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| Levantine Deep Water | |
|---|---|
| Name | Levantine Deep Water |
| Region | Eastern Mediterranean Sea |
| Formation area | Levantine Basin |
| Depth | ~1500–2500 m |
| Salinity | high |
| Temperature | relatively warm |
| Density | high |
Levantine Deep Water The Levantine Deep Water is a water mass occupying deep layers of the eastern Mediterranean Sea formed by dense outflow from the Levantine Basin. It influences circulation across the Mediterranean, connects with waters in the Aegean Sea and Ionian Sea, and affects stratification, biogeochemistry, and deep ecosystems in the region.
The Levantine Deep Water is defined as the dense, warm, saline deep-water layer produced in the Levantine Basin, distinct from the Adriatic Sea-derived Adriatic Deep Water and the Aegean Sea-derived deep waters. It is characterized by relatively high salinity and temperature compared with other Mediterranean deep waters, sits below the Intermediate water and above bottom sediments, and contributes to the Mediterranean thermohaline structure that connects via the Strait of Gibraltar to the Atlantic Ocean and via the Suez Canal region to the Red Sea exchange processes.
Levantine Deep Water forms during intense evaporation and dense water formation events in the Levantine Basin and marginal seas such as the Aegean Sea and the Cretan Sea, influenced by atmospheric forcing from systems like the Saharan Air Layer, North Atlantic Oscillation, and regional cyclones associated with the Eastern Mediterranean climate. Dense water spills and cascading processes along continental slopes involve interactions with current systems including the Atlantic Jet entering through the Strait of Gibraltar and the eastward-flowing Levantine Current, and exchange with the Ionian Sea via the Otranto Channel. Episodic convective events recorded during campaigns by institutions such as the National Observatory of Athens, Istituto Nazionale di Geofisica e Vulcanologia, and Institute of Oceanology research vessels show ventilation pathways that ventilate abyssal layers and modulate Mediterranean overturning circulation.
Physically, the Levantine Deep Water exhibits temperatures higher than typical deep waters of the North Atlantic and salinities among the highest in the global ocean, with densities that drive its descent and lateral spreading. Chemically, it carries nutrient and oxygen signatures traced by parameters measured by programs like World Ocean Circulation Experiment and Mediterranean Science Commission cruises, including low phosphate, variable nitrate, elevated alkalinity, and anthropogenic tracers such as chlorofluorocarbons documented by teams from Scripps Institution of Oceanography and National Oceanography Centre. Its properties evolve through mixing with Eastern Mediterranean Transient-affected waters and water masses influenced by riverine inputs from the Nile River and by processes near the Levantine coast.
Although deep and aphotic, the Levantine Deep Water sustains benthic communities including endemic megafauna and prokaryotic assemblages studied by researchers at Mediterranean Institute of Oceanography and museums like the Natural History Museum, London. It supplies oxygen and organic matter fluxes that regulate deep-sea fauna distributions recorded in surveys by the Hellenic Centre for Marine Research and the University of Barcelona; trophic links involve detritivores, scavengers, and microbial consortia that include archaeal and bacterial taxa catalogued in databases curated by European Molecular Biology Laboratory partners. Changes in deep-water properties impact habitat suitability for species noted by conservation organizations such as the International Union for Conservation of Nature.
Levantine Deep Water interacts with regional features like the Cretan Sea gyres, the Antikythira Strait exchanges, and the Mediterranean Outflow Water dynamics that influence the Gibraltar Arc and adjacent Atlantic inflow. Coupling with the Eastern Mediterranean Transient episodes has been documented to rearrange deep stratification and affect teleconnections to the Black Sea via the Dardanelles and Bosphorus pathways. International collaborations among agencies including UNESCO's Intergovernmental Oceanographic Commission, European Commission projects, and national hydrographic offices coordinate observation arrays and modelling of these interactions.
Human activities influence Levantine Deep Water through climate change driven by greenhouse gas emissions discussed in Intergovernmental Panel on Climate Change assessments, altered precipitation affecting the Nile River runoff, and localized impacts from marine traffic through the Suez Canal and offshore hydrocarbon exploration licensed by governments and companies regulated under frameworks such as the Barcelona Convention. Monitoring relies on moorings, autonomous floats from programs like Argo adapted for the Mediterranean, ship-based CTD sections by institutes including CNRS and Hellenic Centre for Marine Research, and remote sensing support from satellites operated by European Space Agency, with data assimilation into models developed by groups at Mercator Ocean and NOAA.
Sediment cores from the Levantine Basin recovered by expeditions such as DSDP and IODP have preserved signals of past Levantine Deep Water variation via isotopic proxies (oxygen isotopes tied to Milankovitch cycles) and biomarkers analyzed by laboratories at Lamont–Doherty Earth Observatory and Bologna University. Paleoclimate reconstructions link changes in deep-water formation to events like the Younger Dryas-era hydrological shifts, Holocene sapropel layers correlated with Nile discharge and African monsoon variability, and broader Mediterranean responses to glacial–interglacial cycles, informing models of Mediterranean overturning recorded in institutional datasets from PAGES and national paleoceanographic programs.