Ocean Thermal Expansion: In Theory and by a Simple Experiment

Thermal expansion is a concept of sea level changes quite frequently discussed today. The concept goes far back in time and was then known as steric changes in sea level caused by change in temperature or salinity [1]. The Holocene sea level oscillations on a centennial bases were sometimes proposed to be driven primarily by steric sea level changes [2]. Mörner showed [3] that the sea level changes were dominated by glacial eustasy up to about 6000-5000 BP (regardless of tectonic differentiation) and thereafter was dominated by the redistribution of water masses. When satellite altimetry commenced in 1992, the lateral redistribution of water masses over the oceans was well monitored [4], whether caused by lateral dislocation of water masses or by differential thermal expansion (or rather a combination of both). Thermal expansion became a part of the concept of global warming [5], claiming that the general warming from 1970 to 2000 also generated a global sea level rise component due to thermal expansion. Often it is used without basic anchoring in physical and oceanographic facts as straightened out in the Encyclopedia of Coastal Science [6].