Automated Subs And Melting Ice Sheets
Chris - One of our next guests is from the British Antarctic Survey, and that's Povl Abrahamsen and he's going to take us under the ice. Hi Povl.
Povl - Hi.
Chris - Welcome to the Naked Scientist. So how are you exploring what's going on under the surface of Antarctica?
Povl - Well, Antarctic ice shelves can be hundreds of meters thick, floating glaciers. And underneath, they're some of the hardest areas to actually access. So a recent approach has been using robot submarines, AUVs, Autonomous Underwater Vehicles, to go down beneath the ice shelves and explore there.
Chris - And what's down there?
Povl - Well, it's seawater. It's extremely cold. And we're trying to trace what kind of water actually flows beneath there. Is it melting the ice shelves from below? And the only way to really get answers to that question is either to drill in from above or to get submarines, or instruments in from the ice shelf front.
Chris - So what are you actually seeing when you're down there, what have you discovered so far? What are the findings?
Povl - Well some of the most interesting findings were that we have an upward looking sonar that will actually give us a profile of what the base of the ice looks like. We've always assumed that this is completely smooth, that is the surface is completely smooth. But it turns out that actually there are extremely rough areas at the base of the ice shelves.
Chris - Why is that so critical?
Povl - Well it's critical because if we have a rougher area then you get more turbulence at the base of the ice shelf, more heat exchange recurring here.
Chris - Almost like fins on a heat sink. So that speeds up melting does it?
Povl - Yes. That would speed up melting.
Chris - Is it a symptom of melting though, does that mean that the problem is becoming more acute?
Povl - Well we don't exactly know what is causing these areas. We can see that they seem to correspond to some surface features called flow stripes on the surface of the ice shelves, but we're not exactly sure what their significance is, or how they were created, or how they're maintained.
Chris - How do you actually control a submarine down under water? Because one thing that you can't do is have a radio controlled boat, you can't do radio waves can you, so how do you tell your submarine where to go and what to look at, and how do you get it back?
Povl - Well you tell it where to go in advance, so all of that is programmed in, and it will try to then follow these instructions. If it does encounter any obstacles it will try to get around them on the way. And we can track where it is while it's out there. And then it's supposed to come back out to the ship. Or if there's any problem then the ship can tell it to use a homing beacon, to get it to return to the ship.
Chris - And how deep is it going down?
Povl - The deepest we sent it down beneath the ice shelf was about 800 meters, but the deepest it can go is 1500. There's a new version on the drawing board now that goes down to 6000 meters.
Helen - That's an awful long way isn't it. So how long do these things go off on their own for, do you wave goodbye to it for days at a time or is it just a few hours?
Povl - I think the longest mission it's ever been off on was about 30 hours.
Helen - And you're really crossing your fingers it's going to come back.
Povl - Yes.
Chris - Povl have you ever lost one of these, presumably they must cost quite a few million. Has one ever gone AWOL?
Povl - Ah, yes. Unfortunately that has happened.
Chris - Who's the insurance company?
Povl - it's actually not insured.
Chris - Now there's a confession
Povl - Yes, well I think it was determined at the start of the project, that the cost of insuring it would be about the same amount as building a new one. So it wasn't deemed worth it.
Chris - So how many have you lost then?
Povl - There has only been one that was lost.
Chris - So a once in a lifetime experience for the person who lost it, was it? They went shortly afterwards.
Povl - yes there was a fairly gloomy atmosphere on board afterwards.
Chris - Sure. That's Povl Abrahamsen from the British Antarctic Survey.