The Mediterranean is getting saltier

Abstract. The deep waters of the Mediterranean Sea have been getting saltier and warmer for at least the past 40 yr at rates of about 0.015 and 0.04 °C per decade. Here we show that two processes contribute to these increases in temperature and salinity. On interannual time scales, deep water formation events in severe winters transmit increasingly salty intermediate waters into the deep water. The second process is a steady downward flux of heat and salt through the halocline-thermocline that connects the Levantine Intermediate Water with the deep water. We illustrate these two processes with observations from repeat surveys of the western Mediterranean basin we have made over the past 10 yr.

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The Mediterranean is becoming saltier

Ocean Science ◽

10.5194/os-10-693-2014 ◽

2014 ◽

Vol 10 (4) ◽

pp. 693-700 ◽

Cited By ~ 53

Author(s):

M. Borghini ◽

H. Bryden ◽

K. Schroeder ◽

S. Sparnocchia ◽

A. Vetrano

Keyword(s):

Deep Water ◽

Mediterranean Basin ◽

Western Mediterranean ◽

Intermediate Water ◽

Deep Water Formation ◽

The Past ◽

Western Mediterranean Sea ◽

Deep Waters ◽

Western Mediterranean Basin ◽

Water Formation

Abstract. The deep waters of the western Mediterranean Sea have become saltier and warmer for at least the past 40 years at rates of about 0.015 and 0.04 °C per decade. Here we show that two processes contribute to these increases in temperature and salinity. On interannual timescales, deep water formation events in severe winters transmit increasingly salty intermediate waters into the deep water. The second process is a steady downward flux of heat and salt associated with salt finger mixing down through the halocline–thermocline that connects the Levantine Intermediate Water with the deep water. We illustrate these two processes with observations from repeat surveys of the western Mediterranean basin we have made over the past 10 years.

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Changes in ventilation of the Mediterranean Sea during the past 25 year

Ocean Science ◽

10.5194/os-10-1-2014 ◽

2014 ◽

Vol 10 (1) ◽

pp. 1-16 ◽

Cited By ~ 37

Author(s):

A. Schneider ◽

T. Tanhua ◽

W. Roether ◽

R. Steinfeldt

Keyword(s):

Mediterranean Sea ◽

Deep Water ◽

Adriatic Sea ◽

Western Mediterranean ◽

Tyrrhenian Sea ◽

Deep Water Formation ◽

Technical Problems ◽

Water Formation ◽

The Mediterranean ◽

Transient Tracer

Abstract. Significant changes in the overturning circulation of the Mediterranean Sea has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transition (WMT) during the mid-2000s. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of low ventilation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

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Levantine Intermediate and Levantine Deep Water Formation: An Argo Float Study from 2001 to 2017

Water ◽

10.3390/w11091781 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1781 ◽

Cited By ~ 1

Author(s):

Elisabeth Kubin ◽

Pierre-Marie Poulain ◽

Elena Mauri ◽

Milena Menna ◽

Giulio Notarstefano

Keyword(s):

Deep Water ◽

Eastern Mediterranean ◽

Potential Temperature ◽

Sea Surface ◽

Intermediate Water ◽

Deep Water Formation ◽

Argo Float ◽

Levantine Sea ◽

Water Formation ◽

The Mediterranean

Levantine intermediate water (LIW) is formed in the Levantine Sea (Eastern Mediterranean) and spreads throughout the Mediterranean at intermediate depths, following the general circulation. The LIW, characterized by high salinity and relatively high temperatures, is one of the main contributors of the Mediterranean Overturning Circulation and influences the mechanisms of deep water formation in the Western and Eastern Mediterranean sub-basins. In this study, the LIW and Levantine deep water (LDW) formation processes are investigated using Argo float data from 2001 to 2017 in the Northwestern Levantine Sea (NWLS), the larger area around Rhodes Gyre (RG). To find pronounced events of LIW and LDW formation, more than 800 Argo profiles were analyzed visually. Events of LIW and LDW formation captured by the Argo float data are compared to buoyancy, heat and freshwater fluxes, sea surface height (SSH), and sea surface temperature (SST). All pronounced events (with a mixed layer depth (MLD) deeper than 250 m) of dense water formation were characterized by low surface temperatures and strongly negative SSH. The formation of intermediate water with typical LIW characteristics (potential temperature > 15 °C, salinity > 39 psu) occurred mainly along the Northern coastline, while LDW formation (13.7 °C < potential temperature < 14.5 °C, 38.8 psu < salinity < 38.9 psu) occurred during strong convection events within temporary and strongly depressed mesoscale eddies in the center of RG. This study reveals and confirms the important contribution of boundary currents in ventilating the interior ocean and therefore underlines the need to rethink the drivers and contributors of the thermohaline circulation of the Mediterranean Sea.

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Changes in ventilation of the Mediterranean Sea during the past 25 yr

Ocean Science Discussions ◽

10.5194/osd-10-1405-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 1405-1445 ◽

Cited By ~ 3

Author(s):

A. Schneider ◽

T. Tanhua ◽

W. Roether ◽

R. Steinfeldt

Keyword(s):

Mediterranean Sea ◽

Deep Water ◽

Adriatic Sea ◽

Western Mediterranean ◽

Tyrrhenian Sea ◽

Deep Water Formation ◽

Overturning Circulation ◽

Water Formation ◽

The Mediterranean ◽

Transient Tracer

Abstract. The Mediterranean Sea has a fast overturning circulation and the deep water masses are well ventilated in comparison to the deep waters of the world ocean. Significant changes in the overturning circulation has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transit (WMT) near the mid of the decade following. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. This variability is important to understand and to monitor, because ventilation is the main process to propagate surface perturbations, such as uptake of anthropogenic CO2, into the ocean interior. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of stagnation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

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Simulation of fine organic aerosols in the western Mediterranean area during the ChArMEx 2013 summer campaign

Atmospheric Chemistry and Physics ◽

10.5194/acp-18-7287-2018 ◽

2018 ◽

Vol 18 (10) ◽

pp. 7287-7312 ◽

Cited By ~ 10

Author(s):

Arineh Cholakian ◽

Matthias Beekmann ◽

Augustin Colette ◽

Isabelle Coll ◽

Guillaume Siour ◽

...

Keyword(s):

Mediterranean Basin ◽

Mass Concentration ◽

Organic Aerosols ◽

Western Mediterranean ◽

Basis Set ◽

Aerosol Formation ◽

Standard Scheme ◽

Western Mediterranean Basin ◽

The Mediterranean ◽

Fine Organic

Abstract. The simulation of fine organic aerosols with CTMs (chemistry–transport models) in the western Mediterranean basin has not been studied until recently. The ChArMEx (the Chemistry-Aerosol Mediterranean Experiment) SOP 1b (Special Observation Period 1b) intensive field campaign in summer of 2013 gathered a large and comprehensive data set of observations, allowing the study of different aspects of the Mediterranean atmosphere including the formation of organic aerosols (OAs) in 3-D models. In this study, we used the CHIMERE CTM to perform simulations for the duration of the SAFMED (Secondary Aerosol Formation in the MEDiterranean) period (July to August 2013) of this campaign. In particular, we evaluated four schemes for the simulation of OA, including the CHIMERE standard scheme, the VBS (volatility basis set) standard scheme with two parameterizations including aging of biogenic secondary OA, and a modified version of the VBS scheme which includes fragmentation and formation of nonvolatile OA. The results from these four schemes are compared to observations at two stations in the western Mediterranean basin, located on Ersa, Cap Corse (Corsica, France), and at Cap Es Pinar (Mallorca, Spain). These observations include OA mass concentration, PMF (positive matrix factorization) results of different OA fractions, and 14C observations showing the fossil or nonfossil origins of carbonaceous particles. Because of the complex orography of the Ersa site, an original method for calculating an orographic representativeness error (ORE) has been developed. It is concluded that the modified VBS scheme is close to observations in all three aspects mentioned above; the standard VBS scheme without BSOA (biogenic secondary organic aerosol) aging also has a satisfactory performance in simulating the mass concentration of OA, but not for the source origin analysis comparisons. In addition, the OA sources over the western Mediterranean basin are explored. OA shows a major biogenic origin, especially at several hundred meters height from the surface; however over the Gulf of Genoa near the surface, the anthropogenic origin is of similar importance. A general assessment of other species was performed to evaluate the robustness of the simulations for this particular domain before evaluating OA simulation schemes. It is also shown that the Cap Corse site presents important orographic complexity, which makes comparison between model simulations and observations difficult. A method was designed to estimate an orographic representativeness error for species measured at Ersa and yields an uncertainty of between 50 and 85 % for primary pollutants, and around 2–10 % for secondary species.

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Transformation of Levantine Intermediate Water tracked by MedArgo floats in Western Mediterranean

Ocean Science Discussions ◽

10.5194/osd-3-569-2006 ◽

2006 ◽

Vol 3 (3) ◽

pp. 569-584 ◽

Cited By ~ 1

Author(s):

M. Emelianov ◽

J. Font ◽

A. Turiel ◽

J. Solé ◽

P. Poulain ◽

...

Keyword(s):

Mediterranean Basin ◽

General Circulation ◽

Western Mediterranean ◽

Intermediate Water ◽

Thermohaline Structure ◽

Western Mediterranean Basin ◽

Intermediate Waters ◽

Good Agreement

Abstract. A clustering methodology is applied to investigate the thermohaline structure of Levantine Intermediate Water (LIW) in the western Mediterranean basin. 16 free-drifting hydrographic profilers were deployed in the framework of the MFSTEP project (MedArgo component) from September 2003. A total of 925 CTD profiles data collected until the beginning of February 2006 have been used in the analysis. The results are in good agreement with the general circulation scheme for intermediate waters in the basin and confirm the hypothesis about a "discrete-continuous" thermohaline structure of LIW.

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Observations of new western Mediterranean deep water formation using Argo floats 2004–2006

Ocean Science ◽

10.5194/os-4-133-2008 ◽

2008 ◽

Vol 4 (2) ◽

pp. 133-149 ◽

Cited By ~ 61

Author(s):

R. O. Smith ◽

H. L. Bryden ◽

K. Stansfield

Keyword(s):

Mediterranean Sea ◽

Deep Water ◽

Temperature Increase ◽

Deep Convection ◽

Western Mediterranean ◽

Deep Water Formation ◽

Western Basin ◽

Water Formation ◽

Salinity Increase ◽

Mixed Layers

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.

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Will deep water formation collapse in the North Western Mediterranean Sea by the end of the 21st century?

10.1002/essoar.10507698.1 ◽

2021 ◽

Author(s):

Iván Manuel Parras Berrocal ◽

Ruben Vazquez ◽

William David CabosNarvaez ◽

Dimitry Sein ◽

Oscar Alvarez Esteban ◽

...

Keyword(s):

Mediterranean Sea ◽

21St Century ◽

Deep Water ◽

Western Mediterranean ◽

Deep Water Formation ◽

The North ◽

Western Mediterranean Sea ◽

Water Formation ◽

North Western

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Modelling deep-water formation in the North-West Mediterranean Sea with a new air-sea coupled model: sensitivity to turbulent flux parameterizations

10.5194/os-2017-43 ◽

2017 ◽

Cited By ~ 1

Author(s):

Léo Seyfried ◽

Patrick Marsaleix ◽

Evelyne Richard ◽

Claude Estournel

Keyword(s):

Deep Water ◽

Turbulent Flux ◽

Western Mediterranean ◽

Observation Data ◽

Strong Wind ◽

Deep Water Formation ◽

The North ◽

Ocean Atmosphere ◽

Water Formation ◽

North Western

Abstract. In the north western Mediterranean, the strong, dry, cold winds, the Tramontane and Mistral, produce intense heat and moisture exchange at the interface between the ocean and the atmosphere leading to the formation of deep dense waters, a process that occurs only in certain regions of the world. The purpose of this study is to demonstrate the ability of a new coupled ocean-atmosphere modelling system based on MESONH-SURFEX-SYMPHONIE to simulate a deep-water formation event in real conditions. The study focuses on summer 2012 to spring 2013, a favourable period that is well documented by previous studies and for which many observations are available. Model results are assessed through detailed comparisons with different observation data sets, including measurements from buoys, moorings and floats. The good overall agreement between observations and model results shows that the new coupled system satisfactorily simulates the formation of deep dense water and can be used with confidence to study ocean-atmosphere coupling in the north-western Mediterranean. In addition, to evaluate the uncertainty associated with the representation of turbulent fluxes in strong wind conditions, several simulations were carried out based on different parameterizations of the flux bulk formulas. The results point out that the choice of turbulent flux parameterization strongly influences the simulation of the deep water convection and can modify the calculated volume of the deep water formed by up to one order of magnitude.

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Size distribution and optical properties of mineral dust aerosols transported in the western Mediterranean

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-15-21607-2015 ◽

2015 ◽

Vol 15 (15) ◽

pp. 21607-21669 ◽

Cited By ~ 3

Author(s):

C. Denjean ◽

F. Cassola ◽

A. Mazzino ◽

S. Triquet ◽

S. Chevaillier ◽

...

Keyword(s):

Optical Properties ◽

Mediterranean Basin ◽

Mineral Dust ◽

Regional Climate ◽

Source Region ◽

Western Mediterranean ◽

Source Regions ◽

Western Mediterranean Basin ◽

Large Particles ◽

The Mediterranean

Abstract. This study presents in situ aircraft measurements of Saharan mineral dust transported over the western Mediterranean basin in June–July 2013 during the ChArMEx/ADRIMED (the Chemistry-Aerosol Mediterranean Experiment/Aerosol Direct Radiative Impact on the regional climate in the MEDiterranean region) airborne campaign. Dust events differing in terms of source region (Algeria, Tunisia and Morocco), time of tranport (1–5 days) and height of transport were sampled. Mineral dust were transported above the marine boundary layer, which conversely was dominated by pollution and marine aerosols. The dust vertical structure was extremely variable and characterized by either a single layer or a more complex and stratified structure with layers originating from different source regions. Mixing of mineral dust with pollution particles was observed depending on the height of transport of the dust layers. Dust layers carried higher concentration of pollution particles at intermediate altitude (1–3 km) than at elevated altitude (> 3 km), resulting in scattering Angstrom exponent up to 2.2 within the intermediate altitude. However, the optical properties of the dust plumes remained practically unchanged with respect to values previously measured over source regions, regardless of the altitude. Moderate light absorption of the dust plumes was observed with values of aerosol single scattering albedo at 530 nm ranging from 0.90 to 1.00 ± 0.04. Concurrent calculations from the aerosol chemical composition revealed a negligible contribution of pollution particles to the absorption properties of the dust plumes that was due to a low contribution of refractory black carbon in regards to the fraction of dust and sulfate particles. This suggests that, even in the presence of moderate pollution, likely a persistent feature in the Mediterranean, the optical properties of the dust plumes could be assimilated to those of native dust in radiative transfer simulations, modeling studies and satellite retrievals over the Mediterranean. Measurements also showed that the coarse mode of mineral dust was conserved even after 5 days of transport in the Mediterranean, which contrasts with the gravitational depletion of large particles observed during the transport of dust plumes over the Atlantic. Simulations with the WRF mesoscale meteorological model highlighted a strong vertical turbulence within the dust layers that could prevent deposition of large particles during their atmospheric transport. This has important implications for the dust radiative effects due to surface dimming, atmospheric heating and cloud formation. The results presented here add to the observational dataset necessary for evaluating the role of mineral dust on the regional climate and rainfall patterns in the western Mediterranean basin.

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