Comparison of results of AOGCMs in the Mediterranean Sea during the 21st century

Abstract

It is important for policy making to downscale the knowledge derived from global models to smaller areas. However, this is a nontrivial task for the Mediterranean Sea, a semienclosed basin connected to the Atlantic Ocean through the Strait of Gibraltar. The outputs of 12 atmosphere‐ocean general circulation models (AOGCMs) in the Mediterranean Sea are used to examine temperature (T), salinity (S), and sea level changes for the 21st century under three different climate scenarios (committed climate change, SRES A1B, and SRES A2). Warming and salinification are predicted to occur in the basin. The T increases are translated into an average thermosteric sea level rise between 3 and 61 cm over the basin. Under A1B and A2 scenarios, thermosteric sea level rise is accelerated. Under the committed climate change scenario the thermosteric sea level, although increasing, is decelerated. In the Mediterranean, S has a large impact in sea level changes, and projections of steric sea level range between −22 and 31 cm. The contribution of future atmospheric pressure changes on sea level in the Mediterranean Sea is a reduction of up to 0.6 cm. The 20th century model runs indicate that low‐frequency variability is smaller than that observed. The spatial patterns of steric sea level change are not consistent among the AOGCMs in the region. Overall, results indicate large uncertainties regarding the combined effects of T and S on future Mediterranean mean sea level changes based on these simulations, with even greater discrepancies on the patterns of change.