At 120 kilometres across, Thwaites, the so-called doomsday glacier, functions as a plug holding back the mass of the West Antarctic Ice Sheet.
If — or when — the glacier melts, it will result in a world sea level rise of more than half a metre.
But the worst would be yet to come.
The melt will create a space for the ice sheet to flow into, resulting in its disintegration as well, adding another three metres of sea level rise, leaving countless global coastal cities underwater.
The UK and the US led a study called the International Thwaites Glacier Collaboration in 2018 to monitor the rate of the glacier's melting.
Providing measurements for the project will be one of the many tasks of the RRS Sir David Attenborough, which is set to depart for Antarctica.
The research ship, which the public once hoped to name Boaty McBoatface, first set sail last year, delivering supplies to British Antarctic Survey’s (BAS) research stations.
But on Sunday it will head south to begin its first research mission, making use of its 14 laboratories spread over an area the size of two tennis courts.
“We have never had facilities to this scale before,” Elaine Fitzcharles, BAS senior lab manager told The National during a tour of the ship, currently docked at Harwich International Port preparing for departure.
“The complexity of the science we can do on this ship is equivalent to, if not more than we can do in our main office in Cambridge.”
But it is more than a floating research station. As home to about 30 scientists until May, it includes comforts such as a gym and even a sauna, with some areas more akin to those found on a cruise ship than research vessel.
“The ship is a very comfortable place to live and work and we recognise that this is people’s home as well as their place of work,” said captain Will Whatley, 33.
“People need their own space and they need time to relax. So, we try to make time for that as well, because we have got recreational facilities on board. But it can be challenging to make sure all the different demands are met because time is tight. We want to make the best use of this massive capability we have got.”
During its mission, the ship will transfer research teams, food, science equipment, cargo and fuel to BAS research stations.
It will also carry out trials of polar science equipment, as well as tasks such as using floats to collect data to study ocean temperatures.
“If warm water gets into the ice sheet and underneath the ice, it could melt the West Antarctic Ice Sheet from below,” said Jane Francis, director of BAS.
“It’s really critical to understand what’s actually happening. And the Thwaites Glacier is really interesting as it is one of the potential channels of this warm water into the middle of the West Antarctic Ice Sheet.
“What the research project is doing is trying to understand where the warm water is going, how it gets under the ice sheet and then if it melts the bottom of the ice shelf. And then it will lift the ice shelf and the glacier off the rock it is on and allow water to go into the centre of this ice sheet.”
And what is happening in Antarctica matters to the whole world.
The Earth is changing, but the rate is faster in the polar regions than anywhere else, with melting ice that will lead to sea levels rising higher.
“We want to understand how the oceans are changing, we want to understand why the ice is melting,” said Anna Jones, director of science at BAS.
“Is it because of changes in ocean circulation? What’s happening to the temperatures? We have had periods in the Antarctic where the temperatures have been much higher than they should be. Sometimes it’s just for a few days you get these really big increases in temperature.
“There have been places where it’s gone from minus 55 to minus 20, which doesn’t sound too terrible because it’s still below freezing, but it’s 30°C warmer than it should be. So we really need to understand.”
The ship will head south through the Atlantic to the Falklands, a journey which will take three weeks. It will then head to Rothera, its largest research station in the Antarctic, before pausing for a week at Christmas to unload cargo before visiting other stations.
“The rough bit for us is the Southern Ocean,” said Cpt Whatley. "Once we get across that and we are below the Antarctic convergence, it becomes a lot calmer.
“The convergence is what we refer to as the meteorological limit of Antarctica. Once we are below that, the ice kills all the swell and it becomes calmer. But yes, we can have some pretty fierce storms in the Southern Ocean.”
Once it completes its work in the Antarctic, the crew will head to Chile before returning to the UK next May.
Future missions include a trip to Greenland in summer 2024, when the team will visit one of the biggest glaciers in the Arctic.
“It’s losing mass really rapidly,” said Kelly Hogan, a marine geophysicist with BAS.
“About 5 per cent of the ice sheet drains out through this one glacier. It’s been retreating and decaying rapidly for the last 10 or 15 years.
“And right now we think it is almost at a tipping point, where it might suddenly jump back again. We are going to look at how the ice has behaved, has moved back through the fjord by doing this mapping, seeing where it used to be and how it’s moved back.
“Then we are also going to look at, as it’s melting, all that meltwater brings lots of nutrients and good things into the ocean. That changes the productivity of what’s happening in the water.”
Promoting BAS’s work is key to raising awareness about the issue of the world’s changing climate, which is why officials consider the Boaty McBoatface naming episode an “incredibly positive thing”.
The saga began in 2016, when the public was asked to name the UK’s new polar ship. Boaty McBoatface was the runaway winner with 124,109 votes. The second most popular choice, Poppy-Mai, had 34,371.
But under the rules of the competition, the decision ultimately rested with the Natural Environment Research Council. It opted for Sir David Attenborough instead.
Sir David’s presence is felt throughout the ship occasionally when an announcement is made.
“It catches me every time I hear them,” said Carson McAfee, an electronics engineer at British Antarctic Survey, who produced many of the science kits on board and travels with the ship when it is on the move.
“There is a really funny one. My favourite is the one he says the vacuum toilets are down, you can’t use the toilets. And you are thinking 'Attenborough shouldn’t be saying things like that'.”
It is, however, arguably less silly than naming a £200 million ($235.9 million) ship Boaty McBoatface.
Ms Jones said although it would not have been an appropriate name, the competition process served an important purpose.
“It captured the imagination of people who perhaps wouldn’t have noticed a ship otherwise,” she said.
“And they heard this thing that was really funny. So they loved it. It obviously wouldn’t be appropriate for a fantastic piece of science equipment like this wonderful ship we have to have a silly name like Boaty McBoatface.
“So calling it the Sir David Attenborough is perfect, because everybody knows Sir David Attenborough.”
Cpt Whatley said he was “very pleased” the ship, which he played a part in designing, was named Sir David Attenborough.
“He is a good ambassador for everything we do and everything that BAS is trying to achieve,” said the skipper, who joined BAS when he was 19 as a third officer and worked his way up the ranks, receiving command in 2015.
And the name does live on in an autonomous underwater vehicle, which is housed on the ship.
“Boaty McBoatface exists,” said Ms Jones. “It’s still part of the family of instruments we can use.
“On the one hand the ship now has an appropriate name. But the Boaty McBoatface episode lives on.”