Sea levels surged in 2024, rising faster than expected due to warming oceans.
Unlike previous years, where melting ice dominated, thermal expansion drove most of the increase. NASA’s satellite records show sea levels climbing steadily since 1993, with ocean dynamics like winds and El Niño playing a crucial role in heat distribution.
Sea Level Rise Accelerates in 2024
Global sea levels rose faster than expected in 2024, mainly due to the expansion of ocean water as it warmed, a process known as thermal expansion. A NASA-led analysis found that sea levels increased by 0.23 inches (0.59 centimeters) last year, surpassing the predicted rate of 0.17 inches (0.43 centimeters) per year.
“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.”
Thermal Expansion Takes the Lead
About two-thirds of sea level rise in recent years came from melting glaciers and ice sheets, while thermal expansion accounted for roughly one-third. In 2024, that pattern reversed, with two-thirds of the rise driven by the expansion of warming ocean water.
“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.
Decades of Rising Waters
Since the satellite record of ocean height began in 1993, the rate of annual sea level rise has more than doubled. In total, global sea level has gone up by 4 inches (10 centimeters) since 1993.
This long-term record is made possible by an uninterrupted series of ocean-observing satellites starting with TOPEX/Poseidon in 1992. The current ocean-observing satellite in that series, Sentinel-6 Michael Freilich, launched in 2020 and is one of an identical pair of spacecraft that will carry this 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.
Mixing It Up
There are several ways in which heat makes its way into the ocean, resulting in the thermal expansion of water. Normally, 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, 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.
El Niño’s Role in Heat Movement
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.
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3 Comments
“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.”
It looks quite linear to me! https://sealevel.nasa.gov/understanding-sea-level/global-sea-level/overview/
When I was in high school we were going to get extinct by acid rain and a coming ice age.
Climate has never been fixed or stable.
That’s not so bad. We’ll finally get rid of the Netherlands.