scholarly journals In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

2017 ◽  
Author(s):  
Jean-Baptiste Renard ◽  
François Dulac ◽  
Pierre Durand ◽  
Quentin Bourgeois ◽  
Cyrielle Denjean ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Western Mediterranean ◽  
Dust Particles ◽  
Strong Interactions ◽  
Particle Volume ◽  
Western Basin ◽  
Western Mediterranean Sea ◽  
Constant Altitude ◽  
Aerosol Counter

Abstract. Mineral dust from arid areas is a major component of the global aerosol and has strong interactions with climate and biogeochemistry. As part of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) to investigate atmospheric chemistry and its impacts in the Mediterranean region, an intensive field campaign was performed from mid-June to early August 2013 in the western basin including in situ balloon-borne aerosol measurements with the Light Optical Aerosol Counter (LOAC). LOAC is a counter/sizer that provides the aerosol concentrations in 19 size classes between 0.2 and 100 μm, and an indication of the nature of the particles based on dual angle scattering measurements. A total of 27 LOAC flights were conducted mainly from Minorca Island (Balearic Islands, Spain) but also from Ile du Levant off Hyères city (SE France) under 17 Light Dilatable Balloons (meteorological sounding balloons) and 10 Boundary Layer Pressurized Balloons (quasi-Lagrangian balloons). The purpose was to document the vertical extent of the plume and the time-evolution of the concentrations at constant altitude (air density) by in situ observations. LOAC measurements are in agreement with ground-based measurements (lidar, photometer), aircraft measurements (counters), and satellite measurements (CALIOP) in case of fair spatial and temporal coincidences. LOAC has often detected 3 modes in the dust particle volume size distributions fitted by lognormal laws at roughly 0.2, 4 and 30 µm in modal diameter. Particles larger than 40 μm were observed, with concentrations up to about 10−4 cm−3. Such large particles were lifted several days before and their persistence after transport over long distances is in conflict with calculations of dust sedimentation. We did not observe any significant evolution of the size distribution during the transport from quasi-Lagrangian flights, even for the longest ones (~ 1 day). Finally, the presence of charged particles is inferred from the LOAC measurements and we speculate that electrical forces might counteract gravitational settling of the coarse particles.

scholarly journals In situ measurements of desert dust particles above the western Mediterranean Sea with the balloon-borne Light Optical Aerosol Counter/sizer (LOAC) during the ChArMEx campaign of summer 2013

2018 ◽  
Vol 18 (5) ◽  
pp. 3677-3699 ◽  
Author(s):  
Jean-Baptiste Renard ◽  
François Dulac ◽  
Pierre Durand ◽  
Quentin Bourgeois ◽  
Cyrielle Denjean ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
High Sensitivity ◽  
Western Mediterranean ◽  
Dust Particles ◽  
Strong Interactions ◽  
Particle Volume ◽  
Western Basin ◽  
Western Mediterranean Sea ◽  
Aerosol Counter

Abstract. Mineral dust from arid areas is a major component of global aerosol and has strong interactions with climate and biogeochemistry. As part of the Chemistry-Aerosol Mediterranean Experiment (ChArMEx) to investigate atmospheric chemistry and its impacts in the Mediterranean region, an intensive field campaign was performed from mid-June to early August 2013 in the western basin including in situ balloon-borne aerosol measurements with the light optical aerosol counter (LOAC). LOAC is a counter/sizer that provides the aerosol concentrations in 19 size classes between 0.2 and 100 µm, and an indication of the nature of the particles based on dual-angle scattering measurements. A total of 27 LOAC flights were conducted mainly from Minorca Island (Balearic Islands, Spain) but also from Ile du Levant off Hyères city (SE France) under 17 light dilatable balloons (meteorological sounding balloons) and 10 boundary layer pressurised balloons (quasi-Lagrangian balloons). The purpose was to document the vertical extent of the plume and the time evolution of the concentrations at constant altitude (air density) by in situ observations. LOAC measurements are in agreement with ground-based measurements (lidar, photometer), aircraft measurements (counters), and satellite measurements (CALIOP) in the case of fair spatial and temporal coincidences. LOAC has often detected three modes in the dust particle volume size distributions fitted by lognormal laws at roughly 0.2, 4 and 30 µm in modal diameter. Thanks to the high sensitivity of LOAC, particles larger than 40 µm were observed, with concentrations up to about 10−4 cm−3. Such large particles were lifted several days before and their persistence after transport over long distances is in conflict with calculations of dust sedimentation. We did not observe any significant evolution of the size distribution during the transport from quasi-Lagrangian flights, even for the longest ones (∼ 1 day). Finally, the presence of charged particles is inferred from the LOAC measurements and we speculate that electrical forces might counteract gravitational settling of the coarse particles.

scholarly journals The Management of the Beach-Cast Seagrass Wracks—A Numerical Modelling Approach

2020 ◽  
Vol 8 (11) ◽  
pp. 873
Author(s):  
Andrea Cucco ◽  
Giovanni Quattrocchi ◽  
Walter Brambilla ◽  
Augusto Navone ◽  
Pieraugusto Panzalis ◽  
...  
Keyword(s):  
Winter Season ◽  
Numerical Approach ◽  
Posidonia Oceanica ◽  
Western Mediterranean ◽  
Western Mediterranean Sea ◽  
Hydrodynamic Wave ◽  
Selection Of ◽  
Beach Cast ◽  
Modelling Approach

Seagrass wrack are commonly found on the beach face of the sandy shore all around the world and often persists in situ during the whole year, favouring the emergence of conflicts for the use of the sandy coasts for bathing or for other recreational purposes. As a consequence, these deposits are often removed from the beach during the summer months, temporary stocked, and relocated on the shore face in the next autumn or winter season. The selection of the sites on the shoreline where the leaves should be released before the storms season is often an issue, considering the optimization needs between the transportation costs and the oceanographic features of the dumping site. In this study, a numerical approach was proposed to identify the most suitable areas for the autumnal repositioning of the seagrass wracks for two beaches of Sardinia, an island located in the Western Mediterranean Sea where Posidonia oceanica (L. Delile, 1813) is the most widespread seagrass species. The method is based on the use of hydrodynamic, wave, and particle tracking models and provides important indications useful for the management of this type of practice that can be extended to all different type of beaches along the Mediterranean coasts.

scholarly journals Impact of moderately energetic fine-scale dynamics on the phytoplankton community structure in the western Mediterranean Sea

2021 ◽  
Vol 18 (24) ◽  
pp. 6455-6477
Author(s):  
Roxane Tzortzis ◽  
Andrea M. Doglioli ◽  
Stéphanie Barrillon ◽  
Anne A. Petrenko ◽  
Francesco d'Ovidio ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Phytoplankton Community ◽  
World Ocean ◽  
Western Mediterranean ◽  
Water Masses ◽  
Ocean Dynamics ◽  
Western Boundary ◽  
Fine Scale ◽  
Western Mediterranean Sea

Abstract. Model simulations and remote sensing observations show that ocean dynamics at fine scales (1–100 km in space, day–weeks in time) strongly influence the distribution of phytoplankton. However, only a few in situ-based studies at fine scales have been performed, and most of them concern western boundary currents which may not be representative of less energetic regions. The PROTEVSMED-SWOT cruise took place in the moderately energetic waters of the western Mediterranean Sea (WMS), in the region south of the Balearic Islands. Taking advantage of near-real-time satellite information, we defined a sampling strategy in order to cross a frontal zone separating different water masses. Multi-parametric in situ sensors mounted on the research vessel, on a towed vehicle and on an ocean glider were used to sample physical and biogeochemical variables at a high spatial resolution. Particular attention was given to adapting the sampling route in order to estimate the vertical velocities in the frontal area also. This strategy was successful in sampling quasi-synoptically an oceanic area characterized by the presence of a narrow front with an associated vertical circulation. A multiparametric statistical analysis of the collected data identifies two water masses characterized by different abundances of several phytoplankton cytometric functional groups, as well as different concentrations of chlorophyll a and O2. Here, we focus on moderately energetic fronts induced by fine-scale circulation. Moreover, we explore physical–biological coupling in an oligotrophic region. Our results show that the fronts induced by the fine-scale circulation, even if weaker than the fronts occurring in energetic and nutrient-rich boundary current systems, maintain nevertheless a strong structuring effect on the phytoplankton community by segregating different groups at the surface. Since oligotrophic and moderately energetic regions are representative of a very large part of the world ocean, our results may have global significance when extrapolated.

scholarly journals Climatological distribution of dissolved inorganic nutrients in the Western Mediterranean Sea (1981–2017)

2021 ◽  
Author(s):  
Malek Belgacem ◽  
Katrin Schroeder ◽  
Alexander Barth ◽  
Charles Troupin ◽  
Bruno Pavoni ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
World Ocean ◽  
Western Mediterranean ◽  
Inorganic Nutrients ◽  
Data Product ◽  
Western Mediterranean Sea ◽  
Dissolved Inorganic Nutrients ◽  
In Situ Observations ◽  
Nutrient Variability

Abstract. The Western MEDiterranean Sea BioGeochemical Climatology (BGC-WMED) presented here is a product derived from in situ observations. Annual mean gridded nutrient fields for the period 1981–2017, and its sub-periods 1981–2004 and 2005–2017, on a horizontal 1/4° × 1/4° grid have been produced. The biogeochemical climatology is built on 19 depth levels and for the dissolved inorganic nutrients nitrate, phosphate and orthosilicate. To generate smooth and homogeneous interpolated fields, the method of the Variational Inverse Model (VIM) was applied. A sensitivity analysis was carried out to assess the comparability of the data product with the observational data. The BGC-WMED has then been compared to other available data products, i.e. the medBFM biogeochemical reanalysis of the Mediterranean Sea and the World Ocean Atlas18 (WOA18) (its biogeochemical part). The BGC-WMED product supports the understanding of inorganic nutrient variability in the western Mediterranean Sea, in space and in time, but can also be used to validate numerical simulations making it a reference data product.

scholarly journals Climatological distribution of dissolved inorganic nutrients in the western Mediterranean Sea (1981–2017)

2021 ◽  
Vol 13 (12) ◽  
pp. 5915-5949
Author(s):  
Malek Belgacem ◽  
Katrin Schroeder ◽  
Alexander Barth ◽  
Charles Troupin ◽  
Bruno Pavoni ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
World Ocean ◽  
Western Mediterranean ◽  
Inorganic Nutrients ◽  
Data Product ◽  
Western Mediterranean Sea ◽  
Dissolved Inorganic Nutrients ◽  
World Ocean Atlas ◽  
Nutrient Variability

Abstract. The Western MEDiterranean Sea BioGeochemical Climatology (BGC-WMED, https://doi.org/10.1594/PANGAEA.930447) (Belgacem et al., 2021) presented here is a product derived from quality-controlled in situ observations. Annual mean gridded nutrient fields for the period 1981–2017 and its sub-periods 1981–2004 and 2005–2017 on a horizontal 1/4∘ × 1/4∘ grid have been produced. The biogeochemical climatology is built on 19 depth levels and for the dissolved inorganic nutrients nitrate, phosphate and orthosilicate. To generate smooth and homogeneous interpolated fields, the method of the variational inverse model (VIM) was applied. A sensitivity analysis was carried out to assess the comparability of the data product with the observational data. The BGC-WMED was then compared to other available data products, i.e., the MedBFM biogeochemical reanalysis of the Mediterranean Sea and the World Ocean Atlas 2018 (WOA18) (its biogeochemical part). The new product reproduces common features with more detailed patterns and agrees with previous records. This suggests a good reference for the region and for the scientific community for the understanding of inorganic nutrient variability in the western Mediterranean Sea, in space and in time, but our new climatology can also be used to validate numerical simulations, making it a reference data product.

scholarly journals Particulate biogenic barium tracer of mesopelagic carbon remineralization in the Mediterranean Sea (PEACETIME project)

2020 ◽  
Author(s):  
Stéphanie H. M. Jacquet ◽  
Christian Tamburini ◽  
Marc Garel ◽  
Aurélie Dufour ◽  
France Van-Vambeke ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Western Mediterranean ◽  
Central Mediterranean ◽  
Particle Injection ◽  
Western Basin ◽  
Western Mediterranean Sea ◽  
Winter Convection ◽  
Carbon Remineralization ◽  
The Mediterranean ◽  
Heterotrophic Production

Abstract. We report on the sub-basins variability of particulate organic carbon (POC) remineralization in the central and western Mediterranean Sea during a late spring period (PEACETIME cruise). POC remineralization rates (MR) were estimated using the excess non-lithogenic particulate barium (Baxs) inventories in mesopelagic waters (100–1000 m) and compared with prokaryotic heterotrophic production (PHP). MR range from 25 ± 2 to 306 ± 70 mg C m−2 d−1. Results reveal larger MR processes in the Algerian (ALG) basin compared to the Tyrrhenian (TYR) and Ionian (ION) basins. Baxs inventories and PHP also indicates that significant remineralization occurs over the whole mesopelagic layers in the ALG basin in contrast to the ION and TYR basins where remineralization is mainly located in the upper 500 m horizon. We propose that this may be due to particle injection pumps likely driven by strong winter convection in the Western basin of the Mediterranean Sea. This implies significant differences in the remineralization length scale of POC in the central Mediterranean Sea relative to the western region.

scholarly journals Silica cycling in the ultra-oligotrophic eastern Mediterranean Sea

2014 ◽  
Vol 11 (15) ◽  
pp. 4211-4223 ◽  
Author(s):  
M. D. Krom ◽  
N. Kress ◽  
K. Fanning
Keyword(s):  
Mediterranean Sea ◽  
Silicic Acid ◽  
Deep Water ◽  
Phytoplankton Bloom ◽  
Eastern Mediterranean ◽  
Water Concentration ◽  
Western Mediterranean ◽  
Eastern Mediterranean Sea ◽  
Western Mediterranean Sea

Abstract. Although silica is a key plant nutrient, there have been few studies aimed at understanding the Si cycle in the eastern Mediterranean Sea (EMS). Here we use a combination of new measurements and literature values to explain the silicic acid distribution across the basin and to calculate a silica budget to identify the key controlling processes. The surface water concentration of ∼1 μM, which is unchanging seasonally across the basin, was due to the inflow of western Mediterranean Sea (WMS) water at the Straits of Sicily. It does not change seasonally because there is only a sparse population of diatoms due to the low nutrient (N and P) supply to the photic zone in the EMS. The concentration of silicic acid in the deep water of the western Ionian Sea (6.3 μM) close to the S Adriatic are an of formation was due to the preformed silicic acid (3 μM) plus biogenic silica (BSi) from the dissolution of diatoms from the winter phytoplankton bloom (3.2 μM). The increase of 4.4 μM across the deep water of the EMS was due to silicic acid formed from in situ diagenetic weathering of aluminosilicate minerals fluxing out of the sediment. The major inputs to the EMS are silicic acid and BSi inflowing from the western Mediterranean (121 × 109 mol Si yr−1 silicic acid and 16 × 109 mol Si yr−1 BSi), silicic acid fluxing from the sediment (54 × 109 mol Si yr−1) and riverine (27 × 109 mol Si yr−1) and subterranean groundwater (9.7 × 109 mol Si yr−1) inputs, with only a minor direct input from dissolution of dust in the water column (1 × 109 mol Si yr−1). This budget shows the importance of rapidly dissolving BSi and in situ weathering of aluminosilicate minerals as sources of silica to balance the net export of silicic acid at the Straits of Sicily. Future measurements to improve the accuracy of this preliminary budget have been identified.

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