Unstable Antarctica: What's driving ice loss?

Dec 16, 2010 by Kathryn Hansen
When surface winds are strong, they stir the Southern Ocean and lift the warm water (red) onto the continental shelf where the additional heat contributes to melt of the ice shelf. Credit: Frank Ippolito

Scientists have previously shown that West Antarctica is losing ice, but how that ice is lost remained unclear. Now, using data from Earth observing satellites and airborne science missions, scientists are closing in on ice loss culprits above and below the ice.

The findings, presented Dec. 15 at the fall meeting of the American Geophysical Union (AGU) in San Francisco, Calif., are expected to improve predictions of sea level rise.

Time Not Healing Glacial Wounds

A new analysis by Ted Scambos, a glaciologist at the National Snow and Data Center in Boulder Colo., and colleagues found that more than a decade after two major Antarctic ice shelves collapsed, glaciers once buttressed by the shelves continue to lose ice.

Changes are most evident in the West and along the . A spine of mountains forces passing winds to give up their moisture as snow, feeding glaciers that in turn feed the ice shelves that jut out into the Southern Ocean. More than a decade ago, dramatic changes started affecting a series of ice shelves, collectively called Larsen, along the Peninsula's northeast coast. In 1995, Larsen A was the first to collapse followed by a larger loss of Larsen B in 2002. Today, a small piece of the Larsen B and the entirety of the vast Larsen C hang on.

Investigating how the glaciers have responded to the loss of these "dams," Scambos and colleagues tracked elevation information using data from satellites such as NASA's Ice, Cloud and land Elevation Satellite (ICESat) and previous airborne missions. They show that between 2001 and 2006, glaciers feeding Larsen A and Larsen B lost 12 gigatons of ice loss per year, or 30 percent of all ice lost throughout the Peninsula.

Moreover, the continued draw down of glaciers, such as Drygalski Glacier, fifteen years after the loss of Larsen A, have set precedent for what to expect elsewhere. Losses by glaciers that fed the Larsen B, such as Crane Glacier, are likely to continue.

Scambos and a team of colleagues have now placed instruments on glaciers just south of the area where the shelves disintegrated, anticipating that further warming will lead to further glacier speed-ups. The instruments and new aircraft overflights will provide further insight into shelf break-up and the onset of ice acceleration.

West Antarctica is seeing dramatic ice loss particularly the Antarctic Peninsula and Pine Island regions. Ice loss culprits include the loss off buttressing ice shelves, wind, and a sub-shelf channel that allows warm water to intrude below the ice. Credit: NASA/NSIDC

Wind Matters

Further south is West Antarctica's Pine Island Glacier, another site of major ice loss presently draining more than 19 cubic miles of ice per year from the West Antarctic Ice Sheet. It continues to deteriorate rapidly and scientists want to know why.

By combining satellite and airborne data, Bob Bindschadler, a glaciologist with the Goddard Earth Sciences and Technology Center at NASA's Goddard Space Flight Center in Greenbelt, Md., has successfully gained more insight into interactions between the atmosphere, ocean and ice even though the data can’t reveal these connections directly.

Bindschadler and colleagues looked at images from the Landsat satellite and spotted a series of large surface undulations on the ice shelf. Next they matched the undulations with the timing of warm water pulses in the waters adjacent to the ice shelf. When surface winds are strong, they stir the Southern Ocean and lift the warm water onto the continental shelf where the additional heat contributes to melt.

Airborne data showed the ice shelf was up to 150 meters (492 feet) thinner when the warmer water was present, allowing Bindschadler’s team to establish a direct link between the rate of ice shelf melting and atmospheric wind speed. When the team accounted for the heat coming in and the ice lost, they concluded that only 22 percent of the heat is used in melting. Whether the remaining heat might melt additional ice is unknown, but it is clear that the atmospheric circulation has a strong role on the future of the ice shelf and the fate of the ice sheet inland. Stronger winds would lead to an acceleration of ice loss; weaker winds would have a stabilizing effect.

"In short, ice shelves are affected by what winds are doing," Bindschadler said. "As Antarctic Circumpolar winds continue to increase, ice shelves are at increasing risk."

Underwater Channel Promoting Melt?

Taking a closer look at Antarctica's Pine Island Glacier is Michael Studinger, a glaciologist with the Goddard Earth Sciences and Technology Center at NASA Goddard.

Studinger is project scientist for NASA's Operation IceBridge mission -- an airborne science campaign that makes annual surveys of polar snow and ice -- that is helping researchers understand changes to Pine Island and other critical regions along West Antarctica and the Peninsula.

After analyzing data from the mission's first Antarctic deployment in 2009, the team revealed for the first time a curious feature below the Pine Island shelf: a sinuous channel that allows warm ocean water to reach the grounding line, leading to melting of the ice shelf from below.

More information will become available throughout Operation IceBridge, which sustains watch over Earth's poles until the launch of ICESat-2, scheduled for January 2016. In November 2010, teams concluded the second Antarctic campaign during which they flew over sea ice and key including a return mission over Pine Island Glacier. These data will be incorporated into the tools scientists use to refine estimates of future .

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User comments : 8

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ArtflDgr
3 / 5 (2) Dec 16, 2010
according to this there is more ice now...

imgur.com/Su8C7.png
GSwift7
2.3 / 5 (3) Dec 17, 2010
Here's a good place for you to start reading about it:

http://www.noaane...tic.html

Don't be so quick to claim that antarctica is growing. I personally don't think we'll have a good picture of things there until icesat2 is airborn. Aircraft sampling and ground sampling can only do a limited job. It's hard enough to keep track of whether the ground level of places like Houston, TX are rising or falling, much harder to analyze the entire antarctic ice sheet from a few airplane flights a year.
ryggesogn2
1 / 5 (2) Dec 18, 2010
Antarctica is a major land mass covered by ice. I recall a report that under major ice rivers is liquid water lubricating the flow. The weak explanation was that atm heat was conducted through hundreds of meter of ice. No mention was made of the more obvious, pressure or geothermal heat.
frenchie
3 / 5 (2) Dec 19, 2010
@ArtflDgr - I find it interesting that you link to a picture from NSIDC without even mentioning source or other context.

A quick search throughout NSIDC reveals how out of context you use the graph.

Arctic Sea Ice Falls to
Third-Lowest Extent;
Downward Trend Persists
This September, Arctic sea ice extent was the
third-lowest in the satellite record, falling below
the extent reached last summer. The lowest and
second-lowest extents occurred in 2007 and 2008.
Satellite data indicate that Arctic sea ice is continuing a long-term decline, and remains younger
and thinner than it was in previous decades.

http://nsidc.org/..._web.pdf

But hey...Troll on brother
frenchie
3 / 5 (2) Dec 19, 2010
Oh and here's the actual link to the paper (and the actual graph showing the melting season) that you so easily used...It's very interesting how your graph shows ice growth post melting season (duh)but fails to show the summer months which show increasing losses. Note also the larger historic.

Cherry picking data are you?
See below for the warmer summer months leading up to
September.
http://nsidc.org/...ice.html
beelize54
2.3 / 5 (3) Dec 19, 2010
IMO Earth is passing through dense cloud of antineutrinos (dark matter), which are accelerating decay of radioactive elements in Earth mantle and ocean water, thus heating the oceans "from the bottom up". The existence of undewater channel supports this hypothesis well.

http://physicswor...ws/42356

http://www.skepti...tent.gif

Do you remember the 2012 movie?
Skeptic_Heretic
not rated yet Dec 20, 2010
Do you remember the 2012 movie?
I remember it being a movie, ie: fictional story acted out and developed for entertainment.
GSwift7
2.3 / 5 (3) Dec 20, 2010
@ Frenchie:

That's 180 degrees off topic, literally. The article is about antarctic ice loss. In regard to sea level arctic ice isn't much of a factor. The west antarctic ice sheets are shrinking, but some measurements suggest that the total mass of antarctic ice could be increasing. The data is too fuzzy to say for sure though. It's really hard to measure the east antarctic ice mass, but they are working on it. It may also be the case that glaciers in the southern Andes are growing, for the same reason that east antarctic ice may be growing. I don't think very many researchers have a lot of faith in those estimates though.

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