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Greenland's ice mass loss has spread to the northwest

Posted on 30 March 2010 by John Cook

Past studies have found most of Greenland's ice mass loss had occured in the south. However, new research has been published (Khan 2010) examining the pattern of mass loss over the entire Greenland ice sheet (H/T to Riccardo). Satellite gravity data and Global Positioning System (GPS) measurements both find that mass loss has been spreading up along the northwest coast of Greenland, starting in late 2005. This increase in mass loss is shown most dramatically in this animation created by co-author John Wahr:

Ice mass loss from Greenland

GPS data is obtained by placing GPS receivers on bedrock adjacent to the ice sheet. As the massive Greenland ice sheet loses mass, the bedrock undergoes vertical crustal uplift. Bedrock near the Thule Air Base on Greenland's northwest coast rose by about 4 centimeters from October 2005 to August 2009. As accelerating ice mass loss causes accelerated crustal uplift, the observed uplift show strong agreement with the loss of ice mass measured by satellite gravity data. These observations indicate that the accelerated mass loss is dominated by the increasing velocity of outlet glaciers. Large glaciers in the north-west region are sliding downhill faster and dumping more ice in the ocean.

The GPS data provides yet another line of evidence that the Greenland ice sheet has been losing mass at a significant rate. Satellite radar altimetry and airborne laser altimetry have observed thinning near ice sheet margins. Radar interferometric surveys find that glaciers are sliding faster in the ocean. And the overall picture given by the satellite gravity data shows that mass loss of the entire ice sheet is still accelerating (Velicogna 2009).

What will happen to Greenland in the future? Various independent studies predict global sea level rise of around 1 to 2 metres by 2100, with Greenland being a significant contributor (Vermeer 2009, Pfeffer 2008). Models predict that at the rate we're emitting CO2, collapse of the Greenland ice sheet is likely within the next few centuries (Stone 2010). This is backed up by studies of earth's past history which find ice sheets are highly sensitive to warmer temperatures. Global temperatures just 1 to 2°C warmer than now saw sea levels over 6 metres higher than current levels (Kopp 2009).

Science is about piecing together the full body of evidence to improve our understanding. As more data comes in, we're now seeing many lines of evidence painting the same picture. The Greenland ice sheet is highly sensitive to warming temperatures and is likely to contribute sea level rise in the order of metres.

UPDATE 2 Apr 2010: Many thanks to Robert Simmon at NASA who pointed me in the direction of another instructive animation of ice mass loss from Greenland as measured by the GRACE gravity satellites:

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Comments 51 to 69 out of 69:

  1. Let me step back a bit and then focus on the mechanics of glaciers. It would appear that this post was originally wrritten to support the premise that the loss of ice in Greenland is another piece of evidence that the earth is warming due to man's activities. From my persepctive, this is an incorrect assumption and that by understanding the dynamics and mechanics involved with glaciers, we know that advances and retreats of glaciers have happened in the past, well before there was any proposed warming related to increases in atmosphereic CO2. As far as Greenland is concerned, there is a multitude of data available for people to review and publish/speak about their own theories. It would appear that some people posting here do not have an understanding of glaciology, how they are formed, what dynamics they undergo, etc - especially when it comes to assessing what is being observed in Greenland and Antarctica. There are a number of excellent papers that have been written on the subject that I recommend be read: Glacier Mass Balance and Regime: Data of Measurements and Analysis, Mark Dyurgerov, Editors: Mark Meier (INSTAAR), Richard Armstrong (NSIDC), Institute of Arctic and Alpine Research University of Colorado, Boulder, Colorado 80309 The effect of more realistic forcings and boundary conditions on the modelled geometry and sensitivity of the Greenland ice-sheet E. J. Stone, D. J. Lunt, I. C. Rutt, and E. Hanna the journal The Cryosphere (TC).Occasional Paper 55 INSTAAR/OP-55 ISSN 0069-6145 To appreciate the concept of mass balance of glaciers I suggest people visit the World Glacier Monitoring Service at http://www.geo.unizh.ch/wgms/ I also point out my previous reference by Fountain, Lewis and Doran who identifed that the main process whereby glacier lose mass in the polar regions is by sublimation and not melting. The actual article is Spatial climatic variation and its control on glacier equilibrium line altitude in Taylor Valley, Antarctica, Global and Planetary Change Volume 22, Issues 1-4, October 1999, Pages 1-10 and it is NOT the article that was linked by Doug in # 36 (had he looked at the reference he would have noted that I included the name Volume and pages of the publication it appeared in.) In response to GFW # 36, the water vopor content of the world's atmosphere as measured by ballon launches in Boulder Colorado, has increased on average 1% per year since 1980. It is obvious from that build up that the atmosphhere can accommodate more water vapor. In addition, the premise regaring the increased water vapor from sublimation of snow and ice in the polar regions, precipitates back out as snow, not water and contributes to the accumulation of snow in the upper regions of a glacier. Jeff # 37 - I am not where you got your 300 gigatons per year - according to a report entitled " Recent Greenland Ice Mass Loss by Drainage System from Satellite Gravity Observations, originally published in Science Express on 19 October 2006, Science 24 November 2006, the rate is more like a net loss of 113 gigatons per year, obtained from the GRACE mission. I also did not say (or mean to say) that the observations have no scientific basis - it's the definitive conclusions that people make from the observations that are questionable. That position is based on the understanding that the the morpholgy and dynamics of a gacier, let alone one the size of Greenland, are too complex to make conclusions based on a few pieces of data - Jeff # 41 - I don't dispute what you posted - it is in line with normal glacial activity. The one point I will make is what we see happening to glacers today, is not related to what is happening in the atmosphere today but rather it is a result of some past event relative to that glacier. The premise of this blog is to support the contention that gloabl warming is attributable to the burning of fossil fules by man and that the many postings on the blog are meant to debunk the arguments made by people who question that theory. If I am right, then the declaration that "Greenland's ice mass loss has spread to the northwest" was made to further the argument that the earth is warming and is linked to increases in CO2 due to man's activities. My point in joining the discussion is to put forth the position that there are many other valid reasons to support alternative theories as to why Grfeenland's ice mass is in a decline. I certainly am not questioning the interpretation that the mass is on a decline. I do think however some seem to exaggerate claims (such as a loss of 300 megtons per year) and forget to factor in items such as while the fringe is losing mass, the centre of the glacier is accumulating mass. Doug # 42 - My purpose of brining up sublimation is that I do not believe (and it has been confirmed by posts here) that epople really understand the role sublimation plays in the polar regions. It is more significant than most people apparently want to give it. With regards to arctic ice disappearing, my personal view is that it is more related to warmer ocean currents (currents that have been warming since the 30's, plus incrased solar energy in the 1980's. It cannot happen due to a marginal change of 1 degree in air temperature...that was the point I was making. Ricardo # 43 - I did read that article and it is in contrast to that posed by the authors in the articles I mention above. Ned # 44 - I would dispute what you have indicated in your post. The one thing climate models have not been able to forecast (without veering off their temperature relationships) is the accommodation of the melting arctic ice cap and the observations being made in both Greenland and Antarctica. Hence your "The mainstream scientific view of climate change impacts on the mass balance of the Greenland ice sheet is a model of clarity and consistency (both internal consistency and model-observation consistency)." is not valid IMHO. Yes CO2 has increased but so has water vapor, and while some believe that is atrributed ot a feedback mechanism, other disagree. Whatever the reason, water vapor acts much more strongly towards increased CO2 and while models may interprest the results of this warming, as you have indicated, models are a close environment wheras the earth's climate is an open environment. As for polar amplification, there is conflicting views on the validity of that concept after all it was coined by Manabe and Stouffer in 1980 in their climate model's response to increasing green house gas levels. However I did read somewhere (don't have the link..sorry) where the effect of cosmic and solar radiation can be amplified at the poles - something to do with the concentration of the earth's magentic field. Your reference to physical models of glaciers isn't quite right either. Glaciers are reacting today from events that happened previously. Yes they are receeding (while some are advancing) but that is a normal characteristic of them. The current retreating of glaciers has been occurring since the 1930's (and earlier if you want to go back to the last major ice age). As for glaciers moving at an accelerated rate, that can be related to a number of factors, including calfing which is usually followed by an increase in velocity because the ice doesn't have th push that ice that fell off into the ocean. (simplistic but makes the point). In my years working in the field, one thing I have learned is in many instances things are not what they appear to be and consequently I have learned to challenege an argument by identifying alternative theories as to what is happening. That processis actually a part of the scientific process - as soon as we stop questioning the validity of an argument, we stop advancing...nuff said. With regards to Greenland, I encourage you to read the article by Mark Dyurgerov who addresses the issues with Greenland. As for the mechanism you are asking about, it has always been there. Ice melts at 0 degrees C (32F) at sea level. However, snow and ice fields are known to lose their mass at temperatures well below that figure (we are taking significant magnitudes here and not decreases related to slainity etc). That loss happens because of sublimation. I live in a place where we experience warm winter winds from time to time. We can have two feet of snow on the ground and after several days of these winds, that snow can virtually be reduced by a factor of 75% with no water run-off. As for remote sensing identifying melting - sorry it identifies the reduction in mass (gravity survey) - what we need to understand is what factors contribute to that loss in mass. That is waht I have identified in my posts - alternatives to an increase in air temperatures causing ice to melt. GFW # 45 - the water content change I cited was from regular balllon launches from Boulder CO. While the rate may not reflect the entire atmosphere - it does reflect the fact the water content during the period cited did increase (and was reported by the IPCC as to having done so). Also with repect to the increase in ocean levels, not all of it is attributable to melting glaciers. Finally carbon black isn't the same as soot so I believe you are referring to soot (carbon black is manufactured as a additive to rubber products.). Yes microspcopic pieces of carbon from incomplete burning do have a role to play in melting (soot falls on snow/ice, sun radiates energy, soot absorbs sun's energy, soot heats up, snow/ice melts. Initially it was thought that the disappearing snows on Mt. Kilamanjaro was the reult of just that process - they thought it was dust blown up from lower valleys. However after some further studies, the consensus now is the disappearing snow/ice is attributed to sublimation.
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  2. Geo Guy, my point was just clarify that no one belives that the process was just plain melting as if "people posting here do not have an understanding of glaciology". Noteworthy is the paper you quote (Stone et al.) which well describe the complexity other people and myself were trying to push, while you insisted on your point on ablation. I hope that now this oversimplification is over.
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  3. Geo Guy wrote "Yes CO2 has increased but so has water vapor, and while some believe that is atrributed ot a feedback mechanism, other disagree." Geo Guy, please see my comment on the thread "Water Vapor is the Most Powerful Greenhouse Gas." If you can come up with actual citations of the "others" who you claim disagree, please post them in a comment on that thread. (Water vapor is not really on topic in this Greenland's Ice Mass thread.)
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  4. Marcel Bökstedt, here we are talking about Greenland ice sheet, not arctic sea ice.
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  5. Geo Guy, curiously enough the title of the first article for which I provided a link-- as you did not even though you first cited it-- is "Spatial climatic variation and its control on glacier equilibrium line altitude in Taylor Valley, Antarctica." But perhaps two sets of authors with the same names independently tackled the same subject and coincidentally came up with the same title, this coincidence escaping the notice of the journal editors who thus published two papers of the same name, by authors with the same name? My point however is that using glaciers that necessarily achieve mass balance via sublimation because that is the only means they have of shedding mass as a basis for comparison of mass loss by ice sheets and glaciers with drainage readily available is misleading. More, to claim that sublimation trumps other means of mass loss is an unsupported assertion without further work. Have you calculated the potential for mass loss of the Greenland ice sheet due to sublimation? If not, you're not offering a useful counter-hypothesis to the researchers with whom you've placed yourself in contention. You either need to do that work or accept that other researchers have supported their hypotheses while you have not. To do less is not at all persuasive, no matter how many times you repeat yourself. Indeed, you seem to find your own opinions and intuitions more compelling in all cases than actual nitty-gritty research others have performed and published. That of course is your personal choice, you're free to believe whatever you want, but if you're looking to influence others you'll need to roll up your sleeves and make an effort.
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  6. Riccardo - the brief mention of arctic sea ice was my fault. Marginally on topic because the "health" of the sea ice is believed to influence the temperature, and hence the mass loss rate on Greenland. Geo Guy, you're throwing a heck of a lot of words up, without a lot of meaning, and a lot of it is wrong and/or based on obtuse misinterpretations of other commenters here. 300 Gt/y? Check out the (most recent) slope of the green line fit in figure 2 on this page. Yes, we're all very well aware that an ice sheet can grow in the middle while shrinking at the edges. But that graph shows the change in the total, and it's currently 300Gt/y. By the way, saying that H2O that sublimes off an ice sheet can snow back onto it is obviously a possibility. But that's not *loss*. We're talking about the 300Gt/y of net loss. My statement that the *vast* majority of any mass loss from any ice sheet, ice cap, or glacier winds up in the ocean is true. Human dam building and the amount of increase of H2O in the atmosphere are a relative drop in the bucket, so bringing up either only shows how poor your grasp of the big picture is. I never said the converse, that melting ice was responsible for all the sea level rise. Quite the contrary, right now sea level rise is *roughly* half from thermal expansion, and half from melting ice. The Boulder CO balloon measurements were indeed of the stratosphere. The stratosphere contains less than 1% of the atmosphere's H2O. I did the math for you to compare what a 1% change per year in that 1% of the atmospheric total would be in terms of sea level, and it was not noticeable. Carbon black? Ok, I meant black carbon which as that page makes clear is a component of soot. I guess reversing the word order means I don't know anything. /sarcasm My entire point in bringing up black carbon was to point out that people here know very well that there are multiple contributors to global warming and that every time you say something about "don't believe...CO2...sole cause" you're inventing a straw man. So, finally a question for Geo Guy that he should answer before any of us pay any attention to another word he posts. The question is: What is your explanation for the evolution of sea level rise over the past, say 100 to 150 years. Please compare your answer to the consensus view regarding the change in ocean heat content and change in quantity of land-ice over the same period.
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  7. #51 Geo Guy, 300 gigatons per year comes from Velicogna (2009), the latest estimate from GRACE. Measured, not exaggerated. As for whether air temperature or ocean temperature is more important in the acceleration of glaciers in Greenland, that is a good question. But then why is the ocean warming up? In the end, it comes back to the radiative imbalance -- the planet is getting warmer, and some of the heat goes into the atmosphere and a lot goes into the oceans. There was a great figure on this posted here a couple of times recently, but I have been unable to find it....
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  8. Jeff Freymiller @57 Perhaps the diagram you're referring to is the one that appears in the "Response" to Post #13 on the skepticalscience.com discussion Why-is-Greenlands-ice-loss-accelerating?. The accompanying text reads, "The amount of energy that goes into ice melt is fairly small compared to the amount of energy being absorbed by the oceans. In the figure below, all the energy gone into ice melt is included in the red "Land + Atmosphere" segment" The discussion on this page provides a good background to the present discussion.
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  9. #58 CoalGeologist, yes that is exactly the figure I was thinking about. Thanks!
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  10. The current dialog on climate change involves more than just a compilation and interpretation of scientific evidence. We are confronted with diametrically opposed viewpoints on nearly every line of evidence, centered specifically on the question of human attribution. Thus, an equally important issue--and doubtless MORE important in many discussions--is whom to trust as authorities. SkepticalScience.com has placed a priority on evidence reported the peer-reviewed scientific literature, without reference to politics, accusations of deception, or inferences of nefarious goals of climate researchers. From this standpoint, the reference to "Alarmists" in the original Post (#20) by GeoGuy might have been regarded as inconsistent with the Comments POlicy, as the term means "One who causes others to become alarmed without cause". In other words, it implies an intent to cause fear, but without a valid reason. Fortunately, the subsequent discussion has focused exclusively on whether various skeptical arguments can be supported or refuted, based upon evidence in the scientific literature. The term "alarmist" has not appeared again (until now :-( !! ) Bravo to GeoGuy and all respondants to a civil dialog that has been both interesting and informative. The purpose of my present post is to note that we have more to learn from this discussion than arcane details about the rates and underlying causes of loss of ice mass in Greenland, including: 1) Implying an underlying "motive" to those who merely report or discuss research findings is not helpful, assuming the goal is to gain an unbiased understanding of what these findings show, and 2) Asking skeptical questions is not only not wrong, it's the right thing to do in scientific inquiry, assuming that the skeptical hypothesis(es) is testable and refutable by well-documented, verifiable evidence. Anyone who questions the willingness of this site to actively entertain skeptical arguments would do well to read back through the posts and replies.
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  11. Riccardo #54 Is sea ice extent really unrelated to this topic? If it's true that most of the mass loss is due to calving rather than melting in-situ as suggested by many then surely open ocean for longer time periods must have an affect on the rate of ice loss. It would seem common sense that open water facilitates more calving than ice locked sea. The many animations of arctic sea ice suggest there has been change in sea ice freeze in the Baffin/Greenland sea since the 1980's.
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  12. HR, yes there appears to be *some* linkage between sea ice and the glacier flow/calving rate, but it's not quite the same story as how the more permanent ice shelves of Antarctica hold back glaciers there. Sea ice doesn't have the thickness or rigidity of an ice shelf so any back-pressure effect is much weaker. However, the less sea ice there is in general, the less protection Greenland has from warm winds and currents.
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  13. HumanityRules, both are affected by rising temperatures but this is about the only relation between the two. They behave differently, as nicely and concisely explained by GWF.
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  14. #63 Both are affected by climatic conditions. Temperature is part of that.
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  15. It has happened to Greenland in the past when ALL the ice melted. The people had a prosperous time for many years and they enjoyed it.
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    Response: There is no recorded history of the last time ALL the Greenland ice melted - the Greenland ice sheet is at least 400,000 to 800,000 years old.
  16. Acushla - I think you are being suckered by misinformation. There are good historical documents for the Greenland colony - confined to 2 southern fiords and plenty of archeological evidence about the settlement too. The ice sheet was firmly in place then, as now. There is no possible doubt about this.
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  17. In the Northwest of Greenland, just another data point: An ice island four times the size of Manhattan broke off from one of Greenland's two main glaciers, scientists said on Friday, in the biggest such event in the Arctic in nearly 50 years. The new ice island, which broke off on Thursday, will enter a remote place called the Nares Straight, about 620 miles (1,000 km) south of the North Pole between Greenland and Canada. The ice island has an area of 100 square miles (260 square km) and a thickness up to half the height of the Empire State Building, said Andreas Muenchow, professor of ocean science and engineering at the University of Delaware. Muenchow said he had expected an ice chunk to break off from the Petermann Glacier, one of the two largest remaining ones in Greenland, because it had been growing in size for seven or eight years. But he did not expect it to be so large. "The freshwater stored in this ice island could keep the Delaware or Hudson Rivers flowing for more than two years," said Muenchow, whose research in the area is supported by the National Science Foundation. "It could also keep all U.S. public tap water flowing for 120 days." He said it was hard to judge whether the event occurred due to global warming because records on the sea water around the glacier have only been kept since 2003. The flow of sea water below the glaciers is one of the main causes of ice calvings off Greenland. More. U. Delaware release here, includes imagery.
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  18. Fascinating article about Greenland here in the UK's Daily Mail. A reporter visits scientists working this summer on the ice sheet, investigating drainage. Some great photos.
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  19. A little update: Researchers Race to Catch Up With Melting, Shifting Polar Realities When the Petermann Glacier calved an ice island four times the size of Manhattan earlier this month, GPS sensors embedded in the ice and time-lapse cameras sitting on nearby rock were watching. But scientists who put them there were caught off guard. Traveling to northwestern Greenland to retrieve the data that equipment recorded will cost them roughly $93,000, money they currently don't have. That's unfortunate, says Jason Box, a climate scientist at Ohio State University who helped place those instruments, because the difficulty comes as his research team has made a startling discovery. Of the 30 widest glaciers in Greenland, it's the ones in the north -- where Petermann is located -- that are collectively losing the most ice. "The science really hasn't caught up with the observations," he said of those results, which he will present at a scientific meeting this week in Ohio. "The observations are showing really dramatic changes. There is an element of surprise. The fact that there is so much change in northern Greenland is not something the community is aware of yet." Box's dilemma illustrates the difficulty and expense of operating in harsh polar environments, factors that can magnify sheer bad luck. (Scientists set up their monitoring of the Petermann Glacier last summer, when they expected it to calve at any moment.) But the story of the recent calving also offers a window into the intense, ongoing effort by scientists who study the world's ice to improve their understanding of how melting at the poles will contribute to sea level rise. "One of the major impacts [of the calving] will be that we expect Petermann Glacier ... to speed up, something like a factor of two, because glaciers always speed up when ice shelves break off in front of them," said Robert Bindschadler, a senior research scientist at the University of Maryland, Baltimore County, at a recent congressional briefing. "That's an expected consequence. And that's going to increase the drainage of the Greenland ice sheet and contribute to a rise in sea level. But just how quickly the massive freshwater ice sheets in Greenland and Antarctica will melt is still uncertain. And that uncertainty carries over into projections of how high and how fast the world's seas will rise. Just three years ago, the Intergovernmental Panel on Climate Change predicted seas would rise between 7 and 23 inches by 2100 -- but couched that estimate with a giant caveat. The IPCC cautioned that an additional rise could come from rapid and unpredictable melting in Greenland and Antarctica, which it didn't attempt to estimate. "The terminology in a football game is, we punted," said Pennsylvania State University glaciologist Richard Alley, one of the scientists who worked on that portion of the IPCC's wide-ranging fourth assessment report. "We didn't know what to do." Now scientists are scrambling to play catch-up amid high stakes. Greenland's ice alone contains enough fresh water to raise the world's seas by 23 feet. Reconstructions of the Earth's past climate indicate that a temperature rise of roughly 2 to 7 degrees Celsius could cause the Greenland ice sheet to melt entirely, Alley said. "What we find from looking at history -- when the world warms, the Arctic warms more," he said, citing a 2008 federal report on abrupt climate change that he helped author. "When the Arctic warms, Greenland melts." Scientists don't believe the Greenland ice sheet will disappear anytime soon. But if greenhouse gas emissions go unchecked, Earth's climate could reach a tipping point in a decade that would put Greenland's ice on a course to disappear within centuries, Alley said. Satellite measurements show the margins of the Greenland and Antarctic ice sheets are thinning, driven primarily by the acceleration of outlet glaciers like Petermann. "As the Earth is getting warmer, ice sheets are going to shrink and sea level will go up," Bindschadler said. "There is no doubt about it. The key question for experts such as myself are these: How much will sea level go up, and when is that going to happen? That's where research is going right now." More, including many interesting remarks by researchers
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