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.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
If the land is going up in Antarctica and in places like Greenland and Scotland, doesn’t that imply that the land has to “come from somewhere”? And if it comes from somewhere, doesn’t that somewhere have to go “down”? And isn’t a lot of the planet surface ocean bottom? So wouldn’t some of that “going down” be ocean bottom? If so, then the ocean would drop a bit, not rise…
So I’d expect all that melting (if any) to be partly offset by a deeper bucket to put it into. Sizes? Sadly, this is still at the “speculative qualitative phase”, but if anyone has pointers to anything more quantitative…
Yes, exaclty. What rising sea levels?
Where are the before & after pics?
We have produced the pictures of the Submarines at the North Pole in 1959 and on.
Where are AGW’s pictures of rising sea levels?
There aren’t any. Because the sea levels are NOT rising.
I have picture of a Ca. coastal city showing rock formations and the sea level, taken 60 years apart. You cannot tell the difference.
Whatever melting has taken place in the last 60 years, it’s trivial.
Let’s do a topic on Sea Levels. Won’t that be fun.
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.
Liz (10:51:34) :
“If the ice in Antarctic and Arctic is in the water, (icebergs etc) if 7/8th is under water to start with…”
Antarctic ice is mostly on the continent of – Antarctica. That is what that brownish stuff in the picture is. No brownish stuff in the Arctic, so yes the ice there is floating…
Three points:
1. As several posters have noted, this research says NOTHING about the Eastern Antarctic Ice Sheet, where ice is increasing.
2. Post-Glacial Rebound is a process that takes THOUSANDS OF YEARS. The rise we’re seeing today is related less to any CURRENT temperature changes than to temperature changes 10,000 years ago (that’s right, the end of the last glacial period).
3. When confronted with the FACT that ice in Antarctica, as a whole, is on the increase, global warming alarmists fall back on what seems like a counterintuitive explanation of how warmer weather, can in fact, result in more ice. You see, warmer weather means more evaporation of ocean water, which in turn means more precipitation. Precipitation, at least over Antartica, will ALWAYS be in the form of snow (unless the planet warms a hell of a lot more than even the worst alarmists predict). More snow means more ice on the continent. And so, though it seems perverse, warmer weather is perfectly consistent with more ice on Antarctica.
The problem is, if you accept this explanation (and I do), then if Antarctica were truly melting, then it can only be because the planet is getting COOLER.
You can’t have it both ways, alarmists. Either warming causes an increase in ice, or it causees a decrease. But you guys have a long history of taking whatever WEATHER happens to be occuring, anywhere on the planet, and blaming it on global warming. If temperatures increase, it’s global warming. If temperatures decrease, it’s global warming. If ice increases, it’s global warming. If ice decreases, it’s global warming. If sea levels rise, it’s global warming. Is sea levels fall, it’s global warmng. If hurricanes increase, it’s global warming. If hurricanes decrease, it’s global warming. If the upper atmosphere warms more than the surface, it’s global warming. If the surface warms more than the upper atmosphere, it’s global warming. If species die, it’s global warming. If species thrive, it’s global warming.
So I have a question for all of you alarmists out there. What, exactly, would you accept as evidence that global warming is not occurring? Is there anything at all?
Of course, many of you alarmists might ask the opposite question of us skeptics – what would WE accept as evidence that global warming IS occurring? And I will be glad to answer that question. If we had a worldwide, geographically representative, reliably monitored, scrupulously maintained, and UNBIASED temperature record of 100 years or longer, with no “adjustments” made by “scientists” who have a dog in the fight, and that record showed that the “global average temperature” had increased by more than half a degree Celcius over those 100 years, I would accept that as evidence of global warming.
It still wouldn’t prove that the temperature increase is “unusual”, or “unprecedented”, let alone that it was “anthropogenic”. But at least you would have me convinced that temperatures are rising.
Regards,
Trevor
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
“So the take home message is that Antarctica is contributing to rising sea levels. It is the rate that is unclear.”
Translation: “Please, Mr. Gore, don’t call our bosses and demand that we be replaced with hard-core warmists.
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.
rbateman (12:16:20) :
http://www.nasa.gov/images/content/121630main_slr_thermal.jpg
Does it look like sea level rise is more rapid during cooler times? Or am I still blind in one eye and unable to see out of the other.
I was just wondering how these guys can reconcile the “current” ice loss in Antarctica with the “current” 30 year cooling trend on that continent? Particularly when AGW theory states that Antarctica will actually gain ice due to increased precipitation….
The earlier GRACE results were published in Velicogna & Wahr (2006)…
They found that the WAIC was losing ~148 km3 per year of ice mass and that the EAIS was stable from 2002-2005.
This chart summarizes their results. This chart summarizes their results. The green series is the EAIS and the red is the WAIS.
The total ice volume of Antarctica is about 20 to 25 million km3… 90% in the EAIS and 10% in the WAIS. A 148 km3/yr ice loss from the WAIS represents 0.007% per year. A 152 km3/yr ice loss from all of Antarctica represents 0.0008% per year.
So, if the PGR was overestimated, the EAIS (90% of Antarctica) is gaining ice mass and the WAIS (10% of Antarctica) is losing less than 0.007% of its ice volume per year.
Tom:
2″ in 40 years. That’s .05″ / year.
.05″ turns out to be the thickness of a dime.
So, the sea level rise turns on a dime.
So, in 8009, Sacramento, Ca. will be lapped by breakers.
Projecting the NASA trendline, of course, 6000 years into the future.
Not to worry, by then the IPCC will have grown from the Intergovernmental Panel to the Interplanetary Panel.
“I have picture of a Ca. coastal city showing rock formations and the sea level, taken 60 years apart. You cannot tell the difference.
Whatever melting has taken place in the last 60 years, it’s trivial.”
Exactly, I live in coastal Nova Scotia, at the mouth of the Bay of Fundy. I regularly go for walks on the salt marshes that provided hay for the Acadians that settled this area 300 years ago. http://obpl.com/hy-mrsh.html or this one, http://museum.gov.ns.ca/arch/infos/infoaca2.htm
You can still walk the dykes that they built farther up the Bay, http://www.acadian-home.org/IMAGES/Present-day-dike-Hortons-Landing.gif
That green kool aid must taste really good, our province has been sucking it back for years.
Your taxes at work, no time for reality, sigh.
The Pineapple Upside Down Hockey Stick cake goes flat. In Search of-Mannian.
So, everything that they say, invert it.
Then apply the Flatfied correction.
Global Cooling cancels Global Warming.
Sea Levels are rising-dropping faster than anyone had previously forgotten they had imagined.
The Arctic Sea Ice is melt-recovering faster than anyone had mis-predicted.
Hurricanes in the Atlantic are forecast-disappearing faster than you can say bibbity-bobbity-boo.
The coming Ice Age meets Global Warming at Copenhagen, and an immense burst of light takes place as doesn’tMatter meets neverMind.
Enough power will be produced to run CERN for the next year, drop cord not included.
re E.M.Smith (11:19:18) ‘… proxies can be tricky things to domesticate’
Which is why one should only keep the tame ones.
The ones that can be handled most easily.
The ones that are most malleable.
The ones that can be made do what you want them to do.
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.
Isn’t there an active volcano in Western Antarctica ? … that could be causing a vertical uplift of the bedrock ??
Its much worse than we thought!!!!!!!!! 🙂
rbateman (11:46:41) : Where are AGW’s pictures of rising sea levels? There aren’t any. Because the sea levels are NOT rising.
I thought sea levels were still rising (steadily at same rate) as per CSIRO but then encountered David Stockwell’s sea level by altimeter showing fall since 2006 – but data still stops short of today – it could have turned direction again. As to TOPEX/Jason, draw a trend line for TOPEX and another for Jason, and the trend is definitely flattening.
rbateman, as to your NASA pic, I don’t understand where that fits into all the above. Can you help? Does it stop at 2005 because of the evidence David Stockwell shows? Where should it be now?
So what is “THE TRUTH”? heh?
Sadly, oh, sadly, Paul Hudson (of recent fame for his good BBC article giving skeptics an inch) has returned to the fold and his recent piece does the correct genuflecting again and his first commenter says thank you for returning to the fold.
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…
[etc]
There’s something bugging me about the concept of Post Glacial Rebound (PGR) in Antarctica…
If “Antarctica was once buried under a deeper and more extensive layer of ice during a period known as the Last Glacial Maximum”… Why isn’t there a huge unconformity in the ice cores? There’s no section missing from the ice cores. At least not from the ice cores that have been used for temperature and CO2 reconstructions.
If Antarctica was once buried under a deeper and more extensive layer of ice during a period known as the Last Glacial Maximum,” several thousand years of ice deposition should be missing from the Votok and other ice cores starting in the Holocene… But there isn’t any missing section.
I suppose that the Antarctic ice sheet extended farther north, since sea levels were lower during the Pleistocene… So, ice cores closer to the coast should have encountered unconformities… But it doesn’t seem likely to me that Antarctica should have experienced much in the way of PGR.
There are also some publications that suggest that parts of the EAIS might have actually been thinner (or even ice-free) during the Last Glacial Maximum than it is now…
“E.M.Smith (11:42:41) :
If the land is going up in Antarctica and in places like Greenland and Scotland, doesn’t that imply that the land has to “come from somewhere”? And if it comes from somewhere, doesn’t that somewhere have to go “down”?”
You are quite right. When an icecap weighs down the crust the displaced material flows outwards and forms a “forebulge” around the icecap. When the ice melts the material slowly flows back. The “hole” where the ice was fills in and the bulge around it subsides. This is the reason Scotland and Scandinavia is rising while southern England, Netherlands, Northern Germany and most of Denmark is sinking. It’s the same in North America, most of Canada is rising while the southeastern US is sinking. You can easily see this on a map, a sinking coast typically has “rias”, drowned river valleys. There are any number of these from New Jersey southward. The maximum sinking rate is near the Chesapeake, as one might guess and then decreases southward to zero somewhere in the Caribbean.
NSIDC shows increasing total Antarctic sea ice for the past 30 years:
http://nsidc.org/data/seaice_index/images/s_plot_hires.png
Some months show much higher rates of increase. Global total sea ice is also increasing (I’ve lost the link if anyone has it ?).
How exactly do the “grace satelites work. I mean they appparently use models to determine what they actualy measure. Models mean “guess”. We guess how much the tides affect each and every measurement grace makes, we guess how orbital changes effect each and every measurement, we guess how much tidal effects on land effect measurements of gravity, we guess how much density changes in the mantle effect gravitational measurements, This could go on, and on , and on.
Educated guess, well sure, but we know scientist are not immune to political results based on current and future funding.
EM Smith, ocean basins rising or sinking, I do not know. We have only had 10,000 years or so of rapidly rising sea level, which would tend to, over how long?, reverse any rebound from low sea levels. How much earth is deposited into oceans via rivers? How much water enters the atmosphere from space? ???? so many?, so much to learn
I am easily irratated by those who KNOW, and want to determine costly public policy.
Cheers
“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
“Trevor:
“…You can’t have it both ways, alarmists. Either warming causes an increase in ice, or it causees a decrease. But you guys have a long history of taking whatever WEATHER happens to be occuring, anywhere on the planet, and blaming it on global warming. If temperatures increase, it’s global warming. If temperatures decrease, it’s global warming. If ice increases, it’s global warming. If ice decreases, it’s global warming. If sea levels rise, it’s global warming. Is sea levels fall, it’s global warmng. If hurricanes increase, it’s global warming. If hurricanes decrease, it’s global warming. If the upper atmosphere warms more than the surface, it’s global warming. If the surface warms more than the upper atmosphere, it’s global warming. If species die, it’s global warming. If species thrive, it’s global warming.”
Well said. I’ve sent your post to a few of my “alarmist friends”, as it does a great job of summing up their typical responses anytime we enter a discussion about this.
JimB