 |
| A drill rig was used to extract old snow. |
Big
surprises still hide beneath the frozen surface of snowy Greenland. Despite
decades of poking and prodding by scientists, only now has the massive ice
island revealed a hidden aquifer.]
In southeast Greenland, more
than 100 billion tons of liquid water soaks a slushy snow layer buried anywhere
from 15 to 160 feet (5 to 50 meters) below the surface. This snow aquifer
covers more than 27,000 square miles (70,000 square kilometers) — an area bigger
than West Virginia — researchers report today (Dec. 22) in the journal Nature
Geoscience.
"We
thought we had an understanding of how things work in Greenland, but here is
this entire storage system of water we didn't realize was there," said
Richard Forster, lead study author and a glaciologist at the University of
Utah.
The
discovery will help scientists better understand the fate of Greenland's annual
surface melt, which contributes to sea
level rise. When the summer sun warms the Arctic island, a giant water
world of stunning blue lakes and streams appears atop the ice. Tracking this
surface runoff helps scientists account for ice lost to melting each year.
Until now, researchers thought most of this water went to the ocean or refroze
on the ice. Now they've found a new hiding place.
"This
throws an additional complexity into the system," Forster told
LiveScience.
There is
enough water in the snow aquifer to raise global sea level by 0.015 inches (0.4
millimeters), according to a separate study by the same team published Nov. 30
in the journal Geophysical Research Letters (GRL). Every year, Greenland adds
0.03 inches (0.7 mm) of water to global sea level rise from melting snow and
ice, Forster said. [Top
10 Surprising Results of Global Warming]
Where water
flows
No one yet
knows how old the water in the aquifer is, and whether it stays trapped in the
snow or reaches the ocean in slow streams or catastrophic floods. However, the
top of the water table rose after Greenland's
huge surface melt in 2012, the researchers report in their GRL study.
The group
will return to southeast Greenland in the coming years to answer these and
other questions, Forster said. "Just seeing how old it is would answer a
lot of questions," he said.
The final
destination of Greenland's melt water is also key to understanding how the ice
sheet ebbs and flows, because water under the ice sheet lubricates
flowing glaciers. Researchers know some melt water goes to the bottom of
the ice, trickling through cracks and racing through vertical pipes called
moulins. Some of the water also simply refreezes on the surface when winter
comes. Liquid water sitting in buried snow layers can also slowly warm and melt
the ice sheet.
"The
existence of this rather flavorless natural snow cone has many implications for
the future of the ice sheet, some that may make the ice go away faster and
others that help keep the ice a little longer," said Richard Alley, a glaciologist
at Pennsylvania State University, who was not involved in the study. "We
would like to understand these implications better so we can help reduce the
uncertainties about future changes."
Soppy
surprise
Forster and
his colleagues discovered the aquifer in 2011, when a drill punched into
sopping wet snow, as mushy as a summer snow cone treat or a Slurpee. (This was
a year before the big surface melt of 2012.) "Water was pouring out of the
core," Forster said — not what one wants to find when all the electronics
are mounted outside the drill. A video of the event reveals both excitement and
a few choice words among the scientists. [Watch:
Discover Greenland's Hidden Aquifer]
The water
was stored in hard, compacted snow called firn — the remains of the previous
year's snowfall. Forster thinks the aquifer went undiscovered because so much
snow falls in this corner of Greenland.
In
Southeast Greenland, frequent storms crash into tall mountains, dumping more
winter snow there than anywhere else on the icy island. The thick, insulating
snow blanket keeps the watery firn liquid during the freezing winter, like a
down coverlet, Forster said.
Many drillers
have skipped over this part of Greenland because the snow layers are so thick,
Forster said, and most people who are drilling cylinders of ice from the ice
sheet are looking to see the layers compacted over hundreds and thousands of
years. "People who extract ice cores don't want to go through high
accumulation layers," he said. But Forster's team was interested in the
past 10 years of snowfall, so the southeast was a good research spot, he said.
Ground-penetrating
radar, towed by snowmobile, helped the researchers locate more water nearby,
which the group confirmed by drilling in 2011 and 2013. When the researchers
returned home, they searched airborne radar data from NASA's Operation
IceBridge and discovered the true extent of the buried snow aquifer, all in areas
with heavy snowfall. Most of the water is in the southeast, but a few pockets
appeared in the south and southwest, Forster said. "It all corresponds to
these areas of high snow accumulation," he said.
Greenland's
future
Researchers
estimate Greenland has lost more than 200 million tons of ice and snow each
year since 2003. The ice sheet will completely disappear when the planet's
average temperature rises by 2 to 7.2 degrees Fahrenheit (1 to 4 degrees
Celsius) above preindustrial temperatures, as predicted by the latest report
from the Intergovernmental Panel on Climate Change, released in September.
This news were re-posted in my web , from : Yahoo News.
0 comments:
Post a Comment