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Heat from north Atlantic hastens melt of Antarctic ice shelves
canadian goose jacket Thinning of the edges of ice shelves in western Antarctica is accelerating. The warming is not from above, as in the warming atmosphere, but from below. The heat is coming from the ocean. Andrew Thompson has deployed autonomous buoys across the Drake passage, the 800km stretch of water between south America and Antarctica. The buoys measure temperature, salinity and other aspects of ocean water. The passage opened around 41 million years ago and allowed the establishment of the strong Antarctic Circumpolar Current. This current plays a major role in the Earth’s climate, as it receives warm water from the north and distributes it into the Indian and Pacific oceans. As more heat is canada goose outlet locations in toronto being trapped on Earth, much of canada goose outlet this heat is being stored in ocean water and canada goose shop uk the effects are now being seen in Antarctica. canadian canada goose outlet in uk goose jacket
canada goose coats on sale Robyn Williams: Where do you go in the Southern Ocean? canada goose coats on sale
Andrew canada goose outlet london Thompson: Most of my work has been around the Antarctic Peninsula. canada goose parka outlet We’ve worked in the Weddell Sea, which is to the eastern canada goose outlet toronto location side of the peninsula, and we have some work coming up in the Bellingshausen Sea which is actually located along the western side of the peninsula.
canada goose coats Robyn Williams: And you are looking down deep. Do you actually go deep? canada goose coats
Andrew Thompson: Well, not personally, but we have instruments that allow us to go down deep. We’ve been using a type of ocean robotics known as gliders that allow us to actually measure the temperature and salinity properties below the surface.
canada goose Robyn Williams: And they sink down and stay there how long? canada goose
Andrew Thompson: They actually dive continuously, so they will sink down to about 1,000 metres but then they come straight back up, and it takes them a couple of hours to do that, and they will continue sampling up and down for three, four, five months at a time.
Robyn Williams: You must have a vast amount of information then.
Andrew Thompson: Well, that’s one of the nice things, is these persistent measurements have really allowed us to look at how the currents and the circulation are changing with time, and the availability to have more data has allowed us to really understand more about the circulation.
Canada Goose Parka Robyn canada goose outlet store quebec Williams: And when you go down deep, is it very lumpy down there with the equivalent of mountain ranges and suchlike? Canada Goose Parka
Andrew canada goose outlet sale Thompson: Yes, that’s right, we look a lot at what happens at what we call the continental shelf break, so where you transition between a shallow and pretty flat shelf and then go off the continental slope, which is very, very steep. We’ve actually had our gliders bump into those lumpy bits from time to time, so yes, we know canada goose sale uk quite a bit about what the bathymetry looks like.
Canada Goose online Robyn Williams: And they are steering these great bodies canada goose outlet new york of water because if you look at the map there’s a huge amount of ocean down there, almost compared, say, to the northern hemisphere where there is less. Canada Goose online
cheap Canada Goose Andrew Thompson: That’s right. Two years ago in 2016 we were out in a region called Drake Passage, which is between the Antarctic Peninsula and South America and we were actually able to move the gliders all the way across the passage and back during our deployment at that time. cheap Canada Goose
canada goose clearance Robyn Williams: How far is that? canada goose clearance
Andrew Thompson: It’s probably about 600 to 700 km.
canada goose clearance sale Robyn canada goose jacket outlet store Williams: That is vast, isn’t it. And how much do they steer the water overall across the entire southern hemisphere? canada goose clearance sale
canada goose store Andrew Thompson: That’s right, canada goose outlet london uk the current that we’ve been spending a lot of time looking at is what is known as the Antarctic circumpolar current, and this is the very strong current that goes all the way around Antarctica. This circulation is incredibly strong, the circulation or velocity is of a metre per second at the surface. And this is the current that really allows different properties to move from, canada goose outlet in toronto say, the Atlantic Basin into the Indian canada goose outlet belgium and the Pacific. And so these currents that we are looking at are incredibly important for moving different properties around the ocean. canada goose store
canada goose deals Robyn Williams: Right up canada goose womens outlet to the north. canada goose deals
Canada Goose sale Andrew Thompson: That’s right, yes, in fact that’s one of the questions we are trying to answer. What we’ve been looking at is how heat gets towards the coast of Antarctica, and may canada goose outlet in montreal be responsible for melting the underside of ice shelves. And the somewhat remarkable thing is that this heat actually originated from the North Atlantic and actually sank in regions in the Arctic Ocean. Canada Goose sale
Robyn Williams: Right up from the North Atlantic? Further north than here?
buy canada goose jacket Andrew Thompson: Yes, so all the way up off the coast of Greenland sometimes is where this water sinks. You know, it’s still relatively cold but it has enough heat in it to actually melt the underside of the ice shelves. And tracking the pathways for where that heat originated, canada goose outlet niagara falls where it’s actually coming out of the ocean or touching the bottom of these ice shelves are what we are trying to understand. buy canada goose jacket
buy canada goose jacket cheap Robyn Williams: So the entire movement is making the globe gradually warmer overall. buy canada goose jacket cheap
Andrew Thompson: Yes, that’s right, so we have large networks of autonomous floats that we can use to look at globally average temperatures, and they are increasing globally. But what we see is that the pathways by which that heat moves around can lead to certain regions that are warmer, others that are colder. And trying to interpret those patterns has a lot to tell us about how the ocean will change in a different climate.
Canada Goose Outlet Robyn Williams: Have you noticed changes while you’ve been watching, while you’ve been canada goose uk site doing the studies over the years? Canada Goose Outlet
Andrew Thompson: Yes, to a certain extent I think I have. One of the things that has always been a little bit surprising has been that while we are seeing, for instance, sea ice retreating in the Arctic, it’s been relatively stable around Antarctica for the last 20 years so, up until about two years ago in which we’ve seen really rapid changes, especially in this region, the Bellingshausen Sea.
Robyn Williams: Yes, people forget the fact that the ice sheet and the Antarctic can be about 2 km thick, in other words you’ve got a hell of a lot of ice to get through. But in the west and various places where that gigantic famous crack was that we saw in the middle of last year, you’ve got melting going on there and also underneath. So you are saying it’s accelerating now, is it?
canada goose black friday sale Andrew Thompson: Well, that’s what we are trying to work on. Certainly as canada goose outlet in new york you look around West Antarctica there is evidence that the thickness https://www.uscanadagooseoutletsale.com of these floating ice shelves, their thinning has accelerated. And as you mentioned, the interesting thing here is that melting is not happening from above, say due to warming atmosphere, but it’s really happening from below, which really points the finger at the ocean. canada goose black friday canada goose outlet us sale
Robyn Williams: Incredible, isn’t it, and when you go there (a personal question), are you there marooned on a great big ship going up and down, requiring a strong stomach and suchlike?
Canada Goose Jackets Andrew Thompson: Absolutely, Drake Passage can be one of the worst places to actually try and navigate. You have those occasional crossingsthey actually refer to canada goose parka uk it as the Drake Lake when it’s flat, but those are few and far between. I’ve been up on the bridge which could be about four stories above the sea surface and watching waves actually crash onto the window of the bridge. It’s pretty rough in those times Canada Goose Jackets.