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  • 1
    Publication Date: 2020-02-06
    Description: Highlights • We track the preferential pathways of the Mediterranean Outflow Water (MOW). • A topographic analysis method is used to identify the MOW hydrological avenues. • Contour avenues and cross-slope channels have complementary roles steering the MOW. • The MOW is a density-driven current steered by both bottom topography and the Coriolis force. Abstract The Mediterranean Water leaves the western end of the Strait of Gibraltar as a bottom wedge of salty and warm waters flowing down the continental slope. The salinity of the onset Mediterranean Outflow Water (MOW) is so high that leads to water much denser (initially in excess of 1.5 kg m−3) than the overlying central waters. During much of its initial descent, the MOW retains large salinity anomalies – causing density anomalies that induce its gravity current character – and relatively high westward speeds – causing a substantial Coriolis force over long portions of its course. We use hydrographic data from six cruises (a total of 1176 stations) plus velocity data from two cruises, together with high-resolution bathymetric data, to track the preferential MOW pathways from the Strait of Gibraltar into the western Gulf of Cadiz and to examine the relation of these pathways to the bottom topography. A methodology for tributary systems in drainage basins, modified to account for the Coriolis force, emphasizes the good agreement between the observed trajectories and those expected from a topographically-constrained flow. Both contour avenues and cross-slope channels are important and have complementary roles steering the MOW along the upper and middle continental slope before discharging as a neutrally buoyant flow into the western Gulf of Cadiz. Our results show that the interaction between bottom flow and topography sets the path and final equilibrium depths of the modern MOW. Furthermore, they support the hypothesis that, as a result of the high erosive power of the bottom flow and changes in bottom-water speed, the MOW pathways and mixing rates have changed in the geological past.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2007. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 112 (2007): C12005, doi:10.1029/2007JC004145.
    Description: We have evaluated a regional-scale simulation of the Mediterranean outflow by comparison with field data obtained in the 1988 Gulf of Cádiz Expedition. Our ocean model is based upon the Hybrid Coordinate Ocean Model (HYCOM) and includes the Richardson number–dependent entrainment parameterization of Xu et al. (2006). Given realistic topography and sufficient resolution, the model reproduces naturally the major, observed features of the Mediterranean outflow in the Gulf of Cádiz: the downstream evolution of temperature, salinity, and velocity profiles, the mean path and the spreading of the outflow plume, and most importantly, the localized, strong entrainment that has been observed to occur just west of the Strait of Gibraltar. As in all numerical solutions, there is some sensitivity to horizontal and vertical resolution. When the resolution is made coarser, the simulated currents are less vigorous and there is consequently less entrainment. Our Richardson number–dependent entrainment parameterization is therefore not recommended for direct application in coarse-resolution climate models. We have used the high-resolution regional model to investigate the response of the Mediterranean outflow to a change in the freshwater balance over the Mediterranean basin. The results are found in close agreement with the marginal sea boundary condition (MSBC): A more saline and dense Mediterranean deep water generates a significantly greater volume transport of the Mediterranean product water having only very slightly greater salinity.
    Description: National Science Foundation via grant OCE0336799 and the National Ocean Partnership Program (NOPP) via award N000140410676.
    Keywords: Mediterranean outflow ; Entrainment parameterization ; Climate
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 3
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 111 (2006): C09039, doi:10.1029/2005JC003338.
    Description: New satellite-based observations reveal that westward translating anticyclonic rings are generated as a portion of the Somali Current accelerates northward through the Socotra Passage near the mouth of the Gulf of Aden. Rings thus formed exhibit azimuthal geostrophic velocities exceeding 50 cm/s, are comparable in overall diameter to the width of the Gulf of Aden (250 km), and translate westward into the gulf at 5–8 cm/s. Ring generation is most notable in satellite ocean color imagery in November immediately following the transition between southwest (boreal summer) and northeast (winter) monsoon regimes. The observed rings contain anomalous fluid within their core which reflects their origin in the equator-crossing Somali Current system. Estimates of Socotra Passage flow variability derived from satellite altimetry provide evidence for a similar ring generation process in May following the winter-to-summer monsoon transition. Cyclonic recirculation eddies are observed to spin up on the eastern flank of newly formed rings with the resulting vortex pair translating westward together. Recent shipboard and Lagrangian observations indicate that vortices of both sign have substantial vertical extent and may dominate the lateral circulation at all depths in the eastern Gulf of Aden.
    Description: This investigation is a component of the Red Sea Outflow Experiment (REDSOX) sponsored by the U.S. National Science Foundation through grants OCE 98-18464 and OCE 04-24647 to the Woods Hole Oceanographic Institution and OCE 98-19506 and OCE 03-51116 to the University of Miami.
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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