Thermal expansion refers to the process in which an object expands or gets bigger when it is heated. It happens because the particles inside the object move faster and take up more space, causing the object to expand. Full definition
Such a change will cause sea levels to rise (because of thermal expansion of water and melting of glaciers), and will alter the distribution of precipitation. (transitionus.org)
That is because most of the surface level increase is from thermal expansion of the water as the oceans warm. (climate-skeptic.com)
The low thermal expansion coefficient at the cold temperatures of the high southern latitudes, changes in wind patterns and transport of the heat taken up to lower latitudes are all possible explanations. (ipcc.ch)