What is the British Antarctic Survey doing in Antarctica?

What does the British Antarctic Survey's current mission at the South Pole involve? Mike Meredith is a leading oceanographer with the British Antarctic Survey. He’s spent decades studying these fragile waters, and the changes unfolding there. I spoke to him from the ship’s bridge…

Mike - So this expedition is quite a unique opportunity. We come down here quite regularly to make measurements of the ocean and the ice and to better understand our interactions with the atmosphere, structure, climate and influence the ice sheet and therefore sea level rise. But what we find is that we typically come down here in the Antarctic summer. The conditions are relatively benign, you've got long days, you've got very little sea ice. There are, however, some very key processes that happen in the Antarctic winter. So to try and understand those better we need to take advantage of opportunities to come down here in the winter. So that's why we're down here at this time of year and that's why we're making measurements here.

Chris - And what sorts of effects does the Southern Ocean have? Why is it important?

Mike - The Southern Ocean is this water mass that surrounds Antarctica and it's unique in a global context. It's the ocean that joins up the Atlantic and the Pacific and the Indian Ocean. And by doing that it provides this very strong connectivity across the whole globe. Now the ocean circulation as a whole moves vast quantities of heat around the globe, vast quantities of things like carbon which can be drawn down from the atmosphere, and by doing that it has this very strong global effect on climate. The ocean as a whole has absorbed more than 90 percent of the extra heat that has been produced because of global warming. And the Southern Ocean is the key site really where that heat is drawn down into the ocean. So it's doing us a favour in many ways, it's buffering us against the worst extremes of climate change. But this is a favour that comes at a cost because the ocean is warming at a very strong rate and it's also acidifying because of the extra carbon that's going into it and that can have really negative impacts on the marine ecosystem and the animals that live in the ocean.

Chris - When you said that it's important to sample this in the winter so you get that data as well as the summer data, what are you actually measuring though? So you're down there on the RRS David Attenborough. Is this a pot over the side and get some seawater? I mean talk us through what actually is being probed.

Mike - Well the ship itself is bristling with sensors. Ocean temperature, how saline the seawater is, how much oxygen is dissolved in the seawater, how much plankton life there is in the seawater. But also a load of atmospheric variables as well about air temperature and wind speed and so on. So wherever the ship goes it's generating huge amounts of data automatically. But we do need to measure deeper down in the ocean as well and for that we would stop the ship, we would deploy instruments over the side that would be lowered down to just above the seabed and as they go down through the water they will record a whole load of oceanographic variables. In addition to that there is the old tried and tested ways of lowering sampling bottles over the side of the ship and closing those bottles at depth and hauling the water back onto the ship to measure things like nutrient concentrations.

Chris - So I wasn't wrong when I said pot over the side. You are doing some old-fashioned chemistry with literally buckets of seawater coming back aboard to see what's in them.

Mike - Yes they're buckets but they're very clever buckets.

Chris - What's the trend you're seeing though? Because obviously we've got models that we think are telling us the direction of travel and then you can do what you're doing and you can test the reality. Is it playing out the way we expect or are things even worse than we expect?

Mike - We're seeing increasingly the ability of the ocean around Antarctica, the Earth system, the ice to show very rapid changes. A very leading example of that has probably occurred about a decade ago when the sea ice around Antarctica retreated very very suddenly in a way that realistically no one had actually predicted. We know that the sea ice in the Arctic has been retreating strongly for a few decades now and that's easily attributable to global warming and human influence. The sea ice around Antarctica was actually holding on relatively well and possibly even increasing slightly. But then about a decade ago it retreated very very suddenly and we're still trying to unpick exactly why that occurred. It seems to have been that the system changed to a new state. So what is it that pushed us from the old state into the new state? And this is something we see in various aspects of the Antarctic system.

Chris -
What are going to be the impacts of things like this? Because for instance glaciologists have been weighing in, inverted commas, Greenland for the best part of 20 years because we've got satellites that can measure the ice masses there and we know it's losing a couple of hundred billion tons a year, don't we? Does that look similar down in Antarctica then in terms of ice loss and what might be the consequences of that? If Antarctica is denuded of its ice what's going to be the impact?

Mike - There's vastly more ice on Antarctica than there is on Greenland. But Antarctica is often thought of as being two ice sheets, so a West Antarctic ice sheet and an East Antarctic ice sheet. The East Antarctic ice sheets, if it all melted, sea levels would go up globally by something approaching 50 meters. There's a huge amount of ice there. The good news is that that's not going to happen, at least in my lifetime, though there are some signs of changes happening around the fringes of the ice sheet there. The West Antarctic ice sheet is the subject of a lot of concern and a lot of activity. In areas it's retreating very rapidly, it's showing signs of instability and increasingly there are things telling us that it's poised in a way that's unstable. So once it starts changing you get these vicious cycles that kick in and it starts feeding on itself and the changes progress even more rapidly. And although the West Antarctic ice sheet is much smaller it still has the potential to raise sea levels globally by many tens of centimeters and over time, you know, several meters. So obviously this is a very significant impact as this plays out. We're still getting our heads scientifically around where we are on this transition but we do know that sea levels will rise over the course of this century and for centuries to come and Antarctica will be a contributor to that. And what we need to know is better information on the time scales on which that happens, how bad that will get and then what the actual impact will be on coastal states, low-lying islands, developing states and so on which are really on the front line of climate change.