Biggest Single Driver of Global Sea Level Rise is Thermal Expansion of Warming Seawater, Not Melting Ice Sheets or Glaciers, New Paper Confirms

       A new paper published in the journal Science Advances confirms that the biggest driver of global sea level rise is the thermal expansion of seawater. The international researchers analyzed data from tide gauge measurements, satellite records, and ocean-monitoring buoys. While we know that melting glaciers and melting sea ice increase global sea level, the biggest single source, responsible for 43% of global sea level rise, is thermal expansion of the warmer water. Thermal expansion occurs as ocean water heats up, expands, and occupies more space. The researchers found that mountain glacier loss contributed 27% of the rise, while the Greenland Ice Sheet accounted for 15% and the Antarctic Ice Sheet for 12%. Changes in land water storage made up an additional 3%. Thus, the paper shows that only just over a quarter of global sea level rise is caused by ice loss from the Arctic and Antarctic ice sheets. Mountain glaciers contributed as much as both. Of course, ice loss from all three of those sources accounted for 54%, so one could say that total ice loss (from mountain glaciers and the two ice sheets combined) contributes more to sea level rise than thermal expansion. I made a graph below to depict the percentages found in the paper.

     The researchers used a statistical technique known as balancing the global mean sea level (GMSL) budget. Mechanical engineer John Abraham, from the University of St. Thomas in the U.S., noted:

"This work shows that, with better instruments, processes, and smarter analysis, this knowledge gap can be closed. We can [now] explain sea level rise with greater confidence."

     Since 1960, the data shows, global mean sea levels have risen by an average rate of 2.06 millimeters (0.08 inches) per year. However, as Science Alert notes:

“Between 2005 and 2023, they went up by 3.94 millimeters (0.16 inches) per year – about twice the average rate.”

     The researchers noted that using better datasets, such as higher-resolution satellite imagery, has improved estimates of the extent of glacier melt worldwide.

 "The up-to-date community estimates reconcile differences among multiple estimate methods, mitigate the random errors induced by a single source, and reduce the differences from the dataset choice."

     Sea level rise threatens coastal areas with flooding, storm surges, and king tides. The researchers note that even if we could stop carbon emissions now, sea level would continue to rise for another 50 years, resulting in an additional 103 mm of sea level rise, or a little over 4 inches. With continued emissions guaranteed, it will be much more than that.  

     The researchers noted that their analysis does indicate that sea level rise has indeed accelerated, especially since 1993, as the abstract below points out.

 

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Scientists pinpoint biggest driver of sea level rise, and it's not melting ice sheets or glaciers. Curtis Deacon. The Cool Down. June 15, 2026. Scientists pinpoint biggest driver of sea level rise, and it's not melting ice sheets or glaciers

Sea Level Rise Is Accelerating, And We Now Know The Biggest Reason Why. Science Alert. David Nield. June 9, 2026. Sea Level Rise Is Accelerating, And We Now Know The Biggest Reason Why : ScienceAlert

Improved closure of the global mean sea level budget from observational advances since 1960. Huayi Zheng, Lijing Cheng, Sönke Dangendorf, Benoit Meyssignac, Anne Barnoud, Kevin E. Trenberth, John T. Fasullo, and John Abraham. Science Advances. 20 May 2026. Vol 12, Issue 21. Improved closure of the global mean sea level budget from observational advances since 1960 | Science Advances