On the Source of Mediterranean Overflow Water Property Changes

Abstract

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.

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

“…Long-term reanalysis simulations that assimilate in situ measurements and exploit the significant amount of information from observational systems in the Mediterranean are an important step towards reliable reconstructions for "short-term" climatic analysis. Moreover, studies of DWF and circulation on decadal and interdecadal scales must take into account the variability of the inflowing AW and in particular its observed increasing salt content (Lauzier and Sindlinger, 2009). …”

About the origin of the Mediterranean Waters warming during the twentieth century

“…Previous works have already used box-models for analyzing in a simple way the main features of the Mediterranean Sea 160 (Bethoux, 1979), the changes occurred during the twentieth century (Bethoux and Gentili, 1996;Bethoux et al, 1999) and their effects on the Mediterranean waters flowing into the Atlantic Ocean (Lozier and Sindlinger, 2009). …”

“…Bethoux (1979) considered the use of the expression obtained by Whitehead et al (1974) including the effect of rotation. Lozier and Sindlinger (2009) used a box model to study the evolution of the Mediterranean outflow salinity. In this 170 case the volume of Mediterranean waters flowing through the Strait of Gibraltar followed the maximal exchange model by Bryden and Kinder (1991).…”

“…The first one, already commented, was to assume the maximal exchange model proposed by Bryden and Kinder (1991) already used in the box model by Lozier and Sindlinger (2009). The second one was to use the expression proposed by Whitehead et al (1974) …”

Interocean and Interbasin Exchanges

“…Lozier and Sindlinger (2009) used a box model of water mass modification to study the relation between long-term changes of water masses in the Mediterranean Sea and the North Atlantic at intermediate depths. Are the temperature and salinity changes observed at the Mediterranean source large enough to generate significant decadal variability in the intermediate waters of the North Atlantic, and can changes in the salt or heat content of the MOW have a significant impact on changes to the MOC?…”