Antarctic Lake Shake Up
Chris - One place people are very interested in getting into is Lake Vostok. This is a sub-glacial lake. It's a lake of water that's sealed inside the ice of Antarctica, and it's actually one of many. People think that it contains water that's been there for a very long time and might have a unique ecosystem. Life might be living there that's evolved independently form other life on Earth, at least for a long period of time which might mean that there are some interesting things in there. But then somebody came along, someone called Martin Siegert from the University of Bristol, and he's really stirred up a heap of trouble, because he's found, from looking from space, that these lakes might be communicating with each other and that lots of water is moving round.
Martin - Deep beneath the four kilometres of Antarctic ice sheet, we've discovered that a sub-glacial lake has lost, rapidly, a large part of its volume. This water has moved over 200 kilometres in to another sub-glacial lake.
Chris - How did you actually do it though? How do you know that that water has moved around?
Martin - We looked at how the ice sheet surface changes. We had a satellite that looked at ice sheet surface elevation, and we noticed that one part of the Antarctic ice sheet lowered by three to four metres over the course of a year. Two hundred kilometres away, the ice sheet surface elevation went up by about a metre. That's a very unusual change, and there are very few alternative explanations for that amount of surface change. Actually, losing that amount of mass from the centre of East Antarctica, which is a very stable ice mass, it can only be the removal of something really rapid. All the alternatives point to it being water.
Chris - Do you know what's driving that movement of water though? What's pushing it along?
Martin - The base of the East Antarctic ice sheet, much of it is at the pressure melting point. So there's water being melted from the bottom of the ice sheet and al this water will feed down into sub-glacial lakes where it collects. The sub-glacial lakes will be pressurising because water will be coming into them, and the ice sheet will be attempting to hold that back. That's an unstable situation because the ice sheet can't hold it back forever. As the pressure increases to a threshold, the water will escape, so it sort of outbursts.
Chris - People are quite interested in those lakes for the simple reason that they're viewed as time capsules in the case of Vostok and similar bodies. Your work must have those people quite worried.
Martin - Well I don't know about that. It's only been ten years since a paper was published in Nature on Lake Vostok, and since then people have been talking about these lakes as being very isolated and very distinct systems. What we're identifying now is that maybe that's not the case and that it might have to be revised. But it's still very exciting from a sub-glacial point of view. I don't think that it would harm going into to sub - glacial lakes or even belittle the types of science that could go on in those systems.
Chris - The escape of so much water at once: does that have any other consequences in terms of, say, the salinity of the surrounding ocean, animal life, that kind of thing?
Martin - We haven't shown that this water can get to the ice sheet margin, but even if it did, it's quite a large amount of water. It's 1.8 cubic kilometres of water we've seen transferred. But actually that's a very small amount in terms of global ocean values so it wouldn't have much effect.
Chris - Do you think climate change is having any kind of implication or bearing on what's happening here?
Martin - Well I don't think so. The situation that we have is the underside of the Antarctic ice sheet. And remember, this is the East Antarctic ice sheet which is the stable part of Antarctica and there really isn't very much change going on there. What we think we've seen is a process which is common, both now and in the past. This is the first time that anyone's actually seen it.
Chris - And what questions are you now gagging to answer on the basis of the intriguing observation you've got here?
Martin - Well, what we'd like to do is to find more of these processes, both in East Antarctica and in West Antarctica, because we know that a sub-glacial lake has lost mass and that water has flown underneath the ice sheet and into another lake. What we now have to try and do is understand the physics of the problem a bit better and that applies to getting more data, more observations, in order to constrain the system better than we have done up until now.