A Houston-Size Iceberg Just Broke Away From Antarctica

A Houston-Size Iceberg Just Broke Away From Antarctica

It's the Brunt Ice Shelf's single largest calving event since satellite monitoring began in the 1970s.

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This before/after set clearly shows the separation of a massive iceberg from the Brunt Ice Shelf. The before image was taken on January 20 by a USGS satellite, while the second image comes from the EU’s Sentinel-2 satellite on January 24th.
Gif: Sentinel-2 / Copernicus EU / USGS Landsat

Crash diet alert: Antarctica’s Brunt Ice Shelf has slimmed down by about 256 billion tons. As part of a major calving event, an iceberg nearly the size of Houston, Texas, separated from the continent on Sunday, according to the British Antarctic Survey.

It’s the second major iceberg break for the Brunt shelf in recent years. A previous one in February 2021 was, at the time, the largest known Brunt calving since satellite data collection began in the 1970s. That 2021 iceberg, named A-74, was about 470 square miles (1,270 square kilometers) in area. But this week’s has surpassed it, with an iceberg 492 feet (150 m) thick and more than 598 square miles (1,550 square km) across, Dominic Hodgson, a glaciologist with the British Antarctic Survey, told Gizmodo in an email.

The two iceberg formations are part of the same, ongoing calving event, and Hodgson added that “together, they represent a substantial reconfiguration of the ice shelf (and the coastline of Antarctica).”

The Brunt Ice Shelf is located east of the frozen continent’s Transantarctic Mountain range. It’s home to the United Kingdom’s Halley VI Research Station and is one of the most closely monitored ice shelves on Earth. It’s one of the approximately 300 ice shelves along Antarctica’s perimeter, covering about three quarters of its coastline.

This week’s breakaway berg is the largest known for Brunt, but not for the continent overall. That honor goes to A-76, which tore away from the Ronne Ice Shelf in May 2021 and had a surface area of 1,668 square miles.

Antarctic researchers have known for years that a large Brunt calving event was likely at this site. Chasm-1, which became the breaking point, had been active and growing for more than a decade, according to the BAS press statement. And since then, iceberg formation has been a question of when, not if. In 2016, BAS even moved the modular Halley VI more than 14 miles (23 km) inland to avoid the possibility of the research station floating away.

Now that this most recent break is final, scientists expect the newly formed iceberg to follow in the flow-steps of its A-74 predecessor and move along with the Antarctic Coastal Current. BAS will continue to track the as-of-yet unnamed berg.

While the thought of a massive ice chunk larger than most U.S. cities floating off into the Weddell Sea might seem alarming, Hodgson and his research colleagues were careful to note that calving is a normal Antarctic process. Moreover, there’s no evidence that human-caused climate change contributed to this particular iceberg formation.

Antarctica’s land mass is almost entirely covered in an ice sheet that continually flows outward toward the coast from the center. In areas where the coastline is protected enough, that glacial flow forms ice shelves that float atop the ocean but remain attached to the continent. Ice is constantly being pushed out from Antarctica’s center, and so ice shelves are continually in flux. Brunt flows westward at a rate of about 1.24 miles (2 km) each year. “Unsupported by land, eventually the ice shelf weakens to the point where it breaks into icebergs,” explained Hodgson.

Ice shelves are vulnerable to melting from the surrounding air and water temperatures, but Hodgson explained that “atmospheric temperatures over the Brunt Ice Shelf are consistently below freezing, and no warm ocean water currently penetrates into the cavity under the ice shelf.”

However, the same can’t be said elsewhere in Antarctica. On the other side of the Transantarctic Mountains, in West Antarctica, research has demonstrated that the continent is rapidly losing ice, largely due to ocean warming. In total, the continent incurred a net loss of 3 trillion tons of ice between 1992 and 2017, according to one 2018 study. And “this ice loss is expected to accelerate in the future,” Hodgson said.

The Brunt Ice Shelf may not be bearing the brunt of climate change, but Antarctica as a whole is still feeling the effects. Though it’s not a signal of broader warming, an iceberg the size of Houston yeeting itself into the ocean is still a sight to behold. More satellite images are likely to surface in the coming days, but click through to see what scientists have captured so far.

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Chasm-1

Photo of large ice chasm
A 2016 photo of the crack, Chasm-1. The year this photo was taken, Halley VI Research Station was relocated about 14 miles inland to avoid being caught up in the forecast calving event.
Photo: British Antarctic Survey
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Chasm-1 Growing

Chasm-1 Growing

Satellite image of iceberg calving
An satellite image from this year showed Chasm-1 expanding as the unnamed iceberg calved into the Weddell Sea.
Image: Suomi/NPP VIIRS / NASA
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Illustrated GIF

Illustrated GIF

This GIF shows an approximation of the exact moment of separation.
Gif: British Antarctic Survey
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Map Context

Map Context

Map of Antarctica and Brunt Ice Shelf
The Brunt Ice Shelf is located on the eastern coast of the Weddell Sea, in British and Argentinian claimed territory.
Graphic: British Antarctic Survey
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Chasm-1 2022

Chasm-1 2022

Photo of Chasm-1 expanded
Chasm-1 began widening in 2012, after at least 35 years of dormancy.
Photo: Sebastian Gleich 2022 / British Antarctic Survey
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2022 Aerial View

2022 Aerial View

Aerial photo of ice shelf calving
By 2022, Chasm-1 had expanded, and the calving had begun.
Photo: Ian Potten / British Antarctic Survey
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Halley VI

Halley VI

Halley VI Research Station
Halley VI Research Station is modular and built on skis, so the base can be easily separated into parts and moved as needed. If further calving occurs on the Brunt Ice Shelf, the station may well be relocated again.
Photo: British Antarctic Survey
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Aurora Australis

Aurora Australis

The southern lights are a common display over Antarctica during the continent’s winter. It would probably be really neat to see them from Halley IV, but for the past six years, the research station has been kept empty during winter out of caution, “because of the complex and unpredictable glaciological situation.” If the station were to float off into the sea, a rescue would be much more challenging in the 24-hour dark and brutal weather than in the summer months.
The southern lights are a common display over Antarctica during the continent’s winter. It would probably be really neat to see them from Halley IV, but for the past six years, the research station has been kept empty during winter out of caution, “because of the complex and unpredictable glaciological situation.” If the station were to float off into the sea, a rescue would be much more challenging in the 24-hour dark and brutal weather than in the summer months.
Photo: Anthony Dubber / British Antarctic Survey
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Blue Crack

Blue Crack

Footage of the Chasm-1 crack in 2017.
Gif: British Antarctic Survey
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White Canyon

White Canyon

By 2022, Chasm-1's expansion had become apparent.
Gif: British Antarctic Survey
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