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Underwater robots peering under Antarctica’s Thwaites Glacier, nicknamed the “Doomsday Glacier,” saw that its doom could come sooner than expected with an extreme increase in ice loss. A detailed map of the seabed surrounding the ice giant has revealed that the glacier underwent periods of rapid retreat within the last few centuries, which could again be caused by melting driven by climate change.
Thwaites Glacier is a massive chunk of ice – about the same size as the US state of Florida or the entire United Kingdom – that is slowly melting into the ocean off the West. Antarctica. The glacier got its ominous nickname because of the “spine-chilling” implications of its total meltdown, which could raise global sea levels between 3 and 10 feet (0.9 and 3 meters). the researchers said in a statement. Due to climate change, the frozen mass is retreating twice as fast as 30 years ago and is losing about 50 billion tons (45 billion metric tons) of ice annually, according to Thwaites Glacier International Collaboration.
Thwaites Glacier lies far below the ocean’s surface and is held in place by steep points on the sea floor that slow the glacier’s slide into the water. The sections of seabed that underlie the bottom of a glacier are known as “grounding points” and play a key role in how quickly a glacier can retreat.
In the new study, an international team of researchers used an underwater robot to pinpoint one of Thwaites’ previous landing points: a protruding ridge on the seafloor known as the “hump,” which is about 2,133 feet (650 m ) below the surface. The resulting map revealed that at one point during the past two centuries, when the hump was lifting the Thwaites Glacier, the glacier’s ice mass retreated more than twice as fast as it does now.
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The researchers say the new map is like a “crystal ball” that shows us what could happen to the glacier in the future if it breaks away from its current grounding point – which is about 984 feet (300m) below the surface – and is anchored in a deeper like hump. This scenario could become more likely in the future if increasingly warm waters melt the glacier’s cores, according to the statement.
“Thwaites is really being held by his fingernails today,” study co-author Robert Larter, a marine geophysicist with British Antarctic Survey, said in the statement. “We should expect to see big changes in small periods of time in the future.”
Reading between the lines
The researchers pinpointed the bump using the underwater robot Rán (named after the Norse goddess of the sea), which spent about 20 hours scanning a 5-square-mile (13-square-kilometer) section of the former landing spot.
The resulting map showed that the bump is covered with about 160 parallel furrowed lines that give it a barcode-like appearance. These odd-looking grooves, also known as ribs, are between 0.3 and 2.3 feet (0.1 and 0.7 m) deep. The spaces between the ribs are short and wide, between 5.2 and 34.4 feet (1.6 and 10.5 m) apart, but they are usually about 23 feet (7 m) apart.
These ridges are actually tracks that were left behind as the tide briefly lifted the glacier off the sea floor, which pushed the ice mass a little further inland before the tide brought it back down. Each rib represents a single day; Together, the lines depict the gradual movement of the glacier over a period of about 5.5 months. The different depths and spaces between the ribs correspond to the cycle e spring and rough tides, with glaciers moving farther and with greater force during the former. (During spring tides, high tides are higher and low tides are lower.
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“It’s like you’re looking at a tide gauge at the bottom of the sea,” study lead researcher Alastair Graham, a geological oceanographer at the University of South Florida, said in the statement. “It really blows my mind how beautiful the data is.” However, noticeable grooves on the seabed are also a cause for concern, he added.
Based on rib spacing, the researchers estimated that when Thwaites Glacier was anchored to the hump, the ice mass retreated at a rate between 1.3 and 1.4 miles (2.1 and 2.3 km) per year. That means the glacier was retreating almost three times faster than it was between 2011 and 2019, when it was retreating at a rate of about 0.5 miles (0.8 km) a year, according to satellite data.
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The researchers aren’t sure exactly when the glacier settled on top of the hump, but it was definitely within the last two centuries and most likely sometime before the 1950s. The team was unable to obtain the necessary core samples from the bottom of sea to properly age the hump, because increasingly icy conditions around the glacier meant they too had to be rapidly withdrawn from the region, according to the statement. However, the team intends to return soon to properly answer this important question.
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The new findings are troubling because they show that Thwaites Glacier experienced “pulses of very rapid retreat” even before the effects of climate change increased the current rate of ice loss, Graham said. It shows that the glacier has the potential to accelerate much faster if it breaks away from its current grounding point and anchors to a later crash-like grounding point, he added.
Past research using robotic submarines has shown this surprisingly warm water under the glacier it may be melting the lower part of the ice mass, which can quickly push the glacier toward this tipping point.
“As soon as the glacier retreats across [the current] shallow ridge in its bed,” it may take only a few years to accelerate to a similar rate of retraction during the collision era, Larter said.
The study was published online Monday (Sept. 5) in the journal Nature Geoscience (opens in new tab).
Originally published in Live Science.