Thwaites Glacier (Doomsday Glacier)

Thwaites Glacier, also called the Doomsday Glacier, is the widest glacier on Earth. About the size of the state of Florida, it is on the north coast of West Antarctica and part of the West Antarctic Ice Sheet (WAIS), which is about the size of India. Ice loss from this glacier due to global climate change contributes about 4 percent of all global sea-level rise and is increasing. Should melting continue, it could contribute several centimeters of sea-level rise by the end of the twenty-first century. Thwaites Glacier is called the Doomsday Glacier because its ice-ocean system is changing at the fastest rate of any ice-ocean system in Antarctica. Because of its size and location, the glacier helps stabilize the West Antarctic Ice Sheet, slowing its progress into the ocean and its melting. The International Thwaites Glacier Collaboration was formed in 2018 to study and monitor the region.

Background

Antarctica is about 5.5 million square miles (14.2 million square kilometers) in size. About 98 percent of the continent is covered by ice sheets generally defined as three main sectors. East Antarctica, which is larger, is mostly a plateau, while the lower elevation West Antarctica is largely an ice sheet that covers an archipelago. The third ice sheet, the Antarctic Peninsula, is the smallest of the three. The Transantarctic Mountains separate the East and West sectors. The West Antarctic continental ice sheet is notable for several reasons. It comprises about 90 percent of the ice on Earth, 7 million cubic miles (29 million cubic kilometers) of ice, and contains about 80 percent of the planet’s fresh water. Coastal ice includes glaciers, ice sheets, and shelves that regularly calve icebergs into the oceans.

The continent’s geology includes a range of rocks and features. Rocks include fossiliferous sedimentary rocks, lava and deep magmatic rocks, and metamorphic rocks. Antarctica also has glacial deposits and nearly fifty confirmed active volcanoes as well as nearly a hundred unconfirmed subglacial volcanoes. A complete lack of vegetation allows geologists unique access to formations to study how they formed. West Antarctica is primarily crustal blocks and is younger and less stable tectonically than East Antarctica. Most of the crust formed between about five hundred million and ninety million years ago. The average elevation is lower in the West. Thwaites Glacier is part of the geographic region that includes the Ross Embayment, West Antarctic rift system (WARS), and the Marie Byrd Land (MBL) dome.

Thwaites Glacier was first identified by the US Navy in January 1947 during airborne photographic surveys. Extensive mapping of the glacier occurred from 1959 to 1966. The glacier is named for Fredrik T. Thwaites, a glacial geologist and geomorphologist. The US Geological Society’s US Advisory Committee on Antarctic Names chose that name in 1967 in consultation with the US Board on Geographic Names. These bodies work with naming authorities of other Antarctic Treaty nations.

Glaciers form over hundreds of years as snow is compacted into ice. The weight of this snow and ice causes it to flow like a river. Outlet glaciers such as Thwaites flow to the ocean. The portion of Thwaites that is above sea level rises up to 98 feet (30 meters), while underwater the edge of the glacier reaches more than 650 feet (200 meters).

Overview

Part of Thwaites Glacier is anchored to land. A portion of the glacier is an ice shelf over the Amundsen Sea, held up in several places by underwater plateaus. These provide stability for both the ice shelf and the glacier behind it. The ice shelf protects the land-based ice, slowing its flow into the ocean. However, the ice shelf has been getting thinner for decades and is disintegrating.

In February 2019 researchers were able to approach the front of the ice shelf and get within a few hundred meters of it for the first time because the sea was largely free of ice. They knew climate change was changing wind patterns that in turn change ocean currents. This means warm water from the middle of the ocean was pushed onto the Antarctic continental shelf. However, researchers did not know how close the warm water was getting to the glacier or what effect it was having. Using an autonomous underwater vehicle (AUV), they discovered three bedrock channels beneath the ice shelf, two from Amundsen Sea and a third from Pine Island Bay. Warm water from the open ocean was flowing through these channels toward the ice and rapidly melting the underside of the ice shelf. The presence of three channels meant that warm water was eating at the ice shelf from several directions.

Researchers calculated that the ice shelf might last no more than about ten years. Once it was gone, warm ocean water would cause more rapid melting of Thwaites Glacier. A further concern was the ice melt at the points of contact between the ice shelf and the seafloor. If these points of contact disappear, the researchers believe the ice shelf could break free completely. This would destabilize the grounded ice behind it, allowing the glacier to flow into the ocean more quickly, causing increased sea level rise. The scientists said they could only speculate on the speed of melt and possible collapse based on one season of data, but hoped further research would provide more information.

The 2019 discovery and earlier research led the Thwaites Glacier to be nicknamed the Doomsday Glacier. Researchers previously calculated that the complete collapse of the glacier would cause global sea levels to increase by 25 inches (65 centimeters). While some coastal areas would be inundated, that is just one danger the world would face. Higher water levels would lead to more tidal flooding. Hurricane storm surges would be higher, and would cause tremendous destruction. Furthermore, flooding and storm surges would push saltwater into wetlands and marshes. In 2022 the US National Oceanic and Atmospheric Administration (NOAA) reported that about two feet of sea level rise was increasingly likely by 2100 because of emissions to date. Sea level rise of about a foot was expected by 2050. Curbing future emissions could prevent additional sea level rise of up to 5 feet (1.5 meters), or a total of 7 feet (2.1 meters) by 2100. Most of the water contributing to this predicted rise will come from Thwaites Glacier. Nearby Pine Island Glacier is also melting and calving rapidly and contributing to sea level rise.

Bibliography

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