Steric sea level variations in the central-eastern Mediterranean Sea from Argo observations

Temporal variations of the sea level have been assessed by means of satellite altimetry for many years. While the total sea level change is determined by altimetry very precisely, at the level of a few millimeters, knowledge of the effects of mass-related and volume-related contributions is comparatively poor. Here, we report on the effect of volume changes of sea water in the central-eastern Mediterranean Sea. The study is performed on the basis of in-situ data collected by the floats of the Mediterranean and Black Sea Argo Centre (MedArgo) established in 2003. On a grid of 1��1� the total steric sea level variations as well as the individual contributions of thermal and haline expansion are computed. The study reveals a strong volume-related, sea level change at a rate of about 18 mm/year between 2004 and the end of 2008 in the Ionian Sea that is clearly dominated by thermal expansion. In contrast, thermal and haline contributions show opposite trends in the eastern Mediterranean Sea where both effects tend to counteract each other on inter-annual time scales. Steric sea level changes from Argo and the total sea level change from the altimetry satellite mission Jason-1 agree very well in the Ionian Sea, suggesting that most of the observed sea level rise is caused by thermal expansion in this region. However, the comparison of Jason-1 with the steric sea level change computed from Argo data between 2004 and the end of 2007 indicates an unexplained mass loss at a rate of -20 mm/year in the region around Crete.