MSN - AFP, 20 January 2022
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| The A-68 iceberg was one of the largest ever observed |
A giant iceberg that detached from Antarctica in 2017
released the equivalent of 61 million Olympic-sized swimming pools of fresh
water as it melted, according to research published Thursday, raising questions
over the impact on the marine ecosystem.
The monstrous iceberg was twice the size of Luxembourg
when it separated from the Larsen ice shelf, which has warmed faster than any
other part of Earth's southernmost continent.
At 5,719 square kilometres (2,200 square miles) it was
the biggest iceberg on Earth when it formed and the sixth-largest on record,
according to the British Antarctic Survey.
For two years, the trillion-tonne giant known as A-68,
drifted close to home in the cold waters of the Weddell Sea before travelling
northwards and menacing the British island of South Georgia, some 4,000
kilometres (2,500 miles) from its starting point.
The iceberg, by then known as A-68a after a piece
snapped off, came dangerously close to the island in late 2020, raising fears
that it would become stuck on the seabed, block ocean currents and obstruct the
passage of thousands of penguins and seals.
But the new study found that while it did briefly
graze the seabed, the iceberg melted quickly once in the warmer region around
South Georgia and had already lost a significant amount of its bulk by the time
it reached shallower waters.
Researchers who tracked its journey via satellites
calculated that from late 2020 until it melted away in 2021, A-68 released an
estimated total of 152 billion tonnes of nutrient-rich fresh water into the
sea.
That is equivalent to 20 times the water in Scotland's
Loch Ness, or 61 million Olympic-sized swimming pools, said the BAS in a press
release, adding it was "a disturbance that could have a profound impact on
the island's marine habitat".
"This is a huge amount of melt water," said
Anne Braakmann-Folgmann, a researcher at the Centre for Polar Observation and
Modelling (CPOM), who led the research published in the journal Remote Sensing
of Environment.
"The next thing we want to learn is whether it
had a positive or negative impact on the ecosystem" around South Georgia,
she said.
'Classic' route
Researchers said the cold fresh meltwater and
nutrients released as icebergs melt can influence local ocean circulation and
spark biological production.
Braakmann-Folgmann said A-68 had taken a
"classic" route for icebergs in the region, adding that further
research would look to learn more about how these icebergs are affecting the
polar oceans.
Icebergs form when hunks of ice break off from ice
shelves or glaciers and begin to float in open water.
Their formation is part of a natural process, although
one which can be accelerated by warming air and ocean temperatures due to
human-caused climate change.
Earth's average surface temperature has gone up by one
degree Celsius since the 19th century, enough to increase the intensity of
droughts, heat waves and tropical cyclones.
But the air over Antarctica has warmed more than twice
that much.
Ice sheets atop Greenland and West Antarctic hold
enough frozen water to lift oceans a dozen metres (40 feet), drowning cities and
redrawing the planet's coastlines.
Icebergs are traditionally named after the Antarctic
quadrant in which they were originally detected, then a sequential number.
If they break apart more letters are added to
differentiate the fragments.
