Stormy and icy seas - Antarctica: Global Science from a Frozen Continent - page 137

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Stormy and icy seas

EBERHARD FAHRBACH

As we laboured south the storm continued with increasing violence,
for now we were entering the ' Roaring Forties ' . Our vessel staggered
to the crest of mountainous seas and plunged heavily down long
troughs.

Frank Hurley, 1925

The geographical setting

The cold and stormy Southern Ocean surrounds the Antarctic continent and
connects the southernmost parts of three major ocean basins

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the Atlantic, the

Indian and the Paci c Ocean. This stretch of water, although far from most centres

of population, has a crucial effect on the global climate system through its role in the
circulation of the world

s oceans, the uptake of carbon dioxide from the atmosphere
and, through its formation of annual sea ice, an in

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uence on climate elements of

importance to marine productivity.
Formally, its northern limit is now taken as 60 S, corresponding roughly to
the southern boundary of the Antarctic Circumpolar Current and to the northern
limit of sea ice in winter. Covering an area of 20.3million km 2 , its mean depth is
4500m (with its greatest depth being 7235m). However, to appreciate its role in the
climate system, the complete Antarctic Circumpolar Current has to be included
reaching as far north as 40 S. Then, the Southern Ocean covers 70million km 2
which corresponds to 20% of the world s oceans. Where the Drake Passage

separates Cape Horn on the South American side from the South Shetland
Islands on the Antarctic side it is only 800 km wide, whereas the distance from South
Africa (Cape Agulhas) to the Antarctic continent (Dronning Maud Land coast) is
3900 km. To the south the Southern Ocean is limited by the Antarctic coastline of
17 968 km which is largely covered by ice shelves.

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