NASA Research Reveals the True Causes of Sea Level Rise Since 1900

Greenland Ice Sheet Meltwater Rivers

This aerial photograph shows fast-moving meltwater rivers flowing across the Greenland Ice Sheet, a region that, combined with Antarctic meltwater and thermal expansion, accounts for two-thirds of observed global mean sea level rise. Credit: NASA

Scientists have gained new insights into the processes that have driven ocean level variations for over a century, helping us prepare for the rising seas of the future.

To make better predictions about the future impacts of sea level rise, new techniques are being developed to fill gaps in the historic record of sea level measurements. We know the factors that play a role in sea level rise: Melting glaciers and ice sheets add water to the seas, and warmer temperatures cause water to expand. Other factors are known to slow the rise, such as dams impounding water on the land, stymying its flow into the sea.

When each factor is added together, this estimate should match the sea level that scientists observe. Until now, however, the sea level “budget” has fallen short of the observed sea level rise, leading scientists to question why the budget wouldn’t balance.

A new study published on August 19 seeks to balance this budget. By gaining new insights to historic measurements, scientists can better forecast how each of these factors will affect sea level rise and how this rise will impact us in the future.

For example, in its recent flooding report, the National Oceanic and Atmospheric Administration (NOAA) noted a rapid increase in sea level rise-related flooding events along U.S. coasts over the last 20 years, and they are expected to grow in extent, frequency, and depth as sea levels continue to rise.

Sea Levels Infographic

This infographic shows the rise in sea levels since 1900. Pre-1940, glaciers and Greenland meltwater dominated the rise; dam projects slowed the rise in the 1970s. Now, ice sheet and glacier melt, plus thermal expansion, dominate the rise. Tide-gauge data shown in blue and satellite data in orange. Credit: NASA/JPL-Caltech

Factors Driving Our Rising Seas

On reexamining each of the known contributors to sea level rise from 1900 to 2018, the research, led by NASA’s Jet Propulsion Laboratory in Southern California, uses improved estimates and applies satellite data to better understand historic measurements.

The researchers found that estimates of global sea level variations based on tide-gauge observations had slightly overestimated global sea levels before the 1970s. (Located at coastal stations scattered around the globe, tide gauges are used to measure sea level height.) They also found that mountain glacier meltwater was adding more water to the oceans than previously realized but that the relative contribution of glaciers to sea level rise is slowly decreasing. And they discovered that glacier and Greenland ice sheet mass loss explain the increased rate of sea level rise before 1940.

In addition, the new study found that during the 1970s, when dam construction was at its peak, sea level rise slowed to a crawl. Dams create reservoirs that can impound freshwater that would normally flow straight into the sea.

“That was one of the biggest surprises for me,” said lead researcher Thomas Frederikse, a postdoctoral fellow at JPL, referring to the peak in global dam projects at that time. “We impounded so much freshwater, humanity nearly brought sea level rise to a halt.”

Since the 1990s, however, Greenland and Antarctic ice sheet mass loss and thermal expansion have accelerated sea level rise, while freshwater impoundment has decreased. As our climate continues to warm, the majority of this thermal energy is absorbed by the oceans, causing the volume of the water to expand. In fact, ice sheet melt and thermal expansion now account for about two-thirds of observed global mean sea level rise. Mountain glacier meltwater currently contributes another 20%, while declining freshwater water storage on land adds the remaining 10%.

All told, sea levels have risen on average 1.6 millimeters (0.063 inches) per year between 1900 and 2018. In fact, sea levels are rising at a faster rate than at any time in the 20th century. But previous estimates of the mass of melting ice and thermal expansion of the ocean fell short of explaining this rate, particularly before the era of precise satellite observations of the world’s oceans, creating a deficit in the historic sea level budget.

Finding a Balance

In simple terms, the sea level budget should balance if the known factors are accurately estimated and added together. It’s a bit like balancing the transactions in your bank account: Added together, all the transactions in your statement should match the total. If they don’t, you may have overlooked a transaction or two.

The same logic can be applied to the sea level budget: When each factor that affects sea level is added together, this estimate should match the sea level that scientists observe. Until now, however, the sea level budget has fallen short of the observed sea level rise.

“That was a problem,” said Frederikse. “How could we trust projections of future sea level change without fully understanding what factors are driving the changes that we have seen in the past?”

Frederikse led an international team of scientists to develop a state-of-the-art framework that pulls together the advances in each area of study — from sea level models to satellite observations — to improve our understanding of the factors affecting sea level rise for the past 120 years.

GRACE-FO in Orbit

Illustration of GRACE-FO in orbit. Credit: NASA/JPL-Caltech

The latest satellite observations came from the pair of NASA – German Aerospace Center (DLR) Gravity Recovery and Climate Experiment (GRACE) satellites that operated from 2002-2017, and their successor pair, the NASA – German Research Centre for Geosciences (GFZ) GRACE Follow-On (launched in 2018). Additional data from the series of TOPEX/Jason satellites — a joint effort of NASA and the French space agency Centre National d’Etudes Spatiales —  that have operated continuously since 1992 were included in the analysis to enhance tide-gauge data.

“Tide-gauge data was the primary way to measure sea level before 1992, but sea level change isn’t uniform around the globe, so there were uncertainties in the historic estimates,” said Sönke Dangendorf, an assistant professor of oceanography at Old Dominion University in Norfolk, Virginia, and a coauthor of the study. “Also, measuring each of the factors that contribute to global mean sea levels was very difficult, so it was hard to gain an accurate picture.”

But over the past two decades, scientists have been “flooded” with satellite data, added Dangendorf, which has helped them precisely track the physical processes that affect sea levels.

For example, GRACE and GRACE-FO measurements have accurately tracked global water mass changes, melting glaciers, ice sheets, and how much water is stored on land. Other satellite observations have tracked how regional ocean salinity changes and thermal expansion affect some parts of the world more than others. Up-and-down movements of Earth’s crust influence the regional and global levels of the oceans as well, so these aspects were included in the team’s analysis.

“With the GRACE and GRACE-FO data we can effectively back-extrapolate the relationship between these observations and how much sea level rises at a particular place,” said Felix Landerer, project scientist at JPL for GRACE-FO and a coauthor of the study. “All observations together give us a pretty accurate idea of what contributed to sea level change since 1900, and by how much.”

The study, titled “The Causes of Sea Level Rise Since 1900,” was published August 19 in Nature. In addition to scientists from JPL and Old Dominion University, the project involved researchers from Caltech, Université Catholique de Louvain in Belgium, University of Siegen in Germany, the National Oceanography Centre in the United Kingdom, Courant Institute in New York, Chinese Academy of Sciences, and Academia Sinica in Taiwan.

Reference: “The causes of sea-level rise since 1900” by Thomas Frederikse, Felix Landerer, Lambert Caron, Surendra Adhikari, David Parkes, Vincent W. Humphrey, Sönke Dangendorf, Peter Hogarth, Laure Zanna, Lijing Cheng and Yun-Hao Wu, 19 August 2020, Nature.
DOI: 10.1038/s41586-020-2591-3

JPL managed the GRACE mission and manages the GRACE-FO mission for NASA’s Earth Science Division of the Science Mission Directorate at NASA Headquarters in Washington. Based on Pasadena, California, Caltech manages JPL for NASA.

62 Comments on "NASA Research Reveals the True Causes of Sea Level Rise Since 1900"

  1. Simple solution hire aqua engineers from the Netherlands and build more damns that produce Hydropower.

    • You didn’t read the article did you? The dams are balancing the sea level rise.

    • Not a scientist just care about the environment | August 27, 2020 at 12:53 pm | Reply

      Rassalas has a great idea. Dams help balance sea water rise by holding water on land. So building more dams would keep more water on land and help stem the rise of the ocean water.

  2. Scott Campbell | August 24, 2020 at 12:59 am | Reply

    There was no mention of soil erosion and sediment as being one of the factors to consider.

  3. If this is such an issue, why are our politicians, that believe in climate change, buying water front properties?

    I smell bs

    • Bruce Lightfoot | August 25, 2020 at 6:58 am | Reply

      The politicians who can afford waterfront property are old, and will be dead before it becomes a serious problem. Like one of the kings of France said: “After me, the deluge”. They don’t care if their kids lose everything to a storm, and probably just buy lots more insurance than they need so the kids make out just fine anyway.

      The real problem with our climate is just like with a train or the Titanic, some things don’t stop on a dime and you have to plan ahead a bit.

    • Some Random Kid Who Cares For The Environment | August 26, 2020 at 8:25 am | Reply

      I don’t smell it, I think you just shat in your diaper.

  4. So according to the information provided in this article the sea level has risen approximately 7.5 inches in the past 120 years. I’m shaken in my boots.

  5. Ross McCullough | August 24, 2020 at 3:47 am | Reply

    I am amazed that sea level can be measured by a satellite hundreds of kilometers in space to an accuracy of 0.1mm considering waves, air pressure, lunar cycle and temperature variations.
    Magic

    • The satellites can’t!

      The latest generation of Satellites (4th series) are supposed to be considerably more accurate than their predecessors. They will take up to 5 years to configure and supposedly will be accurate up to just over a centimeter. The rate of sea level increases 3 millimeters. More wasted money and resources.

    • Bruce Lightfoot | August 25, 2020 at 7:11 am | Reply

      Nope. Statistics. If somebody wanted to, they could probably scrape your social media files and predict that on a given day of the week there is a 99% chance that you will be in a grocery store at a given time, and what the 3 most likely things are that you are buying.

      All the points you mention are significant variables, but within a range that averages out over time. With only a few data points, we learn nothing. With millions, or billions, we get a good idea of how things are changing. From that we learn trends and can make projections. These are averages, and are better than estimates, but do NOT apply to any one specific point in time or place. A windy day at your beach house will make far more difference, today, than a glacier calving in Antarctica. Millions of repeated events add up. When you see a bee on a flower, it is sometimes a good idea to check and make sure there is not a wasps nest about to fall on your head.

  6. I still can fill a glass of water with ice cubes in it and it does’t overflow when the ice melts. Sure, there is ice on land adding to the total amount of water as it melts, but there is an awfully big set of oceans out there to spread it around.

  7. To Trump 2020 (farewell year let’s hope) we’ve heard that silly statement many times. Politicians buy inland or seaside same as anyone else. Even if people buy on the coast the house is unlikely to be inundated in their lifetime. To Jim, the glass analogy is illogical. If you keep adding water including by melting glaciers the level must rise. Thank God for scientists. At least they know what they are talking about even if it’s a bit difficult to explain to ordinary people. Trust them with our lives.

  8. The article was written without using the word,”clouds”.
    Any atmospheric analysis that omits clouds is useless.

  9. If we all drink more water, we will be healthier and also save the planet. LOL.
    Seriously , I recommend thinking outside the box on this issue, like giant reflector at the equator areas, or moving large amounts of water to low inland areas and deserts

  10. You brain dead are lacking the one major thing !
    Seismic testing has caused ground drainage to slow, all across this planet. adding tons of weight to every continent.
    This compresses the continents inward downward ! Forcing the waters to rise just like adding weight to a boat
    Why are you not speaking about this fact – hiding it, Because you don’t want to upset the apple cart the oil and gas companies have done, are your to blind and have not come to that conclusion yet !

  11. Dennis Wilder | August 24, 2020 at 7:49 am | Reply

    alot of other factors like erosion and nevermind all of the man made items in the ocean like waste trash boats alone how many giant ocean liners are out there just look at how much water is moved by one containership

  12. Paul Parkinson | August 24, 2020 at 7:49 am | Reply

    Why isn’t subduction even mentioned? And no, the oceans have not risen by 7.5 inches in 100 years. There are many photos throughout the years and water lines have not changes except in areas where land has eroded or is sinking due to subduction. This article is a load of bulkshit.

  13. At least they stuck with just measuring sea levels more accurately and trying to straighten out old data issues. Sort of glad they didn’t launch into the old – everything is the fault of humans because the earth couldn’t possibly warm any in its own.

  14. In Scandinavian the land is still raising after last ice age. Wouldn’t that make sea level raise other places in the world.

  15. Has anyone stopped to consider the water effect of the Burning of fossil fuels? 1 gallon of gasoline yields 1.033 gallons of water. How many gallons of water have been released by the burning of coal, natural gas, diesel and heating fuel and gasoline since the discovery of crude oil?

  16. Julius. The most simple observation is actual rise. Actual rise is mere inches. That is the big lie of global warming. All the world is ending folks somehow don’t know this.

  17. Frank J. Verderber BSGS/ASCT | August 24, 2020 at 10:23 am | Reply

    Before the late 80’s the leading cause of ocean increase or decrease was seen as tectonic activity. But now we have the psuedo science of Global warming. If the globe warms it’s because of the Sun, and it’s been doing that since 7,000 BC. The ice caps melted then. This is why we find 2 and 3 thousand yo coastal cities in 100 feet of water. Ignore British Science, and Geology and Anthropology begin to make sense.

  18. pump seawater inland? Yeah, that’s a genius move.

  19. Centralia Pennsylvania needs water pumped into those fire caverns! So does Yellowstone. It might cool that place down avoiding earthquakes ! Lol idk.

  20. Steve the realist | August 24, 2020 at 11:06 am | Reply

    If we take the accuracy of the study as a given, sea level will rise by about one inch every every 16 years.
    Given that varous studies of measurements of sea level show that the sea has been about 400 feet lower than it is now and 15 feet higher than it is now, the rate of sea level rise is not the catastrophe that many believe.
    Obviously earth’s integrated systems are extremely complicated and more will be “learned” as time goes on. For those who deliberately make the “world is coming to an end” arguement, you simply make the more skeptical and rational amoung us see you as bending science to make a political point all the the while scaring our children into believing there is no hope in the future.
    Aside from the fact this is an abuse of children, you offer no comprehensive practical solutions. Banning fossil fuel will not work. Advocating “renewables” without increased nuclear and hydroelectric is not serious.
    Everyone I have ever met would like a cleaner world. If we can all agree with that, then perhaps we can move forward. Science and technology has always moved us forward– put your personal politics aside and we can make the best decisions based on real science and how people throughout the world can prosper.

  21. It is sad when your political party determines whether you believe science or not.

  22. Here’s an experiment,,
    What happens when you add in 1/4 sand or gravel to one cup that is half full of water?
    And here’s a real good one other than land masses of glaciers melting,,
    I’m sure that the Prestigious Science Community has been paying attention to the huge Supervolcano in Antarctica that has sheets of ice melting.
    Namastè

  23. After the Ice Age melted, it left a land mass between Russia and Alaska. Why did this happen ? Was the land more swampy….where there more trees to soak up the water.Hmmmm. Scientists are therorists.

  24. Must you write sensational headlines that make it appear previous explanations of sea level rise were wrong?

    And replying to Jim, whose drink doesn’t overflow when the ice cubes melt – well of course not. One gram of water occupies less space than one gram of ice. That’s why the cubes float. Water is densest at 4C; after that further warning causes it to expand (which is why rising sea water temperatures are contributing to sea level rise.)

  25. It’s Trump! It’s atmospheric carbon! He pulled out the climate accord talks years ago! Now it’s too late! But if we get Joe, Hilary, and Kamala in office NOW, it could all change and the future will be so bright for your children. Think of the children! Greedy self-serving racist climate denier stays = MASS EXTINCTION!!!

  26. Exceptionalism Children | August 24, 2020 at 1:17 pm | Reply

    The comments to this article prove everyone thinks they’re smarter than an expert (? Wouldn’t that make them… never mind) and why America has become a sick, stupid, poor, shithole country. And it’s victims, Americans, screamed for “we need even more of that!”

  27. Wow , NASA reveals how much damage is done by themselves , by over launching environmental space substances , carried away by passon n curiosity, than n a actual need 🤔

  28. Michael Angemeer | August 24, 2020 at 2:14 pm | Reply

    I guess the main question should be, with this increased level of accuracy what are the range of new projections to 2100 and beyond.

  29. Rassalas, you missed the entire point of the article. The current dams are already leveling out the negligible sea level rise.

  30. Steven M Hein | August 24, 2020 at 3:49 pm | Reply

    All seems pretty irrelevant, If scientists who track fresh water data are correct, by the year 2040, the Earth will be 40% short of the necessary water to irrigate our crops and we’ll start dying of starvation.

  31. David Carroll | August 24, 2020 at 6:38 pm | Reply

    Reading these comments, most are really stupid, obviously never studied science,or logic. Perhaps never got past kindergarten. I may be wrong but I would guess most of these people are self-opinionated, self-educated Yanks. That is the real curse on the World. They elected one of their own recently.

  32. Why can’t water be diverted through places like the grand canyon it’s a mile deep. Flood deserts like the Sahara? These kind of places would hold billions of tonnes of water surely?

  33. Can someone invent a stick that freeze the ice at the ice cudes artificially?

  34. Please forgive me if this is a stupid question, but non of these sea level rising theories ever mention the vast amount a shipping tonnage or the land reclamation projects that also displace water? A quick look at a shipping app shows the immense number of vessels that are at sea (very similar to the number of aircraft in the air at any one time). Surely this also has an effect on the rising of the oceans?

  35. @David Chura No it is you who are actually braindead, as your theory assumes the continents are floating on the water as objects in a bathtub. This is silly and untrue, as the continents are on plates and magma and the Earth’s geologic interior. The water is on the surface if the Earth!

  36. wow. some of the comments here are laughable and suggest many are either illiterate or lazy or both. even small increases in sea level can threaten coastal communities and infrastructure that were built based on a stable sea level. we are already seeing the effects of sea level rise in a number of places including Alaska, Humboldt bay, and some islands in south pacific to name a few. grow up people; the only ones politicizing this are the greedy bastards that could care less about anyone else.

  37. I can only talk from the experience of living in the Seychelles for the last 20 years. Every month, almost, the rising sea appears noticeable as demonstrated by beaches disappearing, coastal roads being flooded, hotels being flooded and sea walls being built all over the place. In just those 20 years the coastal map has changed considerably. It seems to me, observing this everyday, that the rise in sea levels is being underestimated.

  38. Joni Boulware | August 25, 2020 at 5:48 am | Reply

    This won’t stop until the next ice age. If you are on an atoll or low elevation island, you may have to abandon it eventually. Venice has never figured out how to keep water out. Ancient port cities in China were abandoned centuries ago. Humans adapt. Keep adapting.

  39. The Arizona Guy | August 25, 2020 at 5:57 am | Reply

    Let the water rise we need more green in the world we are just killing the world by cutting down forest areas causing the global heat rises that has played a big role in the melting of the glaciers and ice for example take away oxygen from a humans body and what happens you cant breathe anymore causing other organs to shut down so when your taking away tons of tree which also make oxygen and helps with climate for other life that’s when you have this chain of reactions simple solution to all of the plant trees that you cut down

  40. Interesting article it’s good to see the satellites AR bringing us more into line with what’s actually going on and unfortunately the comments show that the dumb Burns deep in America and Beyond

  41. Crecencio Elenes | August 25, 2020 at 8:00 am | Reply

    What about the water displacement by the increasing number of ships weighing more than 5000 ton that transport containers full of goods across the world.

  42. So the politico programmed didn’t even see the deforestation caused Deserts and without irrigation to make reforestation to happen, the Desert would remain too large☀️ I choose discussion to agree the way forwards☀️ not politico control freaks … Duurrrhhh!!!

  43. Jason D Maccue | August 25, 2020 at 8:39 am | Reply

    The comments about people being dumb are laughable. Sea has been rising since the end of last ice age and the rate has actually decreased over the last 120 years something this article conveniently omits. To all you haters look it up! The so called experts think you’re dumb. Do you’re own research!

    • ☀️🌈Yea and it iz continuing rising way back in 2020 iz the main concern of people in this discussion … right …☀️

  44. Is the water in the air, via psychrometrics, part of these estimates, e.g. clouds and relative humidity?

  45. Two sentences later I was aware you mammals are not dealing in chances for survival but artificially taking distance from the collective being. MY LIFE HAS VALUE. YOU WILL VANISH AS SO MANY BEFORE. LIFE FINDS A WAY, FOR IT’S AWARE OF THE OPPOSITE.

  46. Christa Charles | August 25, 2020 at 4:19 pm | Reply

    You can see where world war 1 started and the industrialisation for war started. Cows and cars just finished the job…

  47. It’s called earth erosion sediment displacement.. all these brown rivers are carving out land and moving dirt into the oceans causing them to rise..

  48. How much does sedimentation add to this? Does the Earth lose water to outer space, or are we a closed system. Water covered land mass in the past. Water may be at its highest now. Time to come down cyclically.

  49. JULIUS TIMMERMAN | August 25, 2020 at 10:27 pm | Reply

    Seriously Frank….and what was the sun doing before 7000BC. Also think about this. In the past century alone, the earth average temperature has risen by 0.7 degrees – 10 times faster than the average rate of ice age recovery warming. So what has the sun been doing in the last 100 years. Answer – the same as it did in 7000BC. Trust those who know.

  50. In all this climate change hoax nobody ever mentioned the biggest single factor influencing our weather,the sun. But of course that is untaxable.

  51. Some Random Kid Who Cares For The Environment | August 26, 2020 at 8:22 am | Reply

    You know what makes me angry? The fact that every time they mention the sea level rise they say “How it will affect us in the future.” To them it needs to be WILL, I say the fact it MIGHT effect us. There are people that have already started working really hard to slow it down, or maybe even stop sea level rise, and some people (like me) who simply try to limit their waste, use green energy, don’t waste water or just share their thoughts in forums. I don’t think that they should pessimist about sea level rise, no one should be, so no, Trump, you may stand a few comments below me and yu may not be real, but no I don’t smell bs, I think you just shat your pants and didn’t notice because of the diaper.

    No bullshit smelled.

  52. I shall reserve my opinion on the veracity of all this information until said technology can provide us with an accurate weather forecast 😉

  53. The damming segment was quite fascinating. However, if we went that route for a solution, by further increasing the surface area will, in the long run, speed up the evaporation of the fresh water accumulation. Take Hoover damn for example, sure there is less run off from the mountains, but the water that sits there is also dissipating faster than consumption. That water evaporates to somewhere eventually, right?.

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