The Thwaites glacier is holding back global coastal devastation by only the skin of its teeth

This was a pioneering study of the ocean floor, made possible by recent technological advancements in autonomous ocean mapping and a bold decision by the Wallenberg foundation to invest into this research infrastructure. The images Ran collected give us vital insights into the processes happening at the critical junction between the glacier and the ocean today. Anna Wåhlin, University of Gothenburg

Thwaites glacier in West Antarctica is the size of the State of Florida. It has been under scrutiny for decades over fears of warming waters below the ice by tunneling through like a block of swiss cheese. A massive cavity has formed that funnels even more heat into the ice streams underbelly. Sea levels worldwide could rise by as much as 16 feet, submerging cities such as Lagos, Shanghai, London, New York City, and Miami.

The surface air temperatures are bitter cold; in fact, winter 2022 on the ice sheet has been the coldest on record. Simple melting at the surface is not the problem at Thwaites (though that is not true on the peninsula where melt-water lakes have been linked to ice shelf collapse). It is the upwelling of warm water from the southern ocean that will doom coastal habitability in the years and decades to come. 

CNN reports the history that Thwaites, prophetically nicknamed the Doomsday glacier by researchers, since 1973.  

The Thwaites Glacier itself has concerned scientists for decades. As early as 1973, researchers questioned whether it was at high risk of collapse. Nearly a decade later, they found that -- because the glacier is grounded to a seabed, rather than to dry land -- warm ocean currents could melt the glacier from underneath, causing it to destabilize from below.

It was because of that research that scientists began calling the region around the Thwaites the "weak underbelly of the West Antarctic ice sheet."

In the 21st century, researchers began documenting the Thwaites' rapid retreat in an alarming series of studies.

In 2001, satellite data showed the grounding line was receding by around 0.6 miles (1 kilometer) per year. In 2020, scientists found evidence that warm water was indeed flowing across the base of the glacier, melting it from underneath.

And then in 2021, a study showed the Thwaites Ice Shelf, which helps to stabilize the glacier and hold the ice back from flowing freely into the ocean, could shatter within five years.

But a new study published in Nature Geoscience finds that the situation is worse than previously expected. What could be worse than the Thwaite Glacier shattering in five years, you probably think? Well, it’s a little complicated.

Kristen Kuseck translates scientific study into plain English for us. From the University of South Florida College of Marine Science presser:

For the first time, scientists mapped in high-resolution a critical area of the seafloor in front of the glacier that gives them a window into how fast Thwaites retreated and moved in the past. The stunning imagery shows geologic features that are new to science, and also provides a kind of crystal ball to see into Thwaites’ future. In people and ice sheets alike, past behavior is key to understanding future behavior.

The team 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. “It’s as if you are looking at a tide gauge on the seafloor,” said Graham. “It really blows my mind how beautiful the data are.”

Beauty aside, what’s alarming is that the rate of Thwaites’ retreat that scientists have documented more recently are small compared to the fastest rates of change in its past, said Graham.

To understand Thwaites’ past retreat, the team analyzed the rib-like formations submerged 700 meters (just under half a mile) 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.

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

“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,” said Graham.

“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,” said marine geophysicist and study co-author, Robert Larter, from the British Antarctic Survey.  

The grim news continued last month when Reuters wrote that the entire Antarctica coastline crumbles along the edges. 

Los Angeles: Antarctica's coastal glaciers are shedding icebergs more rapidly than nature can replenish the crumbling ice, doubling previous estimates of losses from the world's largest ice sheet over the past 25 years, a satellite analysis showed on Wednesday.

The first-of-its-kind study, led by researchers at NASA's Jet Propulsion Laboratory (JPL) near Los Angeles and published in the journal Nature, raises new concern about how fast climate change is weakening Antarctica's floating ice shelves and accelerating the rise of global sea levels.

The study's key finding was that the net loss of Antarctic ice from coastal glacier chunks "calving" off into the ocean is nearly as great as the net amount of ice that scientists already knew was being lost due to thinning caused by the melting of ice shelves from below by warming seas.

Taken together, thinning and calving have reduced the mass of Antarctica's ice shelves by 12 trillion tons since 1997, double the previous estimate, the analysis concluded.