After a massive iceberg broke away from Antarctica, it revealed a long-hidden world of creatures on the seafloor

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The research vessel Polarstern in the gap between iceberg A74 (right) and Brunt Ice Shelf (left).

  • Last month, an iceberg the size of Los Angeles, called A74, broke off of Antarctica’s Brunt Ice Shelf and floated away.
  • Researchers aboard the Polarstern vessel happened to be nearby, so they investigated the area of the seafloor that had been covered by the iceberg, half a mile down.
  • They found marine creatures that had been hidden for decades, including anemones, sea stars, sponges, marine worms, fish, and sea pigs. They also collected samples.
  • The researchers captured hours of video footage and thousands of underwater images. A selection of their most interesting photos are below.
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The researchers aboard the Polarstern research vessel found themselves in the right place at the right time last month. They were sailing near Antarctica’s northern rim when a giant iceberg broke off the continent.

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Crew members of the Polarstern prepare to deploy an underwater camera system.

The ship was some 3,000 miles from the southernmost tip of South America, not far from the Brunt Ice Shelf, which is replete with giant, growing cracks. On February 26, one of those cracks tore through the shelf, and an iceberg of more than 490 square miles (1,270 square kilometers) splintered off. This known as a calving event.

The iceberg, named A74, is about the size of Los Angeles, and more than 20 times the size of Manhattan. As it moved away from Antarctica, it revealed a part of the sea floor that hadn’t seen sunlight in 50 years.

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A view of the gap between iceberg A74 (right) and the Brunt Ice Shelf, where new ice has started to form.

The Polarstern crew waited for strong winds in the area to abate, then entered the gap between the A74 and the ice shelf on March 13. The scientists’ goal: investigate the portion of the Weddell Sea bed that had been covered by up to 1,000 feet of thick ice for decades.

The Polarstern crew deployed a camera instrument called the Ocean Floor Observation and Bathymetry System, or OFOBS.

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Crew members of the Polarstern prepare to submerge the Ocean Floor Observation and Bathymetry System.

They towed it behind the the ship on a long cable, submerging the OFOBS up to half a mile under the surface.

The OFOBS recorded five hours of footage and took thousands of photos.

The crew also deployed buoys that could measure the temperature and salt content of the water in the newly created gap. Data from the buoys could tell scientists how quickly that part of the Antarctic is warming.

Once OFOBS reached the sea floor, it spotted various creatures living among stones that had tumbled into the water from the ice shelf above.

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A sea anemone attached to a stone under the Antarctic ice.

Most of the creatures the cameras spotted were sessile animals: organisms like anemones that attach themselves to rocks or the ocean floor and don’t move.

Most of the species were filter feeders, like sea sponges.

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A sea sponge nearly a foot wide is affixed to a small seafloor stone.

These immobile creatures eat microscopic algae and other tiny organic particles in the water that float near their stony abodes.

According to Autun Purser, a member of the OFOBS team, the presence of these filter feeders wasn’t a surprise. But some of the findings shocked his team.

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A 1.5-foot-wide stone heavily populated by filter feeding animals, including large sponges.

“I was expecting fewer, larger filter feeding animals (sponges mainly),” Purser, an oceanic researcher with the Alfred Wegener Institute in Germany, told Insider via email from aboard the Polarstern.

That expectation was based, in part, on findings from a group of British researchers that also drilled more than half a mile into the ice shelf last month, 162 miles from the area Purser’s team was exploring. That team found sponges living on stones under the ice.

Purser’s team was startled to see many creatures swimming around, rather than staying stationary.

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A marine worm leaves a spiral trail of poop on the sea floor.

“I was not expecting to see octopus and fish, or many mobile animals, and they were actually there,” he said.

The OFOBS spotted sea cucumbers, brittle sea stars, mollusks, worms, at least five fish species, and two types of octopus.

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A stone housing a brittle sea star, or ophiuroid. The white curled features are the starfish’s arms, raised to help it capture prey and food.

Using a grabbing device aboard the OFOBS, the scientists collected specimens of some of the creatures, as well as silt from sea floor.

The OFOBS also glimpsed a cute type of sea cucumber called a sea pig.

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Sea pigs, or holothurians, feed on organic material on the ocean floor.

These translucent, water-filled creatures have tube-like legs — sometime on their heads — that help them scuttle about in the deepest, darkest parts of every ocean on the planet. 

It’s a bit of a mystery what, precisely, sustained this diverse, underwater ecosystem in the absence of sunlight. Most organic food stuffs and algae hang out in parts of the ocean where they have access to the light they need to survive.

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An anemone surrounded by the poop trails of a long-departed marine worm.

By collecting more seafloor samples and visiting this area of the Weddell Sea again in the future, the Polarstern researchers hope to answer that question.

Purser said the team’s observations show that marine ecosystems can be quite diverse and abundant, even if there’s only a moderate amount of food available.

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A view of the Weddell Swa between the Brunt Ice Shelf and the A74 iceberg that broke off the shelf in February 2021.

“Possibly everything happens over a longer timeframe, animals more slowly growing, etc.,” he added. “But to determine if this is the case, repeat observations of the under-ice community, whilst still under ice, would be needed.”

The team hopes to one day use autonomous underwater robots to investigate parts of the ocean that were formerly trapped under the ice.

This isn’t the first time Antarctica has lost a giant iceberg, and it won’t be the last.

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A crack in the Brunt Ice Shelf that eventually birthed iceberg A74, as seen from the air on January 12, 2021.

“It is entirely natural for sections to calve away from ice shelves. As ice flows off the land, the ice shelf grows and eventually reaches a size which is unstable,” Adrian Luckman, a glaciologist at Swansea University in Wales, previously told Insider. “Some calving events are small and go unnoticed, but every few years a large one such as this happens.”

Researchers aboard the Polarstern said icebergs the size of A74 slough off every decade or so.

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A TerraSAR-X satellite image of the A74 iceberg, left, in the Weddell Sea of Antarctica as it breaks off from the Brunt Ice Shelf.

In 2017, an iceberg the size of Delaware broke off the continent’s Larsen C Ice Shelf.

Luckman thinks another iceberg will break off the Brunt Ice Shelf in the coming weeks or months.

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An iceberg the size of Los Angeles just broke off Antarctica – and it could happen again within weeks

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A view of the North Rift crack on the Brunt Ice Shelf in February 2021.

Antarctica’s Brunt Ice Shelf is replete with giant cracks. 

Scientists have been keeping tabs on the capricious ice for years, and the event they’d been watching out for finally happened on Friday: An iceberg more than 490 square miles (1,270 square kilometers) in size splintered off the shelf. It’s about the size of Los Angeles, and more than 20 times the size of Manhattan. 

The Brunt Ice Shelf is located on Antarctica’s northern rim, some 3,000 miles from the southernmost tip of South America. It has all the key ingredients for a massive calving event – the term for when a chunk of ice breaks off and floats out to sea. The British Antarctic Survey (BAS), had warned since November that the event was “imminent,” since a crack called the North Rift had opened up on the shelf. 

In January, the rift started lengthening by more than half a mile per day. The video below shows the crack from the air.

Early on Friday, the last 1,000 or so feet (a few hundred meters) of the crack tore through the ice, and the ‘berg cracked free.

Converging cracks in the ice

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The North Rift crack in the Brunt Ice Shelf, as seen from the air on January 12, 2021.

The North Rift is the third major crack to develop on the Brunt Ice Shelf since 2011, according to the BAS, which keeps tabs on the region’s ice using satellite imagery.

But this one wasn’t the crack that had researchers concerned. Two other cracks have been accelerating toward each other since 2019, known as the “Halloween crack” and “Chasm 1.” If  those meet, an even bigger iceberg will slough off into the ocean. 

“It seemed as though one of these would eventually lead to a calving event,” Adrian Luckman, a glaciologist at Swansea University in Wales, told Insider. “The development of a new ‘North Rift’ towards the end of 2020 was a bit of a surprise but shows how complex the dynamics of ice shelves can be.”

NASA started tracking the Halloween crack in October 2016 (hence its name). It’s growing eastward from an area called McDonald Ice Rumples – a spot on the shelf’s surface where the ice isn’t flat and instead features crevasses and rifts.

The “Chasm 1” crack is located southeast of the McDonald Ice Rumples and started showing signs of movement in 2012. It started accelerating north in 2019, putting it on a collision course with the Halloween crack. The two are now just 1.2 miles (2 kilometers) apart.

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A map shows cracks on the Brunt Ice Shelf and the British Antarctic Survey’s Halley VI research station, February 26, 2021.

When they converge, a piece of ice about 660 square miles in size could break off the ice shelf.

According to the BAS, neither Chasm 1 nor the Halloween Crack have grown in the last 18 months. But Luckman, who’s been tracking the Brunt Ice Shelf cracks over the past few weeks using satellite imagery, thinks that quiet period is at an end. 

“Chasm 1 will certainly give rise to a further large calving event and I anticipate that this will happen in weeks to months,” he said.

The changing ice forced British researchers inland

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The North Rift crack in the Brunt Ice Shelf, as seen from the air on January 12, 2021.

This isn’t the first time Antarctica has lost a giant iceberg, and it didn’t set any records for size. In 2017, an iceberg the size of Delaware broke off the continent’s Larsen C Ice Shelf. 

“It is entirely natural for sections to calve away from ice shelves. As ice flows off the land, the ice shelf grows and eventually reaches a size which is unstable,” Luckman said. “Some calving events are small and go unnoticed, but every few years, a large one such as this happens.”

It’s difficult for scientists to determine how and why certain cracks in the Antarctic ice suddenly begin to grow, and there’s “no evidence that climate change has played a significant role,” the BAS said in a press release

Still, research shows that warming oceans are speeding up Antarctica’s melting overall. In the 1980s, Antarctica lost 40 billion tons of ice annually. In the last decade, that number jumped to an average of 252 billion tons per year

The instability of the ice has already impacted BAS researchers working at the Halley Research Station, where scientists study space weather and Earth’s atmosphere. In 2017, the expansion of Chasm 1 forced scientists to prematurely end the winter research season at Halley and close the station early

Since the station’s inception in 1956, there have been six Halleys. The station’s current iteration, Halley VIa, moved 14 miles upstream from its original location, which had been to the west of Chasm 1, on the crack’s inland side. 

“Four years ago, we moved Halley Research Station inland to ensure that it would not be carried away when an iceberg eventually formed. That was a wise decision,” Simon Garrod, director of operations at BAS, said in the release. “Our job now is to keep a close eye on the situation and assess any potential impact of the present calving on the remaining ice shelf.”

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The British Antarctic Survey’s Halley VI research station on the Brunt Ice Shelf.

Luckman said he doesn’t think future calving events will pose a threat to the research station.

“Halley VI is on a stable part of the ice shelf,” he said. “But as we have seen, the future behaviour of fracturing ice is very hard to predict.” 

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An iceberg the size of Delaware that was heading straight for a penguin colony island has broken into two pieces

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The iceberg (L) is headed for South Georgia Island, which is home to millions of penguins.

  • A massive iceberg bound for South Georgia Island, which is populated by millions of penguins, has broken into two pieces, scientists tracking its journey said on Friday. 
  • Strong underwater currents caused the iceberg, dubbed A68a, to pivot nearly 180 degrees before splitting apart. It was only 31 miles away from the shores of the island.
  • The iceberg, which was the size of Delaware, threatened to cut off vital ocean access for the island’s penguin and seal population.
  • Even though the iceberg has broken apart, scientists still worry that the larger piece could still hit the island, and endanger its inhabitants.
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An iceberg the size of Delaware, which was on course to crash into an island populated by a penguin colony, has broken into two pieces, scientists tracking its journey said on Friday.

In the last few weeks, the iceberg, dubbed A68a, came dangerously close to South Georgia Island in the south Atlantic, threatening to cut off vital ocean access for the island’s penguin and seal population. 

The island is home to millions of gentoo, macaroni, and king penguins and sea lions, nesting albatrosses, and petrels.

But as the massive iceberg approached the western shelf edge of the island this week, strong underwater currents caused it to turn nearly 180 degrees, Geraint Tarling, a biological oceanographer with the British Antarctic Survey, told the Guardian.

“You can almost imagine it as a handbrake turn for the iceberg because the currents were so strong,” Tarling said, according to the Guardian.

The intense turn caused the large iceberg to break into two pieces, just 31 miles away from the island’s west coast.

The new, smaller piece, which has already been named A68D, is currently moving further away from the original. Scientists are unable to provide an estimate of its size.

The original iceberg is heading south-east, where it is expected to be picked up by another current that will carry it back around toward the island’s east coast. 

Scientists warn that South Georgia Island is not in the clear just yet and that the separate pieces could still cause an environmental disaster for its inhabitants. 

“All of those things can still happen. Nothing has changed in that regard,” Tarling said, according to the Guardian.

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Iceberg A68a (left) and South Georgia Island (right) as seen by satellite on December 14, 2020.

A68a first broke off from an Antarctic ice shelf in 2017 and had been drifting ever since.

As it headed towards South Georgia Island, scientists worried that it would completely destroy the island’s underwater shelf and marine life.

There is also a possibility of the iceberg getting lodged in the island’s shoreline, where it could stay there for 10 years. That would cut access to the ocean for penguin and seal parents, who make trips into the water to fill up on fish and krill to feed their young.

South Georgia Island finds itself in a perilous location because it sits in the middle of an alley of currents that bring bigger icebergs north from Antarctica toward the Equator. 

In 2004, another iceberg, called A38-B, ran aground off the island, killing many seal pups and young penguins. 

Registering a record high temperature of 20.75 degrees Celsius (69.35 degrees Fahrenheit) on February 9, the peninsula is also one of the fastest-warming places on Earth, which has scientists worried that the melting ice will eventually contribute to higher sea levels worldwide.

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