00:00Rapid loss of Antarctic sea ice could be a tipping point for the global climate,
00:06causing sea level rises, changes to ocean currents and loss of marine life that are impossible to reverse.
00:13That's the stark warning from a new scientific study published in the journal Nature.
00:18The authors say the changes are having a knock-on effect across the ecosystem that in some cases amplify one another.
00:26Well, to discuss, we're joined now by glaciologist and ice sheet modeler, Frank Patton.
00:33He's also chair of the Belgian National Committee on Arctic Antarctic Research.
00:38Thanks so much for being with us.
00:40Firstly, explain, if you can, Frank, how exactly the authors of this report came to these conclusions
00:47and how big this decline in Antarctic sea ice is likely to actually be.
00:53Yeah, good evening.
00:56So the authors, they brought together several lines of evidence that was recently collected across the Antarctic.
01:04And this goes from Antarctic sea ice over the ocean circulation over the Antarctic ice sheet,
01:10so the one that is lying on top of the continent, as well as marine biology.
01:18And so if you look at the last century, Antarctic sea ice extent was rather constant,
01:27even with a very small increase in extent.
01:31And then the last years, there was a sudden drop in the extent of the sea ice,
01:36a drop that is larger than anything that can be explained by natural variability over the last 100 years.
01:44And one of the consequences of such a drop in sea ice is that, of course,
01:49when sea ice forms, it expels salt, and that creates denser waters that flow to the bottom.
01:57So now there is less salt expelled, less denser waters,
02:01and that has direct impact on the overturning circulation around the Antarctic.
02:06And the overturning circulation is important for the global climate.
02:11And there is already evidence that there is a slowdown of that overturning circulation.
02:17And then a third line of evidence is that over the last decades,
02:21we saw an increase in ice loss of the Antarctic ice sheet.
02:25And this ice loss is especially due to melting, which is due again to the ocean,
02:34deep water that is pushed up on the continental shelf,
02:38and that interacts with the ice sheet and melts it from there.
02:41That leads to quite important losses of the ice sheet.
02:46And they keep on increasing.
02:49And basically, when you have also less sea ice,
02:53you get an older interaction with that ice sheet,
02:56because then winds and storms get a direct access to the ice sheet,
03:02and they can even help in fragilizing that ice and creating more ice loss.
03:08So you see that all these different systems, they are interrelated,
03:12and even more, they reinforce each other,
03:16so that you get stronger losses because of the interaction of those different systems.
03:23And Frank, you say the situation has been relatively stable for centuries,
03:27but you say we're now moving rapidly into a new era.
03:31So how concerned should we be about all of this?
03:34And is what we're seeing reversible?
03:39Yeah, so the authors, they talk about a regime shift,
03:42and a regime shift is quite important because it means
03:46that the ice sheet or the whole system around the Antarctic
03:50moves into a different state.
03:53And it's a bit like a contrast.
03:55We had different states.
03:56We used to have, in the past, we had ice ages,
04:00which was a different state,
04:01and then warmer periods like we have now,
04:04that's also a different state.
04:05So moving into a different state, yeah,
04:09makes us thinking about what this means for the rest of the world.
04:13And of course, what happens in the Antarctic doesn't stay in the Antarctic,
04:17even though it looks like all the changes are happening there,
04:21but it has directly an impact also for our areas.
04:25Now, you were mentioning about irreversible.
04:28Well, many of these changes are also considered to be irreversible,
04:34at least on timescales of human timescales,
04:37because an ice sheet reacts very slowly to changes in climate.
04:41And we haven't seen all the change yet that should be induced
04:46because of the warming that we are currently experiencing.
04:49And as you say, you know, this is happening very far away from us here in Europe,
04:53but you point out that we are greatly influenced
04:57by what actually happens in the Antarctic.
05:00Exactly, because the Antarctic ice sheet, while it is losing mass,
05:04this is immediately affecting global sea levels.
05:08And this is especially from the Antarctic.
05:12If you have a loss in the Antarctic,
05:14the northern hemisphere is more impacted by those losses
05:19than the southern hemisphere.
05:21And this is because of the changes of mass around the globe.
05:25And that means that we should be very careful in watching
05:29what the Antarctic ice sheet is doing,
05:31because it could, over the next decades or even hundreds of years,
05:35lead to a more important mass loss that we are currently experiencing,
05:39because of all those interactions and sudden tipping points
05:45that may eventually be reached.
05:47So how can we, you know, protect this area and protect sea ice?
05:53You know, is it all about reducing global carbon dioxide emissions
05:58or what exactly needs to be done to help protect the sea ice,
06:01both in the Antarctic and also in the Arctic?
06:05Well, several studies over the last years have shown
06:08that these tipping points can be avoided
06:11if we keep global warming below 2 degrees.
06:14A recent study even mentioned 1.5 degrees.
06:18And this is something that we are dangerously approaching.
06:22So it's clear that reducing as quickly as possible
06:26our emissions will be one of the best ways
06:32for preserving that area,
06:34and not only that area,
06:35but preserving and keeping the climate cool
06:40and also preserving, keeping sea levels
06:42to a level that allows for an adaptation
06:48to rising sea levels that is acceptable.
06:51Okay, Frank, we'll leave it there for now.
06:55Thanks so much for joining us with all of that
06:57and taking us through what it means,
06:59particularly for us here in Europe as well.
07:01That is Frank Patton.
07:02He's a glaciologist and ice sheet modeler,
07:05also chair of the Belgian National Committee
07:07on Arctic Antarctic Research.
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