scholarly journals Changes in the intermediate water masses of the Mediterranean Sea during the last climatic cycle ‐ New constraints from neodymium isotopes in foraminifera

2021 ◽  
Author(s):  
Christophe Colin ◽  
Maxence Duhamel ◽  
Giuseppe Siani ◽  
Quentin Dubois‐Dauphin ◽  
Emmanuelle Ducassou ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Water Masses ◽  
Intermediate Water ◽  
Neodymium Isotopes ◽  
Climatic Cycle ◽  
The Mediterranean

scholarly journals Characterization of the Atlantic Water and Levantine Intermediate Water in the Mediterranean Sea using Argo Float Data

2021 ◽  
Author(s):  
Giusy Fedele ◽  
Elena Mauri ◽  
Giulio Notarstefano ◽  
Pierre Marie Poulain
Keyword(s):  
Mediterranean Sea ◽  
Thermohaline Circulation ◽  
Internal Variability ◽  
Warming Trend ◽  
Atlantic Water ◽  
Western Mediterranean ◽  
Water Masses ◽  
Intermediate Water ◽  
Starting Point ◽  
The Mediterranean

Abstract. The Atlantic Water (AW) and Levantine Intermediate Water (LIW) are important water masses that play a crucial role in the internal variability of the Mediterranean thermohaline circulation. In particular, their variability and interaction, along with other water masses that characterize the Mediterranean basin, such as the Western Mediterranean Deep Water (WMDW), contribute to modify the Mediterranean Outflow through the Gibraltar Strait and hence may influence the stability of the global thermohaline circulation. This work aims to characterize the AW and LIW in the Mediterranean Sea, taking advantage of the large observational dataset provided by Argo floats from 2001 to 2019. Using different diagnostics, the AW and LIW were identified, highlighting the inter-basin variability and the strong zonal gradient that characterize the two water masses in this marginal sea. Their temporal variability was also investigated focusing on trends and spectral features which constitute an important starting point to understand the mechanisms that are behind their variability. A clear salinification and warming trend have characterized the AW and LIW in the last two decades (~0.007 and 0.008 yr−1; 0.018 and 0.007 °C yr−1, respectively). The salinity and temperature trends found at subbasin scale are in good agreement with previous results. The strongest trends are found in the Adriatic basin in both the AW and LIW properties. A subbasin dependent spectral variability emerges in the AW and LIW salinity timeseries with peaks between 2 and 10 years.

DOM DYNAMICS IN THE MEDITERRANEAN SEA. Can a new fluorescence SENSOR contribute to its understanding?

2020 ◽  
Author(s):  
Simona Retelletti Brogi ◽  
Marta Furia ◽  
Giancarlo Bachi ◽  
Vanessa Cardin ◽  
Giuseppe Civitarese ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Mediterranean Sea ◽  
Water Column ◽  
Fluorescence Sensor ◽  
Global Ocean ◽  
Intermediate Water ◽  
Physical Processes ◽  
Open Sea ◽  
The Mediterranean

<p>The Mediterranean Sea (Med Sea) can be considered as a natural laboratory for the study of dissolved organic matter (DOM) dynamics. Despite its small size, it is characterized by the same physical processes and dissolved organic carbon (DOC) concentration and distribution as the global ocean. The Med Sea deep water DOC pool is however older than the Atlantic one and differences in the microbial loop and in DOM dynamics have been observed between the eastern (EMED) and western (WMED) basins. Fluorescence is a fast, cheap and highly sensitive tool to study DOM dynamics, it can therefor give useful information about the main processes affecting DOM distribution.</p><p>The main aims of this study were: (i) to investigate DOM dynamics in both Med Sea basins, in relation to the physical processes (e.g. vertical stratification, irradiation); and (ii) to validate the use of a new fluorescence sensor, developed in the framework of the SENSOR project (POR FESR, Tuscany Region), for the rapid, in-situ measurements of open-sea fluorescent DOM (FDOM). DOM dynamics was investigated by measuring dissolved organic carbon (DOC) and the fluorescence of FDOM. Samples were collected from surface to bottom in 26 stations during the trans-Mediterranean cruise “MSM72”, carried out on board the R/V MARIA S.MERIAN (Institut für Meereskunde der Universität Hamburg). The stations cover both the EMED and the WMED, from Gibraltar to the Crete Island.</p><p>Six fluorescent components were identified by applying the parallel factorial analysis (PARAFAC) to the measured excitation-emission matrices (EEMs). Two components were identified as marine humic-like, two as terrestrial humic-like, one as protein-like and one as polycyclic aromatic hydrocarbon-like (PAH-like).</p><p>Temperature and salinity increased moving from the WMED to the EMED. A surface minimum in salinity, was observed in the WMED, indicating the occurrence of the Atlantic Water (AW), whereas the presence of the Levantine Intermediate Water (LIW) was observed south of Crete. The vertical distribution of both DOC and humic-like FDOM was strongly affected by the water masses circulation and water column stratification. In the upper 200 m, DOC markedly increased from 50 to 80 μM moving eastward, likewise the protein-like component dominates the upper layer and increased moving from Gibraltar to Crete. In contrast, the humic-like components showed a minimum in the surface layer, and a decreasing moving eastward, probably due to photobleaching. The PAH-like component showed its maximum in correspondence with the areas characterized by intensive naval traffic. The accumulation of DOC, observed in the EMED, could be explained by a change in DOM quality, supported by the differences in FDOM.</p><p>In 2 selected stations, the fluorescence of humic-like and protein-like compounds was also measured along the water column by using the new fluorescence sensor and compared with PARAFAC results, in order to evaluate its performance for open sea waters.</p>

scholarly journals The transient distributions of nuclear weapon-generated tritium and its decay product <sup>3</sup>He in the Mediterranean Sea, 1952–2011, and their oceanographic potential

2013 ◽  
Vol 10 (2) ◽  
pp. 649-690 ◽  
Author(s):  
W. Roether ◽  
P. Jean-Baptiste ◽  
E. Fourré ◽  
J. Sültenfuß
Keyword(s):  
Mediterranean Sea ◽  
Transit Time ◽  
Nuclear Weapon ◽  
Eastern Mediterranean ◽  
Decay Product ◽  
Intermediate Water ◽  
Tyrrhenian Sea ◽  
Transit Times ◽  
Time Dispersion ◽  
The Mediterranean

Abstract. We present a comprehensive account of tritium and 3He in the Mediterranean Sea since the appearance of the tritium generated by the atmospheric nuclear-weapon testing in the 1950's and early 1960's, based on essentially all available observations. Tritium in surface waters rose to 20–30 TU in 1964 (TU = 1018 · [3H]/[H]), a factor of about 100 above the natural level, and thereafter declined 30-fold up to 2011. The decline was largely due to radioactive tritium decay, which produced significant amounts of its stable daughter 3He. We present the scheme by which we separate the tritiugenic part of 3He and the part due to release from the sea floor (terrigenic part). We show that the tritiugenic component can be quantified throughout the Mediterranean waters, typically to a &amp;pm;0.15 TU equivalent, mostly because the terrigenic part is low in 3He. This fact makes the Mediterranean unique in offering a potential for the use of tritiugenic 3He as a tracer. The transient distributions of the two tracers are illustrated by a number of sections spanning the entire sea and relevant features of their distributions are noted. By 2011, the 3He concentrations in the top few hundred meters had become low, in response to the decreasing tritium concentrations combined with a flushing out by the general westward drift of these waters. Tritium-3He ages in Levantine Intermediate Water (LIW) were obtained repeated in time at different locations, defining transit times from the LIW source region east of Rhodes. The ages show an upward trend with the time elapsed since the surface-water tritium maximum, which arises because the repeated observations represent increasingly slower moving parts of the full transit time spectrum of LIW. The transit time dispersion found by this new application of tritium-3He dating is considerable. We find mean transit times of 12 &amp;pm; 2 yr up to the Strait of Sicily, 18 &amp;pm; 3 yr up to the Tyrrhenian Sea, and 22 &amp;pm; 4 yr up into the Western Mediterranean. We furthermore present full Eastern Mediterranean sections of terrigenic 3He and tritium-3He age in 1987, the latter one similarly showing an effect of the transit time dispersion. We conclude that the available tritium and 3He data, in particular if combined with other tracer data, are useful for constraining the subsurface circulation and mixing of the Mediterranean Sea.

scholarly journals Glider data collected during the Algerian Basin Circulation Unmanned Survey

2019 ◽  
Vol 11 (1) ◽  
pp. 147-161 ◽  
Author(s):  
Yuri Cotroneo ◽  
Giuseppe Aulicino ◽  
Simon Ruiz ◽  
Antonio Sánchez Román ◽  
Marc Torner Tomàs ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Adaptive Sampling ◽  
Western Mediterranean ◽  
Water Masses ◽  
Control Procedure ◽  
Intermediate Water ◽  
Large Variability ◽  
Distribution Ranges ◽  
Basin Scale ◽  
Deep Layers

Abstract. We present data collected in the framework of the Algerian BAsin Circulation Unmanned Survey (ABACUS) project. The main objective of ABACUS is the monitoring of the basin circulation and of the surface and intermediate water masses' physical and biological properties in a key region of the Mediterranean Sea circulation. Data presented here have been collected through deep glider cruises in the Western Mediterranean Sea during the autumns of 2014, 2015 and 2016; activities at sea are expected to be repeated during the coming years, so that the dataset will be extended. Glider missions were conducted in the Algerian Basin, between the island of Mallorca and the Algerian coast. Across the three glider missions, eight repeated transects were completed which enabled us to investigate the basin-scale circulation and the presence of mesoscale structures, utilising both the adaptive sampling capabilities of the gliders and the higher resolution of the data. After collection, all data passed a quality control procedure and were then made available through an unrestricted repository host by the SOCIB Data Centre at https://doi.org/10.25704/b200-3vf5. The actual dataset spans three autumn seasons, providing an important contribution to the data collection in the chronically undersampled Algerian Basin. Temperature and salinity data collected in the first 975 m of the water column allowed us to identify the main water masses and describe their characteristics, improving the understanding of the dynamics of the region. On the timescale of the project, data show a large variability in the surface layer and reduced variability in the intermediate and deep layers. Our measurements have been successfully compared to data previously collected in the area from 1909 to 2011. Results showed similar overall distribution, ranges and variability to the historical data, with no outliers in the surface or deep layers.

scholarly journals WAVE STATISTICS AND SPECTRAL MONITORING IN THE MEDITERRANEAN SEA (i.e. SICILY CHANNEL): 9 YEARS OF WAVE DATA MONITORING

2012 ◽  
Vol 1 (33) ◽  
pp. 3 ◽  
Author(s):  
Emanuele Terrile ◽  
Gianluigi De Filippi ◽  
Ostilio Spadaccini
Keyword(s):  
Mediterranean Sea ◽  
Wave Spectrum ◽  
Intermediate Water ◽  
Spectral Parameters ◽  
Wave Statistics ◽  
Wave Data ◽  
The Mediterranean ◽  
Sicily Channel ◽  
Wave Models ◽  
Definition Of

The main aim of the work if to define and characterized the wave filed in the intermediate water depth of the mediterranean Sea, in particular in the Sicily channel. Even if is not the appropriate wave spectrum, the jONSWAP spectrum is often used in the Mediterranean Sea as input for the most common third-generation spectral wave models, e.g. SWAN (Booij et al. 1996). The definition of site-specific spectral parameters by means of measured wave data allows to get a better assessment of the wave field in the coastal area with consequent better description of the wave characteristics to be used to design coastal structures.

A neural-based bio-regionalization of the Mediterranean Sea using satellite and Argo-float records

2020 ◽  
Author(s):  
Roy El Hourany ◽  
Chris Bowler ◽  
Carlos Mejia ◽  
Michel Crépon ◽  
Sylvie Thiria
Keyword(s):  
Mediterranean Sea ◽  
Deep Convection ◽  
Global Ocean ◽  
Marine Biodiversity ◽  
Intermediate Water ◽  
Tropical Ocean ◽  
Phytoplankton Diversity ◽  
Winter Convection ◽  
Phytoplankton Communities ◽  
The Mediterranean

&lt;p&gt;The regionalization of the Mediterranean Sea has been the subject of many studies. It is a miniature ocean where most of the processes of the global ocean are encountered (Lejeusne et al., 2010). Several features of the Mediterranean (near-tropical ocean in summer with a well-formed thermocline, near-polar ocean in winter with deep convection, multiple basins with different characteristics) make it a hotspot of marine biodiversity (Coll and al., 2010) and consequently vulnerable to climate change. It is therefore important to characterize the present state of the Mediterranean Sea with robust estimators in order to study the long-term evolution of this mesocosm.&lt;/p&gt;&lt;p&gt;We present a partitioning of the Mediterranean Sea in regions having well defined characteristics with respect to Sea Surface Temperature and surface chlorophyll observed by satellite, and Argo mixed layer depth. This regionalization was performed by using an innovative classification based on neural networks, the so-called 2S-SOM. Its major advantage is to consider the specificity of the variables by adding automatically, through machine learning, specific weights to each of them, which facilitates the classification and consequently highlights the regional correlations. The 2S-SOM provided a well differentiated regionalization of the Mediterranean Sea waters into seven bioregions governed by specific physical and biogeochemical processes such as Intermediate-water formation in the Aegean Sea, large surface currents in the Adriatic and the Alboran, deep winter convection phenomena in the Balearic and stratification phenomena during summer in the eastern part of the Mediterranean Sea.&lt;/p&gt;&lt;p&gt;Besides, in order to highlight the phytoplankton diversity in these regions, we processed the satellite ocean color observations with a specific neural network approach (SOM-PFT, El Hourany et al., 2019). As a result, specific phytoplankton communities characterized by their seasonal variability are associated with the obtained Mediterranean bioregions; the dominance of the Nanophytoplankton groups is largely observed in the western basin during the period ranging from autumn to spring. While the dominance of different types of cyanobacteria Synechococcus and Prochlorococcus is highlighted in summer and more precisely in the waters of the eastern basin. Diatoms dominate throughout the year in the coastal and shallow regions, which can be explained by the presence of terrigenous input necessary for the development of this type of phytoplankton. Diatoms also largely benefit from the strong deep convection in the Balearic Sea marked by a large bloom at the end of winter convection in March.&lt;/p&gt;&lt;p&gt;This work will be further extended to study the phytoplankton diversity at global scale using various data set from the Tara Oceans.&lt;/p&gt;

Offsets and inputs of natural uranium isotopes in the Mediterranean Sea

2020 ◽  
Author(s):  
Evan Border ◽  
Norbert Frank ◽  
Pieter van Beek ◽  
Gideon Henderson ◽  
Joseph Tamborski
Keyword(s):  
Mediterranean Sea ◽  
Black Sea ◽  
Submarine Groundwater Discharge ◽  
Mediterranean Coast ◽  
Natural Uranium ◽  
Water Masses ◽  
Precision Measurements ◽  
Global Ocean ◽  
Uranium Isotopes ◽  
The Mediterranean

&lt;p&gt;High precision measurements of natural uranium isotopes in the Atlantic Ocean, Mediterranean Sea,&lt;br&gt;and Black Sea reveal isotopic makeups which differ significantly from the well-known oceanic&lt;br&gt;composition. In the Mediterranean, water masses are strongly differentiated to the extent that they&lt;br&gt;are able to be fingerprinted on the basis of &amp;#948;&lt;sup&gt;234&lt;/sup&gt;U. Mediterranean deep water masses show the&lt;br&gt;highest enrichment, with an offset with respect to oceanic &amp;#948;&lt;sup&gt;234&lt;/sup&gt;U values of just over 1 &amp;#8240;. The Black&lt;br&gt;Sea shows an even higher offset of up to ~40 &amp;#8240;.&lt;br&gt;This offset provides an opportunity to look into the as of yet largely unstudied uranium inputs to the&lt;br&gt;Mediterranean, in particular rivers and submarine groundwater discharge (SGD), which are thought&lt;br&gt;to play key roles in uranium input to the global ocean. A simple box model, incorporating the&lt;br&gt;Mediterranean and Black Sea data from this study is constructed to provide a first estimate of the U&lt;br&gt;concentration and &amp;#948;&lt;sup&gt;234&lt;/sup&gt;U signature of rivers and SGD necessary for this offset to arise. These&lt;br&gt;estimates are then compared with new measurements of various coastal and submarine springs from&lt;br&gt;along the French Mediterranean Coast as well as with existing riverine data exists to speculate on&lt;br&gt;which inputs may be most responsible for this offset.&lt;/p&gt;

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