Sea Level Rise in 2024 Exceeded Expectations, JPL-Supported Analysis Reveals

Global sea levels rose at a higher-than-anticipated rate in 2024, according to a NASA-led analysis that included significant contributions from researchers at the agency’s Jet Propulsion Laboratory in Southern California.

Communities in coastal areas such as Florida, shown in a 1992 NASA image, are vulnerable to the effects of sea level rise, including high-tide flooding. The data shows sea levels increased by 0.23 inches (0.59 centimeters) per year in 2024, considerably higher than the expected rate of 0.17 inches (0.43 centimeters) per year. Scientists attribute this acceleration primarily to increased thermal expansion of ocean water as it warms during what was the hottest year on record, complemented by meltwater from land-based ice sources like glaciers.

“The rise we saw in 2024 was higher than we expected,” said Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory in Southern California. “Every year is a little bit different, but what’s clear is that the ocean continues to rise, and the rate of rise is getting faster and faster.”

The findings represent a notable shift in the primary drivers of sea level rise. In recent years, approximately two-thirds of the increase resulted from melting ice sheets and glaciers adding water to the oceans, with the remaining third attributed to thermal expansion as seawater warms. However, this pattern reversed in 2024, with thermal expansion accounting for two-thirds of the observed rise.

“With 2024 as the warmest year on record, Earth’s expanding oceans are following suit, reaching their highest levels in three decades,” said Nadya Vinogradova Shiffer, head of physical oceanography programs and the Integrated Earth System Observatory at NASA Headquarters in Washington.

This graph shows global mean sea level (in blue) since 1993 as measured by a series of five satellites. The solid red line indicates the trajectory of this increase, which has more than doubled over the past three decades. Since satellite monitoring began in 1993, the annual rate of sea level rise has more than doubled, with global sea levels increasing by 4 inches (10.1 centimeters) in total over that period. The dotted red line projects future sea level rise. Credit: NASA/JPL-Caltech

This long-term record has been maintained through an uninterrupted series of ocean-observing satellites, beginning with TOPEX/Poseidon in 1992 and continuing with the current Sentinel-6 Michael Freilich spacecraft, which launched in 2020.

The Sentinel-6 Michael Freilich mission, jointly implemented by NASA, the European Space Agency, EUMETSAT, and NOAA, with JPL managing NASA’s contributions, is one of an identical pair of spacecraft designed to extend this critical sea level dataset into its fourth decade. Its twin, the upcoming Sentinel-6B satellite, will continue to measure sea surface height down to a few centimeters for about 90% of the world’s oceans.

This animation shows the rise in global mean sea level from 1993 to 2024 based on data from five international satellites. The expansion of water as it warms was responsible for the majority of the higher-than-expected rate of rise in 2024. Credit: NASA’s Scientific Visualization Studio

Scientists explain that heat enters the ocean through several mechanisms. Under normal conditions, seawater arranges itself into layers determined by water temperature and density. Warmer water floats on top of and is lighter than cooler water, which is denser. In most places, heat from the surface moves very slowly through these layers down into the deep ocean.

However, researchers note that extremely windy areas of the ocean can agitate the layers enough to result in vertical mixing. Very large currents, like those found in the Southern Ocean, can tilt ocean layers, allowing surface waters to more easily slip down deep. The massive movement of water during El Niño — in which a large pool of warm water normally located in the western Pacific Ocean sloshes over to the central and eastern Pacific — can also result in vertical movement of heat within the ocean.

The findings underscore the importance of continued satellite monitoring of Earth’s oceans, a field in which JPL has played a central role through its management of several NASA satellite missions focused on oceanography and Earth science.

For more information about sea level research, visit https://sealevel.nasa.gov/

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