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An iceberg’s climate warning

An iceberg’s climate warning

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When a mega iceberg melted it released 152 billion tonnes of fresh water into the ocean, but that is not what is worrying scientists most. It represents a longer term problem for our planet.


Transcript
Nimo omer, narrating:

Hi, I’m Nimo and this is the Sensemaker. 

One story, everyday, to make sense of the world.

Today, why the disappearance of an iceberg should worry us all.

***

Trillion-tonne iceberg breaks off Antarctica…

Al Jazeera

In 2017 an iceberg that was the size of a small country broke off Antarctica. 

At the time it  weighed a trillion tonnes. That’s right, a trillion – with a T, and covered an area that was over three times the size of London, and twice the size of Luxembourg.

It was given a name fit for a Hollywood disaster movie: Iceberg A-68. Now, this isn’t the first time part of an ice shelf has broken free and floated off into the distance — but the sheer  size of A-68 generated a lot of attention at the time. 

It became something of an internet sensation. In its first two years of freedom, A-68 stayed close to home in the icy waters of the Weddell Sea and it got a lot of attention from researchers: climate scientists wondered  whether more gigantic icebergs were to come, biologists looked  into its impact on ecosystems.  

And, as time wore on, heavy winds, the ocean current and the earth’s rotation meant A-68 drifted north, to warmer waters near South America. Then, after four years, the iceberg’s adventure came to an end.

Satellites showed the “mega-berge” had melted into countless smaller fragments of ice that weren’t  worth tracking anymore.

 But a year after  we said goodbye to A-68, its impact is still being felt  

 Scientists from Leeds University revealed earlier this year that it had released 152 billion tonnes of freshwater into the sea. (That’s the equivalent of 61 million olympic sized swimming pools.)

So I’m Bob ward, I’m the policy and communications director at the Grantham Research Institute on Climate Change.

Bob Ward

Bob Ward has been following A-68’s journey since it first broke free. Its demise worried scientists, and for good reason. It was, after all, one of the biggest recorded icebergs in human history. But, perhaps unexpectedly, it isn’t the 152 billion tonnes of freshwater it  released into the ocean that has caused the most concern. 

Well, it sounds a lot, and it is a lot of water, but compared to the total volume of seawater in the south Atlantic, where it has broken up and melted, it probably won’t make much difference.

Bob Ward

There are three kinds of ice that you need to know about when it comes to melting ice caps and  sea level rise: ice shelves, ice sheets and glaciers. A-68 came from an ice shelf.

It’s a little bit like a floating ice cube. When an ice cube that floats in your drink melts it won’t cause any spillage in your glass because it’s already displaced the amount of water that you would expect. But if you have land-based ice sheets, that causes sea level rise in the same way that dropping an ice cube into a full   glass of water causes it to spill.

Bob Ward

A-68 was like the ice floating in your glass of water, so it didn’t have a significant impact on sea levels when it melted.

In terms of sea level rise it hasn’t made really any difference cause the ice shelf floats anyway. And so it’s already displaced the water and although it’s adding fresh water, it. It kind of doesn’t make any real difference.

Bob Ward

But — and this is important — these ice shelves do play a role in stabilising land based glaciers and ice sheets. They keep them in place. So if pieces the size of A-68 continue to break away, the ice-sheets and glaciers will become far more vulnerable to melting. 

We will end up locking in not just a metre of sea level rise, but several metres of sea level rises over the coming centuries that will fundamentally redraw the map of the world. And we can’t be guaranteed that it will only happen in slow processes.

Bob Ward

And it’s not just sea level rise that’s the issue here.

There is concern at the moment, for instance, about the amount of cold fresh water that Greenland is adding into the north Atlantic and that it might disrupt the so-called Gulf Stream. If the Gulf stream does break because of the addition of cold fresh water, that could mean that the UK starts to experience a climate much more in keeping with say the Scandinavian countries and other countries that are at the same latitude as us.

Bob Ward

So in the short-term, A-68  melting won’t disrupt sea levels all that much. But like most climate change issues, looking at things in the short term isn’t helpful the biggest challenges come later on. So, how could  this affect people on dry land? 

***

Global sea levels are up about 8 centimetres since 1992 and they’re continuing to rise at a rate of 3.4 millimetres per year. That might sound inconsequential but that’s all it takes to put coastal cities like New York, Shanghai, and Miami in serious danger of being under water in our lifetimes. 

Two thirds of Bangladesh is less than five metres above sea level, the country already struggles with devastating floods. As temperatures continue to rise, these issues will only get worse. 

The West Antarctic ice sheet will collapse if global warming hits 2 degrees, which could raise global sea levels by as much as 3 metres.  250 million people live less than five metres above sea level.

The A-68 iceberg wasn’t the first mega-berg, but unfortunately, it also won’t be the last. 

Today’s story was written by Nimo Omer, produced by Chloe Beresford with sound design by Karla Patella.