A new study in the Journal of Geophysical Research: Oceans sheds light on how strong El Nino weather patterns are driving rapid increases in global sea levels.
Surprisingly, the comprehensive study reveals that the primary culprit is not just warming seawater, but the massive transfer of terrestrial water directly from landmasses into the sea.
Researchers from two Chinese universities combined satellite measurements with data from Argo ocean buoys to track these changes.
The team compared two major El Nino events: one from 2014 to 2016, and another from 2023 to 2024. In both cases, sea surface temperatures rose by more than 2 degrees Celsius above normal, leading to sharp increases in global sea levels.
Scientists usually describe sea level rise in two ways. One is called steric rise, which occurs when seawater warms and expands.
The other is barystatic rise, which is caused by water from land and melting ice flowing into the ocean. The researchers found that this type of rise was the main factor during both recent El Nino periods.
Between 2014 and 2016, global sea levels rose by 9.16 millimeters, and about 68 percent of that increase was due to water running off land.
During the 2023 to 2024 El Nino, sea levels rose by 7.70 millimeters, with 81 percent of that rise attributable to land water. This increase happened much faster than before.
Regional weather patterns played a key role. During the first El Nino, Africa lost a large amount of land water, while in the second event, North America contributed less water to the oceans.
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A major lack of rainfall in South America led to fast runoff, sending large amounts of water into the sea. At the same time, warmer Indian Ocean waters, driven by a positive Indian Ocean Dipole, contributed to global sea level rise.
These data come as global climate monitoring is at a key point. The National Oceanic and Atmospheric Administration now predicts there is an 81 percent chance of another strong El Nino developing between October and December 2026.
Scientists warn that this upcoming El Nino could cause sea levels to rise even faster and may break global temperature records before the year ends.