Levantine Intermediate Water

Levantine Intermediate Water
Name	Levantine Intermediate Water
Type	Water mass
Region	Levantine Sea, Eastern Mediterranean Sea
Formation	Late winter convection in the Levantine Basin
Depth	150–400 m (typical)
Salinity	38.9–39.2 PSU (typical)
Temperature	13–16 °C (typical)
Density	σθ ≈ 29.1–29.3 kg m−3

Levantine Intermediate Water Levantine Intermediate Water is an intermediate water mass formed in the eastern Mediterranean Sea that ventilates mid-depth layers of the basin and exchanges with the Adriatic Sea, Aegean Sea, and western Mediterranean through straits and gyres. It plays a key role in the thermohaline structure influencing circulation features such as the Mediterranean Outflow Water, the Atlantic Meridional Overturning Circulation, and the basin-scale thermohaline circulation within the Mediterranean.

Introduction

Levantine Intermediate Water originates in the Levantine Basin and is identifiable by its elevated salinity and intermediate temperature between surface waters and deeper Mediterranean Deep Water masses. It interacts with well-known regions and features including the Strait of Gibraltar, the Ionian Sea, and the Cyprus Eddy, and is monitored by programs and institutions like the Mediterranean Forecasting System, the Intergovernmental Oceanographic Commission, and national institutes such as the Hellenic Centre for Marine Research.

Formation and Characteristics

Formation occurs during late-winter convective events in the Levantine Sea and adjacent basins driven by surface cooling, evaporation over the Eastern Mediterranean, and interaction with shelf processes near the Nile Delta and Syrian coast. Characteristic properties include high salinity (often >38.9 PSU), intermediate potential temperature (≈13–16 °C), and neutral density surfaces around σθ ≈29.1–29.3 kg m−3; these parameters are referenced in studies from organizations such as the National Oceanic and Atmospheric Administration, the European Union research programs, and the National Center for Atmospheric Research. Mixing with overlying Atlantic Water and underlying deep waters such as Western Mediterranean Deep Water and Levantine Deep Water modifies its signature along pathways connecting to the Tyrrhenian Sea, Sicilian Strait, and surrounding basins.

Distribution and Pathways

Levantine Intermediate Water spreads westward from formation sites across the Ionian Sea toward the Sicily Channel and into the western Mediterranean Sea via pathways influenced by mesoscale features like the Alboran Gyre, the Balearic Current, and the Libyan Current. Key exchanges occur through straits and basins including the Strait of Sicily, the Maltese Channel, and the Adriatic Sea via the Otranto Strait. Its advection is modulated by seasonal winds such as the Mistral, the Sirocco, and the Etesian winds, as well as by inflows associated with the Eastern Mediterranean Transient and events recorded by observational networks like Argo and the Mediterranean Ocean Observing System.

Role in Mediterranean Circulation and Climate

Levantine Intermediate Water contributes to the Mediterranean’s layered structure, influencing the formation and renewal of Mediterranean Outflow Water that interacts with the North Atlantic Current and can affect North Atlantic Oscillation teleconnections. It partakes in salt and heat redistribution that affects regional climate patterns over Southern Europe, North Africa, and the Levantine coast, and is implicated in modulating air–sea fluxes measured by campaigns involving the European Centre for Medium-Range Weather Forecasts, the Copernicus Marine Service, and research cruises by institutes such as the Institut français de recherche pour l'exploitation de la mer.

Biogeochemical Properties and Ecological Impact

Levantine Intermediate Water carries distinct nutrient and dissolved oxygen signatures that influence biogeochemical cycles tied to regions like the Pelagie Islands, the Aegean Sea basins, and the Cretan Sea. Its intermediate position affects vertical nutrient supply to euphotic zones near the Sicilian Channel and shapes habitats for organisms documented by projects at the SZN Stazione Zoologica Anton Dohrn, the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, and the Institute of Marine Research. Tracer studies using chlorofluorocarbons, radiocarbon, and stable isotopes by laboratories at the Scripps Institution of Oceanography and the Max Planck Institute for Meteorology help quantify its role in carbon transport and oxygenation affecting benthic communities, fisheries managed under frameworks like the General Fisheries Commission for the Mediterranean.

Observations and Measurement Methods

Observation employs moored arrays, hydrographic sections, and autonomous platforms including Argo floats, gliders operated by the NATO Undersea Research Centre, and shipboard CTD casts from research vessels such as the RV Pelagia, FS Meteor, and RV Mare Nostrum. Remote-sensing products from the Copernicus Programme and assimilative models from the Mediterranean Forecasting System and the HYCOM framework complement in-situ salinity–temperature profiles, oxygen sensors, nutrient analyses, and tracer experiments conducted by collaborative efforts between the European Marine Observation and Data Network and national agencies like CNR.

Variability, Trends, and Climate Change Effects

Levantine Intermediate Water exhibits variability tied to episodic events such as the Eastern Mediterranean Transient and multidecadal changes associated with indices like the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation. Documented trends include changes in salinity, temperature, and formation intensity linked to anthropogenic warming, altered precipitation patterns over the Mediterranean Basin, and modified riverine inputs from the Nile Basin and Ebro River catchments. Climate projections from the Intergovernmental Panel on Climate Change scenarios suggest shifts in formation frequency and properties with implications for ventilation, biogeochemistry, and regional climate feedbacks studied by consortia including the MedECC and the Euro-Mediterranean Centre on Climate Change.

Category:Oceanography