Scientists are preparing to drill into the most inaccessible and least-understood part of Antarctica's "Doomsday Glacier". The Thwaites Glacier in West Antarctica measures around the size of Great Britain, with ice up to 2,000 metres thick in places. If it were to collapse, global sea levels would rise by around 65cm with catastrophic effects.

The glacier is one of the largest and fastest-changing glaciers in the world, but little is known about how warm ocean water is melting it from below. Researchers from the British Antarctic Survey (BAS) and the Korea Polar Research Institute (KOPRI) will use a hot water drill to bore through the ice and deploy instruments to collect real-time data.

The team plans to drill 1,000m through the ice at Thwaites' most vulnerable point, where the warmest ocean water flows under the glacier and melts it from below.

They will also collect sediment and water samples, allowing them to look back in time at what happened to the glacier in the past.

Dr Peter Davis, a physical oceanographer at BAS, said: "This is one of the most important and unstable glaciers on the planet, and we are finally able to see what is happening where it matters most.

"This is an extremely challenging mission. For the first time, we'll get data back each day from beneath the ice shelf near the grounding line.

"We'll be watching, in near real time, what warm ocean water is doing to the ice 1,000 metres below the surface. This has only recently become possible - and it's critical for understanding how fast sea levels could rise."

The drill pumps 90C water at high pressure through a hose to melt the ice. This creates a roughly 30cm-diameter hole, slicing through up to 1 metre of ice every minute.

Once drilled, the holes refreeze within one or two days, so the drill is used periodically to keep them open.

BAS oceanographer and drilling engineer Keith Makinson said: "We're world-leaders in this technology - between us, this team has about 75 years' worth of hot water drilling experience.

"Over the past four decades, it's been amazing to see this technology develop, and now it's helping to answer crucial questions about how we're all going to be affected by climate change and rising sea levels."

Once drilling is complete, the instruments will remain in position for at least a year, transmitting data via Iridium satellites.

The team arrived at the Thwaites Glacier after sailing from New Zealand aboard the Korean icebreaker RV Araon.

Before they made their way across the ice, a remote vehicle was used to tow a ground-penetrating radar and check for hidden crevasses.

Once a safe location had been found, the team completed an 18-mile flight to the drill site, plus more than 40 helicopter rotations to transport 25 tons of equipment.

Expedition leader Dr Won Sang Lee, a principal research scientist at KOPRI, said: "This is polar science in the extreme.

"We made this epic journey with no guarantee we'd even be able to make it onto the ice, so to be on the glacier and getting ready to deploy these instruments is testament to the skills and expertise of everyone involved from KOPRI and BAS."