Antarctique : la banquise plus petite que jamais • RFI

I welcome Simon Rosé, a journalist at the RFI. Hello, Simon. Hello, Juan. Welcome. We have some questions for you this morning. Donald. Juan. How are you? I'm fine. You are in Lomé, in Togo, in the capital. We are listening to you with Simon Rosé. OK. The impact of the Antarctic ice melt has never been so small. Yes. Why don't scientists all agree on the causes? So, it's true that there is a debate on the causes of the ice melt. But first, Simon Rosé, I think it's important to remind all our listeners that at the moment, in this period of the year, the Antarctic ice melt is supposed to be at its maximum size. Yes, it has never been so small in this period of the year. We are leaving the Australian winter, the winter in the South Pole, and it is precisely this period of the year when the ice melt must be at its maximum to face the following summer. Indeed, at the end of this recharge period, we see, compared to the average, 1 million square kilometers of ice melt surface less. It roughly corresponds to the surface of Mauritania, twice that of France. So, this is what is missing to face the summer that will arrive there. And we would be tempted to say that it is the fault of climate regulations, global warming, and obviously, scientists do not agree with them. Well, that's where to put the cursor. In fact, what is surprising is that until 2016, the Antarctic continent, its ice melt, was doing pretty well against global warming, unlike the North Pole, which is breaking records every month. But in 2016, there was a change and the Antarctic began to recharge less well, its ice melted less well, and almost every month since, we have record-breaking ice melt. As for the Côte d'Azur, it is a region that is very complex to model when climatologists put their models in their computers and run it. There are so many phenomena that come into play. For example, there are phenomena that are called retroactions, that is to say that the ice is white. It reflects the light of the sun very well. So when the ice melts, the light of the sun will directly hit the ocean below, which heats it up, which brings back a melting of the ice, and the system behaves like that. So it's a vicious circle. So you have to quantify all that. And it's quite complex. That's why scientists, who like to be careful, like to say things when they're sure, don't go too far when asked. After all, there are phenomena, trends that we see of warming of the upper part of the Antarctic Ocean, that can partly explain this phenomenon of non-reconstruction of the Antarctic ice sheet at the moment. Donald, one last question. Exactly. I heard that melting doesn't impact the water level. How do you explain it? We often say the opposite. I've always heard that, Simon-Rosé. So it's a bit counterintuitive because it's ice sheet. So you take a glass of water, you put an ice cube in it. The ice cube will melt. The water level won't go up because the ice cube is in the water. So it moves water. But when it melts, it's water that comes back in the water. Sea ice sheet, it's the same. It's seawater that froze and then thawed. So we didn't add water to the system. If you want, in our bowl, we didn't add water. There was already some. It just went from ice to liquid state. So the melting of the ice sheet doesn't cause a melt? No, of the ice sheet. Because, on the other hand, the glaciers that are on the Antarctic continent, they're not in the water. So the day they get in the water, there's an extra water input that's going to raise the water level. It is estimated that if the entire Antarctic sheet that is on the Antarctic continent melts, we're talking about several meters, even tens of meters of elevation of the sea level for several centuries. It's the same on the sheet of Greenland, for example, which is on a continent. The North Pole, on the other hand, there's no land below. There's no continent. So it's ice that floats. If the ice that floats melts, it doesn't raise the water. You can do the experiment at home. You take a large basin, you put ice in it. You look at the water level. You wait for it to melt. The water level won't have moved. On the other hand, if you add water to the system, well, of course, it increases.