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!