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.
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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, ‘@ur momisugly 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.