Umthombo 2 - Page 4

New ocean current
A previously unidentified ocean current has been
discovered off south-west Madagascar by a UCT
doctoral candidate. Juliano Ramanantsoa used
observational-system and computer-modelling
data to identify the wind-driven, poleward-flowing
surface current. The Southwest Madagascar
Coastal Current (SMACC), as it is known, is
relatively narrow and shallow – some 300 metres
deep and 100 kilometres wide – and salty.
It flows more intensely in summer, and its
physical impact on the ocean is particularly
noticeable in a rich upwelling of nutrient-dense
waters at the southern end of Madagascar.
This has implications for the commercial and
subsistence fisheries in the region.
Antarctica more exposed to
change than we thought
Research published in Nature
Climate Change by an international,
multidisciplinary team of scientists,
including from UCT, revealed that
bull kelp washed up in Antarctica
had drifted 20 000 kilometres to
reach that shore – making it the
longest known biological rafting
event recorded.
DNA samples taken from the
kelp revealed that one specimen
had drifted all the way from the
Kerguelen Islands and another from
South Georgia. To get there, the
kelp had to pass through barriers
created by polar winds and currents
that were thought to be largely
Observations of kelps drifting
at sea collected by Professor Peter
Ryan of UCT’s Percy FitzPatrick
Institute of African Ornithology
confirmed that kelps regularly
cross the Antarctic Polar Front.
Ryan collected a comprehensive
dataset on drifting kelps during
the three-month Antarctic
Circumnavigation Expedition
in 2016/17.
The finding that kelps can drift
south across the Antarctic Polar
Front means that Antarctica is not
as isolated from the rest of the
world as scientists had thought.
Kelps can carry a suite of
associated intertidal organisms,
which might be able to transform
Antarctic coastal ecosystems as
they become more hospitable
with global warming.

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