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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“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.