Scientists test powerful ocean current off Antarctica
Oceanographers said they had measured a system of mighty currents off
Antarctica that are a newly-discovered factor in the equation of climate
change.
The system, known as Antarctic Bottom Water (AABW), is generated in
clockwise movement in four big sea shelves that abut Antarctica — the
Weddell Sea, Prydz Bay, Adelie Land and Ross Sea.
Extremely cold water sinks to the bottom of these shelves and slides
out northwards along the continental shelf.
At the edge of the shelf, some of the water mixes with a well-known
ocean movement, the Antarctic Circumpolar Current, which sweeps around
the abyss off Antarctica.
The rest of the AABW, though, makes its way northward through a maze
of ridges and gullies, reaching into the southern latitudes of the
Indian and Pacific Oceans and into the Atlantic as far north as southern
Brazil.
The study, led by Yasushi Fukamachi of Japan’s Hokkaido University,
is published online in the journal Nature Geoscience.
Fukamachi’s team used an array of eight seabed sensors, anchored at a
depth of 3,500 metres (11,375 feet) for two years over 175 kilometers
(109 miles) on the Kerguelen Plateau, east of Antarctica, where current
exits from the Prydz Bay shelf.
On average, about eight million cubic metres (280 million cubic feet)
of water colder than 0.2 degrees Celsius (33 degrees Fahrenheit) were
transported northwards over this narrow section, the researchers found.
That is four times more than the previous record documented in an
AABW flow, at the Weddell Sea, on the other side of Antarctica.
Over two years, the Kerguelen monitors recorded the current’s average
speed at more than 20 centimetres (eight inches) per second, the highest
ever seen for a flow at this depth.
The findings are important because ocean currents are major players
in climate change.
AFP |