Perilous Times
Giant Breakaway Antarctic iceberg could change weather patterns
* From correspondents in Paris
* From: AFP
* February 26, 2010 9:59AM
AN iceberg the size of Luxembourg knocked loose from the Antarctic
continent earlier this month could disrupt the ocean currents driving
weather patterns around the globe, researchers said.
While the impact would not be felt for decades or longer, a slowdown in
the production of colder, dense water could result in less temperate
winters in the north Atlantic, they said.
The 2550 sq km block broke off on February 12 or 13 from the Mertz
Glacier Tongue, a 160km spit of floating ice protruding into the
Southern Ocean from East Antarctica due south of Melbourne, researchers
said.
Some 400m thick, the iceberg could fill Sydney Harbour more than 100
times over.
It could also disturb the area's exceptionally rich biodiversity,
including a major colony of emperor penguins near Dumont d'Urville,
site of a French scientific station, according to the scientists.
"The ice tongue was almost broken already. It was hanging like a loose
tooth,'' French glaciologist Benoit Legresy said.
Mr Legresy has been monitoring the Metz Glacier via satellite images
and on the ground for a decade in cooperation with Australian
scientists.
The billion-tonne mass was dislodged by another, older iceberg, known
as B9B, which split off in 1987.
Jammed against the Antarctic continent for more than 20 years, B9B
smashed into the Metz tongue like a slow-motion battering ram after it
began to drift.
Both natural cycles and manmade climate change contribute to the
collapse ice shelves and glaciers.
Tide and ocean currents constantly beat against exposed areas, while
longer summers and rising temperatures also take a toll.
"Obviously when there is warmer water, these ice tongues will become
more fragile,'' Mr Legresy said.
Since breaking off, the iceberg - along with the newly mobile B9B,
which is about the same size - have moved into an ajoining area called
a ploynya.
Distributed across the Southern Ocean, ploynyas are zones that produce
dense water, super cold and rich in salt, that sinks to the bottom of
the sea and drives the conveyor-belt like circulation around the globe.
If these icebergs move east and run aground, or drift north into warmer
climes, they will have no impact on these currents.
"But if they stay in this area - which is likely - they could block the
production of this dense water, essentially putting a lid on the
polynya,'' Mr Legresy explained.
The Metz Glacier Polynya is particularly strong and accounts for 20 per
cent of the "bottom water'' in the world, he added.
Eventually, the icebergs will die a natural death, but their lifespan
depends on where they go.
Adrift, they could melt in a could of decades. If they remain lodged
against the Antarctic landmass, they could persist far longer.