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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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.