Researchers
have discovered a mega-canyon lurking below Greenland’s giant ice sheet — a
snaking canyon at least 450 miles long that’s been a crucial drainage corridor
since before ice covered the island more than 3.5 million years ago.
The
canyon is up to 2,600 feet (800 meters) deep, and its scale in width and length
rivals parts of the Grand Canyon in Arizona. It starts beneath the ice in
central Greenland and winds its way north to drain into the Arctic Ocean,
according to new research from scientists at the University of Bristol, as well
as researchers from Canada and Italy. The finding helps explain why Greenland
doesn’t have pools of water under its ice sheet like Antarctica does: The
canyon may be helping divert meltwater and thus keeping Greenland’s ice sheet
stable.
Radar’s Penetrating Gaze
Ice-penetrating
radar, which at specific frequencies travels through the ice and bounces off
bedrock below, has been used to collect data on Greenland’s features for the
past 40 years. In addition, previous research has showed through surface
topographical measurements that there was some sort of linear landscape feature
beneath the ice, but scientists weren’t sure of its extent.
This
latest research team combined datasets of the ice-penetrating radar data as
well as the topographical information to discover a major subglacial
canyon, which has been what the paper calls a hydraulic pathway for millions of
years. At the canyon’s mouth on the northern edge of the island, the deep fjord
is up to 6.2 miles (10 km) wide. The study appears today in Science.
Greenland’s Underground Funnel
The
water that melts on top of an ice sheet such as Antarctica’s or Greenland’s is
a key focus in current climate models. When meltwater seeps to the bottom of an
ice sheet, it can broadly do one of two things: pool up in a lake or flow out
to sea. And though the science is still developing, it appears that when
water pools up in lakes it lubricates the base of the ice sheet, and
thus makes the ice sheet shift more quickly out to sea. Chunks of ice into the
sea in turn raise global sea levels.
Greenland’s
newfound canyon may thus serve a protective effect for the island’s ice sheet,
though more research on the under-ice water dynamics is definitely needed. And
the discovery of this feature alone is fairly remarkable, as lead author
Jonathan Bamber of the University of Bristol points out:
“With
Google Streetview available for many cities around the world and digital maps
for everything from population density to happiness, one might assume that the
landscape of the Earth has been fully explored and mapped. Our research shows
there’s still a lot left to discover.”
The entire link can be
found at: http://blogs.discovermagazine.com/d-brief/?p=2912
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