One of West Antarctica’s most infamous glaciers, nicknamed the ‘Doomsday Glacier’ due to its potential to trigger coastline-altering amounts of sea level rise, is changing rapidly in response to climate change. But what does the future hold, and what will it mean?
The size of Britain, measuring 120 km across, The Doomsday Glacier, or Thwaites Glacier to call it by its proper name, is the widest glacier in the world. The glacier itself is a frozen river of ice that snakes down from the apex of the West Antarctic Ice Sheet until it meets the frigid waters of the Amundsen Sea, where it spreads out into a floating platform of ice known as an ice shelf.
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However, all is not well with Thwaites. It currently contributes to around 4 per cent of global sea level rises and, like many West Antarctic glaciers, it has been speeding up and losing ice extremely rapidly in recent years – the rate of loss has actually been doubling in the last 30 years.
Much of this is because its underbelly is being melted away by warming ocean waters. Climate change is heating the Southern Ocean around Antarctica, bringing warmer water towards Thwaites, especially deeper below the ocean surface.
The land beneath West Antarctica’s ice is below sea level and parts of the seabed beneath the glacier slope backwards. This means that if relatively warm ocean water gets underneath, it can undercut the ice from below, eroding the glacier and its ice shelf and reducing its stability.
So far, so worrying. But a recent study carried out at the University of California, Irvine suggests that Thwaites may be more vulnerable than previously thought, with seawater pushing beneath the massive block of ice over several kilometres.
This rapid melting is an issue as the glacier contains enough ice to raise global sea levels by 65 cm if it entirely collapses. At current rates, it will contribute around 10 cm of sea level rise by the end of the century.
That’s a lot of sea level rise from one glacier. But there’s another reason that scientists are worried about Thwaites. The glacier acts like a keystone, meaning that a collapse could drag in neighbouring glaciers with it, potentially adding more than 3 metres to global sea levels.
The loss of these important glaciers would be irreversible on human timescales, which makes it a ‘tipping point’.
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Scientists still aren’t sure exactly how much warming would be needed to trigger such a tipping point, but it is likely to be between 1.5°C and 2°C of global warming – a level we are fast approaching. It’s believed we haven’t yet reached a West Antarctic tipping point, but it may be close.
We have already seen greatly accelerated rates of Antarctic ice loss in recent decades, and this will only increase with rising temperatures.
Further warming is locked in over the next few decades because even very concerted efforts to reduce greenhouse gas emissions will not start to noticeably take effect until around 2050.
Recent research suggests this will result in unavoidable increases in future melting; probably enough to trigger the collapse of the Thwaites Glacier. Other scientists have shown that even today’s 1.2°C of climate heating may already be enough to trigger West Antarctic Ice Sheet collapse.
So, sea level rise is inevitable – and potentially quite a lot. But how we respond matters.
Dr Kaitlen Naughten, a scientist at the British Antarctic Survey and author of one of these sobering new studies, has spoken of the need for courage – not hope - in the face of grim scientific conclusions like this.
“Courage means accepting the need to adapt, protecting coastal communities where it’s possible to do so, and rebuilding or abandoning them where it’s not,” she said.
Nearly half the world’s population live within 200 km of a coastline, and a sea level rise of 3 or more metres would inundate many of the world’s major cities, including London, New York and Shanghai.
Courage, then, means adapting our defences for the future we now expect.
London’s Thames barrier was built to withstand a flood that would occur once every 1,000 years. But climate change means these types of floods could occur much more frequently in future – as much as once per decade by 2100.
Already, the barrier is being closed much more often than expected and costs have risen with the seas in response to the rising risk – with the cost of future-proofing it currently estimated at £16 bn.
Thankfully sea level rise will happen much more slowly than the other changes to the climate system that are already having devastating impacts, like heatwaves or droughts. Although further ice loss from glaciers like Thwaites is guaranteed, we have time to prepare for the changes to come.
As Dr Naughten says: “By predicting future sea-level rise in advance, we’ll have time to plan for it – rather than wait until the ocean is on our doorstep.”
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