Sea level has risen three centimeters per decade since the 1990s, says ESA

Sea level has risen on average three centimeters per decade worldwide since satellite measurements began in the 1990s, the European Space Agency (ESA) reported Thursday.

Just over a third of this increase is due to thermal expansion, meaning that as seawater warms it expands.

The remaining nearly two-thirds of the increase is due to freshwater being added to the ocean by melting glaciers and the Antarctic and Greenland ice sheets.

Also by water added to the ocean from land, as a result of the depletion of groundwater storage, according to the ESA.

Scientists look at individual contributions to ocean mass from the Greenland and Antarctic ice sheets and from glaciers around the world, as well as changes in terrestrial water storage.

They are also measured directly by satellites that observe small changes in the Earth’s gravitational pull that involve changes in the masses of ice or water.

ESA’s Climate Change Initiative (CCI) generates continuous spatial records of several variables related to sea level.

The research, led by the Dresden University of Technology and published by Earth System Science Data, shows that the sum of the assessed contributions each month matches the total collected sea level change.

“Establishing this consistent picture of sea level and ocean mass budgets not only required advanced satellite Earth observation and modeling data sets, but also required experts from various disciplines to arrive at a common framework.” , said study lead author Martin Horwath.

The results are in line with previous studies and gain more confidence through advances in data analysis, but also call for further improvements in the understanding of satellite measurements and physical processes.

For example, slow deformations of the solid Earth under the ocean affect satellite observations, and these effects need to be separated from changes within the ocean, explains ESA.

However, “the results obtained from the satellites changed a little when we improved the way of taking into account the massive displacements (of water) on the solid Earth”, warned Benjamin Gutknecht of the University of Dresden (Germany). (I)