Embracing data ‘noise’ brings Greenland’s complex ice melt into focus
by Morgan Kelly, Office of Communications, Princeton Universtity
An enhanced approach to capturing changes on the Earth’s surface via satellite could provide a more accurate account of how ice sheets, river basins and other geographic areas are changing as a result of natural and human factors. In a first application, the technique revealed sharper-than-ever details about Greenland’s massive ice sheet, including that the rate at which it is melting might be accelerating more slowly than predicted.
Princeton University researchers developed a mathematical framework and a computer code to accurately capture ground-level conditions collected on particular geographic regions by the GRACE satellites (Gravity Recovery And Climate Experiment), according to a report in the Proceedings of the National Academy of Sciences. A joint project of NASA and the German Aerospace Center, GRACE measures gravity to depict how mass such as ice or water is distributed over the Earth’s surface. A change in GRACE data can signify a change in mass, such as a receding glacier.
Typically, GRACE data are recorded for the whole globe and processed to remove large regional differences, said lead author Christopher Harig, a postdoctoral research associate in Princeton’s Department of Geosciences. The result is a coarse image that can provide a general sense of mass change, but not details such as various mass fluctuations within an area. Watch the video:
Princeton University researchers developed an enhanced approach to capturing changes on the Earth’s surface via satellite that could provide a more accurate account of how geographic areas change as a result of natural and human factors. In a first application, the technique brought the complexities of Greenland’s massive ice sheet into clearer focus. From 2003 to 2012, the ice sheet experienced patchy fluctuations in ice loss and gain, while the areas of greatest melt gradually migrated from the southeast to the northwest coast. (Video by Christopher Harig)
With their method, Harig and co-author Frederik Simons, an assistant professor of geosciences, can clean up data “noise” — the signal variations and distortions that can obscure satellite readings — and then recover the finer surface details hidden within. From this, they can configure regional information into a high-resolution map that depicts the specific areas where mass change is happening and to what degree.
“We try to do very little processing to the data and stay closer to the real signal,” Simons said. “GRACE data contain a lot of signals and a lot of noise. Our technique learns enough about the noise to effectively recover the signal, and at much finer spatial scales than was possible before. We can ‘see through’ the noise and recover the ‘true’ geophysical information contained in these data. We can now revisit GRACE data related to areas such as river basins and irrigation and soil moisture, not just ice sheets.”
From 2003 to 2010, Greenland overall lost roughly 200 billion tons of ice each year, but glacier activity was regionally inconsistent. Ice loss was concentrated on the southeast and northwest coasts for most of the period, but the area of greatest melt activity began to migrate from the southeast to the northwest coast around 2008. By 2010, the southeast coast displayed only minor ice loss. Meanwhile, the higher and colder interior gained ice mass, as did the southwest coast, slightly, from 2003 to 2006. (Image by Christopher Harig)
The researchers tested their method on GRACE data for Greenland recorded from 2003 to 2010 and brought the complexities of the island’s glaciers into clearer focus. While overall ice loss on Greenland consistently increased between 2003 and 2010, Harig and Simons found that it was in fact very patchy from region to region.
In addition, the enhanced detail of where and how much ice melted allowed the researchers to estimate that the annual acceleration in ice loss is much lower than previous research has suggested, roughly increasing by 8 billion tons every year. Previous estimates were as high as 30 billion tons more per year.
Douglas MacAyeal, a geophysical sciences professor at the University of Chicago, said that the research provides a standardized and accurate method for translating GRACE data, particularly for ice sheets. The sprawling, incomplete nature of the satellite’s information has spawned a myriad of approaches to interpreting it, some unique to specific scientists, he said.
“GRACE data is notoriously noisy and spatially spread out, and this has resulted in ‘ad hoc’ methods for processing mass changes of Earth’s ice sheets that have wildly different values,” said MacAyeal, who is familiar with the Princeton work but had no role in it.
“In other words, each particular investigator ends up getting a different individual number for the net change in mass,” he said. “What this research does is figure out a way to be more thoughtful and purposeful about exactly how to deal with GRACE’s notorieties. This method would allow researchers to standardize a bit more and also to understand more precisely where they are, and where they are not, able to resolve ice changes.”
Despite variations in glacier activity, Greenland experienced a steady ice loss of 200 billion tons annually, which could stack up on all of Manhattan to nearly 12,000 feet, or more than eight times taller than the Empire State Building. Nonetheless, the researchers estimated that the annual acceleration in ice loss is much lower than previous research has suggested, roughly increasing by 8 billion tons every year. Previous estimates were as high as 30 billion tons more per year. (Image by Christopher Harig)
Simons compared the noise that previously obscured a precise view of Greenland’s glaciers to fog on a window. For a small area such as Greenland, the GRACE signal can be easily overwhelmed by noise, which has numerous causes such as the satellite’s orbital position or even the type of mathematics researchers use to interpret data, Simons said.
“Other researchers used less than perfect tools to wipe off the window more or less indiscriminately and quite literally left streaks on the data. They were thus less able to put the continent into the proper focus,” he said.
“We effectively modeled then removed noise to get the ice-loss signal out of the data,” Simons said. “We then recovered relatively tiny variations in ice mass that to others might have looked like noise, but that to us were shown to be signal.”
The Princeton researchers found that Greenland lost roughly 200 billion tons of ice each year during the seven-year period studied, which falls within the range reported by other studies. The amount of ice lost annually could stack up on all of Manhattan to nearly 12,000 feet, or more than eight times taller than the Empire State Building, Harig said.
As expected, ice loss occurred in the lower, warmer coastal areas — as opposed to the higher and colder interior, which gained ice mass — but the melt was concentrated on the southeast and northwest coasts for most of the period studied. Indeed, many coastal areas showed no ice-mass loss, while the ice sheet on the southwest coast actually thickened slightly from 2003 to 2006.
But these trends were more complex when Harig and Simons got into the details. Surprisingly, the location of the greatest melt activity migrated around the island, shifting from the southeast to the northwest coast in just a few years. Ice loss on the southeast coast built up starting in 2003 and hit a highpoint in 2007. In 2008, loss on this coast began to recede and shift toward the northwest coast; by 2010, the southeast coast displayed only minor ice loss, while nearly the entire western coast exhibited the most severe melt. During this transition, melt also receded then picked up again on the northeastern coast with seemingly little overlap with activity elsewhere.
Details such as these can help scientists better understand the interplay between Greenland’s glaciers and factors that influence melt such as ocean temperature, daily sunshine and cloud coverage, Harig said. That understanding can in turn help researchers determine how the Greenland ice sheet responds to climate change — and how much more ice loss to expect. At current melt rates, the Greenland ice sheet would take about 13,000 years to melt completely, which would result in a global sea-level rise of more than 21 feet (6.5 meters), Harig said.
“Scientists are not totally sure what the driving force of the melt on Greenland is on short, yearly timescales,” Harig said. “There is no certainty about which outside factor is the most important or if all of them contribute. Being able to compare what is happening regionally to field observations from other researchers of what a glacier is doing helps us figure out what is causing all this melt.”
Michael Oppenheimer, Princeton’s Albert G. Milbank Professor of Geosciences and International Affairs, said that the new level of detail Harig and Simons provide on Greenland’s glaciers not only gives insight into what is causing the glaciers to melt, but what could possibly happen if they do.
Unlike water in a bathtub, sea-level rise is not uniform, said Oppenheimer, who is familiar with the research but had no role in it. Higher waters in certain locations may depend on which part of an ice sheet melts, he said. And determining which part of an ice sheet is melting the most requires precise details of ice loss and gain for specific glaciers — details that have largely been unavailable, Oppenheimer said.
“Nobody has really been able to take a look at an individual ice sheet and determine the influence that ice loss from different parts of that ice sheet could have on sea levels,” Oppenheimer said.
“The details matter. Being able to pinpoint where and how much ice gain and loss there is tells you something about the driving forces behind it, and therefore how much we can expect in the future,” he said. “A synoptic view at a high resolution is what GRACE always promised, and now this research has helped realize that potential. It’s time to finally milk the data for as much detail as possible.”
Harig is adapting the computer code — which is available online — to study GRACE data on ice loss in Antarctica and water accumulation in the Amazon River basin.
The paper, “Mapping Greenland’s mass loss in space and time,” was published online Nov. 19 in the Proceedings of the National Academy of Sciences. It was supported by a grant from the National Science Foundation.
Doesn’t the Total Mass Change graph show Greenland GAINING 1000 Gt of ice in 2002 and LOSING 1000 Gt of ice in 2011?
Now if we could do this over a full 60 year warm/cold/warm cycle, then we’d know what was going on, not extrapolating billionaire expectations from two weeks of stock market gains. The ice gain or loss seems to me more a matter of snowfall than temperature.
Andrew, there’s something wrong with your comments form. Comments are being submitted but not getting through. Some evil hacker at work blocking comments from posters?
The trouble with noise is to remove it you must know how much of the total signal is noise and the nature of high noise signals is you don’t because both noise and signal look very similar. It is the nature of a very high noise/signal ratio.
So another modelling saga.
It would be interesting to have this data analysis mirrored for another part of the globe without ice to see if there are similar fluctuations. Australia would be a good candidate.
Kim Allen: “Doesn’t the Total Mass Change graph show Greenland GAINING 1000 Gt of ice in 2002 and LOSING 1000 Gt of ice in 2011?”
The vertical axis is mass (actually mass change), the zero line is the average over the observation interval. The chart shows a fairly steady rate of loss of around 200 Gt/yr. Which is the key new result, as Velicogna 2009 concluded an acceleration of -26 ± 14 Gt/yr2.
A big sea level rise is the only massive threat from GW—the only one that would justify cutting CO2 emissions. Rapidly accelerating land-ice melt has been touted as portending such a rise. It’s been one of the highest-ranked “cards” in warmists’ hand. Cutting down its value hurts the strength of warmism’s case.
Hopefully, a further cut-down will happen when GRACE’s Antarctic data is similarly analyzed. Those two findings, in combination with the recent debunking of recent Himalayan glacial loss, would throw a good deal of cold water on the warmists.
Mike McMillan says:
November 29, 2012 at 3:52 am
Now if we could do this over a full 60 year warm/cold/warm cycle, then we’d know what was going on
No. If we could do it over at least a 1000 years,then we might have a slight look into how climate works.
Why do they constantly claim there’s an acceleration in ice loss? That implies that the rate iteself is changing. Since they fit all their data to a single linear projection all the time, you can’t extract an acceleration from this (the derivative of the function is a constant: the slope which is the rate…and it’s a constant, that is, not changing). The only way you could model an accelering rate is to get away from the lines and plot exponentials or some other nonlinear function. And since they never plot anything put lines I can’t see how they can claim an accleration of ice loss…ever.
This post brought back a recent memory of the following paper which used aerial imagery.
Roger Knights says:
November 29, 2012 at 4:45 am
….Those two findings, in combination with the recent debunking of recent Himalayan glacial loss, would throw a good deal of cold water on the warmists.
_________________________________
Just do not expect to ever see such findings in the MSM.
Here is another snow/ice finding you will never see in the MSM: Northern Hemisphere Snow Anomalies (The fall Equinox was September 22, 2012)
At this point I do not trust the global temperature data. It has been messed with too much to actually tell whether we are cooling or not. That chart say we may be.
As someone else mentioned it is the snow accumulation that determines glacial growth.
too nuanced for the MSM, i’m afraid:
29 Nov: AFP: Daniel Johnson: 2012 marked by extreme weather, Arctic thaw: UN
GENEVA — Extreme temperatures, drought, floods and the unprecedented loss of Arctic ice marked global weather in 2012, boosting concern at the march of climate change, the World Meteorological Organization (WMO) said Wednesday.
“Climate change is taking place before our eyes and will continue to do so,” WMO chief Michel Jarraud said, unveiling a weather report that coincided with fresh negotiations on a UN treaty to curb greenhouse gases…
It pointed to Greenland, whose land-based icemelt is considered particularly serious since it can hike sea levels, saying it registered an all-time heat record for May, when the mercury soared to 24.8 C (76.6 F).
Both the Arctic and the Greenland icesheet appeared to be melting “somewhat faster” than predicted five years ago, Jarraud said, adding that “the trend is not only continuing but accelerating.”…
http://www.google.com/hostednews/afp/article/ALeqM5hEsGaDARrTKUmvVVDXOUNSSUooUg?docId=CNG.8ca41360fb09f50e0dc903245b1e9ee5.421
GRACE, altimetry and SAR all measure the same signal and show that Greenland is losing mass. Moreover, the whole ice-sheet was largely in balance as recently as the early 1990’s. The methods show that the ice-loss from Greenland is still accelerating. Read the paper in tomorrow’s issue of Science for more details.
Really a minor point but… As a Swede I know that parts of Sweden, which was covered by two kilometers of ice, has risen at least 200 meter since they got rid of their burden. The coast line then moved guite substantially and keeps on moving. By the way: Land must have risen also when the ice was melting, but I have never seen figures on that. This should, in priciple, contribute to a further rise of the see level already when ice was melting, but the magma presssing land upwards must come from somewhere, where land or the sea bottom then will belowered. Or? Obviously this is definitely “in the long run” and we all know what Keynes said about that.
Gösta Oscarsson
Srockholm
Nope, I agree with Kim Allen, this chart shows Greenland gaining ice mass until about 2006 when it crosses over to losing ice. It does show a declining rate of ice gain, however. Then after 2006-ish it shows ice loss at an (apparently) accelerating rate. That is at least one valid interpretation of this poorly labeled chart.
In my opinion, not a great chart, with similarly bad wording.
Add me to the list of those who are not very impressed. Sorry. They may be very knowledgeable folks trying their best to make sense of the data they have gathered with GRACE, but whenever I see “research” that is dependent on the type of programming and the inherent assumptions within, I lose all faith in their conclusions. The immediate questions that come to mind are: How did they determine which factors cause noise in the signal? How did they determine the amount of noise each adds to the mix? How did they test any of those assumptions before factoring them into their model of noise? If, as they say, “Scientists are not totally sure what the driving force of the melt on Greenland is on short, yearly timescales,” and “There is no certainty about which outside factor is the most important or if all of them contribute.” then why are they factoring out the noise at all? If they can’t/don’t answer those basic questions first why bother moving forward unless it’s just another example of preconceptual science, aka Playstation Scientology?
Maine Snowmobile Assoc. hopes to build trails near wind farms
http://cs.amsnow.com/sno/b/news/archive/2012/11/28/maine-snowmobile-assoc-hopes-to-build-wind-farm-trails.aspx
[snip]
The snowmobile association, which represents 285 clubs, is working with the wind farm owners including: First Wind, TransCanada, Patriot Renewables and other developers on the project.
This could add 600 miles of trails to the 14,000 miles of trails in Maine.
Snow? Global Warming? CO^2? Snowmobiles?
Roger Knights says: “…in combination with the recent debunking of recent Himalayan glacial loss…”
That has been re-debunked in T. Yao et al [Nature Climate Change 2, 663–667 (2012)]. The himalayan glaciers are indeed melting (over the last 30 years.)
And, to be picky, the problem with the Himalayan glacier loss was that it was not documented, not that it wasnt happening.
With current and historical sea rise being roughly a foot per century, I wonder where and how much of the evaporated melt water gets deposited?
Global sea level rises 0.5mm due to this Greenland ice loss. It is probably ongoing for the whole Holocene. I guess we would see higher variability otherwise. Or it might be just bad data.
“We effectively modeled then removed noise to get the ice-loss signal out of the data,” Simons said. “We then recovered relatively tiny variations in ice mass that to others might have looked like noise, but that to us were shown to be signal.”
Oh yeah. The tiny variations looked like signal to them because they had models that established a trend. I can’t think of a better example of confirmation bias. I’m willing to guess that if they had modeled for an increase in ice they would have found tiny variations that looked like noise but were shown “to us” to be signals of ice gain. This a a patent admission of cooking the books.
Another perspective: 200 billion tons of ice/yr is (roughly) equivalent to 4 inches/yr – if my “ballpark” calculations are correct.
Mass of ice sheet: 2.66946 x 10 to the 15th metric tons. They’re not going to run out of ice cubes for their cocktails in Greenland any time soon.
Monitoring of meltwater flow in the streams would give a reliable indication of ice loss. So easy to do with no satellite to launch, no noisy signal to process, no long winded discourse, no doubts of processing quality or fidelity of filtered signal, no esoteric specialization that is opaque to all of science and hence unverifiable, no more claims impossible to investigate, much less opportunity to shovel grist into the propaganda mill. But some scientists are not interested in such a direct approach as the monitoring of meltwater flow. Such simplicity does not appeal to them.
The fact is the processed signal remains theoretical until tested by observations. Observational data is needed to verify the validity of any particular geophysical signal processing. Pretty pictures that seem to work are not of themselves good confirmation. These scientists would do themselves and the rest of us a favor if they were to undertake a practical, independent verification of their claim to have devised a reliable processing method.
Maybe I’m a bit thick this morning, but what did they check these speculations against? The ice was physically measured in these years, how and when?
I get the sense of Garbage in Gospel out again. So the Grace Satellite data is incomprehensible, requires filtering and translation? That is normal with all electronic sensing, but don’t you have this figured out before you launch?
Was Grace so committee designed that even the engineers did not know the operational parameters?
May as well extrapolate Greenland glacial changes by studying the bones of canned herring from the Norwegian fleet.
It would appear that at least for Greenland Ice some sense is beginning to be made in relation to the dynamic processes that result in glacial retreat and growth. There are those of us who view this process is a totally natural thing something that has been going on since the end of the Pleistocene. I am sure that in the near future we will see more adjustments and refinements as the empirical data is gathered and applied to GRACE’s data. In the mean time we will all need to work hard in restraining ourselves and others to not run off believing we know that which we so not but only speculate.
Look at Shepherd et. al. “A reconciled estimate of Ice Sheet Mass Balance” in tomorrow’s Science. Greenland was in mass-balance in the beginning of the 1990’s, after which it has been losing mass at an accelerating rate. So far ~3000km3 of the ice has disappeared and the loss is probably still accelerating.
GRACE, altimetry and SAR are independent techniques and they see essentially the same signal. This mass-loss is real and not some artifact of GRACE-processing.
I thought Grace was recently found very wanting. Aren’t they sending up an improved one? I would like to hear Briggs or McIntyre on converting noise to signal.
In view of the past cooking of the books (no pun intended) regarding global temperature, sea level rise, polar ice measurements and other climate data, I would not trust many of the scientists translating/filtering the GRACE satellite data to not use the processed data to further the global warming/climate change narrative unless there is significant audit and oversight.
Absent actual on-the-ground verification, interpretation of satellite data is subject to the biases and predjudices of the interpreter(s).
” Nonetheless, the researchers estimated that the annual acceleration in ice loss is much lower than previous research has suggested, roughly increasing by 8 billion tons every year. Previous estimates were as high as 30 billion tons more per year. ”
It’s odd that scientists studying gravity don’t understand the meaning of the word acceleration.
8 Gtn/year is a fixed rate of change NOT an acceleration. An acceleration would in units like Gtn/year/year, ie so many tons more EACH YEAR.
Perhaps the press release forgot to ask the authors of the study whether what they’d written made sense.
But of course “acceleration” always sounds more dramatic. Good work Morgan Kelly, Office of Communications, Princeton. You’ve earned your degree in Media Hyper and Propaganda, but I’m sad to say you’ll have to resit the science module.
” including that the rate at which it is melting might be accelerating more slowly than predicted.”
That should read the: study found a fixed rate of ice loss meaning that ice loss is NOT accelerating.
Last year it was “..it is worse than we thought!” With studies like this and the improved cloud models discussed here http://judithcurry.com/2012/11/28/clouds-and-magic/ that meme is losing it’s potency so this year it is extreme weather and increasing wild claims (4 degrees this century).
I see two dynamics at work:
– Scientists are increasingly able to get results published that do not support CAGW theory. I truly wonder if this study would have made it through peer review before Climategate.
– The CAGW loving politicians are increasingly desperate to get their agenda enacted before the CAGW theory falls apart completely.
” I truly wonder if this study would have made it through peer review before Climategate.”
Sorry about commenting on my comment. I’ve mentioned before the gatekeepers at the journals IMHO have the critical role in choosing reviewers. To the extent that they are not choosing CAGW proponents as reviewers (or those reviewers are less willing to review) then the science should gradually become more balanced.
“Nonetheless, the researchers estimated that the annual acceleration in ice loss is much lower than previous research has suggested, roughly increasing by 8 billion tons every year.”
OH , I get it. They just can’t write what they mean.
It is neither “the annual acceleration in ice loss” nor the “ice loss” that increased by 8 billion tons every year. What they are trying to express is that the _rate of ice loss_ is increasing by 8 Gtn/year every year. Note units are wrong in the caption.
Either it’s ” increasing by 8 Gtn/year every year” or an acceleration of 8Gtn/year/year.
So they did find a moderate accleration.
200 Gtn / year loss , increasing by 8 Gtn/year/year
They would do everyone a service if they plotted rate of change if that’s what they want to study. That way it would be fairly flat and negative , with a slight downward slope.
With 2,600,000 km3 of ice on Greenland
that is 2,600,000,000,000,000 tonnes.
There are 1,000,000,000 tonnes per 1 Gigatonne
So we have 2,600,000 Gigatonnes of ice in Greenland.
With a loss of 200 Gigatonnes/year we are seeing a loss rate of 0.0077% per year
So if it remains a linear loss rate, it will all be gone in only 13,000 years.
I figure Antarctica will take a little longer.
The “recent” I used referred to the last ten years, not the last 30 years. (This is like the dispute over whether or not “it’s warming recently.” The answer is Yes (since 1980) and No (since 2000).) Here’s a link to the study I was referring to. Is it true that this more recent paper has re-dunked it?
JS says:
November 29, 2012 at 7:05 am
Global sea level rises 0.5mm due to this Greenland ice loss. It is probably ongoing for the whole Holocene. I guess we would see higher variability otherwise. Or it might be just bad data.
______________________________________________
Holocene sea level rise graph
Tempest in a teapot comes to mind.
Rates of Isostatic Rebound
CostCo says:
November 29, 2012 at 9:16 am
Look at Shepherd et. al. “A reconciled estimate of Ice Sheet Mass Balance” in tomorrow’s Science. Greenland was in mass-balance in the beginning of the 1990′s, after which it has been losing mass at an accelerating rate. So far ~3000km3 of the ice has disappeared and the loss is probably still accelerating.
__________________________________________
And before that it was GAINING ice. link and so far in the North Hemisphere has been increasing in snow in October link
“So if it remains a linear loss rate, it will all be gone in only 13,000 years.”
Just to be pedantic and avoid ridicule from the CAGW crowd, if the ice loss continues to accelerate at 8 GT/year/year as the article says it is now, then in 100 years the loss will be 1000 GT/year etc. So it would take roughly 800 years for Greenland to melt (assuming I got the math right).
So, assuming the affected coastal cities are effectively rebuilt every 200 years, we still have plenty of time to adapt. Perhaps the affected folks will relocate to the newly greened Greenland.
This is a moderately important result because if the acceleration which IIRC last year was hyped as “worse than we thought!” @ 30 GT/year/year then the adaptation window is reduced to a miniscule 400 years.
Since I firmly believe that in 400 years we will be worrying more about the coming glaciation, I only present this post to make sure we skeptics get the math right (assuming I did!!).
Yes, CostCo, but the issue is not the loss of ice but how much, as the Princeton study makes plain. The study addresses the reliability of the signal, unprocessed and processed, and I think you realize that, do you not?
RobertInAz says:
November 29, 2012 at 9:27 am
….The CAGW loving politicians are increasingly desperate to get their agenda enacted before the CAGW theory falls apart completely.
__________________________________
Yeah, they tossed out the IPCC and now use the World Bank as the High Priest at the latest Confab.
I wonder what the Occupy Wall Street crowd thinks about that especially since the World Bank has dramatically increased its loans for coal fired power plants. graph The World Bank has issued over $4 billion in loans for new coal-fired power plants since 2008
Brettonwoods.org states “…every dollar invested in the World Bank from the U.S. is combined with $5 in additional capital from other countries…” So the USA is contributing 20%?
Gail Combs
Exactly- and before it was gaining ice it was losing ice and before that it gained. All a part of Nature’s Grand Design. The recent warming of the oceans (which is not related to atm CO2) is responsible for the latest ice ablation in Greenland, as it is likewise the cause for the accelerated melt of the Arcic Ocean ice this past decade. That trend is over and the minimum ice extent has stabilized since 2007, notwithstanding the aberrant August storm this summer. Greenland ice ablation has also passed its peak and should reach a new equilibrium during this decade, as ocean warming has ceased. When ocean waters cool, the ice mass will accumulate again, in the eternal cycle of nature where nothing remains unchanged.
I found this on ENN. It is a little like Greenland. The last statement is a killer laugh.
From: Andy Soos, ENN
Published November 29, 2012 10:28 AM
Antarctic Melting and Sea Level
Due to its location at the South Pole, Antarctica receives relatively little solar radiation. This means that it is a very cold continent where water is mostly in the form of ice or snow. This accumulates and forms a giant ice sheet which covers the land. New data which more accurately measures the rate of ice-melt could help us better understand how Antarctica is changing in the light of global warming. The rate of global sea level change is reasonably well-established but understanding the different sources of this rise is more challenging. Using re-calibrated scales that are able to weigh ice sheets from space to a greater degree of accuracy than ever before, the international team led by Newcastle University has discovered that Antarctica overall is contributing much less to the substantial sea-level rise than originally thought.
http://www.bbc.co.uk/news/science-environment-20543483
The paper:
https://www.sciencemag.org/content/338/6111/1183
I think the Grace gravity anomaly models need to be re-written now that better glacial isostatic models are available.
The GPS measurements from around Greenland are highly unusual. Some areas are up-lifting at 15 mms/year and others are subsiding at 8 mms/year. Grace doesn’t have the resolution to resolve with this kind of spatial variation.
When the detailed modelling was was re-done from GPS for Antartica, the range of mass balance estimates fell by more than half so I’m still waiting for the Greenland ice-sheet mass balance numbers to be re-written. This study doesn’t really do that, it just tries to take the noise out of the existing Greenland Grace estimates.
CostCo
November 29, 2012 at 9:16 am
###
To be taken cum grano salis.
I remember that headline grabbing “paper” NASA was trumpeting shortly after dis-GRACE was launched, written by some incompetent post grad, claiming that Antarctica was “loosing more ice then models predicted and that it is mans fault”.
The main reason why I remember it is that this was the third NASA sponsored paper that was so bad that it left no doubt that NASA was far more interested in destroying civilization then in advancing science.
RobertInAz says: November 29, 2012 at 11:14 am
“…… if the ice loss continues to accelerate at 8 GT/year/year as the article says it is now, then in 100 years the loss will be 1000 GT/year etc. So it would take roughly 800 years for Greenland to melt (assuming I got the math right)….”
Thanks Robert. Your calculation is in fact correct.
“So, assuming the affected coastal cities are effectively rebuilt every 200 years, we still have plenty of time to adapt. Perhaps the affected folks will relocate to the newly greened Greenland….”
This may be a bigger point than we had expected. Work by Jerry Mitrovica and one of his students (in as yet unpublished work(?)) reveals that a total melting of the Greenland Ice cap would result in an ocean level fall of 100 metres at the Greenland shoreline, due to the removal of the gravitational effects of the lost ice. Of course this means the water accumulates in greater depth nearer the equator but has the effect of slowing the effects of the supposedly warming seas on the ice caps (self regulating to an extent?)
http://youtu.be/RhdY-ZezK7w Jerry Mitrovica is a Professor of Geophysics at Harvard University in the USA. (Note, he is very much pro the CAGW story)
Interesting point: He discusses the work of his young graduate student. When she discovered the phenomenon of the polar tidal gravitational retreat of the seas in response to melting ice caps, (ie something which will alleviate and moderate the severity of such an event) she went to Mitrovica and said:
“What do we do?”
He answered; “Well, we publish it”.
Funny that she felt she had to ask. Perhaps politics and pressures at work? The good thing is at least for for Mitrovica science trumps politics.
Here is some of Natalya Gomez’s fascinating modeling work as discussed above – in fact already published:
http://www.people.fas.harvard.edu/~phuybers/Doc/evolution_ice_sealevel.pdf
Evolution of a coupled marine ice sheet–sea level model
Natalya Gomez,1 David Pollard,2 Jerry X. Mitrovica,1 Peter Huybers,1 and Peter U. Clark3
Received 16 June 2011; revised 18 November 2011; accepted 6 December 2011; published 14 February 2012.
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, F01013, doi:10.1029/2011JF002128, 2012
More Gomez etal 2012 … from the abstract:
http://www.people.fas.harvard.edu/~phuybers/Doc/evolution_ice_sealevel.pdf
Thanks Costco, that starts to answer my comment above.
Greenland mass balance down to -142 GT/year, Antarctic down to -60 GT/year. Contribution to sea level rise only +0.56 mms/year.
https://www.sciencemag.org/content/338/6111/1183
Looking at the graph of Greenland ice mass, I can’t figure out if the loss is a problem of losing ice faster or of not replacing the lost ice.
This is not a trivial situation to resolve. Greenland is a continental-style glacial mass that by material physics has to flow from the center thickness to the edges, where it both melts and calves into the sea. That is what glaciers do (which is why most of the alpine “glaciers” are not glaciers but stagnant ice masses, but tell that to an eco-green.) Unless there is continuous replacement in its heart, all glaciers will flow away until they are too thin to do so any more.
That being explained, any changes in Greenland have to deal with the two means of losing glacial mass. As we learned from the foolishness of the Kilamanjaro “glacier” stories of its extinction, non-replacement can be the reason all by itself (the loss of forest cover at the mountain’s base reduced the humidity and hence precipitation on the top of the mountain). Before we shriek about the Greenland loss to global warming, we need to address the replacement issue.
I believe, though could be again wrong, that there has been more sunshine since the mid-60s, and a lower humidity over Greenland. Both cause sublimation losses to be higher than before during the summer, regardless of temperature changes. If the winter snowfalls are also less than before, following on with the loss of general humidity, then much of the measured current loss could be accounted for by non-warming climatic changes and an associated non-replacement of surface loss. None of this is an aspect of temperature warming, by or not by CO2, but a drier, sunnier local climate.
Dunno. Just looking and thinking.
Bill Illis says: November 29, 2012 at 5:06 pm
“…Greenland mass balance down to -142 GT/year, Antarctic down to -60 GT/year. Contribution to sea level rise only +0.56 mms/year. …”
Or even less – see below. Gives rise to the question: Is Antarctica really melting?
Zwally etal 2011 would indicate no… well, only perhaps a contribution of 0.1 mm/year to SLR.
Two ERS-based estimates, the modified IOM, and a GRACE-based estimate for observations within 1992-2005 lie in a narrowed range of +27 to -40 Gt/year, which is about 3% of the annual mass input and only 0.2 mm/year SLE. Our preferred estimate for 1992-2001 is -47 Gt/year for West Antarctica, +16 Gt/year for East Antarctica, and -31 Gt/year overall (+0.1 mm/year SLE)…
http://icesat4.gsfc.nasa.gov/cryo_data/publications/Zwally-Giovinetto_SurveysInGeophysics_2011-1.pdf
So where does the current SLR come from? Maybe the groundwater guys are correct:
“…. have found, groundwater depletion is adding about 0.6 millimeters per year …. to the Earth’s sea level….” a team of Dutch scientists led by hydrologist Yoshihide Wada, Utrecht University. http://news.nationalgeographic.com/news/2012/05/120531-groundwater-depletion-may-accelerate-sea-level-rise/
Pokhrel estimates a 0.77 mm/year groundwater depletion contribution to SLR
… source: http://www.nature.com/ngeo/journal/v5/n6/full/ngeo1476.html
Has anyone figured out how much heat energy was required to melt that much ice? I wonder what the earh’s temperature would have been if the energy hadn’t been ‘used’ to melt the ice? Are we talking about a serious amount of heat energy or not? It would also give us an idea of what will happen to the earth’s temperature when all the ice is melted.
LetsBeReasonable says: November 29, 2012 at 5:56 pm
“…Has anyone figured out how much heat energy was required to melt that much ice?…”
Perhaps some clues from a publication on the last interglacial – The Eemian.
According to researchers it took temperatures equivalent to future IPCC ‘no action’ 2100 projections PLUS a massive increase in isolation: 60 Wm−2 compared to the 0.85 Wm−2 loading estimated to now occur from CO2 increases.
Significant contribution of insolation to Eemian melting of the Greenland ice sheet (2011) van de Berg etal http://www.staff.science.uu.nl/~broek112/home_files/MB_pubs_pdf/2011_vdBerg_NatGeo.pdf
CostCo
If there is substance to the the Princeton study that is the subject of this post, then your referred study has used obsolete processing of the satellite data, and therefore is unreliable. Poor scientists- all of that work for nought. Note their claim (at BBC) that their work settles the issue definitively.
Markx, it didn’t answer my question, I want to know how much heat energy has been used to melt the ice that has already melted. Then my next question is what would the Earth’s the temperature be if the ice hadn’t been melted and the heat retained in the atmosphere.
Roger Knights says: “GRACE’s Antarctic data is similarly analyzed. Those two findings, in combination with the recent debunking of recent Himalayan glacial loss, would throw a good deal of cold water on the warmists.”
Roger Knights says:”The “recent” I used referred to the last ten years, not the last 30 years.”
and refs Bradley: “ Did you know the Himalayas and nearby peaks have lost no ice in past 10 years?”
(missing lots, read the original posts if you are interested.)
Hmm. The Yao Nature paper is more recent than Bradley’s March ref. But that doesnt matter, you were arguing that the “warmists” had a problem with data, and Yao’s data is pretty extensive. (BTW, their supplementary data was outside the firewall for me, and they have great glacier pictures and maps in there, its worth the trip. Surprising Nature let them get away with it).
Anyway
actually the data is complicated, but the general idea is that glaciers a low elevations are melting, even in the last decade, and glaciers at high elevations (were it is always cold, even today) are growing. I’ll let you try to figure out why, but one hint (spoiler!) is that it is consistent with GW.
So, no, the warmists are always happy these days!
Doug Proctor says: “Greenland is a continental-style glacial mass that by material physics has to flow from the center thickness to the edges, where it both melts and calves into the sea. That is what glaciers do (which is why most of the alpine “glaciers” are not glaciers but stagnant ice masses, but tell that to an eco-green.) Unless there is continuous replacement in its heart, all glaciers will flow away until they are too thin to do so any more.”
Just how does a glacier know if it terminates in the sea or not? The only difference between a alpine glacier and a continental glacier is elevation and, in the case of Greenland and Antarctica, scale.
That said, quite a few glaciers in Glacier NP have stopped moving lately, and are now just permanent ice fields. Is that what you are talking about, perhaps? If so, they are not glaciers any more even if once they were. Pretty sad.
mpainter @ 6:54 PM
“….then your referred study has used obsolete processing of the satellite data, and therefore is unreliable. ”
This conclusion is overstated. These are contemporaneous studies using different approaches that reach essentially the same result for the ice loss rate. The -142 +-49GT/year for Greenland mass loss from 1992 to 2011 from the Science study is essentially indistinguishable from -200 GT/year with no error bound shown for 2002-2010 by the Princeton group. Especially if mass loss was accelerating 1992-2002.
Both studies agree that there is no risk of catastrophic mass loss this century or next. The additional good news from these studies is that should mass loss unexpectedly accelerate, we will have plenty of warning.
LetsBeReasonable says:
November 29, 2012 at 7:21 pm
===============================
Enthalpy of fusion (rounded) 80cal/g
33x 10^7 km^3 ice on earth
Weight of ice 3×10^23g
24×10^24 calories
Now, you answer your second question for us.
RobertInAz
I do not see an equivalence between the figures of the two studies. “Essentialy indistinguishable”
Some might say that this is an overstatement.
Gymnosperm, that is indeed a lot of energy. I don’t know how to apply that figure to calculate the ‘atmospheric heating foregone’ , but I can thank the ice caps for keeping the earth cooler than it would have been otherwise. I imagine the ice caps over Greenland and Antartica will take a while to melt away completely, and I won’t be around when they finally disappear and the heat that used to go into melting them, would go towards heating the atmosphere.
That reduced rate (sea level rise of 21′ in 13,000 yrs) works out to about 4″ century. Head for the hills!
Or not.
We should also note that the Land is rising at an average of 0.3 mms/year (due to rebound from the ice ages). That means the actual sea level rise over the last 20 years relative to the Land from this glacial melt is less than one-quarter of an inch.
After reading the Supplemental, it appears this new study still has not used the more accurate GIA models for Greenland.
The authors speculate that if that were done, the mass balance numbers for Greenland would fall by about the same trend as for Antarctica, or about half.
I guess this was just step one – Greenland will still get revised down to about -80 GTs/year eventually.
http://www.sciencemag.org/content/suppl/2012/11/28/338.6111.1183.DC1/Shepherd.SM.pdf
CAN SOMEONE CONVINCE CHANNEL4 TO STOP THEIR ‘MELTING POLAR CAPS’ STORIES?
C4 editors have really swallowed the global warming lunacy and have repeated this story about 20 time this year alone.
Maybe someone here can convince them to either CHECK THEIR FACTS or just stop reporting lying propaganda as if they were scientifically accepted proofs.
See what I mean here
http://www.channel4.com/news/shrinking-ice-rapid-rate-of-polar-melt-revealed
Thursday 29 November 2012 Antarctica , World Shrinking ice: rapid rate of polar melt revealed
Tom Clarke, Science Editor
The planet’s polar ice sheets are melting three times faster than they were in the the 1990s, a 20-year study of satellite records says.
The definitive analysis of the mass of ice sheets covering Greenland and Antarctica should end decades of speculation about how much their melting may contribute to sea-level rise. The study finds their combined melting has contributed 11.1 milimetres to global sea levels since 1992.
The results come as nations meet in Doha, Qatar, for this year’s global climate change negotiations. Previous estimates of sea-level rise from melting ice date from 2004 and are highly disputed.
We can now say for sure that both Antarctica and Greenland are shrinking
– Andrew Shepherd, University of Leeds
“The measurements we had to hand then couldn’t tell us whether Antarctica in particular was growing or shrinking,” said Andrew Shepherd from the University of Leeds who led the research.
“We can now say for sure that both Antarctica and Greenland are shrinking because of the changes in climate that they’ve been exposed to.”
The researchers combined data from 10 satellites designed to measure ice thickness in different ways. Some use lasers or radar to measure the height of ice, others detect changes in gravity to “weigh” the ice lying over Greenland and Antarctica.
9,000 Lake Windermeres
They concluded Antarctica has lost around 1,320 gigatonnes of ice since 1992. Greenland, which has experienced much greater warming has lost around 2,940 gigatonnes over the same period – equivalent to more than 9,000 Lake Windemeres.
Sea level is rising for a number of different reasons – mainly as the oceans expand as they warm up due to a gradually warming planet. But the contribution of the melting ice caps now accounts for about a third of the rise, the study reveals.
Read more on global warming from Tom Clarke’s recent visit to the Arctic.
http://www.channel4.com/news/tom-clarke-in-the-arctic
The analysis doesn’t sigificantly alter previous, rather uncertain predictions, of how fast ice sheets may be melting. But to have more concrete data will now improve other scientists’ ability to forecast future melt.
“This project is a spectacular achievement,” said Richard Alley, a climate scientist at Penn State University. “The data will support essential testing of predictive models and will lead to a better understanding of how sea-level change may depend on the human decisions that influence global temperature.”
==========
Contact C4 on this page
http://www.channel4.com/news/contact-channel-4-news
or go direct to email –
Email us
If you have a comment for the newsroom please email us at: news@channel4.com
“Both studies agree that there is no risk of catastrophic mass loss this century or next.”
No they don’t. Nobody can guarantee that so far into the future.
“The additional good news from these studies is that should mass loss unexpectedly accelerate, we will have plenty of warning.”
How so? Greenland suddenly accelerated in the 1990’s, I don’t see much advance warning there.
Doug Proctor says:
November 29, 2012 at 5:08 pm
Here is the Humidity:
Graph: Global Relative humidity 1948 – 2008
Graph: Cloud Cover at various levels and Atmospheric Water
Leif Svalgaard says this paper is wrong and the Sun’s TSI is constant.
Judithgate shows the IPCC is doing their darnest to bury any hints that the sun might be a variable star that has a major impact on climate.
However there are plenty of NASA articles that show they really do not understand just how variable the sun is.
NASA Finds Sun-Climate Connection in Old Nile Records
NASA: Quiet Sun Means Cooling of Earth’s Upper Atmosphere
NASA: Giant Breach in Earth’s Magnetic Field Discovered
NASA: SOLAR IRRADIANCE
NASA: Deep Solar Minimum
NASA: SORCE’s Solar Spectral Surprise
NASA: Solar Variability
NASA: Solar Wind Loses Power, Hits 50-year Low
EVE: Measuring the Sun’s Hidden Variability
Sasha says:
November 30, 2012 at 6:15 am
CAN SOMEONE CONVINCE CHANNEL4 TO STOP THEIR ‘MELTING POLAR CAPS’ STORIES?
…………………………
The first thing to look at is ‘Who Benefits”
You can follow the threads of who is in control and what their hidden agenda is from there.
If you want to try getting their attention about their “ME TOO” take on CAGW you can use their own words and the BBC scandal.
Surely the meltwater (at just above 0 deg C) together with the icebergs that end up in the ocean act to reduce the ocean heat content, so reducing the amount of water vapour entering the atmosphere, so reducing any supposed GHG effect in the atmosphere.
A perfect negative feedback, stable system. Or have I missed something.
And it is interesting how many AGW trolls seem to be posting on here today….
Tony, do you have some research that backs up you assertions? I cannot see the connection between ice melting and decreased evaporation when the atmospheric temperature stays constant.
Bill Illis (November 30, 2012 at 3:30 am) wrote:
“We should also note that the Land is rising at an average of 0.3 mms/year (due to rebound from the ice ages). That means the actual sea level rise over the last 20 years relative to the Land from this glacial melt is less than one-quarter of an inch.”
Bill, what is the conventional wisdom on the spatiotemporal variability of this estimate?
Doug Proctor says:
November 29, 2012 at 5:08 pm
Looking at the graph of Greenland ice mass, I can’t figure out if the loss is a problem of losing ice faster or of not replacing the lost ice.
This is not a trivial situation to resolve. Greenland is a continental-style glacial mass that by material physics has to flow from the center thickness to the edges, where it both melts and calves into the sea. That is what glaciers do (which is why most of the alpine “glaciers” are not glaciers but stagnant ice masses, but tell that to an eco-green.) Unless there is continuous replacement in its heart, all glaciers will flow away until they are too thin to do so any more.
Your statement about the geology (geography) of the Greenland Ice Cap is not correct. The degree this affects your conclusion is unclear, but (as this paper also fails to show) the nature of the Greenland Ice cap differs substantially from what what almost everyone believes.
Greenland is a long, nearly triangular shaped island: stretching roughly from New York city on its eastern coast westward over to Chicago, stretching north-south from New York City to the southern tip of Florida. But – important “but here! – what you describe makes it appear that there are the Rockies and Appalachians right in the middle, with its central ice cap going downhill as glaciers headed towards each coast downward towards the sea. If so, melting water would flow under these glaciers and end up (obviously) in the ocean. Given improbable (impossible!) circumstances, this kind of Alpine glacier meltwater is feared (by eco-theists) to accelerate the flow of ice by lubricating the ice-rock boundary, and thus speed up melting and glacier movement. (Odd that this much-feared CAGW-inspired Alpinist glacier acceleration downhill, would,if it existed regularly, would be seen (measured!) as a regular and frequent INCREASE in the downhill movement of the glacier masses worldwide, instead of the reduction (movement uphill!) of the glacier masses. That no such movement is ever seen regularly (almost never!) should be proof that meltwater acceleration is so rare as to be noteworthy by name and date and year in the glacier textbooks, not the common rule of everyday movement.)
But, as mentioned, the geography of Greenland makes such a movement impossible.
Greenland is a bowl or a low saucer-like shape under that ice: A steep, but very short (30 – 40 kilometer!) rise up from the rocky seacoast, then the bare tops of the mountains ranges stretch unbroken around ALL of its coasts, like the rim of the bowl trapping the interior icecap. The interior of these mountain-topped coasts slopes downhill so far that the middle of the island is deep underwater level at the center, then the rock rises again to the mountains on thewest coast. We see a narrow ridge of bare rock again at the western mountains, then a short steep drop back to the sea.
The interior of the central icecap is indeed high (about 3000 meters above sea level), but it slopes so gradually to the outside trapping mountains that the resulting slope cannot “move” the icecap “up and over” the trapping mountains. (That is, the ice cap is nominally 1100 km wide, so its slope is: 3000 meters (ice altitude) – 1000 meters (the nominal “valleys” between its coastal 1700 high peaks) divided by 550,000 meters (the distance between the central ice cap peak and the nominal coastal mountains.) The interior ice CANNOT “flow” to the sea: there are no “rivers” or river networks like the Mississippi, Missouri, Tennessee, Arkansas, and Ohio to “drain” the interior around these mountains. Three isolated coastal glaciers do flow on the cnetral west coast, but these cannot “empty” out the central ice cap: they are too small.
Best seen example: WWII airplanes crashed landed in central Greenland about 60 years ago. They were found under 260 feet of newly-fallen ice and snow. All trapped in the middle of Greenland.
Do the coastal Alpine-like glaciers flow as you describe?
Some do, some don’t. Their net mass is less than 5% of the Greenland central icecap, so the impact is small. The “sea water rise” is even smaller.
Paul Vaughan says:
November 30, 2012 at 1:16 pm
Bill, what is the conventional wisdom on the spatiotemporal variability of this estimate?
——————————
Peltier is the godfather on this.
http://www.psmsl.org/about_us/news/2012/peltier_update.php
http://www.atmosp.physics.utoronto.ca/~peltier/data.php
It varies a lot by location, large positve numbers in those areas which were depressed by the ice age glaciers, and smaller negative numbers in those areas which were uplifted (by near-by depressed areas and by the loss of ocean weight on near-by continental shelf areas as sea levels were lower in the ice ages).
Temporally, there is little change over the last 250 years or 250 years into the future.
LetsBeReasonable says:
November 30, 2012 at 12:57 pm
Tony, do you have some research that backs up you assertions? I cannot see the connection between ice melting and decreased evaporation when the atmospheric temperature stays constant.
_____________________________
SWAG: It is the evaporation from the oceans that counts since they are 70% of the surface area. However if I remember correctly it takes that cold water ~ 800 yrs to make the trip to the equator and become part of ENSO. If you look at the graph we are getting the water from the Medieval Warm period right now.
The rest of your comment deserves to be included as one of Anthony’s “Did You Know?” series. There must be 100 more like it in WUWT’s archives.
Sasha wrote (November 30, 2012 at 6:15 am):
CAN SOMEONE CONVINCE CHANNEL4 TO STOP THEIR ‘MELTING POLAR CAPS’ STORIES?
I saw a very similar story on TV here in Canada. I attribute it to “science by press release”; journalists rarely have any knowledge about anything scientific and are always on the lookout for some story to worry or titilate their viewers / readers. Doha happens to be the scare story of the moment.
Or so it appears to me.
Have you seen ANYTHING in the MSM about the letter sent to Ban Ki-Moon?
IanM
Bill Illis (November 30, 2012 at 3:55 pm) informed: “Peltier is the godfather on this.”
Thanks for the links Bill. I also found a GIA map:
http://upload.wikimedia.org/wikipedia/commons/7/74/PGR_Paulson2007_Rate_of_Lithospheric_Uplift_due_to_PGR.png
What has me thinking about this carefully is something I read last week:
Chao, B.F. (2006). Earth’s oblateness and its temporal variations. Comptes Rendus Geoscience 338, 1123-1129. doi:10.1016/j.crte.2006.09.014.
http://www.earth.sinica.edu.tw/~bfchao/publication/eng/2006-Earth%E2%80%99s%20oblateness%20and%20its%20temporal%20variations.pdf
Bill Illis says:
November 30, 2012 at 3:30 am
We should also note that the Land is rising at an average of 0.3 mms/year (due to rebound from the ice ages). That means the actual sea level rise over the last 20 years relative to the Land from this glacial melt is less than one-quarter of an inch.
=========================
“the Land” ?, I know you can do better Bill Illis, i’ve seen it.
This is a marathon, not a sprint.
Gail Combs says:
November 30, 2012 at 7:20 am
Thank you Gail. These stories persist, somehow inexplicably, and every time someone seemingly kills them off with scientific facts they rise from the dead, more often than Dracula, and haunt our television screens yet again.