Tidal pressure has been observed to push (relatively) warm water under the Thwaites Glacier, exposing a much larger ice surface to the warming pressure. The observations indicate that catastrophic sea level rise could come much sooner than almost everyone is preparing for.
Rising temperatures contribute to higher sea levels by expanding existing water in the ocean, but also by melting the Alpine glaciers and the Greenland ice sheet. All of this will almost certainly increase and cause problems for coastal cities around the world. However, there is much more uncertainty about the rate at which Antarctic ice will melt, potentially multiplying existing flood threat estimates. Despite the vastness of Antarctica, one glacier, the Thwaites, is considered essential and deserves the name “The Doomsday Glacier”.
The Thwaites Glacier is 120 kilometers wide where it reaches the ocean and extends from West Antarctica to an offshore basin. The warming of the air above and the water in front of the Thwaites is causing it to melt, but there are fears of something much worse. Water beneath the Thwaites, where it currently sits at the bottom of the ocean, would expose the ice to much more heat, significantly increasing the rate of melting.
This is where observations by Professor Christine Dow of the University of Waterloo and colleagues come in handy. They have seen evidence in satellite images that water is coming under the glacier every day, lifting it from the seabed, before the weight of the 1.2 kilometers ( The 1200 meter thick glacier causes it to settle back down. The cycle repeats with the tides above 2–6 kilometers (1.2–3.7 mi) from the glacier, but when the sun and moon align to create extreme tidal conditions they can extend up to six kilometers further.
This causes a brief accelerated warming, but the shape of the basin means that if, or more realistically when, the glacier front retreats deeper into the basin, base melting will occur continuously. Two ridges on the seafloor are the planet’s last lines of defense against accelerated melting. The question for humanity is how long we have before both are violated.
Incorrect colorization of satellite images shows the flexing that the Thwaites Glacier experiences as tidal pressure rises and falls as water penetrates miles beneath the ice, accelerating warming.
Image credit: ICEYE; ERIC RIGNOT / UC IRVINE
Dow and co-authors estimate that this will happen in ten to twenty years, and that sea level rise will therefore greatly accelerate. “Thwaites is the most unstable spot in Antarctica and contains the equivalent of 60 centimeters [24 inches] of sea level rise,” Dow said in a statement. “The concern is that we are underestimating the rate at which the glacier is changing, which would be devastating to coastal communities around the world.”
The wealthiest locations can build dikes like the Netherlands, or a tidal barrier like London, but for much of the world this will mean drowning homes and prime agricultural land.
Dow hopes to achieve greater precision about how quickly we can expect these events to occur by refining models of how water flows in and out of the basin, and how saltwater and glacial melt mix there. “Right now we don’t have enough information to say one way or another how much time is left before ocean water intrusion is irreversible,” she said.
However, modeling can only take it one step further without direct observations to calibrate it. Scientific data from Antarctica once developed at a pace comparable to that of glaciers. Eyes in the room have made some aspects a flood, but not operations that require boots on the ground.
“We will be operating on the same real dollar budget in 2024 as we were in the 1990s,” said lead author Professor Eric Rignot of the University of California, Irvine. “We need to expand the community of glaciologists and physical oceanographers to tackle these observational problems sooner or later, but right now we are trying to climb Everest in tennis shoes.”
The research has been published open access in Proceedings of the National Academy of Sciences.