Study predicts more long-term sea level rise from Greenland ice

Study predicts more long-term sea level rise from Greenland ice
The researchers ran their model 1500 times, testing a variety of land, ice, ocean and atmospheric variables to see how they affected ice melt rate - including three possible future climate scenarios (from left to right: low, medium, and high emissions out to the year 2300). Credit: Credits: NASA / Cindy Starr

Greenland's melting ice sheet could generate more sea level rise than previously thought if greenhouse gas emissions continue to increase and warm the atmosphere at their current rate, according to a new modeling study. The study, which used data from NASA's Operation IceBridge airborne campaign, was published in Science Advances today. In the next 200 years, the ice sheet model shows that melting at the present rate could contribute 19 to 63 inches to global sea level rise, said the team led by scientists at the Geophysical Institute at the University of Alaska Fairbanks. These numbers are at least 80 percent higher than previous estimates, which forecasted up to 35 inches of sea level rise from Greenland's ice.

The team ran the model 500 times out to the year 3000 for each of three possible future climate scenarios, adjusting key land, ice, ocean and atmospheric variables to test their effects on ice melt rate. The three climate scenarios depend on the amount of greenhouse gas emissions in the atmosphere in coming years. In the scenario with no reduction of emissions, the study found that the entire Greenland Ice Sheet will likely melt in a millennium, causing 17 to 23 feet of sea level rise.

In the scenario where emissions are stabilized by the end of the century rather than continue to increase, the model shows ice loss falling to 26-57 percent of total mass by 3000. Drastically limiting emissions so they begin to decline by the end of the century could limit ice loss to 8-25 percent. This scenario would produce up to six feet of sea level rise in the next millennium, according to the study.

The updated model more accurately represents the flow of outlet glaciers, the river-like bodies of ice that connect to the ocean. Outlet glaciers play a key role in how ice sheets melt, but previous models lacked the data to adequately represent their complex flow patterns. The study found that melting outlet glaciers could account for up to 40 percent of the ice mass lost from Greenland in the next 200 years.

By incorporating ice thickness data from IceBridge and identifying sources of statistical uncertainty within the model, the study creates a more accurate picture of how human-generated greenhouse gas emissions and a warming climate may affect Greenland in the future.

New research shows an iceless Greenland may be in our future
Ilulissat, known as 'the city of icebergs' sits adjacent to Greenland's Ilulissat Glacier, which flows into the Atlantic Ocean. Such outlet glaciers lead ice sheet loss in Greenland. New research shows that if this loss continues at its current rate, it could result in an ice-free Greenland by the year 3000 and 24 feet of global sea level rise. Credit: Martin Truffer

A clearer picture

Capturing the changing flow and speed of outlet glacier melt makes the updated ice sheet model more accurate than previous models, according to the authors. As ocean waters have warmed over the past 20 years, they have melted the floating ice that shielded the outlet glaciers from their rising temperatures. As a result, the outlet glaciers flow faster, melt and get thinner, with the lowering surface of the ice sheet exposing new ice to warm air and melting as well.

"Once we had access to satellite observations, we were able to capture the surface velocity of the whole Greenland Ice Sheet and see how that ice flows. We recognized that some outlet glaciers flow very fast—orders of magnitude faster than the interior of the ice sheet," said lead author Andy Aschwanden, a research associate professor at the University of Alaska Fairbanks' Geophysical Institute.

IceBridge's detailed ice thickness measurements helped the team to be the first to model these areas where outlet glaciers are affected by warmer ocean waters, as well as to model more of the complex feedbacks and processes influencing ice loss than previously possible. They examined the importance of factors like underwater melting, large ice chunks breaking off of glaciers, changing snowfall rates and rising air temperatures. They also examined factors that could slow down ice loss, like the movement of Earth's surface "bouncing back" from the weight of ice that is no longer there.

"At the end of the day, glaciers flow downhill," Aschwanden said. "That's very simplified, but if you don't know where downhill is, the model can never do a good job. So the most important contributor to understanding ice flow is knowing how thick the ice is."

New research shows an iceless Greenland may be in our future
These maps of Greenland show ice losses under two 'representative concentration pathways' of greenhouse gases in Earth's atmosphere from present day to the year 3000. The RCPs, adopted by the Intergovernmental Panel on Climate Change, reflect higher (8.5) and lower (2.6) greenhouse gas concentrations associated with different levels of emissions from human use of fossil fuels. Currently, the planet is on the higher pathway. Credit: UAF Geophysical Institute

Each of the three emissions scenarios used in the study produced different patterns of ice retreat across Greenland. The least severe scenario showed the ice retreating in the west and north, while the moderate scenario showed ice retreat around the island, except for in the highest elevation areas. The most severe scenario, in which emissions continue to increase at their present rate, showed more than half of the model runs losing more than 99 percent of the ice sheet by 3000.

At its thickest point, the Greenland Ice Sheet currently stands more than 10,000 feet above sea level. It rises high enough into the atmosphere to alter the weather around it, as mountains do. Today, this weather pattern generates almost enough snowfall to compensate for the amount of naturally melting ice each year. In the future, however, melting and flow will thin the interior, lowering it into a layer of the atmosphere that lacks the conditions necessary for sufficient replenishing snowfall.

"In the warmer climate, glaciers have lost the regions where more snow falls than melts in the summer, which is where new ice is formed," said Mark Fahnestock, research professor at the Geophysical Institute and the study's second author. "They're like lumps of ice in an open cooler that are melting away, and no one is putting any more ice into the cooler."

The team stressed that despite the need for ongoing research on exactly how glaciers will move and melt in response to warming temperatures, all of the model runs show that the next few decades will be pivotal in the ice sheet's future outcome.

"If we continue as usual, Greenland will melt," Aschwanden said. "What we are doing right now in terms of emissions, in the very near future, will have a big long-term impact on the Greenland Ice Sheet, and by extension, if it melts, to sea level and human society."

Scientists at the University of Alaska Fairbanks’ Geophysical Institute used data from NASA’s Operation IceBridge to develop a more accurate model of how the Greenland Ice Sheet might respond to climate change in the future, finding that it could generate more sea level rise than previously thought. Credit: NASA / Katie Jepson

Bridging the data gap

The model runs were performed on high-performance supercomputers at NASA's Ames Research Center and the University of Alaska Fairbanks (UAF) using the Parallel Ice Sheet Model (PISM), an open-source model developed at UAF and the Potsdam Institute for Climate Impact Research. NASA also provided funding support for the study. While other ice sheet models could perform the simulations they did, the team said, PISM is unique for its high resolution and low computational cost.

NASA's Operation IceBridge is the world's largest airborne survey of polar land and sea ice. Using an array of aircraft and scientific instruments, IceBridge has collected data between the end of the first Ice, Cloud and Land Elevation Satellite (ICESat) mission in 2010 and the second, ICESat-2, which launched in 2018. It has measured the height of the ice below its flight path as well as the bedrock under the ice sheets.

"NASA's space and airborne campaigns, like IceBridge, have fundamentally transformed our ability to try and make a model mimic the changes to the ice sheet," Fahnestock said. "The technology that allows improved imaging of the glacier bed is like a better pair of glasses allowing us to see more clearly. Only NASA had an aircraft with the instruments and technology we needed and could go where we needed to go."

Banner Image: The Greenland Ice Sheet is the second-largest body of ice in the world, covering roughly 650,000 square miles of Greenland's surface. If it melts completely, it could contribute up to 23 feet of sea level rise, according to a new study using data from NASA's Operation IceBridge.


Explore further

Melting small glaciers could add 10 inches to sea levels

More information: "Contribution of the Greenland Ice Sheet to sea level over the next millennium" Science Advances (2019). DOI: 10.1126/sciadv.aav9396 , https://advances.sciencemag.org/content/5/6/eaav9396
Journal information: Science Advances

Citation: Study predicts more long-term sea level rise from Greenland ice (2019, June 19) retrieved 18 July 2019 from https://phys.org/news/2019-06-iceless-greenland-future.html
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Jun 19, 2019
Who in their right mind, would care about a pile of fear mongering speculations about what MIGHT happen to our decedents, 10 generations from now?

Talk about stupid, meaningless speculations about imaginary nonsense!

The authors should be thoroughly ashamed!....

Jun 19, 2019
"The most severe scenario, in which emissions continue to increase at their present rate, showed more than half of the model runs losing more than 99 percent of the ice sheet by 3000."

-But then, according to Siddharth Singh at The Centre for Research on Energy Security at The Energy and Resources Institute, Delhi (and others)...

"Various studies show that the total remaining recoverable oil resources would last 190 years, natural gas 230 years"

-which means that emissions will not continue to increase at their present rate. And we would have perhaps half a millennium to recover.

But I'm guessing that all that exposed, pristine, unpolluted Greenland real estate would more than make up for all the befouled coastal land that would be inundated.

Win win.

Much easier to redesign from scratch to suit current tech rather than try to adapt obsolete cities based on ancient tech and culture.

If AGW were actually real it would be an excellent excuse wouldn't it?

Jun 19, 2019
I mean really, venice is romantic? Only if you're too drunk to ignore all the floating turds. You can't fix most coastal infrastructure. Half the potable water supplied to Manhattan leaks out of the pipes. Many of these cities have combined storm and sewer systems. The sewage is impossible to treat. They rely on rainstorms to flush their toilets.

And they're totally incompatible with modern transportation, especially self-driving vehicles.

Here's some news...

"[NYC] Mayor Bill de Blasio plans to introduce a bill banning new construction of glass skyscrapers
The bill comes as part of his climate change effort to reduce citywide greenhouse emissions by 30 percent"

-which is of course typical inane Dem bullshit. The best way, again, to maximize efficiency is to start over from scratch.

Jun 19, 2019
I do know that about 20 years ago they started growing cabbage in greenhouses on Greenland, and that they were quite happy to have fresh cabbage for a couple of months a year. Are they growing barley or wheat on Greenland? Do they yet have dairy farms?

Because they did, 1000 years ago, when it was warmer.

Worried about sea level rise? Move to Denver.

Worried about ClimateChange?©™ Plant Trees. Paint all artificial sky facing surfaces a reflective color. And finally tell your betters to stop flying chartered jets to climate change conferences.

Jun 19, 2019
Just more evidence that we need to step up efforts to curb GHGs. Those welcoming the forced migration of millions of people and loss of property should try it out for themselves and see how they like it

Jun 19, 2019
Meanwhile...
Greenland has been cooling since 2005
https://notricksz...2017.jpg

Jun 19, 2019
Anti, don't you ever get embarrassed by your continual misrepresentations of the facts?
You post a link, but only of the tiny, tiny sliver in the study that (barely) supports your point.
Here's the rest of the study. As it clearly states, Greenland continues to warm.
The study's author (Kobashi) would vigorously disagree with your conclusion.
https://www.natur...-01451-7

Jun 19, 2019
If you are curious about Greenland temperature trends try some real science rather than blogs.

https://www.natur...-19992-w

Jun 19, 2019
You obviously never get embarrassed by your stupidity.
How about a bigger sliver, showing Greenland cooling for the last 8000 years.
https://media.spr...HTML.jpg

Jun 19, 2019
The self-righteous beliefs of many researchers make them interpret all the consequences of current global warming as inherently evil. This is due to the religiously rooted notion that humans are not part of nature and any changes we make to the natural world are always a corruption, destruction of what nature in a healthy state would be without out interference. As a result, every scenario is described in the direst, negative terms despite there being a vast number of positive effects.

An inhabitable Greenland is a positive not a negative. Even better is eventually the entire central part of the Island will rapidly rise providing even more land as a result of isostatic rebound.

Drowned coastal areas will be replaced by vast new lands as barren tundra becomes habitable for humans AND animals. It will take place over centuries giving us and nature enough time to adapt effectively if we choose to instead of tilting against windmills.

Jun 19, 2019
Ban Plutonium if you are truly worried about Warming!

Jun 20, 2019
The 500 model runs would cover a lot more scenarios than covered in this article. The focus of the article is just Greenland's contribution, not that of Antarctica as well.

A thing to note is the distinction between weather, short term climate variations, and long term variations. There are decadal long patterns in climate that skews data, as well as short term climate patterns like El Nino and La Nina. There are also a huge swathe of other factors that can lead to cooler weather in some areas due to changes in circulation patterns. The sun's output is also a big factor, it has cycles that can greatly affect temperature. We're at the stage where the sun's output is less as part of the sun's 400 year cycle, so it should actually be cooler now without human contribution.

This potentially means current best estimates of sea level rise by 2250 is understated since the sun's output will start rising again at the end of the century and likely peak around that time.

Jun 20, 2019
Anti, don't you ever get embarrassed by your continual misrepresentations of the facts?
You post a link, but only of the tiny, tiny sliver in the study that (barely) supports your point.
Here's the rest of the study. As it clearly states, Greenland continues to warm.
The study's author (Kobashi) would vigorously disagree with your conclusion.
https://www.natur...-01451-7


Antigoracle and his own sockpuppets have no way to evolve, he still falls down the stairs of his mothers basement everytime he goes down, to be an idiot is his greatest accomplishment to date.

Jun 20, 2019
https://www.ameri...res.html
You will not like the mob rule that is being promoted.


Jun 20, 2019
Take a gander at Greenland's temperature during the 1920-30s, when the world was coming out of the Little Ice-age and anthropogenic CO2 was insignificant compared to now. Reality is not cooperating with the AGW Cults "science".
http://berkeleyea...rend.pdf

Jun 21, 2019
@snoosebaum.
keep it straight guys
https://phys.org/...ear.html
Next time try harder to read/understand the fuller/trending study/results you link to, mate. Check out the closing paragraph:
The temperature change of the current's water is part of a known climate pattern, one that is expected to flip again, and cause more of the melting and ice thinning for which Jakobshavn is known. Although the melting rate has slowed, the glacier continues to contribute to sea level rise, ultimately losing more ice to the ocean than it gains from snow accumulation overall.
Note especially the last sentence.

In future try to at least be a smidge more objective if not completely comprehending of what you repeat/link, @snoose. Good luck to us all. :)

Jun 21, 2019
@antigoracle.
Take a gander at Greenland's temperature during the 1920-30s, when the world was coming out of the Little Ice-age and anthropogenic CO2 was insignificant compared to now. Reality is not cooperating with the AGW Cults "science".
http://berkeleyea...rend.pdf
Silly. Recall that the world was transitioning from wood to coal and oil at a great rate just after 1900. This rate was accelerated in leadup to World Wars I & II. It was a QUADRUPLE-WHAMMY period for increased CO2 emissions, because not only was the world STILL burning wood/peat for fuel, but industrialisation had also led to rampant deforestation; and there was huge expansion of CHEMICALS production for fertilisers, gunpowder etc. The fourth 'whammy' was the two World Wars themselves which saw a huge surge in STEEL and War Machines/Trains/Rail/Engines which FURTHER increased CO2.

You're a "weaponised stupid" stooge and/or "dumb bot", @antigoracle. :)

Jun 21, 2019
Sez the author:

"Greenland's melting ice sheet could generate more sea level rise than previously thought"

"more" ??????

Still awaiting the sea level rise. Maybe I missed it already because I overslept one day during the past 20 years.

Jun 21, 2019
Still awaiting the sea level rise. Maybe I missed it already because I overslept one day during the past 20 years.
.....forgot to mention, the NYC Harbor buoys have not changed poaitional elevation since the onslaught of Greenland's ice melt.

Jun 21, 2019
"June has set a record low of Arctic sea ice, while the extent of melting across the Greenland Ice Sheet this early in the summer has never been seen before.

Recently, temperatures in parts of Greenland soared to 40 degrees above normal, while open water (not covered by sea ice) is already being observed in places north of Alaska where it has seldom, if ever, been observed.
The current sea ice coverage in the Arctic is the lowest ever recorded for mid-June."
https://truthout....-arctic/

When water freezes it expands 10% by volume. When Ice in water thaws, water level in contact with the ice will drop due to reduced displacement volume, this is what is going on right now as Arctic Ocean ice melt continues. However, if there is a replacement supply of water to prevent ocean levels from dropping, NYC Harbors buoys will detect no change, they haven't. Thank you Greenland.

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