Coastal climatology of the North-Western Mediterranean area for long-term and short-term risk assessment.

Author(s):  
Carlo Brandini ◽  
Stefano Taddei ◽  
Valentina Vannucchi ◽  
Michele Bendoni ◽  
Bartolomeo Doronzo ◽  
...  

<p>In this work we present the results obtained through a dynamic downscaling of the ERA5 reanalysis dataset (hindcast) of ECMWF, using high-resolution meteorological and wave models defined on unstructured computation grids along the Mediterranean coasts, with a particular focus on the North-Western Mediterranean area. Downscaling of the ERA5 meteorological data is obtained through the BOLAM and MOLOCH models (up to a resolution of 2.5 km) which force an unstructured WW3 model with a resolution of up to 500 m along the coast. Models were validated through available meteorological stations, wave buoy data and X-band wave radars, the latter for the purposes of wave spectra validation.</p><p>On the one hand, this allowed, by extracting the time series of some attack parameters of the waves along the coast, and according to the type of coast (rocky coasts, sandy coasts, coastal structures etc.), to compute the return periods and to characterize the impact of any individual storm. On the other hand, it is possible to highlight some trends observed in the last 30 years, during which recent research is showing an increasing evidence  of some changes in global circulation at regional to local scales. These changes also include effects of wind rotation, wave regimes, storm surges, wave-induced coastal currents and coastal morphodynamics. For example, in the North-Western Mediterranean extreme events belonging to cyclonic weather-types circulation with stronger S-SE components (like the storm of October 28-30th 2018 and many others), rather than events associated with perturbations of Atlantic origin and zonal circulation, are becoming more frequent. These long-term wind/wave climate trends can have consequences not only in the assessment of long-term risk due to main morphodynamic variations (ie. coastal erosion), but also in the short-term risk assessment.</p><p>This work was funded by the EU MAREGOT project (2017-2020) and ECMWF Special Project spitbran  “Evaluation of coastal climate trends in the Mediterranean area by means of high-resolution and multi-model downscaling of ERA5 reanalysis” (2018-2020).</p>

2017 ◽  
Vol 58 (2) ◽  
pp. 313-323
Author(s):  
Luca Lanteri ◽  
Laura Castellano ◽  
Fulvio Garibaldi

On 9th September 2015 the head of a shark belonging to the genus Alopias, was landed at Camogli harbour in the Ligurian Sea (North Western Mediterranean). The specimen has been caught 16 miles far from the coast (44° 06’ N, 008° 57’ E) as by-catch of the mesopelagic swordfish longline, but only the head was recovered, due to the predatory/scavenging activity by other shark specimens. The specimen was a female of big-eye thresher shark Alopias superciliosus a highly migratory species worldwide distributed in tropical and temperate waters but rarely caught in the Mediterranean Sea. The present record is the northenmost reported for this species in the Mediterranean area and the sixth in Italian waters.


2008 ◽  
Vol 40 (3) ◽  
pp. 359-377 ◽  
Author(s):  
E. LUCCHETTI ◽  
M. TASSO ◽  
P. PIZZETTI ◽  
S. DE IASIO ◽  
G. U. CARAVELLO

SummaryThis paper compares the structures of the surnames of 75 municipal populations living in six north-western Mediterranean regions. Its purpose is to unravel the relations between the local populations in Corsica and Sardinia and the links between these populations and those living in the Italian and French continental territory. On the basis of the matrix of similarity of surnames, some topological representations have been drafted showing the above-mentioned relations between populations under the light of their geographical position, their recent history and studies of genetic analysis. Corsica has an eterogeneous surname structure and evident similarity of the north with Tuscany and some centres of continental France. When only the populations of Sardinia were taken into consideration, it emerged that they differ among each other in relation to their geographical position and their history; when, instead, they were considered in relation to other populations outside the island, it was possible to observe that they form a highly different cluster. This study also identified many differences in the analysed geographical areas of Sardinia. In the minor islands – Elba, Giglio, Capraia – the structure of the surnames has a Tuscan origin as well as some similarity with other geographically distant areas, as in the case of the island of Giglio, if compared with some communities of Liguria.


2020 ◽  
Vol 16 (1) ◽  
pp. 283-298 ◽  
Author(s):  
Pierre Sabatier ◽  
Marie Nicolle ◽  
Christine Piot ◽  
Christophe Colin ◽  
Maxime Debret ◽  
...  

Abstract. North Africa is the largest source of mineral dust on Earth, which has multiple impacts on the climate system; however, our understanding of decadal to centennial changes in African dust emissions over the last few millenniums is limited. Here, we present a high-resolution multiproxy analysis of sediment core from high-elevation Lake Bastani, on the island of Corsica, to reconstruct past African dust inputs to the western Mediterranean area over the last 3150 cal BP. Clay mineralogy with palygorskite and a clay ratio associated with geochemical data allow us to determine that terrigenous fluxes are almost exclusively related to atmospheric dust deposition from the western Sahara and Sahel areas over this period. High-resolution geochemical contents provide a reliable proxy for Saharan dust inputs with long-term (millennial) to short-term (centennial) variations. Millennial variations have been correlated with the long-term southward migration of the Intertropical Convergence Zone (ITCZ), with an increase in dust input since 1070 cal BP. This correlation suggests a strong link with the ITCZ and could reflect the increased availability of dust sources to be mobilized with an increase in wind and a decrease in precipitation over western and North Africa. For centennial to decadal variations, wavelet analyses show that since 1070 cal BP, the North Atlantic Oscillation (NAO) has been the main climatic forcing, with an increase in Saharan dust input during the positive phase, as suggested by previous studies over the last decades. However, when the ITCZ is in a northern position, before 1070 cal BP, wavelet analyses indicate that total solar irradiance (TSI) is the main forcing factor, with an increase in African dust input during low TSI. With climate reanalysis over the instrumental era, during low TSI we observe a significant negative anomaly in pressure over Africa, which is known to increase the dust transport. These two climatic forcing factors (NAO, TSI) modulate Saharan dust inputs to the Mediterranean area at a centennial timescale through changes in wind and transport pathways.


2014 ◽  
Vol 89 (1-2) ◽  
pp. 305-323 ◽  
Author(s):  
Thierry Thibaut ◽  
Aurélie Blanfuné ◽  
Laurent Markovic ◽  
Marc Verlaque ◽  
Charles F. Boudouresque ◽  
...  

2017 ◽  
Author(s):  
Pierre Marrec ◽  
Andrea M. Doglioli ◽  
Gérald Grégori ◽  
Mathilde Dugenne ◽  
Alice Della Penna ◽  
...  

Abstract. Fine-scale physical structures and ocean dynamics strongly influence and regulate biogeochemical and ecological processes. These processes are particularly challenging to describe and understand because of their ephemeral nature. The OSCAHR (Observing Submesoscale Coupling At High Resolution) campaign has been conducted in fall 2015 in which, a fine-scale structure in the North Western Mediterranean Ligurian subbasin was pre-identified using both satellite and numerical modeling data. Along the ship track, various variables were measured at the surface (temperature, salinity, chlorophyll-a and nutrients concentrations) with ADCP current velocity. We also deployed a new model of CytoSense automated flow cytometer (AFCM) optimized for small and dim cells, for near real-time characterization of surface phytoplankton community structure of surface waters with a spatial resolution of few km and a hourly temporal resolution. For the first time with this type of AFCM we were able to resolve Prochlorococcus and Synechococcus picocyanobacteria. The vertical physical dynamics and biogeochemical properties of the studied area were investigated by continuous high resolution CTD profiles thanks to a moving vessel profiler (MVP) during the vessel underway associated to a 1-m vertical resolution pumping system deployed during fixed stations. The observed fine-scale feature presented a cyclonic structure with a relatively cold core surrounded by warmer waters. Surface waters were totally depleted in nitrate and phosphate. In addition to the doming of the isopycnals by the cyclonic circulation, an intense wind event induced Ekman pumping. The upwelled subsurface cold nutrient-rich water fertilized surface waters, characterized by an increase in Chl-a concentration. Prochlorococcus, pico- and nano-eukaryotes were more abundant in cold core waters while Synechococcus dominated in warm boundary waters. Nanoeukaryote were the main contributors (> 50 %) in terms of pigment content (FLR) and biomass. Biological observations based on the mean cell's red fluorescence recorded by AFCM combined with physical properties of surface waters suggest a distinct origin for two warm boundary waters. Finally, the application of a matrix growth population model based on high-frequency AFCM measurements in warm boundary surface waters provides estimates of in-situ growth rate and apparent net primary production for Prochlorococcus (μ = 0.21 d−1, NPP = 0.11 mgC m−3 d−1) and Synechococcus (μ = 0.72 d−1, NPP = 2.68 mgC m−3 d−1), which corroborate their opposite surface distribution pattern. The innovative adaptive strategy applied during OSCAHR with a combination of several multidisciplinary and complementary approaches involving high-resolution in-situ observations and sampling, remote-sensing and model simulations provided a deeper understanding of the marine biogeochemical dynamics through the first trophic levels.


2021 ◽  
Vol 18 (3) ◽  
pp. 937-960
Author(s):  
Caroline Ulses ◽  
Claude Estournel ◽  
Marine Fourrier ◽  
Laurent Coppola ◽  
Fayçal Kessouri ◽  
...  

Abstract. The north-western Mediterranean deep convection plays a crucial role in the general circulation and biogeochemical cycles of the Mediterranean Sea. The DEWEX (DEnse Water EXperiment) project aimed to better understand this role through an intensive observation platform combined with a modelling framework. We developed a three-dimensional coupled physical and biogeochemical model to estimate the cycling and budget of dissolved oxygen in the entire north-western Mediterranean deep-convection area over the period September 2012 to September 2013. After showing that the simulated dissolved oxygen concentrations are in a good agreement with the in situ data collected from research cruises and Argo floats, we analyse the seasonal cycle of the air–sea oxygen exchanges, as well as physical and biogeochemical oxygen fluxes, and we estimate an annual oxygen budget. Our study indicates that the annual air-to-sea fluxes in the deep-convection area amounted to 20 molm-2yr-1. A total of 88 % of the annual uptake of atmospheric oxygen, i.e. 18 mol m−2, occurred during the intense vertical mixing period. The model shows that an amount of 27 mol m−2 of oxygen, injected at the sea surface and produced through photosynthesis, was transferred under the euphotic layer, mainly during deep convection. An amount of 20 mol m−2 of oxygen was then gradually exported in the aphotic layers to the south and west of the western basin, notably, through the spreading of dense waters recently formed. The decline in the deep-convection intensity in this region predicted by the end of the century in recent projections may have important consequences on the overall uptake of atmospheric oxygen in the Mediterranean Sea and on the oxygen exchanges with the Atlantic Ocean, which appear necessary to better quantify in the context of the expansion of low-oxygen zones.


2019 ◽  
Vol 28 ◽  
pp. 102050 ◽  
Author(s):  
Marzia Gabriele ◽  
Fabien Convertini ◽  
Chrystele Verati ◽  
Bernard Gratuze ◽  
Suzanne Jacomet ◽  
...  

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