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By NASA
3 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
Communities in coastal areas such as Florida, shown in this 1992 NASA image, are vulnerable to the effects of sea level rise, including high-tide flooding. A new agency-led analysis found a higher-than-expected rate of sea level rise in 2024, which was also the hottest year on record.NASA Last year’s increase was due to an unusual amount of ocean warming, combined with meltwater from land-based ice such as glaciers.
Global sea level rose faster than expected in 2024, mostly because of ocean water expanding as it warms, or thermal expansion. According to a NASA-led analysis, last year’s rate of rise was 0.23 inches (0.59 centimeters) per year, compared to the expected 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.”
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. The dotted red line projects future sea level rise.NASA/JPL-Caltech In recent years, about two-thirds of sea level rise was from the addition of water from land into the ocean by melting ice sheets and glaciers. About a third came from thermal expansion of seawater. But in 2024, those contributions flipped, with two-thirds of sea level rise coming from thermal expansion.
“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.
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.
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This animation shows the rise in global mean sea level from 1993 to 2024 based on da-ta 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.NASA’s Scientific Visualization Studio 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.
But 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.
Learn more about sea level:
https://sealevel.nasa.gov
News Media Contacts
Jane J. Lee / Andrew Wang
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-0307 / 626-379-6874
jane.j.lee@jpl.nasa.gov / andrew.wang@jpl.nasa.gov
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Last Updated Mar 13, 2025 Related Terms
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By European Space Agency
High above the Arctic Circle, on the rugged terrain of Andøya, three ESA radionavigation engineers take a rare moment to unwind with a game of shuffleboard. Outside, sheep graze under the shimmering northern lights, a serene backdrop to their demanding mission: test how navigation technologies withstand interference signals. With 100TB of data collected over 5 days, their efforts promise to strengthen the reliability of satellite navigation for the benefit of us all.
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By European Space Agency
European scientists are asking volunteers to lie down on a waterbed for 10 days as part of a pioneering dry immersion study to recreate some of the effects of spaceflight on the body.
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By NASA
Explore This Section Webb News Latest News Latest Images Blog (offsite) Awards X (offsite – login reqd) Instagram (offsite – login reqd) Facebook (offsite- login reqd) Youtube (offsite) Overview About Who is James Webb? Fact Sheet Impacts+Benefits FAQ Science Overview and Goals Early Universe Galaxies Over Time Star Lifecycle Other Worlds Observatory Overview Launch Orbit Mirrors Sunshield Instrument: NIRCam Instrument: MIRI Instrument: NIRSpec Instrument: FGS/NIRISS Optical Telescope Element Backplane Spacecraft Bus Instrument Module Multimedia About Webb Images Images Videos What is Webb Observing? 3d Webb in 3d Solar System Podcasts Webb Image Sonifications Team International Team People Of Webb More For the Media For Scientists For Educators For Fun/Learning 6 Min Read NASA’s Webb Peers Deeper into Mysterious Flame Nebula
This collage of images from the Flame Nebula shows a near-infrared light view from NASA’s Hubble Space Telescope on the left, while the two insets at the right show the near-infrared view taken by NASA’s James Webb Space Telescope. Credits:
NASA, ESA, CSA, M. Meyer (University of Michigan), A. Pagan (STScI) The Flame Nebula, located about 1,400 light-years away from Earth, is a hotbed of star formation less than 1 million years old. Within the Flame Nebula, there are objects so small that their cores will never be able to fuse hydrogen like full-fledged stars—brown dwarfs.
Brown dwarfs, often called “failed stars,” over time become very dim and much cooler than stars. These factors make observing brown dwarfs with most telescopes difficult, if not impossible, even at cosmically short distances from the Sun. When they are very young, however, they are still relatively warmer and brighter and therefore easier to observe despite the obscuring, dense dust and gas that comprises the Flame Nebula in this case.
NASA’s James Webb Space Telescope can pierce this dense, dusty region and see the faint infrared glow from young brown dwarfs. A team of astronomers used this capability to explore the lowest mass limit of brown dwarfs within the Flame Nebula. The result, they found, were free-floating objects roughly two to three times the mass of Jupiter, although they were sensitive down to 0.5 times the mass of Jupiter.
“The goal of this project was to explore the fundamental low-mass limit of the star and brown dwarf formation process. With Webb, we’re able to probe the faintest and lowest mass objects,” said lead study author Matthew De Furio of the University of Texas at Austin.
Image A: Flame Nebula: Hubble and Webb Observations
This collage of images from the Flame Nebula shows a near-infrared light view from NASA’s Hubble Space Telescope on the left, while the two insets at the right show the near-infrared view taken by NASA’s James Webb Space Telescope. Much of the dark, dense gas and dust, as well as the surrounding white clouds within the Hubble image, have been cleared in the Webb images, giving us a view into a more translucent cloud pierced by the infrared-producing objects within that are young stars and brown dwarfs. Astronomers used Webb to take a census of the lowest-mass objects within this star-forming region.
The Hubble image on the left represents light at wavelengths of 1.05 microns (filter F105W) as blue, 1.3 microns (F130N) as green, and 1.39 microns (F129M) as red. The two Webb images on the right represent light at wavelengths of 1.15 microns and 1.4 microns (filters F115W and F140M) as blue, 1.82 microns (F182M) as green, 3.6 microns (F360M) as orange, and 4.3 microns (F430M) as red. NASA, ESA, CSA, M. Meyer (University of Michigan), A. Pagan (STScI) Smaller Fragments
The low-mass limit the team sought is set by a process called fragmentation. In this process large molecular clouds, from which both stars and brown dwarfs are born, break apart into smaller and smaller units, or fragments.
Fragmentation is highly dependent on several factors with the balance between temperature, thermal pressure, and gravity being among the most important. More specifically, as fragments contract under the force of gravity, their cores heat up. If a core is massive enough, it will begin to fuse hydrogen. The outward pressure created by that fusion counteracts gravity, stopping collapse and stabilizing the object (then known as a star). However, fragments whose cores are not compact and hot enough to burn hydrogen continue to contract as long as they radiate away their internal heat.
“The cooling of these clouds is important because if you have enough internal energy, it will fight that gravity,” says Michael Meyer of the University of Michigan. “If the clouds cool efficiently, they collapse and break apart.”
Fragmentation stops when a fragment becomes opaque enough to reabsorb its own radiation, thereby stopping the cooling and preventing further collapse. Theories placed the lower limit of these fragments anywhere between one and ten Jupiter masses. This study significantly shrinks that range as Webb’s census counted up fragments of different masses within the nebula.
“As found in many previous studies, as you go to lower masses, you actually get more objects up to about ten times the mass of Jupiter. In our study with the James Webb Space Telescope, we are sensitive down to 0.5 times the mass of Jupiter, and we are finding significantly fewer and fewer things as you go below ten times the mass of Jupiter,” De Furio explained. “We find fewer five-Jupiter-mass objects than ten-Jupiter-mass objects, and we find way fewer three-Jupiter-mass objects than five-Jupiter-mass objects. We don’t really find any objects below two or three Jupiter masses, and we expect to see them if they are there, so we are hypothesizing that this could be the limit itself.”
Meyer added, “Webb, for the first time, has been able to probe up to and beyond that limit. If that limit is real, there really shouldn’t be any one-Jupiter-mass objects free-floating out in our Milky Way galaxy, unless they were formed as planets and then ejected out of a planetary system.”
Image B: Low Mass Objects within the Flame Nebula in Infrared Light
This near-infrared image of a portion of the Flame Nebula from NASA’s James Webb Space Telescope highlights three low-mass objects, seen in the insets to the right. These objects, which are much colder than protostars, require the sensitivity of Webb’s instruments to detect them. These objects were studied as part of an effort to explore the lowest mass limit of brown dwarfs within the Flame Nebula.
The Webb images represent light at wavelengths of 1.15 microns and 1.4 microns (filters F115W and F140M) as blue, 1.82 microns (F182M) as green, 3.6 microns (F360M) as orange, and 4.3 microns (F430M) as red. NASA, ESA, CSA, STScI, M. Meyer (University of Michigan) Building on Hubble’s Legacy
Brown dwarfs, given the difficulty of finding them, have a wealth of information to provide, particularly in star formation and planetary research given their similarities to both stars and planets. NASA’s Hubble Space Telescope has been on the hunt for these brown dwarfs for decades.
Even though Hubble can’t observe the brown dwarfs in the Flame Nebula to as low a mass as Webb can, it was crucial in identifying candidates for further study. This study is an example of how Webb took the baton—decades of Hubble data from the Orion Molecular Cloud Complex—and enabled in-depth research.
“It’s really difficult to do this work, looking at brown dwarfs down to even ten Jupiter masses, from the ground, especially in regions like this. And having existing Hubble data over the last 30 years or so allowed us to know that this is a really useful star-forming region to target. We needed to have Webb to be able to study this particular science topic,” said De Furio.
“It’s a quantum leap in our capabilities between understanding what was going on from Hubble. Webb is really opening an entirely new realm of possibilities, understanding these objects,” explained astronomer Massimo Robberto of the Space Telescope Science Institute.
This team is continuing to study the Flame Nebula, using Webb’s spectroscopic tools to further characterize the different objects within its dusty cocoon.
“There’s a big overlap between the things that could be planets and the things that are very, very low mass brown dwarfs,” Meyer stated. “And that’s our job in the next five years: to figure out which is which and why.”
These results are accepted for publication in The Astrophysical Journal Letters.
Image C (Animated): Flame Nebula (Hubble and Webb Comparison)
This animated image alternates between a Hubble Space Telescope and a James Webb Space Telescope observation of the Flame Nebula, a nearby star-forming nebula less than 1 million years old. In this comparison, three low-mass objects are highlighted. In Hubble’s observation, the low-mass objects are hidden by the region’s dense dust and gas. However, the objects are brought out in the Webb observation due to Webb’s sensitivity to faint infrared light. NASA, ESA, CSA, Alyssa Pagan (STScI) The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
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Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Matthew Brown – mabrown@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
Christine Pulliam – cpulliam@stsci.edu
Space Telescope Science Institute, Baltimore, Md.
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Last Updated Mar 10, 2025 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms
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