Abundance and Temporal Distribution of Beach Litter on the Coast of Ceuta (North Africa, Gibraltar Strait)

Twelve beaches located in Ceuta (Spain) were studied from February to April 2019 to assess litter amounts (expressed as number of items), categories and temporal distribution. At each beach, three surveys were conducted, i.e., one per month (i.e., 36 in total). Selected beaches covered urban (7), rural (2) and remote (3) bathing areas. Plastic represented the dominant material, i.e., 35.2% of all debris, followed by glass (18.2%), pottery/ceramics (14.6%), wood (11.4%), metal (11.4%), paper/cardboard (4.8%), cloth (3.5%), rubber (0.7%), organic (0.3%) and other materials (0.1%). The Clean Coast Index was calculated to classify beaches in five categories for evaluating the cleanliness level of the coast observed at each survey: “Very Clean” (7 surveys), “Clean” (10), “Moderately Dirty” (8), “Dirty” (2) and “Extremely Dirty” (9). Litter occurrence was assessed by the Litter Grade methodology, which allowed to classify beaches in four grades: “A”: very good (0); “B”: good (4); “C”: fair (7); and “D”: poor (25). In a few surveys, some beaches were considered “good”, but their management should not be ignored because in other surveys those beaches reached fair and poor scores. Several potentially harmful litter items were related to beach users. Severe eastern storms removed litter at many of the beaches investigated and favored accumulation at others. Data analysis shows significant differences in litter abundance with respect to site, beach typology and the presence of cleaning operations but no important differences between the studied months. Rural beaches recorded the most litter, followed by urban and remote beaches. All beaches require immediate and more appropriate management actions to improve their environmental status.

De cerca medieval islámica a frente abaluartado: génesis y evolución del Frente de Tierra de Ceuta

From Medieval Islamic Wall to Bastioned Land Front: Genesis and evolution of the Land Front of CeutaCeuta is built on a peninsula at the southern shore of the Strait of Gibraltar. It’s a strategic point for communications between the Mediterranean Sea and the Atlantic Ocean and between two continents: Europe and Africa. As Ceuta ships rule the Gibraltar Strait in Medieval and Modern Ages, main defensive efforts were tuned of to Land Front. Consequently, in 950 ‘Abd al-Rahman III built a new fence in order to protect the madina reusing Roman and Byzantine fortifications. Although repaired and enlarged by Almohads, Marinids, and Portuguese, these walls and towers protected the Land Front of Ceuta until the sixteenth century. But, at this moment, pirobalistic artillery development had made this defensive device obsolete and a new bastioned front, an early and outstanding example of the new Renaissance ideas for the defense of the cities, was built. Archival documents, cartographic sources, etc., let us follow the main lines of this evolution. Recently, an archaeological research project has added new data on how this evolution, from Medieval to Renaissance fortifications, took place.

A geochemical approach to reconstructing sediment dynamic and thermohaline circulation in the western Mediterranean over the last deglaciation

<p>The westernmost Mediterranean basins is an exceptional and sensitive region for reconstructing past climate and oceanographic conditions. Geochemical signatures from diverse sediment records in the Alboran Sea and the Balearic basin, in particular, Ti/ca and Fe/Ca ratios, as proxies for the relative abundance of siliciclastic vs. carbonate fraction, have been investigated. These have also been compared with other previously studied records from the western Mediterranean and the Gulf of Cadiz to elucidate the mechanisms triggering the relative variations between the carbonate and siliciclastic fraction. The lithogenic fraction represents around 70% of the sediment in the Alboran basin, which mainly derived from riverine discharge and coastal erosion. Resuspension of fine sediment particles from the slope and the sea floor by bottom-water currents is a relevant process in these basin. The studied records are located between 850 m and 2400 m below the sea level, under the influence of the Western Mediterranean Deep Water (WMDW), which is restricted to a water depth below 500-600 m and to the Moroccan margin. This deep current is formed in the Gulf of Lion, when the superficial and intermediate waters sink by a density increase, and flow out the basin through the Gibraltar Strait, contributing to the Mediterranean Outflow Water (MOW) along with the Levantine Intermediate Water (LIW). The WMDW formation is enhanced during cold and arid periods. The comparison with other previously studied records, support important variations of the mechanisms triggering the relative contribution of carbonate and siliciclastic fractions during the last 20,000 yrs. The, Ti/Ca and Fe/Ca ratios increased during cold and arid periods, such as the Heinrich Event 1 (HE1) and the Younger Dryas (YD). These changes are more prominent in the Balearic basin and the eastern Alboran basin than in the western Alboran basin and the Gulf of Cadiz. Thus, we hypothesized that the increase in the Ti/Ca and Fe/Ca ratios is rather related to the enhanced WMDW production and more remobilization of fine siliciclastic sediments.</p>

Revision of the Alboran sea Tortonian-Pliocene record: possible new insights on Mediterranean-Atlantic connectivity during the Messinian Salinity Crises

<p>In August of 1970, during Mediterranean Sea Leg 13, when the Glomar challenger ventured Mediterranean waters, nobody was expecting to run into one of the most exiting scientific discoveries regarding the Mediterranean Sea evolution. Cores and seismic surveys made possible the discovery of a basin-wide Messinian evaporitic deposit buried beneath the deep-sea Pliocene sediments which was attributed to the Messinian Salinity Crises (MSC) already known and studied in onshore outcrops in the Apennines. Now, 50 years later the debate regarding the conditions and timing of the deposition of this salt giant is still ongoing as many theories are still open and in search for validating proof.</p><p>One of the main open questions certainly regards the base level drop during the MSC and the location, efficiency and dynamics of the Mediterranean – Atlantic connectivity. The Mediterranean level is thought to have dropped somewhere between a moderate 200 m up to an extreme high amplitude oscillation of 1500 m while according to different schools of thought the watergate to the Atlantic is considered as completely closed, intermittently open or to have been always open during the MSC. Gibraltar strait is the main candidate for a possible gateway during this time interval (5.96-5.33 Ma) as well as the leading cause of the re-establishment of open marine conditions in the Mediterranean. Consequently, understanding its evolution and opening is fundamental to endorse any of the MSC theories and a thorough investigation of the Messinian and early Pliocene sedimentological record of basins in its proximity is highly needed.</p><p>In this optic, the Alboran Sea is the place where many of those answers lie and its worth of further exploration. In the hope of a new oceanographic expedition in the near future, an effort should be made towards gathering and re-interpreting all the available data. We propose a refined planktonic foraminifer chronology of the Alboran DSDP and ODP sites 976B, 121 and 978A with a careful characterization of the main MSC facies that will clarify to a certain extent the MSC expression and the degree of Atlantic water influence in the Alboran basin.</p><p> </p>

“Climate shift of the Atlantic Meridional Overturning Circulation (AMOC) in Reanalyses (ORAS5): possible causes, and sources of uncertainty”

<p>We present preliminary results and insights from the analysis of the ensemble of  Oceanic Reanalysis System 5 (ORAS5), produced by the European Center for Medium Weather Forecast (ECMWF), which reconstruct ocean’s past history from 1979 to 2018, with monthly means temporal and spatial resolution of 0.25° and 75 vertical levels.</p><p>We focused on the AMOC, which can be considered as one of the main drivers of  the Earth’s Climate System, and we observed that the strength at 26.5°N presents a shift in the mean of about 5 Sverdrup in the period 1995-2000 which can be considered as a climate tipping point.  </p><p>We aim to investigate the causes of this reduction and propose three mechanisms responsible for the observed AMOC volume transport reduction: the Gulf Stream Separation path, changes of the Mediterranean Outflow Water (MOW) and the North Atlantic Deep Water (NADW) formation processes in the Labrador Sea respectively.</p><p> </p><p>The Gulf Stream Separation path is investigated by visualizing the barotropic stream function averaged over two periods, before and after the 1995-2000. In particular it is possible to detect a shift in the direction of the barotropic currents, which is enhanced further by seasonal climatology analysis. In the first period (greater volume transport), patterns are more intense, and the Gulf Stream reach higher latitudes, allowing for a more vigorous deep water formation in the Labrador Sea than in the second period. </p><p> </p><p>Moreover, we observe the AMOC volume transport reduction at 26.5°N accompanied with a reduction in the heat fluxes over the Labrador Sea. We think this reduction of heat fluxes has a cascade effect on horizontal averages for temperature, salinity, and potential density profiles, which are manifestations of less deep water production in the Labrador Sea, that can ultimately drive the AMOC weakening. </p><p><br><br></p><p>Finally, the Mediterranean Sea has experienced, in the last decades, a general warming trend, in particular of deep water temperatures since the mid-1980s. It is well known that this warming induce a large variability in the hydrological characteristics of the MOW becoming more likely one key factor driving the AMOC variability observed in ORAS5. In fact, there’s a larger ensemble spread in both the temperature and salinity climatological profiles at 40°N, i. e. in correspondence of the Gibraltar Strait and Gulf of Cadiz.</p><p>This analysis highlights the high sensitivity of the MOW to perturbations producing the different ensemble members of ORAS5.</p><p>Our hypothesis is that the nonlinear interaction between these three mechanisms  could have a complex feedback on the AMOC variability.</p><p> </p><p>In conclusion, our preliminary results brought out the relevance of the deep water formation process in the Labrador Sea, the MOW and the Gulf Stream path as the main sources of the AMOC variability and stability. Besides,  our analysis points out the need for further studies, e. g. increasing resolution at the Straits (like Gibraltar Strait), investigating correlations with the variability of the subpolar gyre and developing conceptual studies, using Intermediate Complexity Models interpreted under the lens of Dynamical System Theory and Statistical Mechanics.</p>

Integrating multiple satellite observations into a coherent dataset to monitor the full water cycle – application to the Mediterranean region

The Mediterranean region is one of the climate hotspots where the climate change impacts are both pronounced and documented. The HyMeX (Hydrometeorological Mediterranean eXperiment) aims to improve our understanding of the water cycle from the meteorological to climate scales. However, monitoring the water cycle with Earth observations (EO) is still a challenge: EO products are multiple, and their utility is degraded by large uncertainties and incoherences among the products. Over the Mediterranean region, these difficulties are exacerbated by the coastal/mountainous regions and the small size of the hydrological basins. Therefore, merging/integration techniques have been developed to reduce these issues. We introduce here an improved methodology that closes not only the terrestrial but also the atmospheric and ocean budgets. The new scheme allows us to impose a spatial and temporal multi-scale budget closure constraint. A new approach is also proposed to downscale the results from the basin to pixel scales (at the resolution of 0.25∘). The provided Mediterranean WC budget is, for the first time, based mostly on observations such as the GRACE water storage or the netflow at the Gibraltar Strait. The integrated dataset is in better agreement with in situ measurements, and we are now able to estimate the Bosporus Strait annual mean netflow.