strait of Gibraltar shows positive and significant trends, also higher in the coupled models. It is suggested that the Mediterranean Sea warming found in most models and in particular in the coupled ones, induces a change of the hydrographic conditions that affects the Strait of Gibraltar. Keywords Mediterranean Sea · Heat budget · Heat content · Strait of Gibraltar · Regional climate modelsAbstract This study evaluates the Mediterranean Sea heat budget components from a set of forced and coupled simulations performed in the frame of the Med-CORDEX project. The simulations use regional climate system models (RCSMs) dedicated to the Mediterranean area and driven by the ERA40/ERA-Interim reanalyses. The study focuses on the period 1980-2010. Interannual variations of the average net heat flux at the sea surface are consistent among models but the spread in the mean values is large (from −4.8 to +2.2 Wm −2 ) with the coupled models showing the lowest heat loss from the sea. For the heat flux at the Strait of Gibraltar both interannual variations and mean values show a large intermodel spread. The basin average temperature shows positive trends with highest values in the coupled models; it also shows interannual variations that are in good agreement with observations. The heat content rate is calculated based on the derivative of the average This paper is a contribution to the special issue on Med-CORDEX, an international coordinated initiative dedicated to the multi-component regional climate modelling (atmosphere, ocean, land surface, river) of the Mediterranean under the umbrella of HyMeX, CORDEX, and Med-CLIVAR and coordinated by Samuel Somot, Paolo Ruti, Erika Coppola, Gianmaria Sannino, Bodo Ahrens, and Gabriel Jordà.

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Mass exchange at the Strait of Gibraltar in response to tidal and lower frequency forcing as simulated by a Mediterranean Sea model

Cited by 12 publications

References 53 publications

Design and validation of MEDRYS, a Mediterranean Sea reanalysis over the period 1992–2013

Design and validation of MEDRYS, a Mediterranean Sea reanalysis over the period 1992–2013

Modelling study of transformations of the exchange flows along the Strait of Gibraltar

Long term evolution of heat budget in the Mediterranean Sea from Med-CORDEX forced and coupled simulations

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