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So the ocean affects climate by
storing and transporting huge amounts of heat
and carbon dioxide, and so if we want to understand
how the climate’s going to evolve in the future
we need to know what’s happening in the oceans.
About 90% of the extra heat energy
that’s been stored by the Earth’s system
over the last 50 years is in the ocean,
so when we talk about global warming we’re really
talking about ocean warming in a real sense.
So one of the main goals of our work in the Southern Ocean
is to measure exactly that, how is the ocean changing
and to learn how ocean changes might affect
things like climate, sea level rise and biological productivity.
The Southern Ocean’s a really important part
of the ocean to study because it’s really unique in a number of ways.
First of all, it’s only in the Southern Ocean
that there’s a band of ocean
that circles around the Antarctica that’s totally unbroken by land,
it’s a continuous channel of water,
and it turns out that the dynamics of the ocean currents
that circulate in that channel are very
different from the rest of the globe.
It’s the home to the world’s largest ocean current,
it carries about 150 million cubic metres of water every second
from west to east south of Australia,
between Australian and Antarctica,
and that connection between the ocean basins that’s formed
by that current transforms the whole global pattern
of ocean circulation and also affects global climate,
not just the climate of the Southern Ocean region.
That strong current, one of things it does is prevent heat
from spreading from the relatively warm northern latitudes
further south, and so it helps contribute to the icy glacial climate
that Antarctica experiences today.
It also has a big impact on Australian climate
because it affects the weather systems that
come across the continent from the south,
so our weather in Australia is largely determined by
what happens in the oceans around us,
either the Pacific, the Indian and the Southern Ocean
for the southern part of the continent.
Another thing that makes the Southern Ocean very different
from the rest of the ocean is that it’s one of the few places,
or the only place where water that’s at depth in the ocean,
three or four thousand metres below the surface in most of the ocean,
rises all the way to the sea surface in the Southern Ocean.
And so it’s the only place where the atmosphere connects to the deep ocean
and that has a lot to do with how much CO2 remains in the atmosphere.