Terry Wilson: The fundamental control of sea level is how much ice is locked up in the polar ice sheets. So if they are indeed losing their mass, that is going into the oceans and causing sea level to rise which is of great societal relevance right now, particularly given the evidence for global warming.
That’s Earth scientist Terry Wilson. Dr. Wilson is part of a research project called POLENET. The project uses GPS and seismic sensors to record the movement of ice and bedrock in Antarctica, the continent of the south pole. Wilson explained why it’s important to monitor the solid bedrock, beneath Antarctic ice – and not just the on-going melting of the ice itself.
Terry Wilson: It’s kind of simple conceptually. If you pile a load of ice on the surface of the earth, even though most people think of it as solid, in fact it bends under the weight of the ice. if you take the ice off the top, it bends back up, which is what we call ‘rebound.’
How much the bedrock rebounds, said Wilson, can help determine how much ice there was before. Wilson said this technique can help determine how much ice has been lost.
Terry Wilson: It’s very significant to work this out now, so we can get a better handle on predicting future behavior of the ice sheet.
The GPS sensors record these movements from space satellites, and seismic sensors record them directly from ground, at the South Pole. The two POLENET monitoring systems work together to measure this movement of the Earth, which is actually very slight – mere millimeters.
Terry Wilson: It’s only through correcting for what the solid earth is doing that our satellite sensors can actually accurately estimate the ice mass change.
Our thanks to:
Terry Wilson
Ohio State University
Columbus, Ohio
It would be nice for the scientist who wants to talk about lost ice to comment on the that that a satellite “Glitch” that missed 190 sq. miles of ice first!
It would be nice for the scientist who wants to talk about lost ice to comment on the satellite “Glitch” that missed 190,000 sq. miles of ice first!
I’m a bit intrigued by this story. I’m missing how the GPS is actually used in the measurement methodology. Is it providing vertical measurements (similar to monitoring volcano ground deformation) or simply tracking the location of where the measurement is being taken by seismographic equipment?
My curiosity is raised because Dr. Wilson places the deformation movement in the range of millimeters whereas the best GPS units have an accuracy of only around a centimeter when configured in a multiple GPS [error correcting] array. It seems to me that the degree of positional error introduced by ionosphere and troposphere delays alone, which vary from even hour to hour, would be in the order of magnitudes relative to the target data resolution.
What we have now are politicians promising to take our taxes and spend those taxes to lower the temperature of the planet earth. Yes I know, it WAS an episode of Star Trek.
Give us a freaking break. This is a fad. It is temporary, like DISCO was, or burning witches. Something else will take its place. Probably sacrificing goats or virgins or something.
And, this is the best part.
We have been telling almost two generations of children over the last 23 years that they will be living on a planet with a severely damaged atmosphere. As in death. As in a living hell on earth.
You greenies will be held responsible for this.
The atmosphere is cooling, the ice is expanding, the seas are not rising — even though carbon emissions are increasing. The evidence is now crystal clear to anyone with an unwashed brain that man-made global warming theory is sheer unadulterated bunkum. So how do the warmers react to the ever more embarrassing evidence that they have hitched their reputations to the biggest anti-scientific scam in history? By ratcheting up the hysteria to fever pitch and shrieking that their predictions about the impending irreversible environmental apocalypse have grievously underestimated the catastrophe which is going to be far, far worse.
At the international climate change conference in Copenhagen this week, we were told that the seas would rise by as much as a metre by 2100, that they would turn into acid, and that even the rainforests would be felled not by the loggers’ chainsaws but by the greatest pollutant in the history of the universe, carbon dioxide.
Hank: The GPS measurements are able to track crustal motion to <1mm/yr (horizontal) and ~1mm/yr (vertical). There is a wealth of work that has shown this now for some time. Dr Wilson is using the Antarctic solid earth measurements for a very important purpose. A recent satellite mission – GRACE – is able to measure total mass change on a region by region basis under the satellites as they orbit the Earth. It cannot, however, seperate out ice mass change from changes in mass in the atmosphere or in the Earth’s mantle. These need to be removed first. Atmospheric pressure is well known, even in Antarctica, but mass motion in the mantle is less well known. But mass motion in the mantle induces changes in the shape of the Earth’s surface and it is this that is being measured by GPS. Correcting for that allows GRACE to measure really accurate ice mass change estimates.
For the others, the picture being presented by independant satellte techniques and centuries of very simple tide gauge measurements shows that sea level has been changing, and more dramatically recently, and that ice is being lost into the oceans from Antarctica and especially Greenland right now. I don’t think hysteria is appropriate, but I think denial is just as dangerous.
Matt King:
Get off the fence and pick a side. How scientific is precaution? So much for it being an exact and conclusive “science” this global warming. Just in case? Give us a break.
So you warm mongers who are scaring our kids by trying to “save” the planet for them are sure that human monkeys can bring this 5 billion year old planet to it’s knees with evil SUV gas and plant food? And we should give more tax money to politicians who promise to take those taxes of yours and ours to LOWER THE TEMPERATURE OF THE PLANET? History is already laughing.
Matt: Thank you for the explanation. I was picturing shorter term deformation measurements like those used in volcano monitoring. I had not considered that the sample points were taken across a full year. I can see how the sample ranges could be trended to a higher degree of resolution across the greater range of time. I am truly impressed that ~1mm/yr is achievable given the fickleness of RF propagation, compaction of the ice flow, and variable expansiveness of soils. But that is what science is about… figuring it out and making sense of the variables.