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Science Show
Antarctic penguin colonies threatened by changing
climate
13 November 2010
Researchers predict serious consequences for large Antarctic penguin colonies as the climate changes. In
just a few decades, ice needed for nesting and feeding will be unavailable. Joellen Russell explains the
changes in train as winds and ocean currents move, as air temperatures swing, at times hotter, at other
times colder and as ocean chemistry changes from an equilibrium position which has allowed life to
flourish.
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Transcript
Joellen Russell: It's an enormous current that you can basically see from space that separates the very
warm waters of the subtropics from the polar waters around Antarctica. The current reaches from the
surface down to 5,000 metres all the way to the bottom. It's so strong that it actually scours the bottom
where it is constrained by topography. The current itself is driven by the westerly winds around
Antarctica which are 30% stronger than the westerlies in the northern hemisphere. So these enormous
winds drive this enormous current which basically communicates the deep water with the surface. The
winds push the water away from Antarctica, all the way around Antarctica.
Robyn Williams: Professor Joellen Russell who is a geoscientist at the University of Arizona, and she is
talking about forces four times more powerful than the Gulf Stream. It's affecting both rains and
temperature in southern Australia in ways not seen in recent times. She is with Alexandra de Blas.
Joellen Russell: They push the water away in the surface layer, and since you can't have a hole in the
ocean, the water has to up-well, and it up-wells from two to three kilometres down, the water comes up,
up, up to the surface. It's amazing. So basically the Southern Ocean is the window between the surface
and the deep ocean and the only place in the global ocean where waters up-well from that deep. It's
unique in all the world, a geologic feature of immense importance to climate.
Alexandra de Blas: Okay, so this is really important in terms of diffusing some of the global warming
that is occurring. The westerlies are changing, we're seeing the weather in southern Australia changed
dramatically. Tell me how it works.
Joellen Russell: We've seen in both the northern and southern hemispheres the westerlies retreating
towards the poles. So we have these winds that wrap around and around the mid-latitudes, and basically
those belts of winds have been moving like shrinking doughnuts towards the poles of both hemispheres.
And in the Southern Hemisphere it's been even more dramatic. In the north it's been about four degrees
of latitude, in the south it's been six degrees of latitude. And since the westerlies carry most of our water
in the winter onto land, when those westerlies move south they take those storms with them and
therefore it is both drier and warmer in Australia.
Alexandra de Blas: Why are the westerlies shrinking?
Joellen Russell: There's two reasons. The first one is global warming where we have increased our CO2
emissions dramatically and the CO2 is basically warming our troposphere, the lower atmosphere, the
atmosphere that we live and breathe in and where we see most of the expression of our winds. As this
warming has been occurring, 0.8 degrees Celsius globally, that warming tends to push the westerlies
basically towards the poles because we are warming from the tropics, pushing out. But also, and this is
maybe even more important, the ozone hole has not healed, and as it is not healing, the temperatures are
dropping in the stratosphere globally and particularly over the South Pole. So seven degrees cooler in the
upper atmosphere over Antarctica.
It is the upper atmosphere, but in the winter when the polar vortex basically forms and opens over
Antarctica, basically the stratosphere almost touches down on the top of Antarctica. So while the
summers are quite a bit warmer, the winters are colder right now and these really frigid outbreaks of
cold, cold air, essentially influenced by the fact that the stratosphere, which touches down in the winter,
is seven degrees colder over Antarctica. And that temperature gradient is basically pulling the westerlies
towards Antarctica because the westerlies are an expression of the maximum temperature gradient in the
atmosphere.
Alexandra de Blas: Why is the stratosphere getting so much colder?
Joellen Russell: There's two reasons. One is that when the CO2 traps more of the Earth's re-radiation
near the surface, the stratosphere cools. However, it is also because with the loss of ozone...ozone, when
it catches UV radiation, breaks apart, releasing heat. With no ozone to catch the UV, we get more skin
cancer, but you also have a cooling stratosphere because no release of heat from the ozone catching the
UV.
Alexandra de Blas: Now that we've got this gradient, what influence is that going to have then on this
important circumpolar current that is so strong?
Joellen Russell: What it does is it basically drives the surface ocean much more strongly. So we expect
to see the current increase. As we blow more water away from Antarctica, it's going to up-well more
strongly, and we believe we already see this. We see melting right where we expect to see it on the
Antarctic peninsular, growth of sea ice where it's coldest in the Ross Sea, these are exactly what one
would expect from anthropogenic climate interference from both ozone perspectives and greenhouse gas
warming. So we have multiple lines of evidence that this is exactly what is going on.
Alexandra de Blas: With these changes occurring, how is that affecting the ecosystems there?
Joellen Russell: This is really worrisome because on the one hand while the bonus would be that the
global climate doesn't warm as quickly because the ocean can take up more heat and carbon dioxide, the
downside is that heat is going into the ocean and it's melting sea ice and Antarctic ice. So the problem is
that ice obligate species like penguins, species that require ice to live for their life cycle are finding it
much more difficult. And I have a paper with David Ainley where we've used the climate models to
predict how soon many of the established large penguin colonies will be in trouble, and our prediction is
that by 2037 we anticipate basically three-quarters of the large penguin colonies will be wiped out.
Alexandra de Blas: In Antarctica?
Joellen Russell: Yes, that's right.
Alexandra de Blas: And why will they be wiped out?
Joellen Russell: Because their ice will melt. We're talking specifically here about Emperor and Adelie
penguins, but they have particular ice needs during their life cycle basically to either nest on or feed
from, and if that ice isn't there then their colonies won't be able to support themselves. There is also the
work with Cynthia Tynan who is an expert in whales, and she and I have been working on a paper
showing that where the up-welling occurs in the ocean is also moving towards Antarctica, and also
potentially being more focused in smaller areas which are less accessible. Essentially the whales are
going to be swimming further for less food. So these are real downsides to the fact that the heat is going
in the ocean. We haven't even touched on the downsides of more CO2 going in the ocean.
Alexandra de Blas: Ocean acidification is the impact.
Joellen Russell: That's it, ocean acidification is the other hard part, and there is a double whammy about
this too. So, ocean acidification, as we add more CO2 to the atmosphere, more of it will dissolve in the
ocean. As it dissolves in the Southern Ocean in particular we are seeing where the water is really cold
and we are quite close to the saturation state for aragonite, which is a form of calcium carbonate, and
calcite as well, as we reach closer and closer to the saturation level where at that point you can no longer
precipitate your shell if you are a little sea snail like a tetrapod, they are already seeing dissolution
events down there. But that's only half due to the fact that we're putting in atmospheric CO2 there's also
the fact that that increase in up-welling water which we are talking about because of the winds is also
contributing to acidification because it is up-welling water that is very acidic. We see an accelerating
change in the pH of the Southern Ocean, which means the base of our food web there, the coccoliths, are
under threat.
We are now pretty certain that there is no way that the winds will go back to their original position, that
this is a longer term shift and that the ozone is not recovering like we expected it to. We are accelerating
our emissions, so these things look relatively permanent. However, if we emit so many greenhouse
gases, so much fossil fuel burning, and right now we are well above our high-end scenarios of 'burn it
all', then eventually we could warm the surface so strongly that even the stronger winds would not be
able to break through and continue to mix the Southern Ocean, at which point that's the end of our deep
ocean sink for carbon dioxide. This is very serious but probably, unless massive mitigation goes on,
inevitable.
Robyn Williams: Well, let's hope not, we like penguins. As for rains, what happens when La Nina
stops? Joellen Russell is a professor of geoscience at the University of Arizona.
Comments (31)
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Add your comment
David Lewis :
15 Dec 2010 11:26:22am
I think Russel's work should be discussed on the Science Show in more depth, as it has profound
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Guests
Joellen Russell
Assistant Professor of Geosciences
Department of Geosciences
University of Arizona
Tucson Arizona USA
http://www.geo.arizona.edu/~jrussell/
Alexandra de Blas
de Blas Communications
http://www.deblas.com.au
Further Information
Antarctic penguin response to habitat change
Presenter
Robyn Williams
Producer
David Fisher
Radio National often provides links to external websites to complement program information. While
producers have taken care with all selections, we can neither endorse nor take final responsibility for the
content of those sites.
Saturday 12 noon
repeated Monday 7pm
Presented by
Robyn Williams
In This Program
12:05: Peak oil - the slow slide down
12:16: Response to Terence Kealey on acne and primates
12:21: Funding research and higher education
12:37: Nanoparticles for diagnostics and light
12:48: Antarctic penguin colonies threatened by changing climate
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