Ocean bottom pressure variability in the Mediterranean Sea and its relationship with sea level from a numerical model

• Rapid (< 2 months) ocean bottom pressure changes in the Mediterranean Sea decoupled between western and eastern subbasins.
• Low frequency steric sea level variability is larger in the western than in the eastern subbasin.
• Low frequency coastal sea level in the Eastern Mediterraneanis representative of averaged ocean mass changes (non-seasonal).

The spatial and temporal scales of variability of ocean bottom pressure (Pb) in the Mediterranean Sea are characterized and their relationship with sea level was assessed using a high resolution eddy-permitting regional ocean model spanning the period 1999–2011. It was found that rapid (periods of a few days) bottom pressure fluctuations are coherent with sea level and are decoupled between the eastern and western basins as a result of topographic constraints. In the longer periods, steric processes gained relevance away from the coast and partially broke the coherence between sea level and Pb, especially on the western basin. Results confirm that sea level changes are predominantly barotropic over most of the basin and at all time scales, except for the annual cycle. Along the coasts sea level fluctuations reflected local steric processes taking place in their vicinity. This effect was stronger on the western basin, whereas the coasts of the Eastern Mediterranean arise as the most suitable proxies for basin wide long term (> 60 days) mean sea level (or ocean bottom pressure) changes at non-seasonal periods.