Greenland ice sheet melt 'off the charts' compared with past four centuries

December 5, 2018, Woods Hole Oceanographic Institution
Large rivers form on the surface of Greenland each summer, rapidly moving meltwater from the ice sheet to the ocean. Credit: Sarah Das, Woods Hole Oceanographic Institution

Surface melting across Greenland's mile-thick ice sheet began increasing in the mid-19th century and then ramped up dramatically during the 20th and early 21st centuries, showing no signs of abating, according to new research published Dec. 5, 2018, in the journal Nature. The study provides new evidence of the impacts of climate change on Arctic melting and global sea level rise.

"Melting of the Greenland Ice Sheet has gone into overdrive. As a result, Greenland melt is adding to sea level more than any time during the last three and a half centuries, if not thousands of years," said Luke Trusel, a glaciologist at Rowan University's School of Earth & Environment and former post-doctoral scholar at Woods Hole Oceanographic Institution, and lead author of the study. "And increasing melt began around the same time as we started altering the atmosphere in the mid-1800s."

"From a historical perspective, today's melt rates are off the charts, and this study provides the evidence to prove this" said Sarah Das, a glaciologist at Woods Hole Oceanographic Institution (WHOI) and co-author of the study. "We found a fifty percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a thirty percent increase since the 20th century alone."

Ice loss from Greenland is one of the key drivers of global sea level rise. Icebergs calving into the ocean from the edge of glaciers represent one component of water re-entering the ocean and raising sea levels. But more than half of the ice-sheet water entering the ocean comes from runoff from melted snow and glacial ice atop the ice sheet. The study suggests that if Greenland ice sheet melting continues at "unprecedented rates"—which the researchers attribute to warmer summers—it could accelerate the already fast pace of sea level rise.

"Rather than increasing steadily as climate warms, Greenland will melt increasingly more and more for every degree of warming. The melting and sea level rise we've observed already will be dwarfed by what may be expected in the future as climate continues to warm," said Trusel.

To determine how intensely Greenland ice has melted in past centuries, the used a drill the size of a traffic light pole to extract ice cores from the ice sheet itself and an adjacent coastal ice cap, at sites more than 6,000 feet above sea level. The scientists drilled at these elevations to ensure the cores would contain records of past melt intensity, allowing them to extend their records back into the 17th century. During warm summer days in Greenland, melting occurs across much of the ice sheet surface. At lower elevations, where melting is the most intense, meltwater runs off the ice sheet and contributes to sea level rise, but no record of the melt remains. At higher elevations, however, the summer meltwater quickly refreezes from contact with the below-freezing snowpack sitting underneath. This prevents it from escaping the ice sheet in the form of runoff. Instead, it forms distinct icy bands that stack up in layers of densely packed ice over time.

The were brought back to ice core labs at the U.S. National Science Foundation Ice Core Facility in Denver, Colo., WHOI in Woods Hole, Mass., Wheaton College in Norton, Mass., and the Desert Research Institute in Reno, Nev. where the scientists measured physical and chemical properties along the cores to determine the thickness and age of the melt layers. Dark bands running horizontally across the cores, like ticks on a ruler, enabled the scientists to visually chronicle the strength of melting at the surface from year to year. Thicker melt layers represented years of higher melting, while thinner sections indicated years with less melting.

Combining results from multiple ice cores with observations of melting from satellites and sophisticated climate models, the scientists were able to show that the thickness of the annual melt layers they observed clearly tracked not only how much melting was occurring at the coring sites, but also much more broadly across Greenland. This breakthrough allowed the team to reconstruct meltwater runoff at the lower-elevation edges of the ice sheet—the areas that contribute to sea level rise.

Ice records provide critical historical context because satellite measurements—which scientists rely on today to understand melting rates in response to changing climate—have only been around since the late 1970s, said Matt Osman, a graduate student in the MIT-WHOI Joint Program and co-author of the study.

"We have had a sense that there's been a great deal of melting in recent decades, but we previously had no basis for comparison with melt rates going further back in time," he said. "By sampling ice, we were able to extend the satellite data by a factor of 10 and get a clearer picture of just how extremely unusual melting has been in recent decades compared to the past."

Trusel said the new research provides evidence that the rapid melting observed in recent decades is highly unusual when put into a historical context.

"To be able to answer what might happen to Greenland next, we need to understand how Greenland has already responded to climate change," he said. "What our ice cores show is that Greenland is now at a state where it's much more sensitive to further increases in temperature than it was even 50 years ago."

One noteworthy aspect of the findings, Das said, was how little additional warming it now takes to cause huge spikes in ice sheet melting.

"Even a very small change in temperature caused an exponential increase in melting in recent years," she said. "So the ice 's response to human-caused warming has been non-linear." Trusel concluded, "Warming means more today than it did in the past."

Explore further: New study highlights complexity of warming and melting in Antarctica

More information: Luke D. Trusel et al. Nonlinear rise in Greenland runoff in response to post-industrial Arctic warming, Nature (2018). DOI: 10.1038/s41586-018-0752-4

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22 comments

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jyro
1.3 / 5 (13) Dec 05, 2018
The modern record is 200 years, Earth's age is 4,000,000,000 years.
The Earth's climate has changed continuously for 4 Billion years. The only constant in Earths climate is change. Climate has changed many times before man and will change after man is gone from Earth. The Universe is dynamic. Man is a brief observer, not the cause.
szore88
1.3 / 5 (12) Dec 05, 2018
NASA says the ice is increasing, so I dont know what to say. More Marxist GW BS, perhaps?
greenonions1
5 / 5 (13) Dec 05, 2018
szore
NASA says the ice is increasing
Really? Could you provide a source for that? I'll give you one that directly contradicts your assertion. Look at the second graph.

https://climate.n...-sheets/

We'll await your response. Failing which - we can have a jolly good laugh at your highly informed discussion -
More Marxist GW BS, perhaps?
greenonions1
4.7 / 5 (14) Dec 05, 2018
jyro
Man is a brief observer, not the cause


Being that you are contradicting the consensus of science on the subject - perhaps you could support with some links. I'll give you one.

Climate-warming trends over the past century are extremely likely due to human activities. In addition, most of the leading scientific organizations worldwide have issued public statements endorsing this position


https://climate.n...nsensus/
snoosebaum
1.4 / 5 (10) Dec 05, 2018
https://notalotof...in-2017/

also to note i see there that there are no stations in central Greenland . I watched all summer@ nullschool , it was freezing there all summer
howhot3
4.7 / 5 (12) Dec 05, 2018
I swear! I'm always amazed at the utterly stupid crap they will say just to be a dipshit denier goon. They are so stupid, the doctor must have spanked them in the face when they were born because it looked so much like an ass.

Well, maybe the doctor was right. I've always found it interesting how climate deniers all have this pug like flattened nose. They also check the mirror a lot because they are vain too. I guess it's part of the mental disorder from the mistaken face beating they took at birth. Same with the other pug goons, szore and jyro. You can bet they are very lonely and ugly pieces of trash.

it was freezing there all summer
. That's not what scientist are saying in their collected data, is it? Yeap, we have a bunch of pug-nosed climate denier goon here.
ThomasQuinn
5 / 5 (14) Dec 06, 2018
NASA says the ice is increasing, so I dont know what to say. More Marxist GW BS, perhaps?


Literally ANYONE who whines about "Marxism" when talking about science today is a right-wing fanatic living in a make-believe world set at least 30 or 40 years in the past.
Da Schneib
4.6 / 5 (11) Dec 06, 2018
What this says is we're gonna get major sea level rise no matter what we do. It's already melting. It's not like it's gonna stop.
aksdad
1.8 / 5 (10) Dec 06, 2018
And yet, strangely, sea level rise continues its leisurely pace with no evidence that the "off the charts" melting of Greenland glaciers has had any noticeable effect. In fact, sea level rise has slowed over the last couple years. See for yourself here:

http://sealevel.colorado.edu/

and here:

https://climate.n...a-level/
Da Schneib
4.6 / 5 (10) Dec 06, 2018
Where do you think it's coming from, @assdad? Mars is leaking on us? Magic water from jebus? Pink unicorns peeing in the ocean?

You are a fool.
pntaylor
5 / 5 (6) Dec 06, 2018
LOL!!! If I could give howhot3 10/5, I would.
snoosebaum
1 / 5 (3) Dec 06, 2018
Global mean sea level rise estimated from satellite altimetry provides a strong constraint on climate variability and change and is expected to accelerate as the rates of both ocean warming and cryospheric mass loss increase over time. In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era.

from
http://sealevel.c...imminent
snoosebaum
1 / 5 (3) Dec 06, 2018
As noted in the previous post, exceptional winter snow accumulation and heavy, summer snowfall, drove the net snow input mass to 130 billion tons above the 1981 to 2010 average. This was followed by a near-average melt and runoff period, resulting in a large net mass gain for the ice sheet in 2018 of 150 billion tons. This is the largest net gain from snowfall since 1996, and the highest snowfall since 1972. However, several major glaciers now flow significantly faster than in these earlier years. The net change in mass of the ice sheet overall, including this higher discharge of ice directly into the ocean, is not clear at this point but may be a smaller loss or even a small gain. This is similar to our assessment for 2017, and in sharp contrast to the conditions for the preceding decade.

from http://nsidc.org/...gorized/ for 2018
snoosebaum
1 / 5 (3) Dec 06, 2018
a special gift for howhotnot

re cental greenland summer temps ;; from https://en.wikipe...mit_Camp

The climate is classified as ice cap, with no month having a mean temperature exceeding 0°C. Typical daily maximum temperatures at Summit Camp are around −35 °C (−31 °F) in winter (January) and −10 °C (14 °F) in summer (July).
snoosebaum
1 / 5 (3) Dec 06, 2018
Internal climate variability across a range of scales is known to contribute to regional sea-level trends1, 2, 3, 4, 5, 6, 7, which can be much larger than the global mean sea-level trend in many parts of the globe. Over decadal timescales, this internal variability obscures the long-term sea-level change3, 6, 8, making it difficult to assess the effect of anthropogenic warming on sea level. Here, an attempt is made to uncover the sea-level rise pattern in the tropical Pacific Ocean associated with anthropogenic warming.

so we have to make an unbiased [ what r the odds ? ] guess [ scientificly derived ]

http://sealevel.c...ic-ocean
howhot3
5 / 5 (6) Dec 06, 2018
So what is the sea level rise rate; isn't it something like 3.1 to 3.4mm/y? Isn't that enough to be concerned about? If it not a concern, then what about the fact that sea level rise is accelerating and matching global temperature increases in lock-step? The small rise that you see is just a puny little taste of what we can expect if global temperatures reach an average 2-4C. The problem is we know exactly what the cause is for the ice melting in Greenland and it's acceleration specifically in the summer months. It's caused by global warming from fossil fuel combustion. It's not going to stop until mankind puts a stop to the fossil fuel consumption. It's that easy and we should all be working towards finding a solution to that that doesn't burden societies with energy poverty.
greenonions1
5 / 5 (6) Dec 06, 2018
Snoosebaum quotes University of Colorado
In stark contrast to this expectation however, current altimeter products show the rate of sea level rise to have decreased from the first to second decades of the altimeter era
What Snoosebaum fails to do is to read the whole site he is linking - which also says
the 1991 eruption of Mt Pinatubo to likely have masked the acceleration that would have otherwise occurred
And further states
barring another major volcanic eruption, a detectable acceleration is likely to emerge from the noise of internal climate variability in the coming decade.
Talk about knowing how to read what you want into science!!!!!
howhot3
5 / 5 (6) Dec 06, 2018
Here is an excellent layman's overview of sea level rise that should give the climate denier types (pug-nosed and all) from the same group that @snoosebaum cookie cutters from.

http://sealevel.c...could-be

Follow the link to the Washington Post article that UColorodo Prof.Steven Nerem contributed. Or to save you time;

https://www.washi...762220e9

230ft of sea rise is not 6inches is it?
snoosebaum
1 / 5 (3) Dec 06, 2018
From your WAPOO ;; #1 '' There is enough water stored as ice to raise sea level 230 feet. ''

so if the summer temps in central Greenland are 14 F and say - 35 in the arctic global temps would have to rise 21 degrees and more to melt all that ice as claimed in the propaganda
snoosebaum
1 / 5 (3) Dec 06, 2018
of course there is no bias in the science @ http://sealevel.colorado.edu/
ie since they added

''Prof. Nerem contributed to this piece in the Washington Post: ''

a newspaper that is always a neutral reporter of all things ,,,,,,,

[ correction ; antarctic '' above ]
Zzzzzzzz
5 / 5 (6) Dec 06, 2018
The modern record is 200 years, Earth's age is 4,000,000,000 years.
The Earth's climate has changed continuously for 4 Billion years. The only constant in Earths climate is change. Climate has changed many times before man and will change after man is gone from Earth. The Universe is dynamic. Man is a brief observer, not the cause.


This displays as basic a misunderstanding of fact as is possible. No one can possibly be as stupid, ignorant, or as willfully brain dead as jyro on this subject. jyro is capable of nothing at all beyond filthy fecal regurgitation. Goodbye, jyro, I will not be soiled by your filthy stench again.
CoffeeSippin
1 / 5 (1) Dec 10, 2018
Is anyone measuring water content in the atmosphere? Bible Revelation indicates 1/3 less sunlight will reach the planet's surface in our lifetime. The warmer the atmosphere the more water it will hold, so yes, sea level rise can easily slow.

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