Mediterranean Sea-Level Variability in the Second Half of the Twentieth Century: A Bayesian Approach to Closing the Budget

摘要

Regional sea levels in the Mediterranean sub-basins, the Black Sea and the Atlantic close to Gibraltar between 1930 and 2015, are constructed, based on high-quality tide-gauge data in the wider Mediterranean area, to identify long-term trends against decadal and multidecadal changes. Regional sea-level variability induced by direct atmospheric forcing and steric changes is determined, respectively, from air pressure and temperature and salinity data. Vertical land movements due to glacial isostatic adjustment are also taken into account. Focusing on linear trend in the period 1950-1990, the individual contributions to the trend are calculated and sea-level budget is examined within each region, according to proposed physical model. The trends with their uncertainty intervals are determined using Bayesian statistics. In the Atlantic off Gibraltar and in the Black Sea, the regional sea-level trends were close to the global values; in the Mediterranean, they were close to zero. Sea-level rise in the Atlantic was supported by regional atmospheric loading and thermohaline changes, while the trend underlying the residual part of sea-level variability was comparable to the global mass contribution. Throughout the Mediterranean and in the Black Sea, atmospheric forcing and steric effects induced lowering of sea level. In the Mediterranean, and partly in the Black Sea, these regional effects compensated the effect of global mass increase. It is concluded that over the 1950-1990 interval, the sea-level budget is closed within the, rather wide, credible limits, which are obtained when autocorrelation of the linear-fit residuals is taken into account.