Antarctic cyclones reshuffle sea ice

Antarctic cyclones
reshuffle sea ice
University of Cape Town (UCT) researchers have measured – for the
first time – the impact of an unusual and intense storm on the sea ice
around Antarctica, home to some of the most severe storms on Earth.
D
PHOTOGRPAH: JEREMY KRAVITZ
uring 2017, UCT researchers
on a cruise to Antarctica saw
first-hand the effects of an
explosive polar cyclone as
it passed over the marginal ice zone:
the section of sea ice close to the open
ocean where atmospheric, oceanic
and ice processes are interlinked. The
cyclone they observed was explosive
because of the sudden, intense
deepening of low pressure at its centre.
What Associate Professor Marcello
Vichi and his colleagues saw provided
the first direct evidence of a winter polar
cyclone rearranging the marginal ice
zone. The storm altered ice distribution
– by increasing waves and drift of floes,
for example – and the effects extended
as far as the Antarctic continent.
After analysing more storms in the
region, the team was able to confirm
how storms in the Southern Ocean
maintain sea ice that is less compact and
more mobile than previously thought.
More to come
As part of future expeditions – one of
which departed during July 2019 –
UCT researchers intend to continue
their research into this phenomenon
as well as the other aspects of Antarctic
sea ice.
The researchers on board the
cruise – 25 from UCT and 70 from the
rest of South Africa and the world –
are studying winter conditions in the
Southern Ocean. Winter cruises such
as this are essential for improving our
understanding of Antarctic sea ice
because, up to now, scientists have
not been able to take many direct
measurements of it during winter.
“Lots of exciting new science is
expected from this project. It will provide
the first coverage of an entire seasonal
cycle of sea ice in the Atlantic sector of
the Southern Ocean,” says Vichi, who
also is the cruise’s chief scientist.
The cruise – which is part of a
project sponsored by the South
African National Antarctic Project
(Southern oCean seAsonaL Experiment,
SCALE) – is a collaboration between
several South African institutions and
international partners in Australia,
France, Germany, Sweden and the
United Kingdom.
Winter in the Atlantic Southern Ocean
aboard the SA Agulhas II. In the distance,
you can see the waves from a polar
cyclone approaching the ship.
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