Depth-dependent temperature change contributions to global mean thermosteric sea level rise from 1960 to 2010

For the last two decades, steric sea level change has been identified as one of the major contributors to the observed sea level rise (Bindoff et al, 2007). This contribution is not steady and varies with time both globally and regionally. Different estimates, based on different analyses and computing strategies of in situ hydrographic data, have found a substantial global ocean warming signal located principally in the upper 500m to 700m depth of the ocean (Lyman et al., 2010), although a deeper ocean signal may also be non-negligible (Purkey and Johnson, 2010). In this study, we analyze the contribution of different oceanic layers to thermosteric sea level changes over the last decades using existing temperature databases. We study the depth and time evolution of thermal expansion and its contribution to sea level. We highlight a 22-year lag of warming at global scale between the upper 300m and 300-700m depth oceanic layers. Comparisons between the different databases and outputs of GECCO Ocean General Circulation Model are also investigated and discussed. We further investigate sea level rate fluctuations and we highlight the contribution of thermal expansion to sea level rate variations, but only down to 300-meter depth.