Scientists Intrigued By Slow-Motion "Icequakes" Rumbling Twice Daily Through W. Antarctic Ice Sheet

[hatrack]

Scientists have discovered massive, slow-motion "ice quakes" trembling twice a day through the West Antarctic Ice Sheet, an Alaska-sized swath of Antarctica. Detective work has traced the source of the shaking to the Whillans Ice Stream, a glacier 100 kilometers across and 1 kilometer thick, which flows from the ice sheet's interior.
It may seem strange that magnitude-7 quakes went unnoticed for so long--a temblor of similar size leveled entire towns and killed at least 15,000 in Turkey in 1999--but people standing on the Whillans Ice Stream never notice the shaking. "The reason that it doesn't rattle the whole continent is that it's a very slow event," says Sridhar Anandakrishnan, a glaciologist at Pennsylvania State University in State College, who made the discovery along with Douglas Wiens, a seismologist at Washington University in St. Louis, Missouri. Normal earthquakes release their energy over a few seconds, but the Whillans's shaking unfolds over 20 minutes.

Wiens first noticed the ice quakes 3 years ago as he analyzed data from 43 seismic sensors across Antarctica. Hoping for faint signals that would help him pinpoint previously unknown faults, he was instead greeted by booming vibrations from the same spot in West Antarctica. Wiens then looked at seismic data collected in 2004, the same year that Anandakrishnan had deployed 16 GPS sensors on the Whillans Ice Stream that tracked the ice's movement every 10 seconds. Most glaciers edge forward continuously, but the Whillans was already known to behave bizarrely: It sits still most of the time, then surges more than a half-meter forward twice per day as ocean tides lift and lower a slab of floating ice that extends from the end of the glacier onto the Ross Sea, just off the coast of Antarctica. By combining the GPS and seismic data, the researchers saw that the ice quakes and glacial surges synchronized perfectly in time, suggesting that the shaking was caused by the ice grinding over a rough spot in the rock below, they report 5 June in Nature.

EDIT

http://sciencenow.sciencemag.org/cgi/content/full/2008/604/3

[phantom power]

1. That's pretty cool.

[Dead_Parrot]

2. Well, duh.

:evilgrin:

[phantom power]

3. ...

:spank:

[XemaSab]

4. I wonder if some of the "white noise" seen on seismographs comes from ice quakes

:shrug:

[Dead_Parrot]

6. Or hillary supporters

I can say that now, right? :evilgrin: :shrug:

[XemaSab]

7. Hillary supporters turning over in their (recent) graves?

:shrug:

[phantom power]

8. Rumors of my death have been exaggerated

[happyslug]

5. This is NOT good....

The West Antarctic Ice Sheet is considered unstable, and has been unstable for the last 10,000 years (Since the North American ICe Sheet Collapse, raising world wide ocean levels, including the Southern Ocean which the West Antarctic Ice Sheet displaces (The West Antarctic Ice Sheet is grounded BELOW sea level, unlike the much larger East Antarctic Ice Sheet).

What I fear, and I am NOT an expert, is that these ice quakes affects how the West Antarctic Ice Sheet is attached to is base AND the surrounding Antarctic Mountains. If the Ice Quakes WEAKEN the hold, that increases the possibilities of a rapid disintegration of the West Antarctic Ice Sheet. IF that happens world wide ocean levels can raise 16 feet almost overnight.

For more see:
http://www.msnbc.msn.com/id/23797247/
http://www.davidsuzuki.org/Climate_Change/Impacts/GlobalMeltdown/Collapsing_Ice_Sheets.asp
http://www.mindfully.org/Air/2005/WAIS-Sea-Levels2feb05.htm
http://en.wikipedia.org/wiki/West_Antarctic_Ice_Sheet
http://www.antarctica.ac.uk/press/press_releases/press_release.php?id=47
http://www.imaja.com/as/environment/can/journal/madhousecentury.html
http://www.commondreams.org/views04/0130-11.htm

More on Antarctic:
http://www.aber.ac.uk/~glawww/antarctic.shtml

[happyslug]

10. One last comment, the problem probably will not appear till March 2009

Right now it is the Antarctic WINTER, so the ice pack is expanding. Come September it will max out in size and start to melt as the Antarctic Spring hits, it will continue to melt till March 2009, when the Antarctic ice pack is at its lowest extent. During late March of any year is when the ice sheet is most likely to break up. After about April 15th, the Ice Pack expands so chances of a break up declines from that point till the Ice Packs is at its maximum sometime around the end of September. Then the Ice starts to melt and the cycle starts all over again.

The big issue is NOT how these ebbs and flows of the Ice Pack do to the Change of the Seasons. but how does these ice quakes affect those parts of the Ice Pack that normally does NOT melt? Does these quakes combined with the melting of the Ice weaken the hold of the Ice Shelves onto the Antarctica land mass? If yes, how? Tough Questions that only time will tell.

[windoe]

9. Ruh Roh....n/t