Podcast: Ocean circulation - Keeping Britain warm

Men with umbrellas

12 November 2013 by Richard Hollingham

This week in the Planet Earth podcast, Stuart Cunningham and Estelle Dumont of the Scottish Association for Marine Science (SAMS) describe their part in a major international scientific project to monitor crucial ocean currents in the North Atlantic which shape Britain's climate.

To assist those who find text-based content more accessible than audio, a transcript of this recording is available below.

Richard Hollingham: This time in the Planet Earth podcast, the ocean currents that shape Britain's climate. I'm Richard Hollingham and where better to talk about Britain's climate than the west coast of Scotland where there's certainly a lot of climate or rather a lot of weather, perhaps. I'm standing on a pebbly beach looking North West towards the dark hills of Mull, across the sound of Lorn and as we're recording here we think we've even been joined by the rounded silky head of a sea otter, and I'm joined here by Stuart Cunningham from the Scottish Association for Marine Science, SAMS, based near Oban who is one of the leaders of a major international scientific campaign to monitor ocean currents in the north Atlantic. I suppose this isn't technically the north Atlantic but we are connected to it and the currents here, these are vitally important for the UK and for Western Europe.

Stuart Cunningham: That's right, Richard. Oceanography is really an integral part of the climate system. So, we say 'what is climate?' well really it's about the sun's energy being moved from equatorial regions to high latitudes and that's the oceans and the atmosphere together which are responsible for that process, and so the ocean currents carry vast amounts of heat northwards, it's given up to the atmosphere and it is particularly critical for the western European and UK climate because that heat comes up into the atmosphere and then is confected over the Atlantic towards Europe and the UK and Scotland in particular, and of course it keeps us much warmer than places with equivalent latitude so we might say we're five to ten degrees warmer on average than other countries at this sort of latitude, Siberia, for example, which is quite a surprising thing.

Richard Hollingham: And the one you're particularly interested in is this vast belt of... what, warm water, but relatively warm water that is coming across the Atlantic and sweeping up and across to this area.

Stuart Cunningham: That's right, really starting in the south Atlantic. It's a remarkable thing that the warm water comes all the way north and ends up really in the Gulf of Mexico and that is where the driver for the Gulf stream, which everyone knows about, is a very fast, very warm current flows rapidly northwards out across the Atlantic and is becoming known as the north Atlantic current eventually, and that forms really the warm water path that flows up through the high latitude subpolar regions and really is affecting our climate.

Richard Hollingham: The reason you are investigating this, and we will come onto what you are doing in a second, but the suspicion is it's changing.

Stuart Cunningham: That's right. Well, we know that the Atlantic Meridian Overturning Circulation, which is the phrase we use to describe warm water coming north and then cold water going south has had an important influence in climate over the paleo records, so there's good evidence from paleo times of how this has changed between glacial and interglacial periods and of course one of the main predictions for climate change forcing and the latest IPCC reports is that this circulation is so important for our climate will slow perhaps by 25% to 50% over the coming century.

Richard Hollingham: Now the project that you're involved in leading is called, not really snappily, but the Overturning in the Subpolar North Atlantic Programme. It's an ambitious international project, a partnership between the Natural Environment Research Council, Canada, The Netherlands, Germany and the United States National Science Foundation. What are you trying to do?

Stuart Cunningham: Well really we're trying to measure the whole circulation from Newfoundland to Greenland to Scotland. An integrated system of observations with many countries participating so that we can have what we say is a 'closed system' so that we observe all parts of the ocean circulation, so that if we observe changes in one part we know whether they've compensated in another part. We have in essence a system whereby we can explain all the changes that are going on.

Richard Hollingham: And you happen to use quite a lot of technology to do this, to take all these measurements of this vast area.

Stuart Cunningham: We're using various sorts of technology, a really intensive application of older technologies, moorings where we anchor long wires to the seabed with traditional recording instruments that we go and collect every year and get the data back, but of course with application of new and exciting technologies like autonomous underwater vehicles, gliders, and so these will form part of the programme and they go off and autonomously monitor ocean currents and the upper kilometre and the deep ocean.

Richard Hollingham: Well I think you've got some of the gliders. Let's go and have a look.

We're on the campus itself, Stuart, and we're heading into one of the labs.

Stuart Cunningham: Yes. This is one of the labs for the north Atlantic glider base, so this is a facility really for European research labs to come and deploy gliders in the north Atlantic.

Richard Hollingham: Through the door and a small laboratory with these... I struggle to describe these. Imagine metre long pear drops. One is bright yellow and one is bright pink and also in here is a [unintelligible], and these are gliders, Estelle.

Estelle Dumont: Yes, exactly. They are autonomous underwater vehicles that we're going to deploy as part of the OSNAP project.

Richard Hollingham: So they're like submarines but they're not controlled in any way. They just, sort of, head off underwater?

Estelle Dumont: We give them some guidance. Once they come up to the surface we the pilots back at the lab and the scientists we direct them with sometimes some comments on where to go, how fast to go, how deep to go, but then once they start diving in the water so basically on their own and so they're doing their own thing, and every time they come back to the surface they will check whether we've left some new instructions and they will also transmit the data they have been collecting.

Richard Hollingham: What are they actually measuring?

Estelle Dumont: Well they are fitted with pretty much the same instrumentation that we're going to find on mooring, only smaller sensors and less of them. So we've got CTD's which is going to measure the connectivity, temperature and the depths at which the glider is and we also have an oxygen sensor and an optic instrument measuring the fluorescence in the water.

Richard Hollingham: This is a technology that the UK really specialises in?

Estelle Dumont: We're getting more and more gliders in the UK. There are quite a few institutes at the moment who are working with gliders and worldwide there seems to be a big enthusiasm for gliders because they are a relatively new technology, they are quite cheap to run compared to big cruisers, they are efficient, they are clean and they have a really long endurance. We can make measurements for six month continuously with them up to 1,000 metres.

Richard Hollingham: Now, Stuart, these are part of what you're doing. You are also using what other submersibles, more traditional things like buoys and things.

Stuart Cunningham: That's right. I guess the largest application of really of well established technology of course in these programmes. You can't have everything at high risk, new and exciting measurements. So our traditional measurements are things that we call moorings, so that's a long wire which is anchored to the seabed and it is held up by buoys and you can attach instruments like conductivity, temperature depth probes, current metres for directly measuring the velocity and in fact that's the largest part of the programme with all our international partners. There's an array of moorings at strategic locations all the way from Newfoundland to Greenland and then across, obviously, to Scotland.

Richard Hollingham: This is a vast experiment isn't it?

Stuart Cunningham: It's a very big experiment and really it's a symptomatic of the big experiment we're doing with Planet Earth. I mean we're changing the climate and so now we are having to ask questions about how the ocean and the atmosphere are responding on these very large time and space scales. So we do these large deployments and people often describe them as monitoring experiments but I rather don't like that because it sounds very passive. The best thing to think about it is as an intergenerational problem type of experiment. We're starting to ask questions about the dynamics of the ocean circulation on these space and timescales and we're learning new and exciting things about how the ocean works on these climate relevant timescales, and that's really what this big programme is about and why we need so many international partners.

Richard Hollingham: Stuart and Estelle, thank you both. I'll take some pictures of the very pretty gliders here which we will put on our Facebook page and also follow us on Twitter, and for the latest news on the natural world, do visit Planet Earth online. That's the Planet Earth podcast from the Natural Environment Research Council. I'm Richard Hollingham, from Oban in western Scotland, thanks for listening.