Arguments
Is Greenland gaining or losing ice?
What the science says...
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Greenland on the whole is losing ice, as confirmed by multiple satellite and on the ground field measurements. |
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Climate Myth...
Greenland is gaining ice
“[E]ven if it were true that Greenland’s ice had been melting at ‘new record’ rates, after seven and a half years of global cooling global warming cannot be the cause. The true position in Greenland is to be found in Johannessen et al. (2005), where satellite altimetry established that the mean thickness of the entire Greenland ice sheet had increased at 2 inches per year – a total of almost 2 feet – in the 11 years 1993-2003.” (Christopher Monckton)
Confusion caused by anecdotes of structures being buried by accumulating snow on Greenland's ice sheet leads some skeptics to believe Greenland is Gaining Ice. As always, the best way to tease out the truth here by following the research of scientists investigating Greenland's ice mass balance.
In general, the best available science tells us that Greenland is losing ice extensively (Figure 1) and that these losses have drastically increased since the year 2000.
Figure 1: Estimated Greenland Ice Sheet mass balance changes since 1950 using three different methods (Jiang 2010). Mass Balance Measurement Techniques are discussed here.
The evidence suggested by a multitude of different measurement techniques suggests that not only is Greenland losing ice but that these ice losses are accelerating at a rapid pace (Velicogna 2009). Further evidence suggests that although ice losses have up to this point primarily occurred in the South and Southwest portions of Greenland, these losses are now spreading to the Northwest sector of the ice sheet (Khan et al 2010).
Although there have been some gains at high altitudes, significant ice losses are occurring at low altitudes (Wouters 2008) along the coastline where glaciers are calving ice into the oceans far quicker than ice is being accumulated at the top of the ice sheet (Rignot and Kanagaratnam 2006).
In conclusion Greenland is losing ice extensively along its margins where fast flowing ice streams are pushing more ice into the ocean than is gained in the center of the ice sheet. For more information on how ice sheets lose mass, a more comprehensive discussion is available here.
Basic rebuttal written by Robert way
Update July 2015:
Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial
Last updated on 6 July 2015 by pattimer. View Archives
The argument is the cause. Without the additional heat loss from the earth (vulcanism) through both tectonics and volcanism it might not be a net loss. In other words the reason behind Greenland's and the Arctics ice melt is in question. See the volcano thread.
Science 4 July 2008: Vol. 321. no. 5885, pp. 111 - 113 DOI: 10.1126/science.1158540
Reports
Large and Rapid Melt-Induced Velocity Changes in the Ablation Zone of the Greenland Ice Sheet
R. S. W. van de Wal,* W. Boot, M. R. van den Broeke, C. J. P. P. Smeets, C. H. Reijmer, J. J. A. Donker, J. Oerlemans
Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years. The positive-feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades.
Institute for Marine and Atmospheric research Utrecht, Utrecht University, Netherlands.
"Our results show that both mass balance components,
SMB and D (eq. S1), contributed equally to the
post-1996 cumulative GrIS mass loss (Fig. 2A)."
But then, Fig.3 shows:
Ice Discharge: -94 Gt/yr
Surface Mass Balance: -144 Gt/yr
Isn't this a contradiction?
Then comes this statement: "A quadratic decrease (r^2 = 0.97) explains the2000–2008 cumulative mass anomaly better thana linear fit (r^2 = 0.90). Equation S1 implies thatwhen SMB-D is negative but constant in time,
ice sheet mass will decrease linearly in time. If, however, SMB-D decreases linearly in time, ashas been approximately the case since 2000 (fig.S3), ice sheet mass is indeed expected to decrease quadratically in time"
What is this "r^2 = 0.97" and how it is related to the equations:
MB = ∂M/∂t = SMB – D (S1)
δM = ∫dt (SMB-D) = t (SMB0–D0) + ∫dt (δSMB–δD) (S4)
Any idea?
in fig. 3 they show mass change for the period 2003-2008; fig. 2A shows the cumulative mass loss from 1960. The former is a rate of mass loss, the latter just a mass.
r^2 is the so called coefficient of determination. In the case of a simple linear fit it's equal to the square of the correlation coefficient. You may (crudely) interpret it as the fraction of the variation explained by the model curve.
This spectacular reduction is, ofcourse, trumpeted around in the media and denial blogs as exiting news, but 104 Gt per year brings it right into the IPCC 2007 ballpark of 100+ Gt per year. It is, however, much lower then the latest GRACE numbers as published by Velicogna et al. 2009 and 2007, but in the same ballpark as GRACE numbers from Luthcke et al. 2007.
The concept of isostatic rebound effecting the GRACE mass numbers isn't new either as it was already mentioned in e.g. the . It just puts some numbers to it.
There's another, somewhat older, that delves into the apparent GRACE overestimation by comparing IceSat to GRACE results. But instead of isostatic rebound it seeks to explain the differences with ice density uncertainties. It also gives an IceSat number of -138 Gt per year for Greenland which is roughly equal to the results of this new research.
So I don't know exactly what the great joy of this report is supposed to be for the contrarians. It just seems to me as confirming, refining and consolidating the science behind the apparent shrinking ice sheets.
... mentioned in e.g. the IPCC 2007 report.
There's another, somewhat older research, ...
Remote sensing data, surface observations and models indicate new records in 2010 for surface melt and albedo, runoff, the number of days when bare ice is exposed and surface mass balance of the Greenland ice sheet. This was especially true over over its west and southwest regions.
Anyone not see the trend?
In simple words, each bar tells us by how many standard deviations melting in a particular year was above the average. For example, a value of ~ 2 for 2010 means that melting was above the average by two times the ‘variability’ of the melting signal along the period of observation.
"The role of albedo and accumulation in the 2010 melting record in Greenland" by M Tedesco, et al, Environmetal Research Letters #6 (January-March 2011)
This paper can be accessed for free at:
http://iopscience.iop.org/1748-9326/6/1/014005/fulltext
From HarperCollins' last statement: "The one thing that is very apparent is that there is no clarity in the scientific and cartographic community on this issue ... ". Dead wrong. There is plenty of clarity on the issue in the science community, it's just that the Times Atlas cartographers got it totally wrong and can't admit it.
In the age of Google Earth and freely-available MODIS imagery, as well as with a media engine keen to highlight "uncertainties" in climate science, such an error, which clouds public understanding of Greenland's actual melt, verges on the unforgivable.
[DB] "the Times Atlas cartographers got it totally wrong and can't admit it."
As one who spent many years as a professional cartographer, this statement (and your closing paragraph) are spot-on.
The mind boggles.
Last updated Nov 2011? I think this needs an update! Come on John, I'm sure you have nothing but time on your hands. :)
I wonder if a Walker type cell could develop between the ever warming Arctic Ocean and the Greenland Ice sheet. Rising warm air contacts the ice, cools and flows down the ice sheet warming by compression and giving its heat to the ice. Warm foen winds cause extreme melting when in contact with ice.
... interesting: I wish I knew the answer to your question!
Recommended supplemental reading:
New Greenland maps show more glaciers at risk by Carol Rasmussen, NASA's Global Climate Change, Nov 1, 2017
I've noticed new claims that Greenland is gaining ice. It seems Steven Goddard (Tony Heller) a graph by Danish researchers on a web page 'Current Surface Mass Budget of the Greenland Ice Sheet'. It was picked up in Goddard's "Deplorable Climate Science Blog" as "Massive Growth In Arctic Ice Since Last Year" and that has been amplified by contrarians who in this case prefer to believe models to satellite data (eg "Grace data update reveals NASA Greenland mass-loss fraud").
The confusion is simply resolved by reading the explanatory text.
Ceddars @16: Based on your summary, Heller seems to be conflating Arctic sea ice with the Greenland ice sheets. Is that the case? (I personally do not wish visit Heller's blog to find out.)
John,
The graph Ceddars linked to (apparently from Goddard's site) is a graph of yearly snowfall and surface snow melt on Greenland.
The paragraph Ceddars quoted correctly describes that more snow falls each year than melts (I think in 2012 more snow melted but most years more snow falls than melts). The graph does not include melting of glaciers or calving of icebergs so it is not a complete record of Greenland ice.
The GRACE gravity data show that more ice melts each year than falls as snow. GRACE measures surface melt and ocean melt.
Sorry, there was an important word missing in my post 16 - Goddard Heller 'misrepresented' the graph, but I was going to be charitable and write 'misinterpreted'. However, it's possible he personally understands the difference between surface and total mass balance but has avoided explaining it.
The minimal text in 'Massive Growth In Arctic Ice Since Last Year' (Nov 2017) concerns both sea ice and the Greenland Ice sheet - it makes no claim the two things are related but leaves readers to draw a conclusion. Previous uses of the DMI graph includes 'Greenland Ice Growth Ahead Of Last Year’s Record Pace' (Oct 2017) which seems oddly careful to specify that DMI does show surface mass balance given that it goes on to talk of 'criminals in the press and academia'; 'Record Greenland Ice Growth Continues' (Sep 2017); 'Scientists Discover That Their Imaginary Greenland Meltdown Is Not Having Any Effect' (June 2016); and over at NTZ 'Danish Meteorological Institute Moves To Obscure Recent Record Greenland Ice Growth' (Gosselin, April 2017) mentions 'massive ice growth' without any sign of being aware of calving loss.
On 24 April Goddard Heller tweeted 'Contrary to the lies of government scientists, Greenland has gained a record 600 billion tons of ice this winter.' I pointed out the possible source of confusion, and Goddard blocked me shortly thereafter.
[JH] Please use Heller's real name.
To clarify the situation regardingGoddard/Heller's use of DMI graphics.
He shows the DMI Accumulative Surface Mass Balance graph (the lower one of the above) in two of his November posts (so far). In the first of these posts (Nov 1) he says "Greenland ice growth is close to last autumn’s record high." (His screen-shot of the graphic does not past Nov 1.) This strongly suggests Heller/Goddard doesn't understand AccSMB.
This was preceeded by a graphic showing the differences between two NOAA SIE graphics aserting "Arctic sea ice extent is up 16% from last year."
This is perhaps no surprise. 2016 was jaw-droppingly un-icy through the Autumn, setting new records for low ice. Using JAXA daily data, 2017 was 14% above 2016 on 30 Oct (& almost 16% up on 2016 on 18 Oct. Yet a percentage is a little silly as a measure - SIE grows over 50% through the month of October). And of course, the whole comment is silly as 2017 remains a very un-icy year, as shown in this JAXA SIE anomaly graphic (usually 2 clicks to 'download your attachment'). 2017 SIE is at present in 3rd place behind 2012 & 2016.
In a second post (Nov 9) Goddard/Heller again posts the DMI Acc SMB graph saying "The last two years have seen near record ice gain in Greenland." Additionally, to back his primary assertion that there has been a massive expansion of thick ice over the last decade, he blinks two DMI graphs (below) but with the thinner sub 1.5m blue and purple sea ice whited out. While the areas of thick ice may be greater 2007-17 as Heller/Goddard says, PIOMAS shows a healthy drop in total sea ice volume between Oct 2007 and Oct 2017 of 990 cu km.
I understand that Greenland is not gaining ice now after the 2000s and it decreases over 300 billions of tons of ice every year. Because of the world temperature increases can cause too much ice loss so it cannot change all of the water from ice to precipitate all of it at the interior. But why Greenland is highly sensitive to warmer temperatures?
Partly because, due to its latitude, it gets a lot of summer insolation from the sun (much more so than does the Antarctic Ice Sheet), and partly due to its proximity to warming ocean currents. Poleward convective energy transportation systems do the rest (helping to raise the ablation line higher up the ice sheet, driving further mass balance changes).