UK scientists are about to set out
for Antarctica to investigate the mighty Pine Island Glacier. The PIG drains about 10% of all the ice sliding off the west of the
continent, and has seen a marked thinning and a surge in velocity in recent
decades. Its contribution to sea level rise is now greater than any other glacier on
the planet.
The British Antarctic Survey-led team hopes its iStar project will provide
new insights into the PIG's behavior. The researchers will gather their measurements using a diverse set of
techniques and technologies, including robotic subs and satellites, and even
instrument-carrying elephant seals.
"We want to improve our understanding of what this glacier is doing and to
use that information to be able to make good predictions for its contribution to
global sea level in the years ahead," said Dr Andy Smith, iStar's science
programme manager at BAS.
"And if we can do that, if we can make those good predictions, then we'll
also have some tools to apply to the rest of the Antarctic and the Greenland ice
sheet as well," he told BBC News.
Dr Smith officially announced the venture on Monday at the British Science
Association annual festival in Newcastle.
The PIG is vast. The glacier runs alongside the Hudson mountains into the
Amundsen Sea, draining an area covering more than 160,000 sq km - about
two-thirds the size of the UK. And it can produce colossal icebergs, such as the
720-sq-km "ice island" that broke off into the ocean in July.
But the PIG's remoteness has made it difficult to study, and it is only in
the past 20 years or so, with the aid of satellites, that scientists have
realized the glacier is undergoing significant change.
The block measures about 720 sq km in area - roughly eight times the size of Manhattan Island in New York
Space data indicates the rate at which it is losing mass is doubling about
every five years. This acceleration has been attributed in part to warmer ocean waters getting
under and melting the PIG's ice shelf - the long floating tongue that protrudes
out into Amundsen Bay. The grounding line - the point where this shelf starts to
become buoyant - has pulled back further and further towards the land.
The iStar project has two major expeditions this Antarctic summer to try to
probe more keenly how the warming of the ocean is affecting ancient glaciers, inland and shelves above the ocean.
The first mission, starting in November, is a 10-week, 1,000km traverse by
tractor across the top of the glacier. One of its tasks will be to map the
rockbed beneath Pine Island Glacier. Much of the traverse data is expected to
feed back into the validation of future space monitoring, says Dr Andy Shepherd
of Leeds University.
In January, iStar's oceanographers are expected to arrive in the Amundsen Sea
onboard the RRS James Clark Ross. They will be putting a fleet of ocean robots known as Seagliders into the
water. These vehicles measure temperature, salinity and current behaviour at
different depths. The gliders will operate in front of the ice shelf. The ship
will, however, release its big unmanned submarine, Autosub, to go under the
shelf. This 7m-long probe will map the cavity and the geometry of a ridge on the
seabed that appears to play a key role in limiting the ingress of warm water
from the ocean.
"We want to look in more detail at the processes that control the exchange of
waters over this ridge,
The ship will only have 30 days in Amundsen Bay to complete its work, but the
scientists plan to leave autonomous instruments behind to gather ocean and ice
information throughout the winter. It is in winter, also, when the elephant
seals will do their work. Researchers from St Andrews University have developed small sensors that can
be glued to the animals' coats. These gather data, such as water temperature and
saltiness, as the seals swim. The measurements are fed back to the UK via satellite whenever the seals
surface. Eventually, after several months, the mammals moult and the sensors
fall off.
The study will take about six years and will help us to understand the dynamics of global warming and the contribution of glacier melting to rising sea levels.
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