British Antarctic Survey scientists use seals and robotics to unlock deep climate secrets of Southern Ocean
Oceanographer Michael Meredith, from BAS in Cambridge, is helping to conduct the Orchestra programme.
Seals fitted with trackers, robotic gliders and research vessels equipped with laboratories – just some of the tools being deployed by the team behind the five-year Orchestra project.
Its aim is to help scientists better understand how the swirling seas around Antarctica act like a giant brake on climate change.
Drawing down heat and carbon, the vast Southern Ocean has limited the impact of global warming.
But the harsh conditions have made studying its processes – and crucially, what might happen to them - very challenging.
Now armed with their new arsenal of techniques and technology, scientists aim to gather huge amounts of data that will give us a proper picture of what might happen over the coming century.
Oceanographer Michael Meredith, of the British Antarctic Survey (BAS) in Cambridge, said: “We are trying to increase our understanding of global climate and our ability to predict it. One of the biggest weaknesses in our understanding is the oceans in general and the role of the oceans around Antarctica in particular.
“The Southern Ocean is a vast area that joins up the Atlantic, the Pacific and the Indian Ocean. For reasons to do with ocean circulation, this area has a really strong impact on global climate.
“The problem has been that it’s so far away and it’s such a hard place to work because of the rough seas, the ice and the icebergs so we get very little data from the Southern Ocean, especially in winter, when the conditions are at their harshest.
“There’s a real knowledge gap of how the Southern Ocean works and interacts with the climate. We’re trying to fill that gap and get better ideas of how we can improve climate protection.”
Orchestra (Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports) is focusing on the Southern Ocean because of its unique qualities.
There, water from a kilometre or two down that is part of the global ocean circulation ‘upwells’ to the surface, where it interacts with the atmosphere before sinking down into the interior again.
“It can take down carbon and heat with it – including the carbon humanity has part there by burning fossil fuels and so on - and it can store it away for hundreds of years,” said Mike.
“Essentially, the Southern Ocean is doing us a big climate favour. If that heat or carbon stays in the atmosphere, the rate of global warming in the atmosphere would be very much higher than it is.”
About 30 per cent of human-produced carbon dioxide emissions have been absorbed by the oceans since the industrial revolution.
And, astonishingly, it is believed that 93 per cent of the total extra heat in the Earth system since the onset of global warming has been absorbed by the ocean.
The BAS, based in Madingley Road, says the 170 terawatts absorbed is equivalent to the power that would be required for each of the seven billion people on Earth to operate 16 1,500-watt hairdryers continuously.
We also know that while the Southern Ocean occupies about one-fifth of the total ocean area, it absorbs about three-quarters of the heat taken into the ocean and about half of the CO2.
“What we don’t know is the really detailed processes of how that happens, the rate at which that happens and how that is going to change,” says Mike. “If the rate changes over the next few decades, it will have a huge impact on global climate change.”
Driving the upwelling of old waters to the surface in the unbounded Southern Ocean are very strong westerly winds that blow in a continuous loop, with Antarctica at the middle. They push the water northwards, away from the Antarctic, drawing up water from the depths.
Amid this hostile environment, scientists at BAS, in partnership with a range of national and international partners, including the National Oceanography Centre and British Geological Survey, are deploying an extraordinary range of tools.
Among the tried-and-tested techniques are using the BAS’s research vessel, the RRS James Clark Ross – and in a couple of years, the RRS David Attenborough will come online.
“We lower instruments from the ship and measure how much heat and carbon is in it. We collect water samples and make measurements right down to the seabed, bringing them back on board to analyse them in the ship’s laboratories.
“It’s labour-intensive but they are the benchmark measurements and allow us to characterise what the ocean is doing to the climate system at the moment.”
It is a method only suitable for the Antarctic summer - but there is need for year-round data.
“A lot of the key processes we think happen in winter so increasingly we’re looking to use robotics techniques,” said Mike.
“We are using passive floats that drift through the ocean and periodically sink down to about 2,000 metres depth and rise up to the surface, making measurements as they go, then transmit their data via satellite.”
These floats, which can operate for years, are pre-programmed before they are deployed to be carried wherever the ocean currents take them.
The team is also using autonomous glider vehicles, controlled from the UK.
“We can deploy them from ship or land stations in the Antarctic,” said Mike. “They fly through the ocean and make measurements between the surface and about 1,000 metres down.
“They surface every few hours to report their data back by satellite. When they surface, we can send new commands and tell them to go in a new direction or target different features. They are the next level up of intelligence.”
The team has also adopted a tactic from marine biologists tracking seals.
“The tags they developed measured temperature and how salty the water is, so it’s invaluable data for oceanographers as well,” said Mike. “The ones we’re deploying will be on Weddell seals and there’s a lot of work being done with elephant seals too.
“They live in the Southern Ocean year-round. They swim thousands of kilometres and can dive hundreds of metres so the data coverage you can get by piggy-backing on these seals really does enhance what we’re able to do.”
The researchers measure how warm the water is, the salt content and how much carbon is in it. They can even detect how much of the carbon is ‘human-produced’ by measuring the amount of CFCs which have been drawn down by the ocean.
“We also measure dissolved oxygen, how rapidly the ocean is mixing and the level of nutrients, which is important for plankton production but also gives us information on how the water is circulating,” said Mike.
Early data from Orchestra, which launched in April 2016, has yielded some significant results.
“So far, it’s preliminary but we are finding some interesting changes, especially in the very deepest layers of the Southern Ocean,” reveals Mike. “This is where very, very dense water forms next to Antarctica. It sinks right down to the seabed and then it spreads out up the Atlantic, the Pacific and the Indian Ocean. It floods the whole abyss of the global ocean.
“We’re finding out that this water is getting warmer in the long-term and we’re getting more information on why. But it’s still uncertain area of research and we haven’t published the results.
“We are trying to work out whether it’s part of a long natural cycle. It’s more likely though that it’s to do with human activities – greenhouse gases, fossil fuels.”
The team is looking to make predictions over a timescale of decades to a century or more. But one challenge is that natural variation in the data is to be expected due to changes in the powerful winds.
“That’s why we need the floats, the gliders and the data over a long period,” said Mike. “If you’re going to make long-term planning decisions, like how high to build a flood barrier, or what level of defences you need around the coast, or long-term investment in agriculture, then that’s the sort of timescales you need to think of,” said Mike.
The BAS team is now preparing for its busiest period, with many due to spend November and December out in Antarctica, and there will be teams there through to March and April.
Mike is taking a year off from fieldwork as he has just taken a role with the IPCC - the Intergovernmental Panel for Climate Change.
His research – and that of all his colleagues on the £8.4million Orchestra programme funded by NERC (Natural Environment Research Council) – will play a significant role in helping us to unlock some of the deepest secrets of our changing climate.
“This is the some of the work we’ve been building up to for the past 10 or 20 years, and I’m getting to do it, so this is very exciting,” said Mike.
‘More losers than winners’ as seafloor warms
A study of marine invertebrates in the seas around Antarctica has found that there will be more losers than winners over the next century as the seafloor warms.
By 2099, an average warming of 0.4 of a degree is predicted. It will be still be too cool for species from neighbouring continents to invade or colonise Antarctica but it will impact on unique local species, a British Antarctic Survey team concluded.
They examined the potential distribution of 963 species of shelf-dwelling marine invertebrates under a warming scenario produced by computer models.
Some species will benefit but they concluded that 79 per cent of the species native to the region will lose out. Some 398 (41 per cent of species studied) are expected to lose less than 10 per cent of their current habitat while 18.6 per cent could lose between 10 and 40 per cent.
Those animals adapted to the coldest water on Earth, such as in the Weddell and Ross Sea, will be most affected and areas of the West Antarctic Peninsula may become too warm for many native species.
Dr Huw Griffiths, from BAS, lead author of the study published in the journal Nature Climate Change, said: “While a few species might thrive at least during the early decades of warming, the future for a whole range of invertebrates from starfish to corals is bleak, and there’s nowhere to swim to, nowhere to hide when you’re sitting on the bottom of the world’s coldest and most southerly ocean and it’s getting warmer by the decade.”
