Vanadium behaviour in the global ocean and in the Mediterranean Sea

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.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 &#8220;MSM72&#8221;, carried out on board the R/V MARIA S.MERIAN (Institut f&#252;r Meereskunde der Universit&#228;t Hamburg). The stations cover both the EMED and the WMED, from Gibraltar to the Crete Island.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).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 &#956;M 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.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.

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A nested Atlantic-Mediterranean Sea general circulation model for operational forecasting

Ocean Science ◽

10.5194/os-5-461-2009 ◽

2009 ◽

Vol 5 (4) ◽

pp. 461-473 ◽

Cited By ~ 124

Author(s):

P. Oddo ◽

M. Adani ◽

N. Pinardi ◽

C. Fratianni ◽

M. Tonani ◽

...

Keyword(s):

Mediterranean Sea ◽

General Circulation Model ◽

Ocean Circulation ◽

General Circulation ◽

Circulation Model ◽

Ocean Model ◽

Global Ocean ◽

Lateral Boundary ◽

The Mediterranean ◽

The Impact

Abstract. A new numerical general circulation ocean model for the Mediterranean Sea has been implemented nested within an Atlantic general circulation model within the framework of the Marine Environment and Security for the European Area project (MERSEA, Desaubies, 2006). A 4-year twin experiment was carried out from January 2004 to December 2007 with two different models to evaluate the impact on the Mediterranean Sea circulation of open lateral boundary conditions in the Atlantic Ocean. One model considers a closed lateral boundary in a large Atlantic box and the other is nested in the same box in a global ocean circulation model. Impact was observed comparing the two simulations with independent observations: ARGO for temperature and salinity profiles and tide gauges and along-track satellite observations for the sea surface height. The improvement in the nested Atlantic-Mediterranean model with respect to the closed one is particularly evident in the salinity characteristics of the Modified Atlantic Water and in the Mediterranean sea level seasonal variability.

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The Mean Sea Level Equation and Its Application to the Mediterranean Sea

Journal of Climate ◽

10.1175/jcli-d-13-00139.1 ◽

2014 ◽

Vol 27 (1) ◽

pp. 442-447 ◽

Cited By ~ 16

Author(s):

N. Pinardi ◽

A. Bonaduce ◽

A. Navarra ◽

S. Dobricic ◽

P. Oddo

Keyword(s):

Surface Water ◽

Mediterranean Sea ◽

Sea Level ◽

Water Flux ◽

Mass Conservation ◽

Volume Transport ◽

Conservation Equation ◽

Global Ocean ◽

Mean Sea Level ◽

The Mediterranean

Abstract A formalism to obtain a mean sea level equation (MSLE) is constructed for any limited ocean region and/or the global ocean by considering the mass conservation equation with compressible effects and a linear equation of state. The MSLE contains buoyancy fluxes terms representing the steric effects and the mass flux is represented by surface water fluxes and volume transport terms. The MSLE is studied for the Mediterranean Sea case using a simulation experiment for the decade 1999–2008. It is found that the Mediterranean MSL tendency is made of a steric contribution that is almost periodic in time superimposed on a stochastic-like signal due to the mass balance, dominating the MSL tendency. The MSL tendency stochastic-like term is a result of the imbalance between the volume flux at Gibraltar and the area average surface water flux.

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An integrated open-coastal biogeochemistry, ecosystem and biodiversity observatory of the Eastern Mediterranean. The Cretan Sea component of POSEIDON system

10.5194/os-2018-3 ◽

2018 ◽

Author(s):

George Petihakis ◽

Leonidas Perivoliotis ◽

Gerasimos Korres ◽

Dionysis Ballas ◽

Constantin Frangoulis ◽

...

Keyword(s):

Data Acquisition ◽

Mediterranean Sea ◽

Added Value ◽

Global Ocean ◽

Marine Policy ◽

Physical Parameters ◽

Test Bed ◽

Chl A ◽

The Mediterranean ◽

Cretan Sea

Abstract. There is a general scarcity of oceanic observations that concurrently examine air–sea interactions, coastal-open ocean processes, and biogeochemical (BGC) parameters, in appropriate spatiotemporal scales, and under continuous, long-term data acquisition schemes. In the Mediterranean Sea, the resulting knowledge gaps and observing challenges increase, due to its oligotrophic character, especially in the eastern part of the basin. The oligotrophic open Cretan Sea's biogeochemistry is considered to be representative of a greater Mediterranean area up to 106 km2, and understanding its features may be useful on even larger oceanic scales, since the Mediterranean Sea has been considered a miniature model of the global ocean. The spatiotemporal coverage of BGC observations in the Cretan Sea has progressively increased over the last decades, especially since the creation of the POSEIDON observing system, which has adopted a multiplatform-multiparameter approach, supporting BGC data acquisition. The current POSEIDON system's status includes open and coastal sea fixed platforms, a Ferrybox (FB) system, and Bio-Argo autonomous floats, that deliver remotely Chlorophyll-a (Chl-a), O2, pH and pCO2 data, as well as BGC-related physical parameters. Since 2010, the list has been further expanded to other BGC (nutrients, vertical particulate matter fluxes), ecosystem and biodiversity (from viruses up to zooplankton) parameters, thanks to the addition of sediment traps, frequent R/V visits for seawater-plankton sampling, and of an ADCP delivering information on macrozooplankton-micronekton vertical migration (in the epi-, mesopelagic layer). Gliders and drifters are the new, currently under integration to the existing system, platforms, supporting BGC monitoring. Land-based facilities, such as data centers, technical support infrastructures, calibration laboratory, mesocosms, support and give added value to the observatory. The data gathered from these platforms are used to improve the quality of the BGC-ecosystem model predictions, which have recently incorporated atmospheric nutrient deposition processes and assimilation of satellite Chl-a data. Besides addressing open scientific questions at regional and international level, examples of which are presented, the observatory provides user oriented services to marine policy-makers and the society, and is a technological test bed for new and/or cost-efficient BGC sensor technology and marine equipment. It is part of European and international observing programs, playing key role in regional data handling and participating in harmonization and best practices procedures. Future expansion plans consider the evolving scientific and society priorities, balanced with sustainable management.

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The shifting distribution of Mediterranean fishes: a spatio-temporal assessment based on Local Ecological Knowledge .

10.31230/osf.io/zgupd ◽

2019 ◽

Cited By ~ 2

Author(s):

Ernesto Azzurro ◽

Valerio Sbragaglia ◽

Jacopo Cerri ◽

Michel Bariche ◽

Luca Bolognini ◽

...

Keyword(s):

Mediterranean Sea ◽

Temporal Dynamics ◽

Local Ecological Knowledge ◽

Rapid Change ◽

Species Abundance ◽

Global Ocean ◽

Small Scale ◽

Ecological Knowledge ◽

The Mediterranean ◽

Spatio Temporal

A major problem worldwide is the rapid change in species abundance and distribution, which is rapidly restructuring the biological communities of many ecosystems under changing climates. Tracking these transformations in the marine environment is crucial but our understanding is often hampered by the absence of historical data and by the practical challenge of survey large geographical areas. Here we focus on the Mediterranean Sea, a region which is warming faster than the rest of the global ocean, tracing back the spatio-temporal dynamic of species, which are emerging the most in terms of increasing abundances and expanding distributions. To this aim, we accessed the Local Ecological Knowledge (LEK) of small-scale and recreational fishers reconstructing the dynamics of fish perceived as ‘new’ or increasing in different fishing area. Over 500 fishers across 95 locations and 9 different countries were interviewed and semi-quantitative information on yearly changes in species abundance was collected. Overall, 75 species were mentioned by the respondents, being the most frequent citations related to warm-adapted species of both, native and exotic origin. Respondents belonging to the same biogeographic sectors described coherent spatio-temporal dynamics, and gradients along latitudinal and longitudinal axes were revealed. This information provides a more complete understanding of recent bio-geographical changes in the Mediterranean Sea and it also demonstrates that adequately structured LEK methodology might be applied successfully beyond the local scale, across national borders and jurisdictions. Acknowledging this potential through macro-regional coordination, could pave the ground for future large-scale aggregations of individual observations, increasing our potential for integrated monitoring and conservation planning at the regional or even global level.

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

10.5194/egusphere-egu2020-12004 ◽

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

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.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.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.This work will be further extended to study the phytoplankton diversity at global scale using various data set from the Tara Oceans.

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Offsets and inputs of natural uranium isotopes in the Mediterranean Sea

10.5194/egusphere-egu2020-20226 ◽

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

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

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Long term changes in the deep sea: examples from two Mediterranean Channels

10.5194/egusphere-egu2020-4499 ◽

2020 ◽

Author(s):

Katrin Schroeder ◽

Sana Ben Ismail ◽

Jacopo Chiggiato ◽

Mireno Borghini ◽

Stefania Sparnocchia

Keyword(s):

Climate Change ◽

Mediterranean Sea ◽

Deep Sea ◽

Deep Ocean ◽

Western Mediterranean ◽

Global Ocean ◽

Marginal Sea ◽

The Mediterranean

Climate change is one of the key topics of our century. The study of processes related to climate change in the atmosphere, the open ocean, the deep sea or even in shallow coastal waters require sustained long-term observations, often deploying sophisticated and expensive equipment. According to the Deep-Ocean Observing Strategy (DOOS, http://deepoceanobserving.org/), the deep ocean (below 200 m water depth) is the least observed, but largest habitat on our planet by volume and area. With more than 90% of anthropogenic heat imbalance absorbed by the oceans, monitoring long-term changes of its heat content, and over its full depth, is essential to quantify the planetary heat budget.The Mediterranean Sea is a mid-latitude marginal sea, particularly responsive to climate change as reported by recent studies. Straits and channels divide it into several sub-basins and the continuous monitoring of these choke points allows to intercept different water masses, and thus to document how they changed over time. This monitoring, in many cases, is done under the umbrella of the CIESM Hydrochanges program (http://www.ciesm.org/marine/programs/hydrochanges.htm). Here we report the long-term time series of physical data collected in two of these choke points: the Sardinia Channel (1900 m) and the Sicily Channel (400 m).The Sardinia Channel allows the Western Mediterranean Deep Water (WMDW) to enter the Tyrrhenian Sea (depths > 3000 m), connecting it with the Algerian Sea (depths > 2500 m). This water mass has experienced a significant increase of heat and salt content over the past decades, due both to a gradual process and to and abrupt event, called Western Mediterranean Transition (WMT). The monitoring at the sill (1900 m) of the Sardinia Channel since 2003 shows this very clearly, and the interannual trends are significantly stronger than the global average trends.The Sicily Channel (sill at 400 m) separates the Mediterranean in two main basins, the Eastern Mediterranean Sea and the Western Mediterranean Sea. Here the thermohaline properties of the Intermediate Water (IW) are monitored since 1993, showing increasing temperature and salinity trends at least one order of magnitude stronger than those observed at intermediate depths in the global ocean.We investigate the causes of the observed trends and in particular discuss the role of a changing climate over the Mediterranean, especially in the eastern basin, where the IW is formed. The long-term records in two Mediterranean channels reveal how fast the response to climate change can be in a marginal sea compared to the global ocean, and demonstrates the essential role of long time series in the ocean.

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An integrated open-coastal biogeochemistry, ecosystem and biodiversity observatory of the eastern Mediterranean – the Cretan Sea component of the POSEIDON system

Ocean Science ◽

10.5194/os-14-1223-2018 ◽

2018 ◽

Vol 14 (5) ◽

pp. 1223-1245 ◽

Cited By ~ 10

Author(s):

George Petihakis ◽

Leonidas Perivoliotis ◽

Gerasimos Korres ◽

Dionysios Ballas ◽

Constantin Frangoulis ◽

...

Keyword(s):

Data Acquisition ◽

Mediterranean Sea ◽

Added Value ◽

Global Ocean ◽

Sensor Technology ◽

Marine Policy ◽

Test Bed ◽

Chl A ◽

The Mediterranean ◽

Cretan Sea

Abstract. There is a general scarcity of oceanic observations that concurrently examine air–sea interactions, coastal–open-ocean processes and physical–biogeochemical processes, in appropriate spatiotemporal scales and under continuous, long-term data acquisition schemes. In the Mediterranean Sea, the resulting knowledge gaps and observing challenges increase due to its oligotrophic character, especially in the eastern part of the basin. The oligotrophic open Cretan Sea's biogeochemistry is considered to be representative of a greater Mediterranean area up to 106 km2, and understanding its features may be useful on even larger oceanic scales, since the Mediterranean Sea has been considered a miniature model of the global ocean. The spatiotemporal coverage of biogeochemical (BGC) observations in the Cretan Sea has progressively increased over the last decades, especially since the creation of the POSEIDON observing system, which has adopted a multiplatform, multivariable approach, supporting BGC data acquisition. The current POSEIDON system's status includes open and coastal sea fixed platforms, a Ferrybox (FB) system and Bio-Argo autonomous floats that remotely deliver fluorescence as a proxy of chlorophyll-a (Chl-a), O2, pH and pCO2 data, as well as BGC-related physical variables. Since 2010, the list has been further expanded to other BGC (nutrients, vertical particulate matter fluxes), ecosystem and biodiversity (from viruses up to zooplankton) variables, thanks to the addition of sediment traps, frequent research vessel (R/V) visits for seawater–plankton sampling and an acoustic Doppler current profiler (ADCP) delivering information on macrozooplankton–micronekton vertical migration (in the epipelagic to mesopelagic layer). Gliders and drifters are the new (currently under integration to the existing system) platforms, supporting BGC monitoring. Land-based facilities, such as data centres, technical support infrastructure, calibration laboratory and mesocosms, support and give added value to the observatory. The data gathered from these platforms are used to improve the quality of the BGC-ecosystem model predictions, which have recently incorporated atmospheric nutrient deposition processes and assimilation of satellite Chl-a data. Besides addressing open scientific questions at regional and international levels, examples of which are presented, the observatory provides user-oriented services to marine policy makers and the society, and is a technological test bed for new and/or cost-efficient BGC sensor technology and marine equipment. It is part of European and international observing programs, playing a key role in regional data handling and participating in harmonization and best practices procedures. Future expansion plans consider the evolving scientific and society priorities, balanced with sustainable management.

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