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.
“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”
It’s kept the same rate before CO2, and the same rate after CO2.
Someone could actually come to the conclusion that global warming has had no effect on it at all.
But Anthony, the last 80 years were “unprecedented”
Whatever the capabilities of GRACE may be, regarding supposed ice measurements it is clearly used only as a propaganda tool.
I can just see a bunch of guys funded by the AGW machine sitting around a computer fiddling with the adjustable parameters and fudge factors in their models, trying to get whatever kind of raw data the thing produces to show unprecedented, massive, and accelerating ice loss. agian.
reality be damned.
Since you are so confident that GRACE data are so contaminated with isostatic adjustment that they cannot be used to estimate ice sheet mass loss, perhaps you would like to critique the method used to correct for the isostatic trend.
The method is described at http://grace.jpl.nasa.gov/data/pgr/
I am sure those who developed the method would be delighted to be advised of their errors.
Alternatively, just carry on with the “I don’t believe it, therefore it must be wrong” argument.
All normal melt of glaciers is now re-defined as abnormal, i.e., UNPRECEDENTED! Run away, run away, run away! Funny walk. Handstand. Word to your mother. And in a moment of calm reflection, perform an AGW Genuflect before the mighty Hansen, from whom all knowledge comes in flaming rhetoric of falling skies and rising seas…. Amen.
Actually, it looks like the rate was fairly constant until 1964, where it paused until 2001. The rate from 2001 to 2006 was then extremely high.
Gotta luv the link to “alarmist” media site! http://www.hindustantimes.com/Chunk-of-Greenland-glacier-breaks-up-overnight/Article1-571649.aspx
Also note that if polar ice melts and sea level rises, then length of day (LOD) increases. LOD is routinely measured with enormous accuracy; enough to show any sea level rise. The is nothing to indicate that LOD has increased recently.
The only thing that seems ‘unprecedented’ in the photo of the Jakobshavnis Glacier is the almost complete lack of retreat from 1964 to 2001.
richard telford
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.
If you ever read in the MSM or other public that the retreat of Greenland glaciers is “unprecedented” you have to look at history. History shows us the following.
http://www.greenland-guide.gl/leif2000/history.htm
http://www.ngu.no/en-gb/Aktuelt/2008/Less-ice-in-the-Arctic-Ocean-6000-7000-years-ago/
With regard to “unprecedented rate of warming” then research says no:
http://www.agu.org/pubs/crossref/2006/2006GL026510.shtml
Now, where do we go from here? Can what we have seen in the last 35 years be explained by natural variation? Well, if it’s not unprecedented then the answer is clearly yes.
There will not be much difference in isostatic behavior between mountain tops and nearby valleys, isostasy doesn’t change over short distances, the Earth’s crust is too stiff.
Otherwise you are right about the essential impossibility of measuring glacier thickness at the centimeter or millimeter precision claimed.
By the way here is a very interesting and balanced paper on the Jakobshavn Isbrae, actually written by glaciologists (i e people who actually study glaciers):
http://www.igsoc.org/journal/54/184/j07j061.pdf
Your statement above “In order to interpret gravity data, you need to have bedrock reference points below the ice. This is an impossible task for several reasons.” is entirely FALSE. Gravity data are often used to DETERMINE depth to bedrock and this method, coupled more recently with both seismic and ice penetrating radar, provides a good estimate of Greenland’s topography beneath the ice.
The GRACE data interpretation is based on loss of mass. Gravity data can detect loss of mass without knowing anything about layering or composition. The rapid and accelerating loss of mass in Greenland measured by the GRACE project has been attributed to ice loss. Greeland’s accelerating loss of ice has also been supported by other methods including flow rates and altimetry providing further confirmation of the GRACE results. Your conclusion that the “the interpretations of gravity anomaly data are flawed” without knowledge of the depth of bedrock is baseless.
Hi Steven. If you are going to make arguments from sea level, then you need to consider the Steric contribution. Between 1993 and 2003, the world ocean rose around the equivalent of 5200 cubic kilometers. The OHC has been dropping slightly since 2003, so if sea level really is continuing to rise on roughly the same trend, then the slack has been taken up by ice melt. However, the sea level rise seen in 2009 is mostly due to thermal expansion just before the el nino, and I would expect to see a sharp downswing in sea level rise over the next quarter.
Upshot is, trying to guage ice melt volumes from sea level change isn’t easy.
richard telford says:
Since you are so confident that GRACE data are so contaminated with isostatic adjustment that they cannot be used to estimate ice sheet mass loss, perhaps you would like to critique the method used to correct for the isostatic trend.
Fair enough. But just to keep things on an even keel, you should have read the information at the link you provided, which states:
“The “best” model we recommend is now based on Paulson et al (2007), with an uncertainty of +/- 20%.
The 20% value is somewhat ad-hoc, and comes from looking at results for various viscosity values and alternative deglaciation models for Antarctica and Greenland. This +/-20% probably over-estimates the uncertainty in northern Canada, where the deglaciation history is reasonably well-known; and it probably underestimates the uncertainty in Antarctica and Greenland, where the ice history is not as well-known.”
I think I’ll stick with what Steve, and the staff at GRACE, have to say for now.
You know what?
If these posts were actually science (it’s actually nothing more than cherry picking), you’d expect the author to actually publish something worthy in the well respected peer reviewed climate science literature.
Since the author says that something is “flawed” without any actual scientific evidence, we immediately know that whatever it is is not flawed (things stated in Bizzaro World are best left to those who live in Bizzaro World (yes is no, you know the drill)).
I do find WUWT highly amusing and entertaining though.
As I remember, Greenland was kicking in around 275 cubic km/year at the height of the melt in the 90’s
They have “GRACEd” us with their knowledge of ice that shatters on demand,
Of seas that rise and rise again and crash against the land,
They fiddle with a knob or two and cry, “The world is drowning!”
If I could laugh right in their face, I would, to stop their moaning,
But nothing now will stop this farce and fools deluded NEVER stop
If predicting future firestorms brings income to their grasp,
Then predictions will continue, out of hand and infinite,
Chicken littles squawking in a flock while science is re-writ…
The Jason/Topex sea level rise tends to level for periods, 2 to 3 years, then push up to a new level. Over the satellite record, this stair step rate has remained at 3.2mm per year. It dropped to 3.1 for a bit a few years ago, but that was a start-point, end-point thing. With a variation between readings of 10 to 15 mm, any melting contribution would be completely buried in the noise.
The GRACE satellites use super-high precision measurements of each other’s position, but that isn’t gravity. That’s used to roughly calculate the gravitational field, but it takes years of measurements to get the resolution down, and even at that, I doubt they’ve got it down to where they can detect melting ice, much less distinguish melting ice from rebound.
Off topic: I believe that the oceans are in bad shape but I cannot believe that these guys attribute all the problems to too much CO2 instead of things like overfishing, agricultural runoff, industrial pollution, dumping of raw sewage….
http://news.yahoo.com/s/mcclatchy/20100704/sc_mcclatchy/3555649
Annoying.
I also don’t believe in the second law of thermodynamics. I mean, just watch how life contradicts it.
Conclusion – all science must therefore be wrong.
This post is a joke.
REPLY: Ah, Luis, we can always count on you to say silly and negative things, either here, or wherever you frequent. Always predictable, keeping the hype alive, you are. -A
tty
Greenland is almost 3,000 km long. There can be huge differences in isostasy between a mountain peak and a valley 500 km away.
The volume of the world ocean is 1.3 billion cubic kilometers. Most calculators don’t have enough digits to give a decimal answer to 7/1,300,000,000 and have to show it in exponential notation 5.3 times 10 to the negative 9th.
If GRACE measurements are correct and Greenland is losing 200 cubic kilometers per year it’s still literally just a drop in the bucket. That’s enough to add 0.5 millimeters per year to sea level or a whopping 2 inches per century.
Strangely enough the satellites that measure global sea level found the rate the oceans are rising declined steadily from 2002 to 2008 even as other satellites (GRACE) found that ice melt in Greenland had doubled while Antarctica stayed more or less constant. If the amount of water entering the ocean from glacier melt doubled yet the rate the oceans were rising declined substantially the only explanation for that is that the oceans got colder during that period of time so much that thermal contraction more than counter-balanced the meltwater addition.
So if we look at the ocean, which is the single most reliable signal of global warming, the globe overall has been cooling except for the arctic region. The ocean doesn’t lie. Its volume tells us what’s really happening with the climate. Everything else is weather.
EFS_Junior
How is your fastest Arctic ice melt on record coming along?
All these disagreements over measurements got me thinking….scientists don’t even agree on the height of Mt. Everest and it is a relatively static object. How are we going to get scientists to agree on measuring sea ice, global avg temp, historical temps, etc etc.
tallbloke,
Increasing heat content of the oceans makes the melt argument even more untenable.
The question I have about the progressively increasing sea levels is ‘Do we really know that this rise is caused by increasing ocean volume?’ If MSL is measured relative to the center of the Earth, then a very-very small percentage change in the overall density of the planet could have the same effect.
We like to think that the size of the Earth is absolutely fixed and unchanging, but chemical reactions driven by heat and pressure deep in the Earth could be causing the continuous evolution of gases that would force a gradual inflation of the Earth — perhaps only to be relaxed after the next huge supervolcano eruption. If this were the case, then we might expect to see a slight pause in MSL increase after each major normal volcanic eruption.
EFS_Junior says:
July 13, 2010 at 1:04 pm
“You know what?
If these posts were actually science (it’s actually nothing more than cherry picking), you’d expect the author to actually publish something worthy in the well respected peer reviewed climate science literature.
Since the author says that something is “flawed” without any actual scientific evidence, we immediately know that whatever it is is not flawed (things stated in Bizzaro World are best left to those who live in Bizzaro World (yes is no, you know the drill)).”
So whenever someone who hasn’t published in a peer reviewed journal tells you something you deduce that it’s wrong?
I wonder how you survive a single day.
EFS_Junior says:
July 13, 2010 at 1:04 pm
You know what?
If these posts were actually science (it’s actually nothing more than cherry picking), you’d expect the author to actually publish something worthy in the well respected peer reviewed climate science literature…..
______________________________________________________________
“the well respected peer reviewed climate science literature” ???? Please now I have to clean my computer screen off. Where the heck have you been for the last ten months or so???
See: the assassination of science for a close look at how your tarnished peer reviewed climate science actually works.
Richard, EFS_Junior and Luis,
I have not seen your critical thinking and esteemed debating skills employed over at the wabett hole where the Bishop of Bunnies is touting how Greenland contains “Quick Ice”.
http://rabett.blogspot.com/2010/07/what-goes-up-often-melts-down.html
stevengoddard says:
July 13, 2010 at 12:46 pm
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.
———————
Greenland’s contribution to sea level rise is currently about 10% of the total. Changes in such a small contribution this can easily be lost in the noise caused by steric effects on a short time scale.
————-
John W. says:
Fair enough. But just to keep things on an even keel, you should have read the information at the link you provided, which states:
“The “best” model we recommend is now based on Paulson et al (2007), with an uncertainty of +/- 20%.
————
Glad you read that. Now you need to show how large the uncertainty is relative to the ice melt signal. Only if the uncertainty is large relative to the signal is Goddard justified in dismissing the GRACE data.
007, ‘@ 1.33pm,
But, but, but we have all these electronic ways of measuring things now and as everyone knows if you push a button on a computer it gives you THE ANSWER (Lol)
My emphasis above and it’s not true at all. Ice melt can accelerate but thermal expansion can decelerate by an equal or greater amount at the same time. That appears to be exactly what happened during the period of study by GRACE. Meltwater contribution roughly doubled yet the rate of sea level rise fell in half. Thermal expansion slowed down far more than increased meltwater could make up for it.
EFS_Junior says:
July 13, 2010 at 1:04 pm
If these posts were actually science (it’s actually nothing more than cherry picking), you’d expect the author to actually publish something worthy in the well respected peer reviewed climate science literature.””
And have Mann and Jones review it. LOL
stop it Junior, my sides are hurting…………
richard telford
Re : 10%.
So you are saying that Greenland is contributing 30 mm /century to sea level rise. Just over one inch, per century. LOL
Better raise taxes to stop that disaster.
I have been places where the incoming tide raises sea level by five feet in less than a minute.
Dave Springer
Sea surface temperatures were at a record maximum recently. I don’t buy the ocean cooling theory.
This is slightly off topic but I hope know the answer to this question:
GPS measurements have been used in conjunction with tide gauge measurements to measure sea level rise with sub-millimeter accuracy: (Wöppelmann, G., B. Martin Miguez, M.-N. Bouin, and Z. Altamimi. 2007. Geocentric sea-level trend estimates from GPS analyses at relevant tide gauges world-wide. Global and Planetary Change, 57, 396–406). The measured rate of sea level rise is between 1.6 and 1.8 mm/year.
Topex / Jason satellite altimeter measurements consistently show 3.2 +- 0.4 mm/year rise. That’s TWICE the rate of sea level rise measured by GPS systems. Why such a discrepancy? Based on the redundancy of satellites in the GPS systems, (the US system currently has 32 while GLONASS has 21), and the constant measurements taken by the GPS systems, I believe the GPS measurements are probably more accurate. After all, we measure relative plate motions with these things. Anybody know the answer?
Did anyone read the wiki entry?
“The second mechanism is a “Jakobshavn effect”, coined by Terry Hughes,[18], where a small imbalance of forces caused by some perturbation can cause a substantial non-linear response. In this case an imbalance of forces at the calving front propagates up-glacier. Thinning causes the glacier to be more buoyant, even becoming afloat at the calving front, and is responsive to tidal changes. The reduced friction due to greater buoyancy allows for an increase in velocity. The reduced resistive force at the calving front is then propagated up glacier via longitudinal extension in what R. Thomas calls a backforce reduction.[7] This mechanism is supported by the data indicating no significant seasonal velocity changes at the calving front and the acceleration propagating upglacier from the calving front.[19] The cause of the thinning could be a combination of increased surface ablation and basal ablation as one report presents data that show a sudden increase in subsurface ocean temperature in 1997 along the entire west coast of Greenland, and suggests that the changes in Jakobshavn Isbræ are due to the arrival of relatively warm water originating from the Irminger Sea near Iceland.[20] Recent large calving events where the glacier produces icebergs have also been found to trigger earthquakes due to the icebergs scraping the bottom of the fjord.[3]”
Steve,
I don’t know which sea level rise rates you are looking at- but if they relate to the graph you posted, it is only going in one direction–“unequivocally” upwards. No reasonable person could look at the graph and think otherwise.
With the greatest respect, it is your analysis that is flawed.
MJK
stevengoddard says:
July 13, 2010 at 2:08 pm
I see that you are avoiding answering where you think the processing error is in the GRACE data.
Not that I would have expected you to. Never admitting an error and scurrying onto the next doubtful point is much more typical behaviour of the climate skeptic.
On to your latest evasion: does it matter? We are now at a moment in history where we have the option to do something to safeguard our future. By the time that Greenland is melting fast enough to satisfy the most devout skeptic, we will probably be committed to endure much more melting (or geoengineering).
The tide may rise five foot a minute, but the water’s gone six hours later. Meltwater from Greenland will inexhorably rise over centuries.
EFS_Junior says:
If these posts were actually science (it’s actually nothing more than cherry picking), you’d expect the author to actually publish something worthy in the well respected peer reviewed climate science literature.
______________________________
No Junior, most of the people of science here are simply pointing out the peer reviewed cherries that your authorities have picked.
I learned at school that water shrinks on cooling, like everything else, but differs from the rule in that it begins to expand at 4 degrees. ( this why you have to leave an air space above containers in your freezer). Presumably the reverse occurs on melting, so if Arctic ice melts for whatever reason does it not then shrink until it reaches 4 degrees ? If so no increase in ocean volume would result from melting ice until it melted AND reached 4 degrees. Is this correct and does it have any bearing on the observation that ocean levels have not risen any faster since melting has ( allegedly )accelerated? I realise floating ice is not supposed to affect levels but would the shrinkage till it reaches 4 degrees nevertheless apply ? Is this relevant?
I hate to be the one asking dumb questions, but I don’t at all understand what I’m looking at in that picture.
1. Is the ice moving from left-right or from right-left?
2. Is the calving location in the picture at the line marked 2001?
3. If answer to 1 is right to left, and answer to 2 is ‘yes’ then the picture suggests that the calving location has advanced from 2006 to 2007, (the date the picture was taken, per the wiki). How to explain this? Perhaps the calving point varies seasonally?
The Greenland melt rate was higher in the 1930s. The Greenland temperatures correlate to the AMO. See: http://www.appinsys.com/GlobalWarming/RS_Greenland.htm
richard telford:
Would you admit that much of Greenland was once not covered in ice? Certainly, much more of Greenland than is not covered in ice today?
My understanding is that this is well known, well documented fact from writings throughout history. (Not to mention artifacts – human and vegetation – that are found after areas of ice melt.)
And prior to that, was not most of Greenland covered in ice as it is today? Again, I believe this to be well established fact.
Given these 2 facts, does it not mean that at least once in history much of the ice on Greenland melted?
If so, why should we be alarmed that it is (once again) melting now?
No sarcasm implied, truly curious on this.
Chris Korvin says:
July 13, 2010 at 2:36 pm
“I learned at school that water shrinks on cooling, like everything else, but differs from the rule in that it begins to expand at 4 degrees. ( this why you have to leave an air space above containers in your freezer). Presumably the reverse occurs on melting, so if Arctic ice melts for whatever reason does it not then shrink until it reaches 4 degrees ? If so no increase in ocean volume would result from melting ice until it melted AND reached 4 degrees.[…]”
Principle of Archimedes; the mass of a floating thing is equivalent to the mass of water it pushes aside. That’s why melting sea ice, no matter how it changes its density, will lead to a rise or fall of sea level, just like a melting ice cube in a glass of water will not change the level of water in the glass.
richard telford says:
July 13, 2010 at 2:31 pm
“[…]We are now at a moment in history where we have the option to do something to safeguard our future.[…]”
That’s a meaningless sentence, think about it.
KD
Certainly, Greenland’s ice-sheet was much reduced in the last interglacial (the Eemian) and sea-levels were several metres higher. It is this certainty of higher sea-levels were Greenland to melt substantially that is the greatest concern.
richard telford
Hansen and others say that soot is largely responsible for Arctic warming and glacial melt. One study from UC Davis said 95%.
You may believe that buying a Prius is helping out the Polar Bears, but it really has no impact on them whatsoever.
Nope. You’ve confused rise with rate of rise. True that except for a couple brief periods during the precision satellite record (1991-present) of sea level the oceans have risen every year but the rate of rise decreased substantially during the time that GRACE (2002-2009) measured a doubling of ice loss in Greenland.
If both sats are accurate then ice melt rate accelerated while global warming decelerated even more resulting in a decreased rate of sea level rise. No other explanation fits the data.
I suppose someone has to say it.
The alarmists want the glaciers’ retreat to reverse, towards their circa 1850 ideal state.
The fact that a decine in temperature to the 1850s’ level would be a food production catastrophe – more failed monsoons, plus contraction in the size of agricultural areas able to support grain production in North America, Europe and Russia – seems to be irrelevant.
Trillions of tax dollars spent to weaken western economies to support an exceptionally dodgy theory, which if correct, would further weaken western economies. How does this compute?
One thing is for sure, the subject of Greenland’s ice and glaciers is a very sore point for AGW supporters. Steve – please keep rubbing salt in the wound.
richard telford – I don’t get it… if history shows us that the ice-sheet can be much reduced without AGW, then why, exactly, is it that we have the belief that stemming CO2 will prevent the ice-sheet from being much reduced again?
Seems like many are suggesting we spend billions of dollars tilting at a windmill that, frankly, we have no evidence that we can prevent or even slow. Doesn’t seem like sound investing to me.
DirkH says:
July 13, 2010 at 2:52 pm
richard telford says:
July 13, 2010 at 2:31 pm
“[…]We are now at a moment in history where we have the option to do something to safeguard our future.[…]”
That’s a meaningless sentence, think about it.
KD: I couldn’t agree more. How is it that anyone really believes we have the option to “do something to safeguard our future”.
It seems so mind-blowingly naive to think changing our emissions can have an impact significant enough to prevent ice-sheets from melting that HISTORY HAS SHOWN HAVE MELTED WITHOUT THE PRESENCE OF HUMAN EMISSIONS.
It strikes me as identical to those who choose to build/live in floodplains… exactly how’s that working for you?
KD
ps – for the record, I live on top of a hill in Wisconsin that is part of a glacial terminal moraine. I KNOW that means my land was once under a glacier. That’s the bad news. The good news is, given the speed with which glaciers tend to move, I think I’ll see it coming this time!
DirkH:
July 13, 2010 at 2:50 pm
Sorry, but that only counts for floating ice. If you put an ice cube in a glass and fill it to the rim, even when the icecube melts it will not flow over the edge.
Greenland, as the name states is ice on land.
“I also don’t believe in the second law of thermodynamics. I mean, just watch how life contradicts it.”
Your confusion is result of calculating the change in entropy of a system and ignoring the entropy change of the surroundings.
For instance, life decays rapidly when placed in a vacuum.
If you can find a verifiable event which violates the 2nd law, you will not only become famous, you will become wealthy beyond your wildest dreams.
stevengoddard says:
July 13, 2010 at 1:33 pm
EFS_Junior
How is your fastest Arctic ice melt on record coming along?
_________________________________________
Also known as a straw man.
How’s your Arctic sea ice extent increasing by 50K/year coming along?
ROTFLMFAO!
I am sure DirkH is correct concerning the floating ice cube , though has he not dropped a rather important “not” in his reply ….either that or I am really confused . I wont argue with Archimedes, but I was not fretting about the density or the mass which assuredly does not change,but I am still not smart enough to understand.Think of an iceberg recently calved, from a glacier, floating in the ocean. As water drips off it surface to add to the volume of the Arctic ocean and thus contributes to rising ocean levels, that water as it hits the ocean is presumably at or very close to zero degrees as it has only just melted.From that moment until it reaches 4 degrees does it not shrink? And all the other drops of water that fall into the ocean. The ice below the surface will also shrink will it not, till it reaches 4 degrees? It seems to me that the total volume of the newly calved iceberg plus the water that results from its melting will not cause the ocean level to rise until they reach 4 degrees.I was thinking the reason ocean levels are reported to have not risen as much as expected might be because that wont happen till all the arctic ocean is above 4 degrees. Probably nonsense. Just a thought.
mjk
Some basic knowledge of calculus is need to understand the graph.
http://img709.imageshack.us/img709/8536/sealevelchange.gif
The graph shows rate of change vs time (i.e the first derivative dX/dt.) The slope of the graph is the second derivative (d2X/dt2.) The slope is negative, which means a downwards curvature and therefore a decreasing rate of melt over time.
Instead of telling me my analysis is flawed, perhaps take a first semester calculus class at your local community college.
@ Steven Goddard & mjk
Gentleman, Lets not get ad hominem now.
Slapping each other around the ears with studies and facts is so much more usefull.
Much better for the discussion as well.
Please debate with fact instead of insults.
This is an impossible task for several reasons.
“This is an impossible task for several reasons” is global warming’s middle name. Or is “unprecedented” its middle name? Or is it “we must act now”? Or is it “rotted ice”? Or is it “consensus among scientists”?
Enough. I’m nauseated now, and bored.
KD says:
July 13, 2010 at 3:13 pm
richard telford – I don’t get it… if history shows us that the ice-sheet can be much reduced without AGW, then why, exactly, is it that we have the belief that stemming CO2 will prevent the ice-sheet from being much reduced again?
—————
During the Eemian, the Earth’s orbital configuration was different, with more solar radiation in high northern latitudes during summer. It was this extra radiative heating (together with positive feedbacks, e.g. albedo changes) that caused much of the GIS to melt. This is well understood, and won’t happen again for some time.
Now there are different processes causing temperature changes at high latitudes. Ones that we have the opportunity to minimise.
@ Chris Korvin:
July 13, 2010 at 3:28 pm
“I was thinking the reason ocean levels are reported to have not risen as much as expected might be because that wont happen till all the arctic ocean is above 4 degrees. Probably nonsense. Just a thought.”
The highest density is at 4 C. From -X to 4 C. it will expand, from 4 -till X it will decrease in density. Everything above 4 C will give a lower level.
gravity smavity
Glaciers have always advanced and retreated:
Glaciers even advanced and retreated during the very cold Younger Dryas. It always happens. It would be unprecedented if they didn’t advance and retreat.
Pardon my bafflement, but, concerning the opening overhead image of the glacier, when was there high altitude arctic photography in the early 19th century? How is it possible to show continuous glacier through the 1851 contour and earlier? Or is this the miracle of Photoshop?
As to the comparison of GRACE with GPS, I would hesitate to claim much for GPS. The accuracy of the system is worst in the vertical dimension, and can be as much as meters. But I do not automatically accept the interpretation of GRACE data as meaning Greenland icecap loss. Just because that interpretation is plausible does not mean it is correct. It requires confirmatory ground evidence.
And as for sea levels, I will propose this change of view: mean sea level is irrelevant; what is relevant is the high tide level. Has anyone followed the time history of high tide levels? Or the statistics of anomalous high tides? I walk on the beaches that I walked on as a boy, half a century ago, and they look the same.
steve goddard says, “The long term rate has not changed…the retreat occurs in spurts”
*************
While I agree the retreat has occurred in spurts from 1851 to 2001, it certainly appears that during the last decade, the Jakobshavn Glacier has lost at least 1/3 of the total 60 km.
You can sugar-coat it all you want, and even say the long-term rate has not changed, but when the glacier has retreated over 20 km of the entire 60 km retreat that started in 1831 just since 2001, it seems to me there is a huge question you have missed.
Just look at the years you have cataloged: 1851; 1875; 1883; 1902; 1913; 1929; 1931; 1953; 1964; and then a quick succession of years to the present: 2001; 2002; 2003; 2004; 2005; 2006; although we’re missing 2007-2010.
Hey, I could be wrong, but it seems you’ve missed a huge “what’s up with that,” point!
lakota2012
Many movements in nature occur in spurts. The San Andreas fault has not moved near Los Angeles for 250 years, but when it does – it will move a lot.
Stresses build up and then tend to get released quickly.
EFS_Junior
Back on the ignore list.
Whenever you have nothing intelligent to say, you just make up a random quote and attribute it to me.
Yes, of course consequences if the alarmists were able to return us to the Little Ice Age are irrelevant to them. In point of fact, that is not their aim at all. They would rather the glaciers melted, the seas rose, the land became a desert. That would ‘prove’ that their dire predictions were coming true, and they could then say, “We will be your saviors. Just do as we say, and follow our rule, and all will be well.”
/Mr Lynn
It’s asking a lot to expect people to believe any reports about glaciers with GlacierGate still fresh in their minds:
richard telford says:
July 13, 2010 at 3:50 pm
Now there are different processes causing temperature changes at high latitudes. Ones that we have the opportunity to minimise.
Warming at higher latitudes is not occurring the way global warming scenarios say it will. But you want the reader to infer it is.
So prove it.
Also prove your bizarre statement about changing weather.
I think it’s a little disingenuous to say phrase it like that. “Half the retreat occurred prior to 1931 with half of it since.” Actually, the vast majority of that second half has occurred in the last 9 years. The 1931-2000 period saw very little retreat. So, while it is accurate to say it occurs in spurts, this has been one hell of a spurt. Just admit that rather than glossing over the blatantly obvious. It makes you and everybody else look bad and puts you in the same camp as the alarmists who will completely ignore the dynamics that could have increased retreat since 2001 that likely have very little to do with CO2 warming.
steve, it’s not the “spurts” I’m questioning, but the rapid succession of those dramatic chunks lost from 2001 to the present, that appears to be more than 20 km of the entire 60 km loss from 1831. Looks like about 40 km was lost between 1831 and 2001 — a 170 year span — and then a whopping 20 km was lost from 2001 to the present or 9 years.
That seems to be cause for concern that you missed. “What’s up with that?”
“I don’t know which sea level rise rates you are looking at- but if they relate to the graph you posted, it is only going in one direction–”unequivocally” upwards. No reasonable person could look at the graph and think otherwise.”
And no-one is. Really you warmists really ought to read the other side’s positions before you start.
The CO2 theory is not that the earth is warming. We already know that. It is that warming is accelerating out of control due to GHG.
The constant rise in water level is a major issue for this theory, as it does not correlate to CO2 levels.
Melting glaciers are not an indication that the earth is warming. Only that the current temperatures are higher than keeps them at equilibrium.
Steve,
looking at the ‘calculus’ picture you embedded above, what are you referring to when you say ‘the slope is negative’?
Looking at the most recent data, the slope looks most definitely positive.
It may be that I am seriously confused on this matter and I think a more thorough explanation is in order.
Given I am also staring at a first principles calculation of the anti-symmetric portion of the molecular polarizability tensor, I think your poor explanation has little to do with who has or has not taken a calculus class at one’s local community college.
Moreover, there was a paper in Nature Geosciences a couple years back that pointed to the recent Jackobsianndaidnkkkkj glacial melt being due to fluctuations in the Gulf stream, causing warmer water to come in contact with the ice Greenland. Having spoken with a young glacialogist/hydrologist not too long ago, this seems like the most likely culprit for the recent retreat. According to this guy, fishing records also showed similar warm waters in the 1920’s and 1930’s, when there was a similar retreat of the glacier, as seen above.
Considering that, I think the real question is, why didn’t the glacier grow during the times when the Gulf Stream wasn’t sending warm water its way? Transients from the warm water are likely several years, if not decades, long, but it makes me wonder at least.
[snip OK this is just sniping – cut it out both of you – Anthony]
maxwell
The trend line (thick blue) slopes down towards the right. That is negative slope.
http://img709.imageshack.us/img709/8536/sealevelchange.gif
Snowguy716
Let me say it again. There is nothing disingenuous about it and it is just as true as when I said it the first time. In fact it is understatement, actually more than half occurred in the first 80 years.
“About half of that occurred in the first 80 years (prior to 1931) and the other half has occurred in the last 80 years. “
Jakers said: ‘Actually, it looks like the rate was fairly constant until 1964, where it paused until 2001. The rate from 2001 to 2006 was then extremely high.’
That would be the lag.
lakota2012
There was also a large spurt from 1929-1931.
Maybe the diameter of earths crust in the deep ocean troughs shrank a bit since 2001 – lol
That way GRACE could be correct to claim the greenland and antarctic ice can melt faster without sea level rise.
Push the crust up on land somewhere where there isnt ice and voila! Mass is conserved.
Ah, Luis, we can always count on you to say silly and negative things, either here, or wherever you frequent. Always predictable, keeping the hype alive, you are. -A
Thanks for the compliment. What do you expect from any sane person when he reads something as this:
Conservation of mass. If ice melt has accelerated, sea level rise has to accelerate as well.
As if sea level rise was only a product of how Greenland’s ice sheet was behaving…
The sheer simpletonic nature of what’s being produced here is hilarious. And you think this is better than the so-called “arrogant” folks out there. Oh boy…
Dear Jon P:
I have not seen your critical thinking and esteemed debating skills employed over at the wabett hole where the Bishop of Bunnies is touting how Greenland contains “Quick Ice”.
I have little time for my entertainment. I spare them here, for instance, because the gratification I get from the unintended silliness portrayed here is quite awesome. That site seems less fun.
Agile Aspect,
Sorry for being the most recent victim of my sarcasm. Unintended and I apologize for any inconvenience to your embarrassment.
And now I see there’s a new gate in town. All shouting for their Bernsteins… ahah
apparently the sea levels are not changing as much as shown in the graph:
Interview: Dr. Nils-Axel Mörner
http://www.climatechangefacts.info/ClimateChangeDocuments/NilsAxelMornerinterview.pdf
Tide gauging is very complicated, because it gives different answers for wherever you are in the world. But we have to rely on geology when we interpret it. So, for example, those people in the IPCC [Intergovernmental Panel on Climate Change], choose Hong Kong, which has six tide gauges, and they choose the record of one, which gives 2.3 mm per year rise of sea level. Every geologist knows that that is a subsiding area. It’s the compaction of sediment; it is the only record which you shouldn’t use.
Now, back to satellite altimetry… From 1992 to 2002, [the graph of the sea level] was a straight line, variability along a straight line, but absolutely no trend whatsoever. We could see those spikes: a very rapid rise, but then in half a year, they fall back again. But absolutely no trend, and to have a sea-level rise, you need a trend. Then, in 2003, the same data set, which in their [IPCC’s] publications, in their website, was a straight line—suddenly it changed, and showed a very strong line of uplift, 2.3 mm per year, the same as from the tide gauge. And that didn’t look so nice. It looked as though they had recorded something; but they hadn’t recorded anything. It was the original one which they had suddenly twisted up, because they entered a “correction factor,” which they took from the tide gauge. So it was not a measured thing, but a figure introduced from outside. I accused them of this at the Academy of Sciences in Moscow—I said you have introduced factors from outside; it’s not a measurement. It looks like it is measured from the satellite, but you don’t say what really happened. And they answered,that we had to do it, because otherwise we would not have gotten any trend!
… So all this talk that sea level is rising, this stems from the computer modeling, not from observations. The observations don’t find it!
“lakota2012 says:
July 13, 2010 at 4:50 pm
steve, it’s not the “spurts” I’m questioning, but the rapid succession of those dramatic chunks lost from 2001 to the present, that appears to be more than 20 km of the entire 60 km loss from 1831. Looks like about 40 km was lost between 1831 and 2001 — a 170 year span — and then a whopping 20 km was lost from 2001 to the present or 9 years.
That seems to be cause for concern that you missed. “What’s up with that?””
Whats with all this cherry-picking? facts are facts. Greenland was warmer in the early 1990’s then 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 why this is happening? You have not referenced one study that says “this is occuring because…”
I will give you a hint, its not temperature related. I can prove that in 10 seconds. And sea level is not rising any faster then it was 10 years, ago, so unless this ice does a magical disappearing act, its not really understood what is really going on with the glacier….
As for the rate of ice loss:
The two main ingredients in any PGR model are
the ice (deglaciation) history
the viscosity profile of the mantle
The “best” model we recommend is now based on Paulson et al (2007), with an uncertainty of +/- 20%.
So if you use the recommended model, you get 20% error. In science, we would call this completly unreliable. And yet so called scientists still use this to model ice loss? Have they lost their minds?
The Wizard of Hansen says :
stevengoddard
July 13, 2010 at 5:25 pm
Some people are having trouble grasping data in the real world. They have ulterior motives methinks.
Well, I’ve had it with the bickering on this post. But I have to comment on this:
@richard telford says:
July 13, 2010 at 3:50 pm
“…Now there are different processes causing temperature changes at high latitudes. Ones that we have the opportunity to minimise….”
Well, smart guy, why don’t you tell us what those processes are, and lay out the means to stem them, rather than sniping at Goddard about satellite measurements that are so imprecise that it’s possible ice is increasing in Greenland. While you’re at it, explain to us poor little dolts (I’ll match my degrees against yours) how historical temperature measurements that trend down (e.g. Darwin, New Zealand, many others) when “adjusted” by the priesthood now show incredible warming trends. And while you’re at it…oh, never mind. You get the point (I hope). Get your own blog and give us the “final” word. The check is in the mail.
Luis Dias
You are obviously a very, very smart and wise person.
Please tell us why sea level is rising so very much slower than Dr. Hansen predicted.
I’ll start by stating that my knowledge of the GRACE system is next to nonexistent. However, from the picture that appeared at URL: “http://grace.jpl.nasa.gov/data/pgr/” I get the sense that GRACE estimates the time-rate-of-change of the distribution of near Earth surface mass by (a) accurately measuring as a function of time the change in distance between a pair of (or possibly more than two) Earth-orbiting satellites, and (b) from this time changing distance measurement deduces the time-rate-of-change of near-Earth-surface mass distribution. Such a technique may in fact produce estimates of the time-rate-of-change of near-Earth-surface mass (expressed in millimeters of equivalent H20 per year), but I’m highly skeptical. For example, if someone told me this technique could detect the movement by one inch per year of the mass of a thimble, my BS meter would peg and I’d assign the statement to the nonsense pile. On the other hand, if someone told me the technique could detect the presence of a new “moon-sized” mass orbiting the Earth at a height of 1,000 miles, I’d believe them. The issue then boils down to the sensitivity expressed as some combination of mass, distance, and time of the estimation technique.
The trajectory of an object orbiting the Earth is a function of the totality of the forces that act on the object. This includes gravitational forces (from all celestial objects, not just the Earth), friction forces, solar wind, possibly electromagnetic forces if electric charge can “accrue” on the orbiting object, etc. The vector sum of all these forces dictates the motion of the object. The paper at the referenced URL states:
“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 include the effects of a dynamic ocean response through the sea level equation, and we use the formulation of polar wander described by Mitrovica et al (2005). We include the effects of center-of-mass motion; although those effects contribute to our mass results only through the sea level equation, because we omit degree-one terms when computing the mass anomalies included here (see below). The mantle viscosity model is a 4-layered approximation to Peltier’s (2004) VM2 viscosity profile:
lithospheric thickness: 90 km
upper mantle viscosity: 0.9E21 Pa-sec
lower mantle viscosity: 3.6E21 Pa-sec
upper mantle/lower mantle boundary radius: 1170 km
The PGR Stokes coefficients were converted into estimates of the rate of change of surface mass, expressed in mm/yr of equivalent water thickness. Degree-one terms were omitted when computing the mass, because they are not included in the GRACE solutions. The results were smoothed using a Gaussian averaging function of 300 km radius. The mass estimates are provided on a 1 x 1 degree grid, spaced a half-degree apart.”
To me there seems to be a number of assumptions that bring into question the ability to measure mass (ice) movement (from Greenland’s glaciers wo where I’m not sure, but I assume the sea) over a period of a few years. For example, the Earth is not spherical (as assumed) but is more closely an oblate spheroid–making the gravitational force of the Earth a function of latitude. When predicting the mass-distribution of the non-surface portions of the Earth, I’m sure the GRACE scientists and engineers use a mass distribution model much more sophisticated than a sphere. But the question then arises, is this mass distribution static with time? If not, could internal mass distribution with time changes (i.e., mass movement below the surface of the Earth) produce the observed “satellite separation behavior?”
Assumptions for the lithosphere, upper mantle, and lower mantle properties were stated. But no mention is made of the effects of drag (friction) on the orbiting satellites. No mention is made of the solar wind. No mention is made of the effects of other celestial objects. In fairness, such descriptions would require many more pages of text and may be included in the references. As such, it may in fact be the case that the GRACE team has attempted to account for these effects. However, it seems to me their efforts to show Greenland glacier ice loss/gain might be a self full-filling endeavor. In particular, (a) make a reasonable static model for all the forces acting on the satellites, and (b) because almost no static model will be perfect, it is unlikely the “reasonable static model” will predict the measured time-rate-of-change of satellite separation distance, and then (c) estimate at what rate and how much mass (assumed to be ice) must be added to (or subtracted from) the geographical areas defined by Greenland and the Antarctic to make the model of the satellite separation agree with the measurements of that separation. Such a methodology would prove loss or gain of Greenland/Antarctic ice mass ONLY TO THE DEGREE THAT ALL OTHER TIME-VARYING FORCES ACTING ON THE SATELLITES HAVE BEEN ACCOUNTED FOR TO SUFFICIENT ACCURACY. For example, could the measured satellite separation distance be consistent with a redistribution of mass below the mantle?
To fully understand all the assumptions, omissions, mathematical treatments (estimations, measurement processes, numerical integrations, etc.) would require months if not years. I have neither the time nor the inclination to attempt such an understanding. However, given academia’s support of AGW and JPL’s association with the California Institute Of Technology I remain skeptical of the “GRACE-estimated” Greenland glacier ice loss until verified by independent means.
“As if sea level rise was only a product of how Greenland’s ice sheet was behaving…”
That makes no sense, but I assume you mean that sea level has nothing to do with melting of ice sheets? That would grab me as something even more skeptical then me…shrug, don’t know what to say. As for GRACE-estimated, the best model produces 20% error….and thats the error they know about…assuming no other issues with the constants they use.
It is ironic that some are claiming that cooling of the oceans is hiding an increase in ocean mass due to glacier melting due to AGW. How can the oceans cool, if the still rising CO2 is leading to a warming globe?
The oceans are the major reservoir of heat energy in the weather/climate system. If they are cooling, then the system is cooling, and CO2-forcing of AGW is refuted.
Incidentally that much-reproduced map showing the inexorable retreat of the ice-front since 1850 is wrong. 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.
richard telford says:
July 13, 2010 at 3:50 pm
During the Eemian, the Earth’s orbital configuration was different, with more solar radiation in high northern latitudes during summer. It was this extra radiative heating (together with positive feedbacks, e.g. albedo changes) that caused much of the GIS to melt. This is well understood, and won’t happen again for some time.
Would you like to cite the paper that nails this “This is well understood” condition down and can accurately predict when it will happen again. Not just the abstract please as such a remarkable piece of work deserves world wide acclaim.
GeoFlynx says:
July 13, 2010 at 12:58 pm – Your conclusion that the “the interpretations of gravity anomaly data are flawed” without knowledge of the depth of bedrock is baseless.
Here’s your chance to produce some data, GeoFlynx. Please list the density of the sub-ice rock to two decimal places in g/ml, for blocks of 1 cubic km each, over the Greenland landmass and 50 km out to sea, to a depth of 50 km. When you can do that, you will put a base under “baseless” knowledge.
richard telford invited us to look at project page:
http://grace.jpl.nasa.gov/data/pgr/
WHICH PGR SOLUTION SHOULD I ADD TO THE DATA?
If you download the data from this site, NO PGR CORRECTION IS NEEDED. We have selected for you a reasonable one, and removed it from the data.
PGR is an area of active research. In fact, GRACE will provide additional constraints to retrieve PGR.
The two main ingredients in any PGR model are
the ice (deglaciation) history
the viscosity profile of the mantle
The “best” model we recommend is now based on Paulson et al (2007), with an uncertainty of +/- 20%.
The 20% value is somewhat ad-hoc, and comes from looking at results for various viscosity values and alternative deglaciation models for Antarctica and Greenland. This +/-20% probably over-estimates the uncertainty in northern Canada, where the deglaciation history is reasonably well-known; and it probably underestimates the uncertainty in Antarctica and Greenland, where the ice history is not as well-known.
So we need to know the history of the ice melting to feed into a computer model adjust the GRACE data for rebound to estimate current ice melting. Sounds rather chicken and egg, and once again relies on speculative models of mantel rebound.
Any such speculative model needs to be calibrated and FACT before it can be accorded any value. That does not appear to be the case here.
But don’t worry folks, as with the temperature record , they have already made the necessary adjustments before releasing the data.
stevengoddard says:
July 13, 2010 at 1:35 pm (Edit)
tallbloke,
Increasing heat content of the oceans makes the melt argument even more untenable.
The point is, it 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.
So it is likely there is more melting at the moment, but from the polar ice not so much Greenland, and it’s not due to a long term warming trend, but shorter term internal ocean heat balance adjustment.
In fact, Greenland normally has no icecap whatsoever, when looking at Greenland’s entire past experience. Even during the present ice age and the last 14 million years, Greenland usually experienced periods of persistent glaciation only in the northern half of the subcontinent, with glaciation of the whole of Greenland confined to the few exceptional time periods non-representative of its normal conditions. The only reason Greenland is currently experiencing such extensive glacial conditions is the ongoing ice age in which we are experiencing a temporary interglacial warming before returning to the full glacial conditions of an ice age. Since we are in the latter stages of an interglacial warming, it should surprise no one to discover melting glacial ice and rising seas until such time as the full glacial conditions resume. Once the present ice age comes to its natural end, the Earth’s entire icecap must melt, the seas rise, and the Earth returns to its normally much warmer conditions. These normal conditions for the Earth will mean and average global increase of air temperature of about 10C.
Thank you D. Patterson
tallbloke
Didn’t we have record high SSTs recently?
Two points, one minor.
First, the minor point. Stevegoddard 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.” This first part of this is almost, but not quite, true. The melting of the ice also cools the ocean, which shrinks, reducing sea level. However, a rough calculation shows that this shrinkage is only of order 1% of the volume of ice that melts (because the thermal expansion coefficient varies quite strongly with temperature, the precise figure depends on where the cooling occurs; I made the extreme assumption that it occurs mainly in tropical waters at 20C; with more realistic assumptions the shrinkage is much less). Moreover, if mass is added to the oceans the sea floor will be depressed, offsetting (but not eliminating) the rise. Steve’s conclusion is essentially correct, but not quite as fundamental as he claims.
Second, GRACE measurements allow (subject to various assumptions and caveats) the synthesis of a gravity map. Because the map is not obtained directly from the measurements, significant artefacts may be present. It is the kind of result that, in the absence of direct confirmation, needs to be treated with caution. That’s just the map. But the main problem with the argument here is that there are no measurements by which GRACE can – even in principle – distinguish ice loss from crustal movements. All we have to go on is a model, with no actual evidence to back it up, purporting accurately to describe what is in fact a rather poorly understood subject. The basic geology is simply not known. It is entirely possible that the whole of the GRACE anomaly is down to tectonic shifts; the “ice loss” could even be a net ice gain; or on the other hand it could be two or three times greater than estimated. You can model to your heart’s content, but when the basic data aren’t there, you’ve got nothing. To draw any valid scientific conclusion we need some other independent measurements, such as GPS measurements of the height of the surface and base of the ice sheet across Greenland.
snowguy716 says, “Actually the vast majority of that second half occurred in the last 9 years. The 1931-2000 period saw very little retreat. So while it is accurate to say it occurs in spurts, this has been one hell of a spurt. Just admit that, rather than glossing over the blatantly obvious.”
***************
Exactly! Glossing over the blatantly obvious that the largest amount of the 60 km loss occurred in the past decade, surely does only a disservice to the science, since the retreat is clearly marked by those losses and the year it happened. With the exception of the 1929-1931 spurt, all the other losses happen over many years or even decades, until the yearly losses starting in 2001.
Seems to me it is “cherry-picking” by trying to break this event firmly in half by 80-year segments, instead of realizing the obvious loss over the past 9 years, or even those years between 2001 and 2006 when approximately 20 km was lost. This event can clearly be broken into 20 km. loss segments, from about 1851 to 1913 or 62 years; from 1913 to 2001 or 88 years; and the most recent between 2001 to 2006 or 5 years.
Am I also to believe that the record Arctic ice-melt year of 2007, showed no retreat on the Jakobshavn Glacier? That’s very curious considering the rest of the Arctic, even though some areas are more prone in certain years to a warming or cooling than others. Seems to me the next decade will be under intense scrutiny after the last.
If anyone wants to support the measurements made by GRACE can they please explain to us why the following features are absent from its output: The Rocky Mountains and The Mid-Atlantic Ridge, and also explain why the Himalayas have an opposite gravity anomaly to the Andes.
As far as I can see GRACE struggles to tell us anything meaningful about mountains six miles high let alone glaciers.
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”
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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?
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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).
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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.
Let’s take a look at Ohmura et al. 1999 which is so important to your argument that the GIS is “gaining substantial mass”. I’d recommend reading it, except that it is in a fairly obscure journal that doesn’t even have the abstracts online. Fortunately, it was cited by the third IPCC report, and therein is sufficient information to understand something about the paper.
First, its over a decade old, and based on older data. Is it still a valid description of the mass balance?
Second, melt ablation is given, but not iceberg discharge. Since iceberg discharge is similar in magnitude to ablation, this creates a slight problem when attributing the difference between accumulation and ablation to mass gain.
Third, these figures are based on a GCM. Most skeptics abhor these models, but I’m so glad that you trust them.
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Please read an undergraduate text on ice sheet flow.
More later.
This article is steeped in ignorance. No, this article is the archetype of ignorance. The fundamental usage of GRACE is to examine time-variable signals in the Earth’s gravity field- an incredibly important detail that Mr Watt chooses to overlook in his unshakable analysis of the validity of NASA’s project. Because these gravity signals vary on the time scale of months, seasons or years, they are known not to be due to the long-standing features of our planet. When was the last time you saw a mountain change dramatically in a month? The bedrock under the Greenland Ice Sheet is not changing significantly on an annual time scale and thus is not one of the signals interpreted by GRACE scientists. So, WATT might change that fast? Ice and water. Greenland has a great amount of seasonal surface melt water than can be seen on any satellite photos beginning in June of each summer. Certainly, water is one aspect that can change. And that water is really just melted snow from the surface of the Ice Sheet so, obviously the surface elevation of the Ice Sheet can change in that time. In the deep interior, people track the ablation of ice from the surface and this is known to occur on a relatively short time scale. The bedrock underneath Greenland is not changing. It is Archean cratonic blocks that have been wedged together for the last 1800 million years. If you want to attribute seasonal GRACE gravity changes to something in the bedrock underneath the GIS, you might want to propose a means of altering a 1.8 billion year old mass of metamorphic rock that has survived 3 million years of Northern hemisphere glacial cycles on an annual time scale.
There is so much more to say but, judging by what you absorbed on the GRACE project before writing this egregious article, you’ll only half-read my response anyway.