Doomsday glacier threatening to raise global sea level by 7ft

USA: Doomsday glacier threatening to raise global sea level

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Antarctica’s Thwaites Glacier is “hanging on by its fingernails” as the Florida-size glacier could raise the global sea level by 7ft. This massive ice stream is already in a phase of fast retreat leading to widespread concern about exactly how much, or how fast, it may give up its ice to the ocean. Marine geophysicist Alastair Graham, at the University of South Florida’s College of Marine Science, explained why the glacier has been an important consideration for scientists trying to make predictions about global sea level rise.

Speaking to CNN’s New Day, Mr Graham said: “It’s the biggest worry in terms of climate science in Antarctica right now.

“This thing is losing about 50 billion tonnes of ice to the ocean per year.

“We’ve been worried about it for several decades but we’re even more worried about it right now because of this new study we’ve just conducted which looked into the past of this glacier and what it’s done in the last 200 years.

“What we’re finding by using underwater robots that are mapping the seabed around the Thwaites Glacier is that there have been times in the past where the glacier has actually been melting twice as fast as it is right now.

“This is causing some concern to say the least.”

Experts suggest a total loss of Thwaites and surrounding icy basins could raise sea levels from three to 10 feet.

However, the study indicates the glacier could see big changes over small timescales in the future.

Alarmingly, analysis of the new images indicates that the rate of Thwaites’ retreat that scientists have documented more recently is small compared to the fastest rates of change in its past.

Marine geophysicist and study co-author Robert Larter from the British Antarctic Survey said: “Thwaites is really holding on today by its fingernails, and we should expect to see big changes over small timescales in the future – even from one year to the next – once the glacier retreats beyond a shallow ridge in its bed.”

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The images show geologic features that are new to science, and also provide a kind of crystal ball to see into the future of the glacier.

Researchers documented more than 160 parallel ridges that were created, like a footprint, as the glacier’s leading edge retreated and bobbed up and down with the daily tides.

Mr Graham added: “It’s as if you are looking at a tide gauge on the seafloor.

“It really blows my mind how beautiful the data are.”

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The team analysed the formations 700 metres beneath the polar ocean and factored in the tidal cycle for the region – as predicted by computer models, to show that one rib must have been formed every single day.

They suggest that at some point in the last 200 years, over less than six months, the front of the glacier lost contact with a seabed ridge and retreated at a rate of more than 2.1 kilometres per year (1.3 miles per year) – twice the rate documented using satellites between 2011 and 2019.

Dr Graham said: “Our results suggest that pulses of very rapid retreat have occurred at Thwaites Glacier in the last two centuries, and possibly as recently as the mid-20th Century.”

To collect the imagery and supporting geophysical data, the team – which included scientists from the United States, the United Kingdom, and Sweden – launched a state-of-the-art orange robotic vehicle loaded with imaging sensors called Ran during an expedition in 2019.

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