From University of Texas, Austin via Eurekalert
New ground measurements made by the West Antarctic GPS Network (WAGN) project, composed of researchers from The University of Texas at Austin, The Ohio State University, and The University of Memphis, suggest the rate of ice loss of the West Antarctic ice sheet has been slightly overestimated.
“Our work suggests that while West Antarctica is still losing significant amounts of ice, the loss appears to be slightly slower than some recent estimates,” said Ian Dalziel, lead principal investigator for WAGN. “So the take home message is that Antarctica is contributing to rising sea levels. It is the rate that is unclear.”
In 2006, another team of researchers used data from the Gravity Recovery and Climate Experiment (GRACE) satellites to infer a significant loss of ice mass over West Antarctica from 2002 to 2005. The GRACE satellites do not measure changes in ice loss directly but measure changes in gravity, which can be caused both by ice loss and vertical uplift of the bedrock underlying the ice.
Now, for the first time, researchers have directly measured the vertical motion of the bedrock at sites across West Antarctica using the Global Positioning System (GPS). The results should lead to more accurate estimates of ice mass loss.
Antarctica was once buried under a deeper and more extensive layer of ice during a period known as the Last Glacial Maximum. Starting about 20,000 years ago, the ice began slowly thinning and retreating. As the ice mass decreases, the bedrock immediately below the ice rises, an uplift known as postglacial rebound.
Postglacial rebound causes an increase in the gravitational attraction measured by the GRACE satellites and could explain their inferred measurements of recent, rapid ice loss in West Antarctica. The new GPS measurements show West Antarctica is rebounding more slowly than once thought. This means that the correction to the gravity signal from the rock contribution has been overestimated and the rate of ice loss is slower than previously interpreted.
“The published results are very important because they provide precise, ground-truth GPS observations of the actual rebound of the continent due to the loss of ice mass detected by the GRACE satellite gravity measurements over West Antarctica” said Vladimir Papitashvili, acting director for the Antarctic Earth Sciences Program at the National Science Foundation, which supported the research.
WAGN researchers do not yet know how large the overestimation was. A more definitive correction will be conducted by other researchers who specialize in interpreting GRACE data. Previous estimates of postglacial rebound were made with theoretical models. Assimilation of the direct GPS results into new models will therefore produce significant improvements in estimations of ice mass loss.
The results will appear in “Geodetic Measurements of Vertical Crustal Velocity in West Antarctica and the Implications for Ice Mass Balance” (M. Bevis et al., 2009), published in the electronic journal Geochemistry, Geophysics, Geosystems of the American Geophysical Union and the American Geochemical Society. [View the paper at: http://www.agu.org/journals/gc/gc0910/2009GC002642/ ]
A team from The University of Texas at Austin’s Jackson School of Geosciences (Ian Dalziel, lead principal investigator), The Ohio State University’s School of Earth Sciences (Michael Bevis), and The University of Memphis’ Center for Earthquake Research and Information (Robert Smalley, Jr.) performed the WAGN project.
The network consists of 18 GPS stations installed on bedrock outcrops across West Antarctica. Precise, millimeter level, three-dimensional locations of the stations, which are bolted into the bedrock, were determined during measurements made from 2001 to 2003 and from 2004 to 2006, the two measurements being at least three years apart. The difference in the positions during the two time periods indicates the motion of the bedrock.
The WAGN data were supplemented with data from the first year of the Polar Earth Observing Network (POLENET) project, a project to establish a more sophisticated, continuously recording network of GPS and seismic stations, including the already established WAGN sites. POLENET will further improve our understanding of the interaction between the solid earth and ice sheets at both poles. The lead principal investigator of the U.S. Antarctic contribution to POLENET is Terry Wilson of The Ohio State University.
The West Antarctic GPS Network and the U.S. Antarctic contribution to the Polar Earth Observing Network of the International Polar Year were both funded and logistically supported by the Office of Polar Programs of the National Science Foundation.
Lucy Skywalker (13:32:05) :
The melting should relate to the sea levels/warming.
I really cannot tell you why NASA has no graph beyond 2005 on that site.
Perhaps it’s the rate of rise/melting/warming is not as significant as predicted by some.
Which relates back to West Antarctic Sheet melting/ice loss. The rates of increase are immersed in the noise of land-mass movements and expansion-contraction of warming/cooling oceans.
It’s a Signal to Noise Ratio thing, Lucy.
The other thing about NASA is that Congress has not been exaclty kind to them regarding funding and demands they place on them.
I had thought that after the Hubble thing and the public outcry to save it, that we had demonstrated to Congress that we value what they do.
I would like to hear NASA’s side of it. Are they swimming in data they have not the funds to process? I wonder.
I know that by doing diferential GPS measurements you can improve accuracy. But mm accuracy? realy? Also, GPS is not very accuriat for vertical measurements. it seems to be about 3times worse than horizontal measusements.
I suppose these guys are smart, and compensated for all that, but seems a little odd.
There is a substantial literature on glacial isostasy and its effects on local and global sea level and Earth Rotation.
Search on names like WR Peltier, Kurt Lambeck and RI Walcott as examples. There are many more as well.
rbateman (11:46:41) :
Yes, exaclty. What rising sea levels?
Where are the before & after pics?
You obviously missed Anthony’s post Maldivians sink to new low with an underwater publicity stunt. Clear proof that sea levels have risen dramatically recently, probably more than Gore or Hansen could hope for. ;^)
Skeptic Tank (11:10:03) :
“Nope! There are GEICO rejects that work for the US government and the ones that couldn’t get on there, work at the UN.”
Warming Alarmism. So easy a caveman can do it.
“So the take home message is that Antarctica is contributing to rising sea levels. It is the rate that is unclear.”
Antarctic ice has been growing for 30 years. Global sea ice is now increasing. How could this be in any way contributing to sea level rise? Unless of course researchers with “take home messages” have discovered a fourth phase for the water molecule, new “AGW ice” with a higher specific gravity than liquid water.
I can see a few other possible explanations for tiny uplift on the west Antarctic continent besides rebound as ice melts. Has there been a similar measurement on the east of the continent to detect the depression from 30 years of increasing ice? What about the underwater volcanoes recently found off west Antarctica? Any chance boring old tectonics may have a role?
Jeff in Ctown (Canada) (14:11:57) :
I know that by doing diferential GPS measurements you can improve accuracy. But mm accuracy? realy? Also, GPS is not very accuriat for vertical measurements. it seems to be about 3times worse than horizontal measusements.
I suppose these guys are smart, and compensated for all that, but seems a little odd.
We can only hope that GPS is that accurate even in the vertical measurement. I shudder every time I hear that “scientists” are making compensations for anything.
Re: Robert M. (10:38:58) – lol – thanks for a good laugh
Re: Sean (10:07:54) — good to see people are thinking about this
Re: E.M.Smith (11:19:18) — I’m exploring it further:
Vaughan, P.L. (2009). (DRAFT) Combined Oscillations of Terrestrial Polar Motion, Solar System Dynamics, & the Lunar Nodal Cycle.
http://www.sfu.ca/~plv/DRAFT_VaughanPL2009CO_TPM_SSD_LNC.htm
As you can see (if you have the time/patience to read through it line-for-line), I next have to incorporate info about nutation cycles.
Related:
Some around here might find this noteworthy:
Vaughan, P.L. (2009). 11.1 Year Cycle in Solar System Dynamics.
http://www.sfu.ca/~plv/VaughanPL2009_11.1aCycleSSD.htm
(freshly updated – more updates forthcoming…)
******************
Konrad (14:48:46) :
I can see a few other possible explanations for tiny uplift on the west Antarctic continent besides rebound as ice melts. Has there been a similar measurement on the east of the continent to detect the depression from 30 years of increasing ice? What about the underwater volcanoes recently found off west Antarctica? Any chance boring old tectonics may have a role?
********************
Glad I saw your post. I was thinking the same thing. Ground in various regions around the world rise and fall without any involvment from ice. Once again, we have a proxy that responds to more than one independent variable.
I read somewhere that the high level of GPS accuracy comes from leaving the receiver/recorder system at a stable location, like the bare rock of a nunatak peak, and leaving it there for weeks to months. Every reception reduces the error by a small amount. Given enough measurements, mm. accuracy may be possible. Can our new hire at the GPS Co. put the question to the old hands at coffee break?
rbateman (12:16:20) :
http://www.nasa.gov/images/content/121630main_slr_thermal.jpg
So this is the latest graphic I could find on the NASA site for Sea Levels.
2005.
It’s now late 2009.
Maybe the graph only goes to 2005 because that is when sea levels finished rising, the Colorado uni graph shows that pretty clear. NASA should be ashamed.
http://sealevel.colorado.edu/
Lucy Skywalker (13:40:36) “However, I’d still like to hear other skeptics’ opinions on his comments:
“… Well, as odd as it may seem, global warming may well be responsible [for increased Antarctic sea-ice], according to Jinlun Zhang, an oceanographer at the University of Washington.
He has pieced together a complex computer model that helps explain why Antarctic sea ice is growing even with signs that ocean and air temperatures are on the rise. The key is that warming temperatures can lead to more stratified ocean layers…””
2 words:
Barkin
Sidorenkov
(…btw I don’t consider myself a ‘skeptic’, but rather a ‘non-alarmist’.)
Here is how GPS can be used to measure in mm:
http://www.radiometrics.com/alber_grl97.pdf
Oh, and I guess it was made by engineers, not sciencetists 😉
John Nicklin (14:47:51) :
Do you live in the Maldives? I don’t.
But there a plenty of other low-lying Islands to examine.
Los Angeles is known to be sinking, but you don’t hear of advancing tides taking out major portions of that city. At 1″ per century, coupled with 2″ in the last 40 years, the sea has risen with respect to LA a shocking 3″.
Wow.
LAX – Los Angeles International Airport 100′ elevation.
The airport will be inundated at present sinking/sea rise in 16,000 years.
Trevor (12:01:08) “You can’t have it both ways, alarmists. If [….], it’s global warming. If [….], it’s global warming. If [….], it’s global warming. […]”
Nice – almost ROTFL here, at the 2+2=5 “simplification”.
—
Meanwhile, belief in truth & reality remains an option for some …
Sidorenkov, N.S. (2003). Changes in the Antarctic ice sheet mass and the instability of the Earth’s rotation over the last 110 years. International Association of Geodesy Symposia 127, 339-346.
East Antarctica is a craton ” A core of stable continental crust within a continent and composed wholly or largely of Precambrian rocks with complex structures.”,i.e. is relatively stable geologically, has 90% of the continents ice and growing. The geology of West A is vastly different,geologically active with mountain building with slopes that grow glaciers that tip into the sea (like the west coast of North America).
So all of this ‘shock,horror’ about WA loosing ice is a bit precious,sure get the RATE of loss a bit more accurate but you cannot compare stable EA with mountainous WA and expect the same ice retention…….one continent two vastly different geologies.
Please, can someone give me some advice. I am considering attending a meeting of my state’s “Legislature’s Public Utilities and Technology Interim Committee’s meeting this Wednesday in the a.m. Roy Spencer (Heartland Institute) and Jim Steenburgh (U of Utah) have been invited to give presentations. If I were to go, I’d like to take copies of the best article that would sway the opinions of this group of lawmakers that AGW is a fraud foisted upon the public and their pockets.
Any suggestions? If so, please give a web link to the article. Again this meeting is Oct 21st in the morning. Thanks for your help.
“JimB (13:59:53) :
“Liz (12:02:42) :
EN Smith, cheers, tried the gin recipe – superb. Going to try other spirits for the next few evenings, do you think it will work with Rum and coke and ice? lol”
Don’t try it with tequila…I still haven’t found my pants.
JimB”
Me too, and I had a mytery NZ$300 EFTPOS debit that night as well. Oh, lsoing your pants and that myster debit was caused by global warming, or was it the other way around? Hummm….it was a rather large quantity of tequila, so I am told.
Every scientist after spending hundreds of thousands of dollars needs to announce some exciting conclusions before he can ask for more money. This is another example. The end result is the ice is continuing to melt as it has for the last 20,000 years. Oh hum.
Paul Vaughan (15:25:46) :
Related:
Some around here might find this noteworthy:
Vaughan, P.L. (2009). 11.1 Year Cycle in Solar System Dynamics.
http://www.sfu.ca/~plv/VaughanPL2009_11.1aCycleSSD.htm
(freshly updated – more updates forthcoming…)
Noted!
Sioned L
You might try this site (wattsupwiththat.com) and the references to the phoney “hockey stick” and the “loss” (or destruction?) by the British university group of the world wide temperature data supporting their claimed last 100 years of the earth’s temperature rise of 0.7C. Both are key arguments in the IPCC reports and are collapsing.
Paul Vaughan (16:32:09) :
Trevor (12:01:08) “You can’t have it both ways, alarmists. If [….], it’s global warming. If [….], it’s global warming. If [….], it’s global warming. […]“
Nice – almost ROTFL here, at the 2+2=5 “simplification”.
But two plus two can equal five, for extremely large values of two.
These days, of course, any value of ‘two’ that is ‘adjusted’ by Al Gore Warmists will almost certainly be ‘three’ anyway, or course. So it’s even worse than we thought – it’s six!
Trevor:
From the article linked to by Lucy above.
http://www.bbc.co.uk/blogs/paulhudson/2009/10/the-polar-ice-conundrum.shtml
Paul Vaughan:
“Nice – almost ROTFL here, at the 2+2=5 “simplification”.
–
Meanwhile, belief in truth & reality remains an option for some …”
Not sure I understand you here Paul. Are you saying that *I* am guilty of oversimplification, and not believing in truth and reality? Or that the alarmists are guilty of same?
Wondering Aloud (10:26:13) :
“WAGN ? I think I would avoid accronyms with WAG in them. Although there are a number of networks like the GHCN in which WAG would be an appropriate one.”
I was thinking the same thing, regarding WAG Network. I mean, sheeze. I want to respect the science here, but…c’mon!