Physical forcing and physical/biochemical variability of the Mediterranean Sea: a review of unresolved issues and directions for future research

Abstract

The importance of the Mediterranean Sea for the world ocean has long been recognized. First, the Mediterranean sea has a profound impact on the Atlantic ocean circulation and, consequently, on the global thermohaline conveyor belt. Maps of the Mediterranean salty water tongue exiting from the Gibraltar strait at intermediate depths and spreading throughout the Atlantic interior are well known since the 1950s. Through direct pathways to the Atlantic polar regions or through indirect mixing processes, the salty Mediterranean water preconditions the deep convection cells of the polar Atlantic. There the North Atlantic Deep Water is formed which successively spreads throughout the world ocean constituting the core of the global thermohaline circulation. <br><br> Even more importantly, the Mediterranean Sea is a laboratory basin for the investigation of processes of global importance, being much more amenable to observational surveys because of its location in mid-latitude and its dimensions. Both the western and eastern basins in fact possess closed thermohaline circulations analogous to the global conveyor belt. A unique upper layer open thermohaline cell connects the eastern to the western basin and, successively, to the north Atlantic through the Gibraltar strait. In it, the Atlantic water entering into Gibraltar in the surface layer, after travelling to the easternmost Levantine basin, is transformed into one of the saltiest water masses through air–sea heat and moisture fluxes. This is the salty water which, crossing the entire basin in the opposite direction below the surface Atlantic water, finally exits from the Gibraltar strait at mid-depths. <br><br> Both the western and eastern basins are endowed with deep/intermediate convection cells analogous to the polar Atlantic deep convection cells or to the intermediate mode water ones. Deep and intermediate water masses are therefore formed in different sites of the entire basin. Because of their easily accessible locations, these convection cells are much more amenable to direct observational surveys and mooring arrays. <br><br> An ubiquitous, energetic mesoscale and sub-mesoscale eddy field is superimposed to and interacts with the sub-basin scale, wind-driven gyres that characterize the upper thermocline circulation. Three different scales of motion are therefore superimposed producing a richness of interaction processes which typify similar interactions in unexplored ocean regions. <br><br> Both wide and narrow shelves are present separated by steep continental slopes from the deep interiors. Cross-shelf fluxes of physical as well biogeochemical parameters are crucial in determining the properties of the shallow versus deep local ecosystems and their trophic chain. Most importantly, the Mediterranean Sea is a basin of contrasting ecosystems, from the strongly oligotrophic deep interiors to the fully eutrophic northern Adriatic characterized by recurrent, anomalous algal blooms and related anoxia events. <br><br> This review focuses on the identification of the...

A Connectivity-Based Eco-Regionalization Method of the Mediterranean Sea

“…The region V can correspond to the meandering stream identified by [34] or considered as interannual variability by [31]. The South-eastern Levantine has a region O with a stable boundary #7.…”

Untangling biogeochemical processes from the impact of ocean circulation: First insight on the Mediterranean dissolved barium dynamics

“…First, observations of the various components of the Mediterranean biological carbon pump provide organic carbon fluxes varying by at least 1 order of magnitude [Santinelli et al, 2010;Sternberg et al, 2007], highlighting the need to better balance the regional carbon budget [Malanotte-Rizzoli et al, 2014]. First, observations of the various components of the Mediterranean biological carbon pump provide organic carbon fluxes varying by at least 1 order of magnitude [Santinelli et al, 2010;Sternberg et al, 2007], highlighting the need to better balance the regional carbon budget [Malanotte-Rizzoli et al, 2014].…”

Cyclic fluctuations of blue whiting (Micromesistius poutassou) linked to open‐sea convection processes in the northwestern Mediterranean

“…Many of the theories aimed at explaining recruitment variability based on biotic or abiotic processes have been developed in hydrodynamically energetic systems, such as upwelling systems and the subarctic areas, and at the limits of the species’ geographical ranges (e.g., Myers, ; Hátún et al ., ), where conditions of strong environmental variability translate in high variability in fish production. The Mediterranean is generally considered an oligotrophic sea, but there are some areas that are very active hydrodynamically, such as the Gulf of Lions, Tyrrhenian, Adriatic and Aegean Seas (Malanotte‐Rizzoli et al ., ). Blue whiting, a cold‐water species that inhabits these and adjacent areas, shows cyclical variations (Bas, ; Bas and Calderón‐Aguilera, ) that could be related to recruitment variability, analogous to the temperate North Atlantic Ocean.…”