Why NASA says 2024’s average sea level rise was ‘unexpected’

CINCINNATI (WXIX) - NASA’s Jet Propulsion Laboratory said in a press release that the average sea level rise measured in 2024 was “unexpected.” With 2024 being the warmest year on record, the change in sea level was also notable.

“So, in the ’90s, we had a sea level rise of about 2 millimeters a year on average,” said Severe Fournier, an ocean scientist with NASA’s Jet Propulsion Laboratory. “We saw it’s recently been more around 4.5 millimeters on average. It varies from year to year and last year, we were closer to 6 millimeters a year. It was because it was a really warm year.”

Fournier says instruments in the oceans and space are key to finding what is causing the sea to rise.

“There are literally robots in the ocean with thermometers on them, and they can measure the temperatures of the water column everything they are,” Fournier said. “So we have a bunch all over the global ocean. They can measure the component of the sea level rise that is due to thermal expansion.”

Thermal expansion of water at a global level happens when ocean temperatures are relatively warm. This causes the sea level to rise.

Another contributor to the rising sea level is the melting of glaciers and ice sheets.

Normally, more than half of the sea level rise is caused by melting sea ice, but 2024’s sea level rise was primarily caused by thermal expansion.

Fournier says this is because of warm air temperatures on top of already-warm ocean temperatures.

“About half of last year was still under an El Nino, so we had warmer temperatures in the Pacific Ocean,” Fournier said.

As the average sea level rises, coastal communities are left facing high tide more frequently. Experts say beach erosion and flooding are both concerns moving forward.

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