Patrick Marsaleix

In order to understand and predict coastal flooding processes in rocky environments, it is necessary to take into account bottom roughness, which plays a key role in wave transformation processes and in general coastal dynamics. The present work aims to implement a parameterisation of roughness-induced dissipation in 3D non-hydrostatic phase-resolved wave models, based on the Symphonie code (MARSALEIX et al., 2019). The modified model is compared with laboratory experiments carried out on a surf zone with a linear slope (DEALBERA et al., 2024). Different irregular waves were tested on various configurations of bottom roughness (represented by block configurations of different sizes and distributions). Wave generation and dissipation induced by breaking were first parametrised with respect to laboratory data on smooth bottoms. The different roughness cases were then studied on the basis of two distinct strategies for parameterising bottom friction, namely the bottom stress approach and the canopy drag approach. The performance of these two approaches is assessed by comparing the model results with measurements of the cross-shore significant wave height profile for different bottom configurations. On the basis of this work, recommendations on the choice of dissipation parameterisations will be made.

The Rhodes Gyre is a cyclonic persistent feature of the general circulation of the Levantine Basin in the eastern Mediterranean Sea. Although it is located in the most oligotrophic basin of the Mediterranean Sea, it is a relatively high primary production area due to strong winter nutrient supply associated with the formation of Levantine Intermediate Water. In this study, a 3D coupled hydrodynamic-biogeochemical model (SYMPHONIE/Eco3M-S) was used to characterize the seasonal and interannual variability of the Rhodes Gyre’s ecosystem and to estimate an annual organic carbon budget over the 2013–2020 period. Comparisons of model outputs with satellite data and compiled in situ data from cruises and BioGeoChemical-Argo floats revealed the ability of the model to reconstruct the main seasonal and spatial biogeochemical dynamics of the Levantine Basin. The model results indicated that during the winter mixing period, phytoplankton first progressively grow sustained by nutrient supply. Then, short episodes of convection driven by heat loss and wind events, favoring nutrient injections, organic carbon export, and inducing light limitation on primary production, alternate with short episodes of phytoplankton growth. The estimate of the annual organic carbon budget indicated that the Rhodes Gyre is an autotrophic area with a positive net community production in the upper layer (0–150 m) amounting to 31.2 ± 6.9 g C m^-2 year^-1. Net community production in the upper layer is almost balanced over the seven-year period by physical transfers, (1) via downward export (16.8 ± 6.2 g C m^-2 year-1) and (2) through lateral transport towards the surrounding regions (14.1 ± 2.1 g C m^-2 year^-1). The intermediate layer (150–400 m) also appears to be a source of organic carbon for the surrounding Levantine Sea (7.5 ± 2.8 g C m^-2 year^-1) mostly through the subduction of Levantine Intermediate Water following winter mixing. The Rhodes Gyre shows high interannual variability with enhanced primary production, net community production, and exports during years marked by intense heat losses and deep mixed layers. However, annual primary production appears to be only partially driven by winter vertical mixing. Based on our results, we can speculate that future increase of temperature and stratification could strongly impact the carbon fluxes in this region.

This study proposes new insights for the interpretation of GEOVIDE particle measurements. Potential resuspension sites due to internal tides (ITs) have been identified along the western Iberian shelf slope using a tidal regional model. Iberian shelf is mainly a source of lithogenic material whereas Galicia Bank is a source of biogenic matter. The potential pathways for particles from the resuspension sites toward the GEOVIDE stations are identified using IBIRYS reanalysis to infer their transport by the ocean circulation. It appears that each station is influenced by a specific pathway and mixed particles from several resuspension sites. This methodology reveals that the criticality of the bathymetry slope, commonly used to track resuspension sites from internal waves, is not sufficient to investigate ITs. An explicit resolution of ITs using a numerical tidal model is required for an exhaustive identification of the resuspension sites.

This study proposes new insights for the interpretation of GEOVIDE particle measurements. Potentiel resuspension sites due to internal tides (ITs) have been identified along the western Iberian shelf slope using a tidal regional model. Iberian shelf is mainly a source of lithogenic material whereas Galicia Bank is a source of biogenic matter. The potential pathways for particles from the resuspension sites toward the GEOVIDE stations are identified using IBIRYS reanalysis to infer their transport by the ocean circulation. It appears that each station is influenced by a specific pathway and mixed particles from several resuspension sites. This methodology reveals that the criticality of the bathymetry slope, commonly used to track resuspension sites from internal waves, is not sufficient to investigate ITs. An explicit resolution of ITs using a numerical tidal model is required for an exhaustive identification of the resuspension sites.

This study details sediment resuspension due to internal tides (ITs) and the subsequent propagation of suspended particles along and off the Iberian continental slope. Five resuspension sites are i...

The Levantine basin is the area of formation of the Levantine Intermediate Water. In this study, a 3D hydrodynamic-biogeochemical model (Symphonie/Eco3MS) was used to gain understanding in the dynamics of dissolved oxygen in the Levantine basin and estimate its annual budget and its interannual variability over the period of 2012-2020. Comparisons of model results with compiled in situ data from cruises and Argo floats showed that the model was able to reproduce well the seasonal variability of the dissolved oxygen. They also show that during winter, surface temperature decreased, generating  oxygen  undersaturation in the Levantine basin that absorbed atmospheric oxygen. From March to September, due to the increase of surface temperature the basin became oversaturated and released oxygen into the atmosphere. The estimate of the annual oxygen budget revealed that the Levantine basin acted as a sink of atmospheric oxygen. Gain of oxygen in the upper layer through air-sea exchanges and biogeochemical processes were counterbalanced by the loss of oxygen through physical processes via downward export into  intermediate depths and lateral transport towards the western regions. At the annual scale, the air-sea oxygen exchange term dominated the biogeochemical process term in the budget. Regarding the spatial distribution, maximum annual atmospheric oxygen uptake and biogeochemical fluxes were found in the Levantine Intermediate Water formation area of the Rhodes gyre where oxygen-poor and nutrient-rich waters were supplied in the upper layer and surface temperature was minimum. The current study revealed high interannual variability with large oxygen uptakes and physical exports during winters marked by intense heat losses.

This study details sediment resuspension due to internal tides (ITs) and the subsequent propagation of suspended particles along and off the Iberian continental slope. Five resuspension sites are identified along the western Iberian shelf slope using a tidal regional model of the Bay of Biscay and Iberian continental shelf. Two sites are sources of lithogenic material, one is a source of biogenic matter, and two are sources of a mixture of both. The potential pathways for particles from the resuspension sites toward the GEOVIDE stations are identified using IBIRYS reanalysis to infer their transport by the ocean circulation. It appears that each station is influenced by a specific pathway and mixed particles from several resuspension sites. This methodology enables us to establish more realistic interpretations of the geochemical in situ observations combining distinct modeling of ITs and oceanic circulation as well as in situ sediment properties. It also reveals that the criticality of the bathymetry slope, commonly used to track the potential occurrence of ITs, is not sufficient to investigate their role in sediment resuspension. An explicit resolution of ITs using a numerical tidal model is required for an exhaustive identification of the resuspension sites.