Thwaites Glacier is a large and wide glacier in Antarctica, located east of Mount Murphy on the Walgreen Coast of Marie Byrd Land. It was first seen by scientists in 1940, mapped between 1959 and 1966, and officially named in 1967 after Fredrik T. Thwaites, an American glaciologist. The glacier flows into Pine Island Bay, part of the Amundsen Sea, at speeds faster than 2 kilometers (1.2 miles) per year near its grounding line, which is the point where the glacier meets the sea bed. The fastest-moving ice is found between 50 and 100 kilometers (31 and 62 miles) east of Mount Murphy. Like other icy regions on Earth, Thwaites Glacier has been harmed by climate change, and it is one of the most noticeable examples of glacier retreat since 1850.

Thwaites Glacier is closely watched because it could raise global sea levels. Since the 1980s, Thwaites and Pine Island Glaciers have been called the "weak underbelly" of the West Antarctic Ice Sheet because they are especially vulnerable to permanent melting, even with small amounts of warming. If these glaciers collapse, the entire ice sheet may also eventually melt. This idea comes from scientific studies and observations showing that both glaciers are moving faster, their surfaces are sinking, and their grounding lines are retreating. Scientists believe these glaciers will likely collapse even without further warming. Because of the serious risks it poses, some media have called Thwaites Glacier the "Doomsday Glacier," though scientists disagree with this nickname.

The Thwaites Ice Shelf, a floating piece of ice that holds back part of the glacier, may collapse within 10 years after 2021. Once the ice shelf disappears, the glacier’s movement is expected to speed up. Currently, Thwaites contributes 4% of global sea level rise, but this could quickly increase to 5% and grow further. While the ice lost from Thwaites in this century would raise sea levels by only a few centimeters, the melting would accelerate rapidly in the 22nd and 23rd centuries. The entire glacier contains enough ice to raise global sea levels by 65 centimeters (25.5 inches), more than twice the total rise so far. Some scientists have suggested engineering solutions to slow the glacier’s melting, but these ideas are new, expensive, and their success is not certain.

Location and features

Thwaites Glacier is located at the northern edge of the West Antarctic Ice Sheet, near Pine Island Glacier. Both glaciers lose ice from their grounding lines into Pine Island Bay, which is part of the Amundsen Sea. The fastest ice movement happens between 50 and 100 kilometers (31 to 62 miles) east of Mount Murphy, where ice can move more than 2 kilometers (1.2 miles) each year. Thwaites Glacier is 120 kilometers (75 miles) wide, making it the widest glacier in the world. It covers an area of 192,000 square kilometers (74,000 square miles), larger than the U.S. state of Florida (170,000 square kilometers or 66,000 square miles) and slightly smaller than the island of Great Britain (209,000 square kilometers or 81,000 square miles). The glacier’s ice is between 800 meters (2,624.5 feet) and 1,200 meters (3,937 feet) thick. When large pieces of ice break off at the glacier’s edge, which meets the sea, the glacier loses a massive amount of ice. The largest ice loss events occur on the glacier’s western side and can be detected by special equipment up to 1,600 kilometers (990 miles) away.

The first official sighting of Thwaites Glacier’s coastline is believed to have happened during Richard E. Byrd’s third Antarctic expedition in 1940. Detailed maps of the glacier’s surface were created between 1959 and 1966. In 1967, the glacier was named after Fredrik T. Thwaites, a scientist who studied glaciers but never visited the area. Researchers from McMurdo Station and the International Thwaites Glacier Collaboration (ITGC) study the glacier today.

The Thwaites Glacier Tongue, also called the Western Glacier Tongue, was a floating part of the glacier located about 30 miles (48 kilometers) east of Mount Murphy. It was first mapped using 65,000 aerial photos taken during Operation Highjump in 1947. At that time, it was 95 kilometers (59 miles) long and 60 kilometers (37 miles) wide. By 1967, during Operation Deepfreeze, the glacier tongue had moved 75 kilometers (47 miles) north and had broken into many icebergs, forming the Thwaites Iceberg Tongue. These icebergs covered an area about 150 kilometers (93 miles) long and 35 to 65 kilometers (22 to 40 miles) wide. Over time, the icebergs drifted and broke apart, eventually becoming smaller and scattered. By 2016, the last remaining part of the glacier tongue, covering 470 square kilometers (180 square miles), had completely broken apart. This mix of icebergs is still called by its old name and may help keep the glacier stable. However, if sea ice around it melts, more icebergs may break off. Scientists have used a computer program from microbiology to study the glacier’s cracks and predict how they might affect its stability.

On March 15, 2002, an iceberg named B-22 broke off from the glacier. This iceberg was 85 kilometers (53 miles) long and 65 kilometers (40 miles) wide, covering an area about the size of Rhode Island. Most of it broke apart quickly, but the largest piece, B-22A, drifted near the glacier for years. In 2012, it became stuck on the seafloor and helped stabilize the glacier. In 2022, it started moving again and is expected to remain in the ocean for a long time.

Glaciers in Antarctica often have ice shelves, which are large floating ice platforms that help keep glaciers stable. Thwaites Ice Shelf is 45 kilometers (28 miles) wide and at least 587 meters (1,926 feet) thick. It rests partly on an underwater mountain 50 kilometers (31 miles) offshore. While it only covers the eastern part of the glacier, its presence helps reduce large ice loss on that side. Some scientists believe that if the ice shelf collapses, the glacier could become unstable and collapse over time. However, other studies suggest that losing the ice shelf might not change the glacier’s movement much.

Underneath Thwaites Glacier, swamp-like canals and streams exist. These canals feed streams, and the dry areas between them slow the glacier’s movement. This friction helps keep the glacier stable in the short term. As temperatures rise, these streams grow and form larger structures. In 2019, NASA discovered an underwater cavity beneath the glacier that is nearly 350 meters (1,148.5 feet) tall and 4 kilometers (2.5 miles) wide. Its area is about two-thirds the size of Manhattan.

In 2014, scientists found that heat from geothermal activity beneath Thwaites Glacier is nearly twice the global average and about 3.5 times higher in hotspots. By 2017, researchers mapped 138 volcanoes under the West Antarctic Ice Sheet, 91 of which were previously unknown. Marie Byrd Land, where Thwaites and Pine Island Glaciers are located, has about one volcano for every 11,200 square kilometers (4,300 square miles). This density is high but lower than in other volcanic areas like the East African Rift or Antarctica’s central rift. Heat from these volcanoes can increase melting, and the risk of eruptions may rise as ice loss causes the land to rise. Marie Byrd Land and the central rift also contain most of West Antarctica’s 29 volcanoes taller than 1 kilometer (0.62 miles), though they are still covered by ice.

Importance

Between 1992 and 2017, Thwaites Glacier moved backward by 0.3 km (0.19 mi) to 0.8 km (0.50 mi) each year, depending on the area studied. Over this time, it lost more than 600 billion tons of ice. This loss contributed to about 4% of the rise in global sea levels during that period. If all the ice in Thwaites Glacier melted (a process expected to take many centuries), it could raise global sea levels by 65 cm (about 25 and a half inches). This amount is more than twice the total sea level rise that happened between 1901 and 2018 (estimated at 15–25 cm [6–10 inches]). However, it would still be much smaller than the total sea level rise expected in the future, especially if global temperatures rise significantly.

Concerns about the West Antarctic Ice Sheet (WAIS) collapsing quickly due to climate change were first raised in a 1968 study by glaciologist J. H. Mercer. These concerns were repeated in a 1978 study by Mercer and another in 1973. In 1981, scientists suggested that the Amundsen Sea region, including Thwaites and Pine Island Glaciers, was the weakest part of the WAIS. They argued that the collapse of these glaciers could lead to the collapse of the entire ice sheet. This idea was supported by radar data from the 1960s and 1970s, which showed that the glacier bed in Pine Island Bay slopes downward and lies below sea level. This shape, combined with nearby strong ocean currents, makes these glaciers especially vulnerable to rising ocean temperatures. Later research confirmed that Thwaites Glacier is likely to have the biggest near-term effect on sea levels, even from climate changes that have already occurred. Scientists now agree that losing Thwaites Glacier could lead to the loss of the entire WAIS, which would raise sea levels by about 3.3 meters (10 feet) over several centuries or millennia.

As scientists learned more about Thwaites Glacier’s role in future sea level rise, some began calling it the "Doomsday Glacier." The term first appeared in a 2017 article by Jeff Goodell in Rolling Stone magazine. While some scientists have accepted this nickname, others, including experts like Ted Scambos, Eric Rignot, Helen Fricker, and Robert Larter, have criticized it as overly alarming and inaccurate.

Observations and predictions

In 2001, Eric Rignot studied radar data from Earth Remote Sensing Satellites 1 and 2. He found that the grounding line of Thwaites Glacier had moved back 1.4 km (0.87 mi) between 1992 and 1996. The glacier was losing ice quickly, about 16 billion tonnes each year, which meant the retreat would likely continue. Later analysis showed that for every 0.1 °C (0.18 °F) rise in ocean temperature, melting at the glacier’s base would increase by 1 m (3.3 ft) per year. In 2002, scientists from Chile and NASA used a P-3 Orion plane to collect radar and laser data. They confirmed the glacier was thinning and retreating faster, and found that the shape of the seabed did not stop the glacier from moving back quickly. These findings led to more research by the University of Texas at Austin in 2004–2005 and NASA’s IceBridge Campaign from 2009–2018. Data from IceBridge showed that parts of the glacier are 1.5 mi (2.4 km) below sea level.

In 2011, IceBridge data revealed a rock ridge 700 m (2,300 ft) tall that helps hold the glacier in place. In 2013, scientists noticed a slight increase in ice flow speed, which was linked to melting from lakes under the glacier. Ice loss had grown from about 16 billion tonnes per year between 1992 and 1996 to around 50 billion tonnes per year between 2002 and 2016. Over 14 years, this loss raised global sea levels by 2.07 mm.

A 2014 study said Thwaites Glacier would contribute less than 0.25 mm of sea level rise per year in the 21st century, but this could rise to over 1 mm per year during its collapse. In 2018, scientists predicted that ice loss from Thwaites alone over 30 years would add 5 mm to sea levels. However, projections for 100 years varied between 14 and 42 mm, depending on ice sheet conditions. The models could not account for the possible collapse of the eastern ice shelf.

In 2017, British and American scientists started the International Thwaites Glacier Collaboration (ITGC), a five-year mission with over 100 researchers and a $50 million budget. In 2020, ITGC found that water near the glacier’s base was 2 °C (36 °F) above freezing. In 2023, researchers drilled a 587-meter-deep hole and used a robotic submarine to study the glacier’s underside. They found cracks covering 10% of the glacier’s base, which caused 27% of its ice loss. They also discovered that layers of fresh meltwater and salty ocean water slowed melting compared to predictions.

In 2021, ITGC research suggested the Thwaites Ice Shelf, which holds back part of the glacier, could collapse within five years. This would increase the glacier’s contribution to sea level rise from 4% to 5%. In 2021, scientist Erin Pettit said major ice loss from Thwaites and the West Antarctic Ice Sheet could happen "within decades" if emissions do not drop.

A 2022 study used seabed "ribs" to estimate Thwaites’ past movement. It found the glacier moved 2.1 km (1.3 mi) per year in the last two centuries, twice the speed observed between 2011 and 2019. If the glacier retreats beyond a stable seabed, it could move at similar speeds again. In 2023, researchers found that during the Last Glacial Maximum, ice in Norway retreated 50–600 meters per day, much faster than today. If Thwaites reaches a flat seabed, it could retreat quickly. This does not change the glacier’s overall melting rate.

A 2023 model showed that melting at Thwaites strengthens warm ocean currents, which in turn speeds up melting. This feedback increased melting by 30% over 12 years, equal to what might happen in a century without the feedback. A 2023 study also predicted that water temperatures in the Amundsen Sea could rise three times faster than historical rates even with moderate warming.

In 2024, researchers found that the glacier’s grounding zone is 2–6 km (1.2–3.7 mi) wide, regularly exposed to water. During strong tides, meltwater flows 6 km (3.7 mi) inland, increasing ice loss. This could double previous projections.

A 2014 study said only the lowest warming scenario could save Thwaites. Otherwise, it would collapse in 200–900 years, adding over 1 mm of sea level rise annually until it disappears. A 2022 study said the entire West Antarctic Ice Sheet could take 2,000 years to collapse after crossing a tipping point, which may occur with 1.5 °C of warming.

In May 2023, a 500-year model of Thwaites’ future was studied, but the analysis was incomplete.

Engineering options for stabilization

Some engineering plans have been suggested to help stabilize Thwaites Glacier and nearby Pine Island Glacier. These plans aim to stop warm ocean water from reaching the glaciers, which would otherwise cause them to collapse even if global temperatures do not rise further. In 2018, one idea was to build barriers at the grounding line of Thwaites Glacier. These barriers could either strengthen the glacier or block some of the warm water. The simplest option would be to reinforce the grounding line, but this would be as large and complex as the biggest engineering projects ever done by humans. This method has only a 30% chance of success. A more effective approach would be to block at least 50% of the warm water flow, but this would be much harder to do. Some scientists believe this plan might not work or could even speed up sea level rise. The original proposal suggested testing this idea on smaller glaciers, like Jakobshavn Glacier in Greenland, first. The authors also noted that this method would not stop sea level rise caused by ocean warming and would not work long-term without reducing greenhouse gas emissions.

In 2023, a new idea was proposed: installing underwater curtains made of flexible material and attached to the sea floor in the Amundsen Sea. These curtains could stop warm water from reaching the glaciers. This method would cost less and last longer than rigid structures. The curtains would be placed 600 meters deep to avoid damage from icebergs and would be 80 kilometers long. If successful, this could help the Thwaites and Pine Island ice shelves grow back to their size from 100 years ago, stabilizing the glaciers. However, building this in Antarctica would be very challenging due to extreme conditions and a lack of specialized ships and equipment. No new technology would be needed, as similar methods have been used for laying underwater pipelines.

The project would take about 10 years to complete and cost between $40 billion and $80 billion initially. Annual maintenance would cost $1–2 billion. For comparison, a seawall to protect New York City might cost twice as much alone. Global costs to adapt to rising sea levels caused by glacier collapse are estimated at $40 billion each year. The authors said their plan could be as cost-effective as other climate solutions, like stratospheric aerosol injection (SAI) or carbon dioxide removal (CDR). SAI would cost between $7 billion and $70 billion annually, while CDR powerful enough to meet climate goals could cost between $160 billion and $4,500 billion each year.