Preliminary DMS image of the new rift in Greenland’s Petermann
Glacier, directly beneath the NASA Operation IceBridge aircraft. (Gary
Hoffmann/NASA).
This
story has been updated.
The
first photographs of a new and ominous crack in Greenland’s enormous Petermann
Glacier were captured by a NASA airborne mission Friday.
NASA’s
Operation IceBridge, which has been flying over northwest Greenland for the
past several days, took the photos after being provided coordinates by Stef
Lhermitte, a professor at Delft University of Technology in the Netherlands,
who had spotted the oddly located chasm by examining satellite images.
[In
Greenland, a once doubtful scientist witnesses climate change’s troubling toll]
The
NASA pictures make clear that a significant new rift has opened near the center
of the glacier’s floating ice shelf — an unusual location that raises questions
about how it formed. Moreover, this crack is not so distant from another much
wider and longer crack that has been slowly extending toward the shelf’s center
from its eastern side wall. The two cracks are clearly visible in this image
taken from the aircraft:
Aerial
photos of Petermann Glacier reveal new, dangerous cracks in the ice. The Post's
Chris Mooney explains what that means for the glacier's future. (The
Washington Post)
Still,
there’s good precedent for worrying about what could happen at Petermann. When
two prior ice islands broke off the glacier in 2010 and 2012 — the 2010 island
in particular was extremely large — the events drew major media attention and
were even discussed in a hearing before Congress.
“Last
week, an ice sheet covering 100 square miles broke off Greenland,” then-Rep.
Edward J. Markey (D-Mass.), the chairman of the Select Committee on Energy
Independence and Global Warming, said at
the opening of the hearing in summer 2010. “This giant ice island is more than
four times the size of Manhattan. It is the largest piece of Arctic ice to
break free in nearly half a century.”
Those
past breaks also caused the glacier’s floating ice shelf to become much smaller
than it had been before. Here’s a figure, courtesy of Jason Box of the
Geological Survey of Denmark and Greenland, capturing the glacier’s shrinkage:
Petermann
Glacier has grown back somewhat since those breaks because of its steady
flow outward (at a rate that appears to be accelerating somewhat). But if the
next piece breaks off, the red line in the graph above would plunge once again.
Box estimated the resulting ice island would be some 50 to 70 square miles in
size, or more than twice the size of Manhattan.
NASA’s Operation IceBridge is
a research mission in which instrumented aircraft are flown over ice at both
poles — both Greenland and Antarctica — to collect data about the state of
polar ice and how it is changing. IceBridge operates over Greenland at this
time of year and snapped the photos on what appeared to be a crystal-clear day
at the glacier.
It has
also taken recent photos of other nearby glaciers, such as Heilprin and
Upernavik, and the state of floating sea ice in the channel between
northwestern Greenland and northeastern Canada, in addition to its extensive
data-gathering work.
After
seeing the new NASA images, Lhermitte responded that it was “amazing to see the
rift from nearby after studying it from space for several days.” But, he added,
“From these images alone, it is difficult to already say anything about what
exactly caused the crack on this unusual spot.”
The
crack appeared in the middle of the floating shelf, rather than on one of its
sides, as is typical of this glacier — leading Lhermitte to wonder whether it
could have been caused by the ocean waters below the shelf.
You can
bet that scientists will be conducting a great deal more research on this
crack, what caused it and whether it might precipitate bigger changes to
Petermann Glacier.
No comments:
Post a Comment