Dr Jane Francis, University of Leeds
Part of the show Science in Antarctica
Chris - Now, lots of people when you say "Antarctica" think very very cold. But it wasn't always that way, was it?
Jane - No, I mean like you say most people when they think of Antarctica they think of ice caps and glaciers and very cold temperatures but for most of Antarctica's history and I'm talking about millions of years now in geological time it was actually green and it was covered with lush, dense forests.
Chris - How warm was it?
Jane - Well the interesting thing is that even though more than 99% of Antarctica's covered in ice, the most common fossil that you can find in Antarctica is probably fossil wood. And what we can do is use fossil plants that we find in the rocks, so fossil wood, leaves, even the flowers. We can use those to reconstruct the vegetation and from there we can work out what the temperature was. So if we go back say 50 million years ago, to what we call sub-tropical to warm temperate which means very nice indeed thank you, warm summers and warm winters.
Chris - Not that grossly dissimilar to here then?
Jane - Well, even warmer than here actually, much more pleasant. And no signs of ice at all. A very different world.
Chris - And the point is that was 50 million years ago. It's very different today. So what's changed to make such a profound shift in the way that things happen in Antarctica now?
Jane - Well the most interesting thing is that Antarctica actually has been over the South Pole for at least 100 million years so when I say that there were forests in Antarctica people usually say to me "oh well does that mean the Antarctic continent was on the equator?" And that's not the case at all. Geologists have looked at the rocks and they've found signals in the rocks to show us Antarctica was over the South Pole. So that means the earth's climate was much warmer in those days. Probably that's partly because there was higher levels of carbon dioxide. So that's one reason why we look into the past and do these paleoclimate studies, it really is a mirror image of what we might be seeing in future with higher carbon dioxide levels. But also Antarctica was part of a much bigger landmass in the past called Gondwana. And all the southern hemisphere continents were amassed together so there was this big landmass over the pole. So Antarctica wasn't sort of isolated in its icy tomb of water as it is now.
Chris - So presumably because there were all those land masses jammed together, the ocean circulations would have been quite different then, and that may have had an impact on the temperatures.
Jane - Yes. Well what we think happened is that the ocean currents that flowed around the equator were warmed up by the equatorial temperatures and because of the position of the coastlines around Gondwana, those warm water masses were pushed all the way down to Antarctica. So they could get rid of all this warm moist air over the continent and keep the continent warm. And then those water currents went back to the equator again and warmed up. Whereas today you see Antarctica is completely isolated, South America, South Africa and Australia moved away millions of years ago. And now we have the circum - Antarctic current and it flows around Antarctica and that keeps it really cold. That water, that current never gets the chance to warm up, and so Antarctica is just frozen inside.
Chris - Doesn't the same thing happen in the air above Antarctica in the sense that you end up with this big sort of whirlpool going round in the air which is why you end up with CFCs and things dumping there which is why we ended up with an ozone hole.
Jane - Yeah it's a very specific, small, climate of it's own above Antarctica. I always think of it as a big deep freeze. It has a big block of ice on it that's up to 3, 4 kilometres thick and it's just sitting there. It's so big it has it's own internal freezer in it.
Chris - Now the last vestige of the connection between those other big continents and the Antarctic continent was that the corner of Australia where Tasmania is and that kind of thing?
Jane - No actually that split away some 100 million years ago. The last connection actually was with South America. And that wasn't very long ago, geologically speaking; probably the deep water flowed between Patagonia and the Antarctic Peninsula, the bit that sticks up like a finger, about sort of 20 million years ago. Before that it was joined, so that's why, when we find a lot of fossils of animals and plants we also find quite close relatives of them in South America today. And no doubt in the past, millions of years ago they could have quite easily walked all the way from South America into Antarctica. And if you go further back in time when Gondwana existed you could have had a nice holiday walking all the way from the equator all the way through Antarctica and out to Australia and you wouldn't have had to get your feet wet.
Chris - So how deep would you now have to go through the ice to find the kinds of fossilised specimens that you've been looking at?
Chris - now when somewhere gets isolated like that for a considerable period, the wildlife that evolves tend to be pretty specialised doesn't it, so do those fossils give you and revelations as to some pretty funky animals that would have been living there at that time?
Jane - Well the history of Antarctica's really interesting because the fossil history is quite different from the animals and plants that live there now so for example the plants we have in the forests, we have a lot of tropical plants that are mixed with plants that grow today, in say Tasmania. So we get sort of Tropical vines, and some really big bushy plants. In terms of animals, we have dinosaurs of course. We've got dinosaur bones from Antarctica, and we also have some primitive mammals. Some colleagues of mine in Argentina have been finding primitive mammals like Sloths and little rat-like animals. And then of course, penguins. But the penguin fossils that we find, actually the interesting this is that we find penguin bones in the same bed of rock as we find our sub-tropical plant fossils. So penguins that first lived in Antarctica certainly didn't live on the ice, as you can imagine them today. They lived in the seas around the edges of these forests.
Chris - So they didn't evolve to live in icy conditions at all, they evolved to live in much warmer environments
Jane - They certainly did, yes.
Chris - So how the hell have they coped with that sudden and dramatic shift in how they go about their life? How would they have foraged, what would they have eaten? Or would they have had pretty much the same foraging lifestyle, they simply would have done it in the warmer water?
Jane - Well I'm not sure how they lived, I mean what we know from the penguin fossils that we find in Antarctica is that well there's one very famous penguin fossil of a type of penguin that had toe bones, when we construct the penguin that had these large toe bones, it was at least 6ft high, so can you just imagine that, a 6ft high penguin wandering around in the warm waters of tropical Antarctica?
Chris - And the fact that it was 6 feet high, is that a reflection on the fact that it was a lot warmer? Have penguins shrunk down to minimise their heat losses now, because it's so cold, is that what's forced them to be smaller?
Jane - I have no idea because I'm not a penguin expert but I don't think so. If you look at an emperor penguin today, I met some emperor penguins a few years ago, and I'm not a very tall person but they came up to above my waist and they've got big curved beaks, so they look pretty formidable.
Chris - As someone said to me the other day Jane, that's a lot of chocolate, isn't it, a 6 foot high penguin?
Jane - It sure is!
Chris - That's Jane Francis from the University of Leeds.