Ventilation of deep waters in the Adriatic and Ionian Seas following changes in thermohaline circulation of the Eastern Mediterranean

2006 ◽  
Vol 31 ◽  
pp. 239-256 ◽  
Author(s):  
BB Manca ◽  
V Ibello ◽  
M Pacciaroni ◽  
P Scarazzato ◽  
A Giorgetti
Keyword(s):  
Thermohaline Circulation ◽  
Eastern Mediterranean ◽  
Deep Waters

scholarly journals Comparison of Hydrocarbon-Degrading Consortia from Surface and Deep Waters of the Eastern Mediterranean Sea: Characterization and Degradation Potential

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2246
Author(s):  
Georgia Charalampous ◽  
Efsevia Fragkou ◽  
Konstantinos A. Kormas ◽  
Alexandre B. De Menezes ◽  
Paraskevi N. Polymenakou ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Oil Spills ◽  
Eastern Mediterranean ◽  
Sole Source ◽  
Eastern Mediterranean Sea ◽  
Deep Waters ◽  
Degradation Rates ◽  
Polycyclic Aromatic ◽  
Set Up

The diversity and degradation capacity of hydrocarbon-degrading consortia from surface and deep waters of the Eastern Mediterranean Sea were studied in time-series experiments. Microcosms were set up in ONR7a medium at in situ temperatures of 25 °C and 14 °C for the Surface and Deep consortia, respectively, and crude oil as the sole source of carbon. The Deep consortium was additionally investigated at 25 °C to allow the direct comparison of the degradation rates to the Surface consortium. In total, ~50% of the alkanes and ~15% of the polycyclic aromatic hydrocarbons were degraded in all treatments by Day 24. Approximately ~95% of the total biodegradation by the Deep consortium took place within 6 days regardless of temperature, whereas comparable levels of degradation were reached on Day 12 by the Surface consortium. Both consortia were dominated by well-known hydrocarbon-degrading taxa. Temperature played a significant role in shaping the Deep consortia communities with Pseudomonas and Pseudoalteromonas dominating at 25 °C and Alcanivorax at 14 °C. Overall, the Deep consortium showed a higher efficiency for hydrocarbon degradation within the first week following contamination, which is critical in the case of oil spills, and thus merits further investigation for its exploitation in bioremediation technologies tailored to the Eastern Mediterranean Sea.

scholarly journals Tracers confirm downward mixing of Tyrrhenian Sea upper waters associated with the Eastern Mediterranean Transient

2010 ◽  
Vol 7 (4) ◽  
pp. 1533-1557
Author(s):  
W. Roether ◽  
J. E. Lupton
Keyword(s):  
Deep Water ◽  
Time Scale ◽  
Eastern Mediterranean ◽  
Western Mediterranean ◽  
The Other ◽  
Tyrrhenian Sea ◽  
Convective Mixing ◽  
Deep Waters ◽  
Major Process ◽  
Gibraltar Strait

Abstract. Observations of tritium and 3He in the Tyrrhenian Sea, 1987–2009, confirm the enhanced convective mixing of intermediate waters into the deep waters that has been noted and associated with the Eastern Mediterranean Transient in previous studies. Our evidence for the mixing rests on increasing tracer concentrations in the Tyrrhenian deep waters, accompanied by decreases in the upper waters, which are supplied from the Eastern Mediterranean. The downward transfer is particularly evident between 1987 and 1997. Later on, information partly rests on increasing tritium-3He ages; here we correct the observed 3He for contributions released from the ocean floor. The Tyrrhenian tracer distributions are fully compatible with data upstream of the Sicily Strait and in the Western Mediterranean. The tracer data show that mixing reached to the bottom and confirm a cyclonic nature of the deep water circulation in the Tyrrhenian. They furthermore indicate that horizontal homogenization of the deep waters occurs on a time scale of several years. Various features point to a reduced impact of Western Mediterranean Deep Water (WMDW) in the Tyrrhenian during the enhanced-convection period. This is an important finding because it implies less upward mixing of WMDW, which has been named a major process to enable the WMDW to leave the Mediterranean via the Gibraltar Strait. On the other hand, the TDW outflow for several years represented a major influx of enhanced salinity and density waters into the deep-water range of the Western Mediterranean.

scholarly journals Diagenetic control of nitrogen isotope ratios in Holocene sapropels and recent sediments from the Eastern Mediterranean Sea

2010 ◽  
Vol 7 (1) ◽  
pp. 1131-1165 ◽  
Author(s):  
J. Möbius ◽  
N. Lahajnar ◽  
K.-C. Emeis
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
Surface Sediments ◽  
Eastern Mediterranean ◽  
Nitrogen Isotope ◽  
Organic C ◽  
Deep Waters ◽  
Spatially Distributed ◽  
Temporal And Spatial ◽  
Recent Sediments

Abstract. The enhanced accumulation of organic matter in Eastern Mediterranean sapropels and their unusually depleted δ15N values have been attributed to either enhanced nutrient availability which led to elevated primary production and carbon sequestration or to enhanced organic matter preservation under anoxic conditions. In order to evaluate these two hypothesis we have determined Ba/Al ratios, amino acid composition, N and organic C concentrations and δ15N on sinking particles, surface sediments, eight spatially distributed core records of the youngest sapropel S1 (10-6 ka) and older sapropels (S5, S6) from two locations. These data suggest that (i) temporal and spatial variations in δ15N of sedimentary N are driven by different degrees of diagenesis at different sites rather than by changes in N-sources or primary productivity and (ii) that present day TOC export production would suffice to create a sapropel like S1 under conditions of deep-water anoxia. This implies that both enhanced TOC accumulation and δ15N depletion in sapropels were due to the absence of oxygen in deep waters. Thus preservation plays a major role for the accumulation of organic-rich sediments casting doubt the need of enhanced primary production for sapropel formation.

scholarly journals The Summer Circulation in the Gulf of Suez and Its Influence in the Red Sea Thermohaline Circulation

2017 ◽  
Vol 47 (8) ◽  
pp. 2047-2053 ◽  
Author(s):  
S. Sofianos ◽  
W. E. Johns
Keyword(s):  
Red Sea ◽  
Thermohaline Circulation ◽  
Water Mass ◽  
Cold Season ◽  
Gulf Of Suez ◽  
Summer Circulation ◽  
Deep Waters ◽  
Hydrological Structure ◽  
Water Formation ◽  
Northern Red Sea

AbstractThe Gulf of Suez is accepted as an important location for Red Sea Deep Water formation, but the circulation and exchange with the Red Sea around the year remains elusive. A summer cruise in the area gives the opportunity to investigate features of the summertime hydrological structure and exchange with the Red Sea. An inverse estuarine circulation and exchange with the Red Sea is evident. The topographic patterns of the gulf play an important role in the circulation. Two sills, one in midbasin and a second at the mouth of the gulf, inhibit the bottom flow, topographically trapping waters that were formed in the cold season. Although the water mass characteristics of the outflowing waters during the other seasons are not directly related to the deep waters, they can influence the water column structure of the northern Red Sea. A simple box model shows that their contribution can have a significant influence in the formation of the intermediate layer. A hypersaline (40.6 psu) but relatively warm (23°C) water mass, originating in the Gulf of Suez, is detected at intermediate depths (100–150 m), with a strong signal in the western part of the Red Sea.

scholarly journals The <sup>226</sup>Ra-Ba relationship in the North Atlantic during GEOTRACES-GA01

2017 ◽  
Author(s):  
Emilie Le Roy ◽  
Virginie Sanial ◽  
Matthew A. Charette ◽  
Pieter van Beek ◽  
François Lacan ◽  
...  
Keyword(s):  
North Atlantic ◽  
Thermohaline Circulation ◽  
Water Mass ◽  
Continental Margins ◽  
Strongly Correlated ◽  
North East ◽  
The North ◽  
Deep Waters ◽  
Similar Chemical ◽  
The North Atlantic

Abstract. We report detailed sections of radium-226 (226Ra, T1/2 = 1602 y) activities and barium (Ba) concentrations determined in the North Atlantic (Portugal-Greenland-Canada) in the framework of the international GEOTRACES program (GA01 section – GEOVIDE project, May–July 2014). Dissolved 226Ra and Ba are strongly correlated along the GA01 section, a pattern that reflects their similar chemical behavior. Since 226Ra and Ba have been widely used as tracers of water masses and ocean mixing, we investigated more thoroughly their behavior in this crucial region for thermohaline circulation taking advantage of the contrasting biogeochemical patterns existing along the GA01 section. We used an Optimum Multiparameter (OMP) analysis to distinguish the relative importance of physical transport (water mass mixing) from non-conservative processes (sedimentary, river, or hydrothermal inputs; uptake by particles, and dissolved-particulate dynamics) on the 226Ra and Ba distributions in the North Atlantic. Results show that 72 % of the 226Ra and 68 % of the Ba can be explained by conservative mixing along the section and therefore, they can be considered as conservative tracers of water mass transport in the ocean interior. However, regions where 226Ra and Ba displayed non-conservative behavior were also identified, mostly at the ocean boundaries (seafloor, continental margins, and surface waters). Elevated 226Ra and Ba concentrations found in deep waters of the West European Basin reflect that lower North East Atlantic Deep Water (NEADWl) accumulates excess 226Ra and Ba from sediment diffusion during transport. In the upper 1500 m, deficiencies in 226Ra and Ba are likely explained by their incorporation in planktonic siliceous shells, or in barite (BaSO4) (Bishop, 1988). Finally, since Ba and 226Ra display different source terms (mostly deep-sea sediments for 226Ra and rivers for Ba), strong decoupling between 226Ra and Ba were observed at the land-ocean boundaries. This is especially true in the shallow stations near the coasts of Greenland and Newfoundland where high 226Ra / Ba ratios at depth reflect the diffusion of 226Ra from sediment and low 226Ra / Ba ratios in the upper water column reflect the input of Ba associated with meteoric waters.

scholarly journals Lithistid Demosponges of Deep-Water Origin in Marine Caves of the North-Eastern Mediterranean Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Andrzej Pisera ◽  
Vasilis Gerovasileiou
Keyword(s):  
Deep Water ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Western Mediterranean ◽  
Elevated Concentration ◽  
The North ◽  
Deep Waters ◽  
Marine Caves ◽  
North Eastern ◽  
Tropical Areas

Desmas-bearing demosponges known as lithistids have heavily silicified skeleton and occur typically in bathyal environments of warm and tropical areas but may be found in certain shallow marine caves. Here we report, for the first time two lithistid species, i.e., Neophrissospongia endoumensis, and N. cf. nana, that were earlier known from Western Mediterranean marine caves, from four marine caves in the north-eastern Mediterranean, and their congener Neophrissospongia nolitangere from deep waters (ca. 300 m) of the Aegean Sea. All marine caves, and sections within these caves, where lithistids occur, have freshwater springs. We interpret this surprising association between lithistids and freshwater input by elevated concentration of silica in water in cave sections where such springs occur, being 8–11 times higher in comparison with shallow water outside caves, and comparable to that of deep waters, that promoted lithistids’ development. One of the studied caves harbored an abundant population of N. endoumensis which formed large masses. The age estimation of these lithistids, based on known growth rate of related deep-water sponges, suggest that they could be approximately 769–909 years old in the case of the largest specimen observed, about 100 cm large. These sponges could have colonized the caves from adjacent deep-water areas not earlier than 7,000–3,000 years ago, after the last glaciation, because earlier they were emerged. High variability of spicules, especially microscleres, and underdevelopment of megascleres may be related to silicic acid concentration.

scholarly journals Performance of the Adriatic Sea and Coast (AdriSC) climate component – a COAWST V3.3-based coupled atmosphere–ocean modelling suite: atmospheric dataset

2021 ◽  
Vol 14 (6) ◽  
pp. 3995-4017
Author(s):  
Cléa Denamiel ◽  
Petra Pranić ◽  
Damir Ivanković ◽  
Iva Tojčić ◽  
Ivica Vilibić
Keyword(s):  
Climate Models ◽  
Thermohaline Circulation ◽  
Climate Model ◽  
Adriatic Sea ◽  
Eastern Mediterranean ◽  
Regional Climate ◽  
Regional Climate Models ◽  
Evaluation Study ◽  
Ocean Model ◽  
Climate Studies

Abstract. In this evaluation study, the coupled atmosphere–ocean Adriatic Sea and Coast (AdriSC) climate model, which was implemented to carry out 31-year evaluation and climate projection simulations in the Adriatic and northern Ionian seas, is briefly presented. The kilometre-scale AdriSC atmospheric results, derived with the Weather Research and Forecasting (WRF) 3 km model for the 1987–2017 period, are then thoroughly compared to a comprehensive publicly and freely available observational dataset. The evaluation shows that overall, except for the summer surface temperatures, which are systematically underestimated, the AdriSC WRF 3 km model has a far better capacity to reproduce surface climate variables (and particularly the rain) than the WRF regional climate models at 0.11∘ resolution. In addition, several spurious data have been found in both gridded products and in situ measurements, which thus should be used with care in the Adriatic region for climate studies at local and regional scales. Long-term simulations with the AdriSC climate model, which couples the WRF 3 km model with a 1 km ocean model, might thus be a new avenue to substantially improve the reproduction, at the climate scale, of the Adriatic Sea dynamics driving the Eastern Mediterranean thermohaline circulation. As such it may also provide new standards for climate studies of orographically developed coastal regions in general.

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