scholarly journals The Mediterranean Sea Overturning Circulation

2019 ◽  
Vol 49 (7) ◽  
pp. 1699-1721 ◽  
Author(s):  
Nadia Pinardi ◽  
Paola Cessi ◽  
Federica Borile ◽  
Christopher L. P. Wolfe

AbstractThe time-mean zonal and meridional overturning circulations of the entire Mediterranean Sea are studied in both the Eulerian and residual frameworks. The overturning is characterized by cells in the vertical and either zonal or meridional planes with clockwise circulations in the upper water column and counterclockwise circulations in the deep and abyssal regions. The zonal overturning is composed of an upper clockwise cell in the top 600 m of the water column related to the classical Wüst cell and two additional deep clockwise cells, one corresponding to the outflow of the dense Aegean water during the Eastern Mediterranean Transient (EMT) and the other associated with dense water formation in the Rhodes Gyre. The variability of the zonal overturning before, during, and after the EMT is discussed. The meridional basinwide overturning is composed of clockwise, multicentered cells connected with the four northern deep ocean formation areas, located in the Eastern and Western Mediterranean basins. The connection between the Wüst cell and the meridional overturning is visualized through the horizontal velocities vertically integrated across two layers above 600 m. The component of the horizontal velocity associated with the overturning is isolated by computing the divergent components of the vertically integrated velocities forced by the inflow/outflow at the Strait of Gibraltar.

Eos ◽  
2018 ◽  
Vol 99 ◽  
Author(s):  
Pascal Conan ◽  
Pierre Testor ◽  
Claude Estournel ◽  
Fabrizio D'Ortenzio ◽  
Xavier Durrieu de Madron

A new special issue of JGR: Oceans and JGR: Atmospheres presents new insights into the dynamics of dense water formation in the western Mediterranean Sea and its biogeochemical consequences.


2014 ◽  
Vol 59 (1) ◽  
Author(s):  
Salvatore Mele ◽  
Maria Pennino ◽  
Maria Piras ◽  
José Bellido ◽  
Giovanni Garippa ◽  
...  

AbstractThe metazoan parasite assemblage of the head of 30 specimens of the Atlantic chub mackerel (Scomber colias) from the western Mediterranean Sea was analysed. Eight species of parasites were found, four mazocraeid monogeneans: Grubea cochlear (prevalence = 10%), Kuhnia scombercolias (59%), K. scombri (52%), Pseudokuhnia minor (86%); three didymozoid trematodes: Nematobothrium cf. faciale (21%), N. filiforme (41%), N. scombri (7%); and one laerneopodid copepod: Clavelissa scombri (7%). Results were compared with previously published data from 14 localities of the eastern Mediterranean Sea and the Atlantic Ocean, using non-parametric univariate and multivariate analyses, and the whole parasite fauna of S. colias was compared with that of the congeners (S. australasicus, S. japonicus and S. scombrus). Parasites showed to reflect the biogeographical and phylogenetic history of host. From a methodological point of view, the use of both non-parametric univariate and multivariate techniques proved to be effective tools to detect dissimilarities between parasite assemblages.


Author(s):  
Enric Massutí ◽  
J.A. Reina-Hervás ◽  
Domingo Lloris ◽  
L. Gil de Sola

The capture of five specimens of Solea (Microchirus) boscanion (Osteichthyes: Soleidae), a species previously unrecorded in the Mediterranean, is reported from the Iberian coast (western Mediterranean). The main morphometric and meristic measurements of this species with data of the other sympatric, and morphologically very similar, soleids Microchirus variegatus and Buglossidium luteum are also given. The record is discussed in relation to climate change and competition between species.


2010 ◽  
Vol 7 (4) ◽  
pp. 1533-1557
Author(s):  
W. Roether ◽  
J. E. Lupton

Abstract. Observations of tritium and 3He in the Tyrrhenian Sea, 1987–2009, confirm the enhanced convective mixing of intermediate waters into the deep waters that has been noted and associated with the Eastern Mediterranean Transient in previous studies. Our evidence for the mixing rests on increasing tracer concentrations in the Tyrrhenian deep waters, accompanied by decreases in the upper waters, which are supplied from the Eastern Mediterranean. The downward transfer is particularly evident between 1987 and 1997. Later on, information partly rests on increasing tritium-3He ages; here we correct the observed 3He for contributions released from the ocean floor. The Tyrrhenian tracer distributions are fully compatible with data upstream of the Sicily Strait and in the Western Mediterranean. The tracer data show that mixing reached to the bottom and confirm a cyclonic nature of the deep water circulation in the Tyrrhenian. They furthermore indicate that horizontal homogenization of the deep waters occurs on a time scale of several years. Various features point to a reduced impact of Western Mediterranean Deep Water (WMDW) in the Tyrrhenian during the enhanced-convection period. This is an important finding because it implies less upward mixing of WMDW, which has been named a major process to enable the WMDW to leave the Mediterranean via the Gibraltar Strait. On the other hand, the TDW outflow for several years represented a major influx of enhanced salinity and density waters into the deep-water range of the Western Mediterranean.


2019 ◽  
Author(s):  
Piero Lionello ◽  
Dario Conte ◽  
Marco Reale

Abstract. Large positive and negative sea level anomalies at the coast of the Mediterranean Sea are linked to intensity and position of cyclones moving along the Mediterranean storm track, with dynamics involving different factors. This analysis is based on a model hindcast and considers nine coastal stations, which are representative of sea level anomalies with different magnitude and characteristics. When a shallow water fetch is present, the wind around the cyclone center is the main cause of sea level positive and negative anomalies, depending on its onshore or offshore direction. The inverse barometer effect produces a positive anomaly at the coast near the cyclone pressure minimum and a negative anomaly at the opposite side of the Mediterranean Sea, because a cross-basin mean sea level pressure gradient is associated to the presence of a cyclone. Further, at some stations, negative sea level anomalies are reinforced by a residual water mass redistribution within the basin, which is associated with a transient response to the atmospheric pressure forcing. Though the link between presence of a cyclone in the Mediterranean has comparable importance for positive and negative anomalies, the relation between cyclone position and intensity is stronger for the magnitude of positive events. Area of cyclogenesis, track of the central minimum and position at the time of the event differ depending on the location where the sea level anomaly occurs and on its sign. The western Mediterranean is the main cyclogenesis area for both positive and negative anomalies, overall. Atlantic cyclones mainly produce positive sea level anomalies in the western basin. At the easternmost stations, positive anomalies are caused by Cyclogenesis in the Eastern Mediterranean. North Africa cyclogeneses are a major source of positive anomalies at the central African coast and negative anomalies at the eastern Mediterranean and North Aegean coast.


Ocean Science ◽  
2007 ◽  
Vol 3 (2) ◽  
pp. 245-258 ◽  
Author(s):  
G. M. R. Manzella ◽  
F. Reseghetti ◽  
G. Coppini ◽  
M. Borghini ◽  
A. Cruzado ◽  
...  

Abstract. The Ships Of Opportunity Program in the Mediterranean Sea was established at the end of 1999, in the framework of the Mediterranean Forecasting System – Pilot Project (MFS-PP). Many improvements have been made in data collection, transmission and management. Calibration of selected XBTs and a comparison of XBTs vs. CTDs during some research cruises have assured the quality of the data. Transmission now allows receiving data in full resolution by using GSM or satellite telecommunication services; management is offering access to high quality data and view services. The effects of technological and methodological improvements in the observing system are assessed in terms of capability to represent the most important circulation features. The improved methodologies have been tested during the Mediterranean Forecasting System – Toward Environmental Prediction (MFS-TEP) – Targeted Operational Period (MFS-TOP), lasting from September 2004 to February 2005. In spite of the short period of measurements, several important aspects of the Mediterranean Sea circulation have been verified, such as eddies and gyres in the various sub-basins, and dense water formation processes in some of them (vertical homogeneous profiles of about 13°C down to ~800 m in the Provençal, and of about 14.9°C down to ~300 m in the Levantine have allowed defining an index of dense water formation).


2017 ◽  
Vol 123 ◽  
pp. 118-128 ◽  
Author(s):  
Gianmarco Ingrosso ◽  
Manuel Bensi ◽  
Vanessa Cardin ◽  
Michele Giani

Ocean Science ◽  
2008 ◽  
Vol 4 (2) ◽  
pp. 133-149 ◽  
Author(s):  
R. O. Smith ◽  
H. L. Bryden ◽  
K. Stansfield

Abstract. The deep convection that occurs in the western basin of the Mediterranean Sea was investigated using Argo float data over two consecutive winters in 2004–2005 and 2005–2006. The results showed deep mixed layers reaching 2000 m in surprising locations, namely the eastern Catalan subbasin (39.785° N, 4.845° E) and the western Ligurian subbasin (43.392° N, 7.765° E). Subsequently, new deep water was formed in March of 2005 and 2006 with θ=12.89–12.92°C, S=38.48–38.49 and σθ=29.113 kg m−3. The deep water produced in the Ligurian subbasin during 2006 was more saline, warmer and denser than any historical observations of western Mediterranean deep water. The results show S, θ and σθ in the western Mediterranean deep water are higher than 1990s values, with a salinity increase of 1.5×10−3 yr−1, a temperature increase of 3.6×10−3 °C yr−1 and a density increase of 4.0×10−4 kg m−3 yr−1 apparent from a dataset of western Mediterranean deep water properties spanning 1955–2006.


2004 ◽  
Vol 34 (3) ◽  
pp. 685-692 ◽  
Author(s):  
Jesús García Lafuente ◽  
Javier Delgado

Abstract An accidentally released drifter in the eastern section of the Strait of Gibraltar, whose successive positions were tracked by the Argos surveillance system, was advected more than 170 km around the western Alboran gyre in the Alboran Sea of the western Mediterranean Sea during four days. The drifter trajectory along the gyre's periphery was wavelike around a hypothetical smoothed streamline, with a period of 35 h and an amplitude of approximately 2 km. Temperature observations confirm the wavelike nature of the trajectory. Neither tidal currents within the Alboran basin nor wind-related forcing are able to explain the observed path. The interaction of the incoming Atlantic jet and the western Alboran gyre at the place where they meet together with the existence of relative vorticity pulses of the Atlantic jet associated with tidal currents in the strait is put forward as a likely mechanism that generates short-scale eddies in which the drifter could have been trapped. The subsequent advection of such an eddy around the gyre would depict the observed wavelike trajectory.


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