By Steve Goddard, as a follow up to this story
‘http://en.wikipedia.org/wiki/File:Jakobshavn_retreat-1851-2006.jpg
The press has been getting worked up about a 7 km² chunk of ice which broke off the Jakobshavn (Greenland) glacier on July 6. Is this an unusual event?
Since 1831, the glacier has retreated about 60km, as seen in the image above. About half of that occurred in the first 80 years (prior to 1931) and the other half has occurred in the last 80 years. The long term rate has not changed. As you can see, the retreat occurs in spurts, with quiesced periods in between.
We keep hearing over and over again theories about huge recent increases in melt from Greenland and Antarctica, supposedly based on GRACE gravity anomaly data. If this were actually happening, sea level rise would absolutely have to accelerate to match. Where else can the melted ice go, but to the sea?
But sea level rise rates have generally declined since 2006, with the exception of the El Niño spike.
http://sealevel.colorado.edu/current/sl_noib_global_sm.jpg
The sea level data unequivocally shows that accelerated melt is not happening.
Now, let’s look at the size of the chunk which broke off from Jakobshavn – in green.
That represents 0.0003% of the Greenland ice sheet in area, and a much smaller percentage of the volume, which is 2,800,000,000,000 cubic metres.
A huge chunk of glacial ice sunk the Titanic almost 100 years ago. Where did that chunk come from? Enough alarmism, please.
In order to interpret gravity data, you need to have bedrock reference points below the ice. This is an impossible task for several reasons.
1. Any place where the ice is deep is, by definition, buried in ice.
2. There is almost no bedrock exposed in the interior of Greenland, as seen in the satellite image below. The few places where you can find bedrock are mountain tops, which exhibit very different isostatic behaviour than the valleys which are – buried in ice.
Conclusion – the interpretations of gravity anomaly data are flawed.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
I think its a mistake to look at one glacier or one icefield.
Has anyone looked at the debris fields on the ocean bed around the Jakobshavn glacier? This would give us a historical picture of its ebb and flow.
One other point about the Jakobshavn glacier is that it was floating until very recently. Thus its melt and calving would have no impact on sea rise.
“There exists an air photograph taken by USAF in 1946 that shows that the ice-front was then in about the same place as in 2003 (the photograph is on p. 141 in this paper: http://www.igsoc.org/journal/54/184/j07j061.pdf). The glacier actually advanced several kilometers 1946-53 and then stood more or less still during the rest of the twentieth century.”
Yes, that is right. Comparing the time-line photo on wiki with the photo in the paper shows that 2003=1946. Looking at the paper and the wiki time-line photo, it is clear the author of the wiki photo cherry picked the dates.
Reading the paper in detail some key facts stand out.
1. There were significant advances in the 1890s and the 1920s and a smaller advance in the 1950s.
2. Glacier advance and retreat is dependent upon the interplay of the various ice tributaries that meet at the glacier terminus.
3. Glacier advance and retreat were greatly affected by the flotation of the glacier due to glacier thinning.
4. Changes in glacier flow are highly dependent upon the weather in the previous two decades.
ben says, “What’s with all this cherry-picking? facts are facts. Greenland was warmer in the early 1990’s than it is today. It was also warmer in the late 30’s, etc.
So we have glaciers advancing…. into the ocean and this is cause for concern when we have no idea of why this is happening. You have not referenced one study that says “this is occurring because….”
****************
No “cherry-picking” at all ben, and it is YOU that certainly needs to reference some “facts” about Greenland temperatures today, the early 90’s and the late 30’s to have any credibility. I was merely using the above article and the time lines drawn by others, without trying in the least to provide a cause — only EFFECT! Never once did I mention temperatures in Greenland or elsewhere for that matter, reasons why the Jakobshavn Glacier has been in retreat for over one and a half centuries, or provide reasons why the glacier has appeared to apparently increase its loss since 2001.
While I certainly agree that “facts are facts,” I merely questioned those facts and the time line above, showing that a full one-third of the Jakobshavn Glacier’s retreat over the past 160 years happened from 2001 to the present. Are you having problems with those facts, and only feel the need to throw out unreferenced “facts” of your own?
Again…..here are the facts without any causes behind them:
1851-1913, or 62 years, the first 20 km of the glacier is lost
1913-2001, or 88 years, the second 20 km of the glacier is lost
2001-2006, or 5 years, the last 20 km of the glacier is lost
Why, in your scenario of a warmer Greenland in the late 30’s and early 90’s, did the Jakobshavn Glacier not lose massive mass during those time periods, yet lost a full one-third of the 60 km from 2001 to 2006?
ben says, “I will give you a hint, it’s not temperature related. I can prove that in 10 seconds.”
****************
Many scientists have already proven your statement false, since melting glaciers on Greenland create moulins of falling water inside those glaciers, that in turn lubricate the underside of the glaciers on the rock they are sliding, thus increasing their forward momentum and loss into the ocean through calving. It most certainly is temperature-related, melting the glaciers and forming moulins of falling water.
Steve says:
“The sea level data unequivocally shows that accelerated melt is not happening.”
The amount of melt increase reported by GRACE is a tiny fraction of the ERROR in the sea level data.
Regardless of the accuracy of GRACE (I have my own doubts here), using a less precise proxy to confirm or refute GRACE’s accuracy seems like pure folly and there is nothing “unequivocal” about it.
I hate to see your stronger points undermined by this lapse in analysis.
stevengoddard says:
July 14, 2010 at 6:18 am
tallbloke
Didn’t we have record high SSTs recently?
Yes. That’s what I already pointed out:
“The point is, [OHC] hasn’t been increasing for 7 years now, but slightly decreasing. The sea level rise has flattened off, but hasn’t gone negative. So melt must be a bigger contributor to current sea level rise if the metrology is correct. This seems intuitively correct, as the ocean surface temp has risen as the heat-energy sequestered in it has started rising back to the surface since the sun went quiet.“
According to New Scientist (spit):
GREENLAND lost 1500 cubic kilometres of ice between 2000 and 2008, making it responsible for one-sixth of global sea-level rise.
But don’t panic yet, the Greenland ice sheet is around 2.85 MILLION cubic kilometers of ice.
1500/7=215km^3/year
2.85×10^6/215km^3/year=13255 years.
Should be ok until well into the next ice age…
I’ve just noticed this:
“Our best model uses the global ICE-5G deglaciation model of Peltier (2004). It assumes an incompressible, self-gravitating Earth. The mantle is a Maxwell solid, and overlies an inviscid core. The viscosity and all other rheological parameters depend on radius, but they are independent of latitude and longitude (i.e. we are assuming a spherically symmetric Earth). ”
We know, from the fact of continental drift and plate tectonics, that “the viscosity and other rheological parameters” are not “independent of latitude and longitude”, but vary sufficiently to cause significant non-uniform crustal movements, of the same order of magnitude as the GRACE anomalies. Therefore the model is false; specifically, it is not adequate to calibrate the GRACE results, though it may of course have some utility as an approximation for other purposes.
That’s overwhelmingly simplistic nonsense. There are a multitude of factors which affect the movements of different segments of a glacier. The interplay of these factors for and against movement are far more complex than talking about just moulin drainage. The galcier under discussion was subject to a considerable amount of basal lubrication for many years, yet it did not increase the flow to the sea because the flow of the glacier was impeded by groundings at its terminus. The grounding led to the glacier broadening, thinning, thickening, and thinning again as the interplay of forces, decreases in mass, and increases in mass changed while the glacier was grounded and ungrounded. Trying to pin recent movements soley or principally upon basal lubrication from moulin drainage is an absurd oversimplification of the known events.
Steve Goddard said:
Conservation of mass. If ice melt has accelerated, sea level rise has to accelerate as well.
This is an fundamental principle which can not be hand-waved away or ignored. It is a show stopper for any theory that Greenland and Antarctic ice melt has accelerated.
************************
Speaking of calculus (which you do in a later comment), wouldn’t we expect the rate of sea level rise to slow if the rate of ice melt remained constant? Since Earth is a sphere, it would take a greater volume of ice melt to raise sea level the next millimeter than it did the previous one. This argument also assumes that the shores of each island and continent are vertical rather than sloped as they are in the real world. Taking that into account certainly forces one to reject the idea that glacial melt volume and sea level change must have a linear relationship. Using this model, it would require an appropriate yearly increase in the volume of glacial melt to keep the rate of sea level rise linear. Even a small yearly increase in melt may not be enough to keep the increase in sea level linear. Similarly, it may take a significant acceleration of the melt to cause a small acceleration in sea level rise.
In any event, your application of the conservation of mass principle is misplaced. Nowhere in that “fundamental principle” does it state that mass is related to volume.
lakota2012 says:
July 14, 2010 at 8:28 am
Lakota, for goodness sake! Educate yourself, look at the paper suggested by tty:
tty says:
July 13, 2010 at 11:29 pm
In that paper you will see that you are utterly mistaken if you believe that the glacier has continually retreated. It hasn’t; look at the aerial photograph taken in 1946 (page 141), the ice front there is about the same as it was in 2002. In 1953 it had ADVANCED about 10km from the 1946 position.
Paul Birch says:
July 14, 2010 at 3:25 pm
“Therefore the model is false”
————————–
All models are wrong, but some are useful.
It is not useful to declare that because there is some uncertainty, the model is false. What matters is how large the uncertainty is relative to the size of the effect being examined. If the effect is large relative to the uncertainty, the model is useful. Focusing on the uncertainty (fairly typical behaviour here) is missing half the picture.
You seem to think that the scientists that use these data are not aware of these problems. Have you read any of the literature to confirm this, or are you relying on your prejudices?
MartinGAtkins says:
July 14, 2010 at 12:32 am
Summer insolation at 65º was about 10% higher than modern in the Eemian. See this graph, or find the raw data at http://www.ncdc.noaa.gov/paleo/data.html , such high values will not be repeated for over 200ka.
Given this extra energy, is it any surprise that the Arctic was warm in the Eemian?
You are fixed on the (very old) Eemian cycle. Greenland (the entire earth – as shown by over 500 research papers) was significantly warmer a mere 800-odd years ago during the MWP.
No earth rotation or polar variation can explain that. CAGW fails because you cannot explain the 66 year short-term cycle of temperature, nor the longer 800 year cycle of temperature.
We are recovering from the Little Ice Age low temperature of 1600-1700 – Obviously, average temperatures are rising. Prior to that, the MWP of 900-1100 was hotter than today. Prior to that the Dark Ages were cooler, the Roman WAM Period was slightly hotter.
Each hot point has been lower than the previous high 800 years before. Your real concern should be the upcoming Ice Age as we drop 5 miles of ice on Chicago. Again.
Basal lubrication theory is widely stated – but never proven in fact because it (like the “death spiral” lowering Arctic ice extent) is false. It is based on soley on simplistic theories of ideal laboratory conditions
RACookPE1978 says:
July 16, 2010 at 12:34 pm
What is the evidence that supports your personal rejection of the basal lubrication theory? A review of the literature? Experiments? Fieldwork? Or are you relying on a highly tuned gut feeling?
Field observations (Rockies, Sierra, Yosemite, Spain, Alpine, Austrian/Slovakian, Carpathians, Alleghenies, Appalachian Mountains.
32 years fluid flow, nuclear and nuetron flux analysis, 3d FEA and computer modeling of fluids and piping design, heat transfer, thermodynamics, civil and structural design, metalurgy and machining, welding, casting, mold design.
Couple of other classified things.
Give me your assumed case study dimensions of your assumed glacier that is “supposed” to undergo basal lubrication and sudden slipping.
RACookPE1978 says:
July 17, 2010 at 10:13 am
I look forward to the paper you must be able to write from such a wealth of relevant experience (but I’d omit the metalurgy – glaciers are made of ice). It will surely be publishable in Nature or Science. Don’t delay, it’s your chance to be a hero and prove all those scientists wrong.
????
Shear strength od solids, stress (intergranular and cross-granular, fracture mechanics, strain curves and reactions = the flow of solids (ANY solids) under stress, crystal growth and shear strength, melting and recrystallization, isophase changes as solids heat and cool and melt and reheat, heat transfer across phases ….
To blindly discredit metallurgy (by an assumed glacier specialist? – We do not know your level of knowledge about anything) shows the actual level of knowledge glacier specialists might have.
I repeat, define the glacier you claim will undergo a “tipping point” and undergo catastrophic melting/sliding. By the way, the earlier reference about glacier intermittent speeds can’t translate the alpine or central glacier fields – the measurements are across the the last few km (the bare tip of a glacier already supported only by water in fjord.) Irrelevant to glacier sliding down a rocky valley, and irrelevant to static central ice fields that have increased in depth by 300 feet in 60 years.
What length? What width? Depth at center? Speed at what temperature of the ice at what years? Speed of center of flow, speed at edge of ice? Depth (height of ice) at tip? Meltwater rate out at the tip? (Depth of water stream out from under the glacier at the tip, temperature of water, flow rate at times of year?) Air temperature at upper field? Air temperature at tip? Elevation of bare rock at top of field? Elevation of bare rock at tip? Rate of change (contour) of the valley center from the ice field at the top to the tip? Radius of curvature of valley? Type of rock under the glacier? Variation of snowfall of upper field across years of the study?
You claim catastrophic globally destructive ice melts due to glacier flow. Back up your claim with numbers.
I made no claim, neither to my expertise nor to glacier behaviour.
You made the claim that basal lubrication theory is false, but have utterly failed to substantiate this claim. A list of your expertise does not constitute evidence.
Now you make the new claim that the “central ice fields that have increased in depth by 300 feet in 60 years.” Perhaps this will be easier for you to substantiate. (NB 300 feet depth increase is not equivalent to 300 feet of accumulation, as the latter ignores ice flow)
What ice flow (under or around) the planes?
Both the (very light weight fighters with small wing area) airplanes and the heavier, wide wing planned bombers were found upright, on ice with wheels down and parked at the same elevtion.
“Ice flow” would have “floated” the fighters substantially away from each other, and even more differently than the bomber, and at different rest angles. Ice accumulation on fixed aircraft does not move the aircraft.
How do you establish that increased ice mass across central Greenland has not depressed the central rocky subsurface and lifted the (non-ice-covered) small outer mountains that GRACE used as a GPS (assumed baseline!) reference.
RACookPE1978 says:
July 17, 2010 at 3:58 pm
What ice flow (under or around) the planes?
————-
Several web pages say the planes moved a mile. The book, “The lost squadron: a true story”, might give a more authoritative answer.
You have a strange notion of how ice flow in an ice sheet might occur. The cartoon at http://www.iceandclimate.nbi.ku.dk/research/flowofice/ might help. Stress increases with depth, so most of the flow occurs deep in the ice sheet and the surface is moved passively (except at the ice divide).
????
The surface is moved passively? Except that the surface seems to have risen 300 feet from where it was in the early 1940’s. A mile sideways? Not surprising. We could not plot any points by celestiaal navigation to a mile accuracy in the 1970s’. The vertical “movement” is the deposited new snow and ice.
This from NASA in 2006.
This situation would be consistent with reports based on remote sensing from satellites. A NASA press release on March 8, 2006, reported this based on satellite observations by ICESat: (quoted from http://icesat.gsfc.nasa.gov/)
The Greenland ice sheet gained more ice from snowfall at high altitudes than it lost from melting ice along its coast. Image left: The Greenland ice sheet gained more ice from snowfall at high altitudes than it lost from melting ice along its coast. Credit: NASA/SVS
In Greenland, the survey saw large ice losses along the southeastern coast and a large increase in ice thickness at higher elevations in the interior due to relatively high rates of snowfall. This study suggests there was a slight gain in the total mass of frozen water in the ice sheet over the decade studied, contrary to previous assessments.
The following for Greenland’s ice sheet, courtesy of:
http://bprc.osu.edu/wiki/Greenland_Factsheet
Accumulation and Ablation
* Area of net accumulation: 1.472 x 106 km2 (Benson, 1962)
* Area with net ablation: 0.255 x 106 km2 (Benson, 1962)
* Total accumulation: 516 km3 y-1 (Ohmura et al. 1999)
* Total melt ablation: 347 km3 y-1 (Ohmura et al. 1999)
o of which 244 km3 y-1 drains from the ablation area and the remaining (103 km3 y-1) from the accumulation area.
* Net accumulation 271 x 1012 kg/yr (Ohmura et al. 1999)
Thus, yes – Greenland’s ice sheet is gaining substantial mass per year, and yes, the GRACE assumptions (requiring a loss of ice to correct for a rise in the elevation of underlaying bedrock) are incorrect. Far easier to assume the underlaying bedrock is getting driven lower by a rise in height of the ice sheet.
Note also that the these many tons of water are simply and easily (as always) removed from under the glaciers by flowing to the center of each valley (for outer rim glaciers) and out from under the glacier. The 2 – 4 meter rises and falls under the glacier ice in the baseplate bedrock allow ample room and flow paths for all water to escape. None can be trapped permanently or temporarily under the glacier to “float” the glacier and reduce friction. Water flow area under glaciers will vary by glacier and steepness of the glacier valley, but will be 1% to 6% of the total exposed bedrock.
Exaggerations of basal flow are simply that.