NASA Study Reveals Leaks In Antarctic 'Plumbing System'

Science Daily ^ | 2-15-2007 | NASA/Goddard

[blam]

Source: NASA/Goddard Space Flight Center
Date: February 15, 2007

NASA Study Reveals Leaks In Antarctic 'Plumbing System'

Science Daily — Scientists using NASA satellites have discovered an extensive network of waterways beneath a fast-moving Antarctic ice stream that provide clues as to how "leaks" in the system impact sea level and the world's largest ice sheet. Antarctica holds about 90 percent of the world's ice and 70 percent of the world's reservoir of fresh water.

From December 2003 to December 2005, MODIS captured these two images showing a draw down of water in a subglacial lake (left)and the rise of water in the same subglacial lake (right). Color coded ICESat tracks across both images indicate rises and falls in the elevation of the lake's water. (Credit: NASA)

With data from NASA satellites, a team of scientists led by research geophysicist Helen Fricker of the Scripps Institution of Oceanography, La Jolla, Calif., detected for the first time the subtle rise and fall of the surface of fast-moving ice streams as the lakes and channels nearly a half-mile of solid ice below filled and emptied. Results were presented Thursday at the annual meeting of the American Association for the Advancement of Science (AAAS) in San Francisco. The study will be published in the Feb. 16 issue of Science magazine.

"This exciting discovery of large lakes exchanging water under the ice sheet surface has radically altered our view of what is happening at the base of the ice sheet and how ice moves in that environment," said co-author Robert Bindschadler, chief scientist of the Laboratory for Hydrospheric and Biospheric Sciences at NASA's Goddard Space Flight Center, Greenbelt, Md.

"NASA's state-of-the-art satellite instruments are so sensitive we are able to capture an unprecedented three-dimensional look at the system beneath the thick ice sheet and measure from space changes of a mere 3 feet in its surface elevation. That is like seeing an elevation change in the thickness of a paperback book from an airplane flying at 35,000 feet."

The surface of the ice sheet appears stable to the naked eye, but because the base of an ice stream is warmer, water melts from the basal ice to flow, filling the system's "pipes" and lubricating flow of the overlying ice. This web of waterways acts as a vehicle for water to move and change its influence on the ice movement. Moving back and forth through the system's "pipes" from one lake to another, the water stimulates the speed of the ice stream's flow a few feet per day, contributing to conditions that cause the ice sheet to either grow or decay. Movement in this system can influence sea level and ice melt worldwide.

"There's an urgency to learning more about ice sheets when you note that sea level rises and falls in direct response to changes in that ice," Fricker said. "With this in mind, NASA's ICESat, Aqua and other satellites are providing a vital public service."

In recent years, scientists have discovered more than 145 subglacial lakes, a smaller number of which composes this "plumbing system" in the Antarctic. Bindschadler and Fricker; Ted Scambos of the National Snow and Ice Data Center in Boulder, Colo.; and Laurence Padman of Earth and Space Research in Corvallis, Ore.; observed water discharging from these under-ice lakes into the ocean in coastal areas. Their research has delivered new insight into how much and how frequently these waterways "leak" water and how many connect to the ocean.

The study included observations of a subglacial lake the size of Lake Ontario buried under an active area of west Antarctica that feeds into the Ross Ice Shelf. The research team combined images from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard NASA's Aqua satellite and data from the Geoscience Laser Altimeter System (GLAS) on NASA's Ice Cloud and Land Elevation Satellite (ICESat) to unveil a multi-dimensional view of changes in the elevation of the icy surface above the lake and surrounding areas during a three-year period. Those changes suggest the lake drained and that its water relocated elsewhere.

MODIS continuously takes measurements of broad-sweeping surface areas at three levels of detail, revealing the outline of under-ice lakes. ICESat's GLAS instrument uses laser altimetry technology to measure even the smallest of elevation changes in the landscape of an ice sheet. Together, data from both have been used to create a multi-year series of calibrated surface reflectance images, resulting in a new technique called satellite image differencing that emphasizes where surface slopes have changed.

Note: This story has been adapted from a news release issued by NASA/Goddard Space Flight Center

[2nd Bn, 11th Mar]

I am tired of Senators and I'm doubly tired of climatology.
I think I'll go the range this weekend.
When does baseball season start, again?

Semper Fi,

[3niner]

Since we've only observed this recently, we should assume that it's a new phenomenon, rather than something that's been going on for millions of years.

[burzum]

This is nice to know, but it has less importance due to the IPCC report downgrading the likeliness of Antarctic ice melting. The current IPCC report (only the executive report (PDF) has been released) notes that Antarctica ice loss should be minimal until after 2100 because the ice is too cold and the models predict increased precipitation in Antarctica. Due to this (and the Greenland ice loss downgrade) most models now only predict a 20 to 50 cm rise in ocean levels due to the seawater heating up and glaciers melting. Al Gore is going to feel sad since his 20 ft sea level rise now looks incredibly unlikely even by the UN. The IPCC report does note that dynamic ice loss events could change this forecast but since they haven't demonstrated any likely candidates yet (perhaps they are in the full report) I would have to assume that they are classifying those types of events in the "what if" category (like what if someone decided to nuke Antarctica 1000 times).

I can't wait until the full IPCC report comes out because I am trying to figure out what they are talking about with the 1.6 W/m² radiative forcing (with 1-sigma ranges apparently from 0.6 W/m² to 2.4 W/m²). It appears to me that their 2-sigma values would overlap 0 W/m² which is probably from where the 90% probability that they listed comes from (with 10% less than 0 W/m²). If this is the case then they are dramatically overstating the importance of the calculated radiative forcing in the same way that stating that the gravitational acceleration was 9.8 m/s² (with 1 sigma values from 4.0 m/s² to 16.0 m/s²) would be too imprecise a measurement of g to be of great use.

[Kirkwood]

"Antarctica holds about 90 percent of the world's ice and 70 percent of the world's reservoir of fresh water."

Reservoir: a natural or artificial place where water is collected and stored for use, esp. water for supplying a community, irrigating land, furnishing power, etc.

Is it honest to call Antarctica a fresh water reservoir when it is essentially inaccessible to anyone not living there?

[ApplegateRanch]

The study included observations of a subglacial lake the size of Lake Ontario buried under an active area of west Antarctica that feeds into the Ross Ice Shelf.

The one thing glaringly missing is the DEPTH of any or all these lakes.

And, other than scale, how is this any different than what happens under any glacier?

[ApplegateRanch]

Noun
reservoir

1. A place where anything is kept in store; especially, a place where water is collected and kept for use when wanted, as to supply a fountain, a canal, or a city by means of aqueducts.
2. A small intercellular space, often containing resin, essential oil, or some other secreted matter.
3. A supply or source of something.

[Kirkwood]

"3. A supply or source of something."

So explain how you will get this supply to come out of you bathroom faucet?

I think this is just liberalspeak. The Antarctic may hold most of the earth's freshwater, but it may as well be on the moon. It will never actually be used as a source of potable water for the world.

[ApplegateRanch]

So explain how you will get this supply to come out of you bathroom faucet?

Hey, I just supply the dictionary definition, not the plumbing! It is a reserve supply, which will eventually melt and fall as rain or snow, recharging the aquifer from which you obtain your water supply. ;)

I do understand also, that if you wait long enough, Antartica will once again rejoin with us, thanks to the magic of plate techtonics.

[Kirkwood]

If it melts, it turns into seawater. If it evaporates it could fall as rain on some landmass, but evaporation means it can't be defined as a reservoir.