Thick cloud cover briefly fell away to reveal this first image of icebergs breaking away from the Sulzberger Ice Shelf due to sea swell from the Tohoku Tsunami, which had originated 8,000 miles away about 18 hours earlier. The icebergs can be seen behind a thin layer of clouds just off the ice shelf near the center of the image. Source: MODIS Rapid Response/NASA |
A
NASA scientist and her colleagues were able to observe for the first
time the power of an earthquake and tsunami to break off large icebergs a
hemisphere away.
Kelly
Brunt, a cryosphere specialist at Goddard Space Flight Center,
Greenbelt, Md., and colleagues were able to link the calving of icebergs
from the Sulzberger Ice Shelf in Antarctica following the Tohoku
Tsunami, which originated with an earthquake off the coast of Japan in
March 2011. The finding, detailed in a paper published online today in
the Journal of Glaciology, marks the first direct observation of such a
connection between tsunamis and icebergs.
The
birth of an iceberg can come about in any number of ways. Often,
scientists will see the towering, frozen monoliths break into the polar
seas and work backwards to figure out the cause.
So
when the Tohoku Tsunami was triggered in the Pacific Ocean on March 11
this spring, Brunt and colleagues immediately looked south. All the way
south. Using multiple satellite images, Brunt, Emile Okal at
Northwestern University and Douglas MacAyeal at University of Chicago
were able to observe new icebergs floating off to sea shortly after the
sea swell of the tsunami reached Antarctica.
To
put the dynamics of this event in perspective: An earthquake off the
coast of Japan caused massive waves to explode out from its epicenter.
Swells of water swarmed toward an ice shelf in Antarctica, 8,000 miles
(13,600 km) away, and about 18 hours after the earthquake occurred,
those waves broke off several chunks of ice that together equaled about
two times the surface area of Manhattan. According to historical
records, this particular piece of ice hadn’t budged in at least 46 years
before the tsunami came along.
And
as all that was happening, scientists were able to watch the Antarctic
ice shelves in as close to real-time as satellite imagery allows, and
catch a glimpse of a new iceberg floating off into the Ross Sea.
