An in-depth reassessment of scientific data has revealed that the rate of sea level rise is accelerating and the main factor may simply be the process known as thermal expansion.
Although the melting of glaciers and the reduction of ice sheets are commonly cited as factors contributing to the gradual rise in sea levels, the slow and continuous expansion of the oceans often goes unnoticed.
However, a new one, recently published in the magazine Science Advancesshows that this phenomenon is precisely the main cause of rising sea levels around the world.
As ocean water warms, it expands, in a process known as thermal expansionwhich means that sea water takes up more volume. According to the study authors, This expansion of water is the main cause of sea level rise.
The analysis, carried out by an international team of scientists, helps resolve some of the discrepancies identified in previous studies on sea level, in which key factors, including melting ice and warming oceans, did not fully explain the observed increase.
“For years, there was a frustrating gap between the observed rise of the oceans and what we could explain based on individual causes”, explains the mechanical engineer John Abrahamresearcher at the University of St. Thomas, in the United States, and lead author of the study.
“We can now explain sea level rise with greater confidence”, adds the researcher.
The study authors divided the analysis into three periods: a long-term view, from 1960 to 2023, covered by tide gauges and satellites; between 1993 and 2023, corresponding to the era of satellite images; and the years 2005 to 2023, when scientists began using ocean monitoring buoys known as Argo floats.
Since 1960, data collected in the study shows, global average sea levels have risen at an average rate of 2.06 millimeters per year. But the climb is accelerating: between 2005 and 2023, the increase was 3.94 millimeters per year, smile until good of the average rate.
As for the factors that contribute to this rise, the researchers concluded that the expansion of warmer oceans accounts for 43% of the increase. THE melting of mountain glaciers represents 27%the Greenland ice sheet 15% and the Antarctic ice sheet 12%. The remaining 3% is due to changes in water storage on land.
Zheng H., Abraham J. et al. / Science Advances
Causes of global mean sea level rise since 1960
“Although previous studies have managed to close the budget for global mean sea level, their results differed due to different choices of datasets,” the researchers write.
Millions of lives and livelihoods are believed to be threatened in the coming decades by rising sea levels, and the long-term effects will affect all inhabitants of the planet — whether they live near the sea or not.
Rising sea levels will disrupt food webs, trade links and . Some degree of damage is now inevitable, but its size has not yet been determined.
“Understanding the causes of sea level rise is indispensable for projecting future sea level changes and supporting climate adaptation and mitigation efforts,” the study authors conclude.
