“…Several past studies have shared this focus. In particular, Boukthir and Barnier (2000) noted that although strong evaporation over the Mediterranean Sea is the principal mechanism that gives the water its characteristic high salinity, the interannual variability of the freshwater air-sea flux is driven by changes in precipitation. From a study of interannual variability in the surface freshwater flux, these authors found that the freshwater deficit increased between 1979 and 1993 mainly due to a decrease in precipitation.…”
A recent study of the eastern North Atlantic detailed significant increases in the temperature and salinity of the Mediterranean Overflow Water (MOW) from 1950 to 2000. To examine the degree to which the source waters, which spill over the sill at the Strait of Gibraltar, could be responsible for these observations in the open Atlantic, a box model of water mass transformation by marginal seas was employed. Time series for the salinity of the inflowing North Atlantic surface waters, freshwater fluxes in the Mediterranean (evaporation and precipitation and river runoff), and the volumetric flow rates for the inflow and outflow across the Strait of Gibraltar were used to predict the salinity of the source waters to the North Atlantic from 1950 to 2000. Results from this calculation reveal that source water changes have minimal impact on MOW property changes on interannual and decadal time scales. It is suggested instead that circulation changes within the open Atlantic alter the advective-diffusive pathways of MOW such that property changes within the MOW reservoir are created.
“…Several past studies have shared this focus. In particular, Boukthir and Barnier (2000) noted that although strong evaporation over the Mediterranean Sea is the principal mechanism that gives the water its characteristic high salinity, the interannual variability of the freshwater air-sea flux is driven by changes in precipitation. From a study of interannual variability in the surface freshwater flux, these authors found that the freshwater deficit increased between 1979 and 1993 mainly due to a decrease in precipitation.…”
A recent study of the eastern North Atlantic detailed significant increases in the temperature and salinity of the Mediterranean Overflow Water (MOW) from 1950 to 2000. To examine the degree to which the source waters, which spill over the sill at the Strait of Gibraltar, could be responsible for these observations in the open Atlantic, a box model of water mass transformation by marginal seas was employed. Time series for the salinity of the inflowing North Atlantic surface waters, freshwater fluxes in the Mediterranean (evaporation and precipitation and river runoff), and the volumetric flow rates for the inflow and outflow across the Strait of Gibraltar were used to predict the salinity of the source waters to the North Atlantic from 1950 to 2000. Results from this calculation reveal that source water changes have minimal impact on MOW property changes on interannual and decadal time scales. It is suggested instead that circulation changes within the open Atlantic alter the advective-diffusive pathways of MOW such that property changes within the MOW reservoir are created.
“…In addition, the second half of the twentieth century has seen a high rate of dam constructions for Mediterranean rivers, the building of the Aswan Dam in 1964 being the most impactful intervention, which greatly reduced (by about 50%, according to ref. 4) the freshwater input to the sea.Figure 1( A ) The Mediterranean Sea where deep (yellowish ellipses) and intermediate (reddish ellipses) water formation sites are highlighted as well as the circulation schemes for the Atlantic Water (AW, light blue arrow) and the Levantine/Cretan Intermediate Waters (LIW/CIW, red arrow), the black rectangle indicates the monitored area; ( B ) zoom on the Sicily Channel where the positions of the two moorings (C01 and C02) are shown (red diamonds), that allow both branches of the bifurcated LIW/CIW flow (red arrow) to be intercepted; ( C ) vertical schematic section of the 150 km-long transect between Tunisia and Sicily (black line in ( B )), showing the two-layer system of water masses flowing in opposite directions (AW in light blue flowing eastward; IW in orange flowing westward, where the darker orange indicates higher salinity, the salinity maximum identifying the core of the IW) and the positions of instruments along the C01 and C02 lines located in two parallel deep trenches. The data discussed in the paper come from the conductivity-temperature sensors at about 400 m depth, located in the intermediate water (IW) (the yellow stars).…”
The Mediterranean Sea is a mid-latitude marginal sea, particularly responsive to climate change as reported by recent studies. The Sicily Channel is a choke point separating the sea in two main basins, the Eastern Mediterranean Sea and the Western Mediterranean Sea. Here, we report and analyse a long-term record (1993–2016) of the thermohaline properties of the Intermediate Water that crosses the Sicily Channel, showing increasing temperature and salinity trends much stronger than those observed at intermediate depths in the global ocean. We investigate the causes of the observed trends and in particular determine the role of a changing climate over the Eastern Mediterranean, where the Intermediate Water is formed. The long-term Sicily record reveals how fast the response to climate change can be in a marginal sea like the Mediterranean Sea compared to the global ocean, and demonstrates the essential role of long time series in the ocean.
“…A great number of studies have dealt with the Mediterranean heat (Bethoux 1979;Bunker et al 1982;May 1986;Garrett et al 1993;Gilman and Garrett 1994;Castellari et al 1998;Matsoukas et al 2005;Ruiz et al 2008;Criado-Aldeanueva et al 2012) and water budgets (Bethoux 1979;Peixoto et al 1982;Bryden and Kinder 1991;Harzallah et al 1993;Gilman and Garrett 1994;Castellari et al 1998;Angelucci et al 1998;Bethoux and Gentili 1999;Boukthir and Barnier 2000;Mariotti et al 2002;Mariotti 2010;Romanou et al 2010;CriadoAldeanueva et al 2012), but only in the most recent ones, which use longer datasets, is the attention focused on the interannual variability and its forcing mechanisms. For instance, Criado-Aldeanueva et al (2012) reported three different periods in the precipitation and evaporation anomalies: from the early 1950s to the late 1960s, a positive trend is observed that changes to negative until the late 1980s, when it changes sign again.…”
Interannual to interdecadal precipitation P, evaporation E, freshwater budget (E 2 P), and air-sea net heat flux Q have been correlated with the North Atlantic Oscillation (NAO), eastern Atlantic (EA), eastern Atlantic-western Russia (EA-WR), and Mediterranean Oscillation (MO) climatic indices to explore the influence of atmospheric forcing in the Mediterranean freshwater and heat budget variability. The effect of the MO pattern has similarities with that of the NAO, but MO influence is more intense. On an annual basis, the MO index gives the highest correlation with all the variables considered, and during its negative phase, it exerts a stronger influence than the NAO and is associated with higher P and, especially, enhanced evaporative losses in the Levantine subbasin. The EA pattern does not significantly affect P in the Mediterranean, but a high correlation is found for E and Q from 1979. The EA-WR mode plays a significant role in annual net heat flux since variations in its sign have the potential to induce seesaw variations in the heat budgets of the eastern and western subbasins, as previously found by Josey et al., for wintertime.
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