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Tag: Icebergs

  • Scientists Went Looking for Shackleton’s Endurance. They found a Hidden Fish City in Perfect Formation Instead

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    While tracing the footsteps of polar explorer Sir Ernest Shackleton and his ill-fated Endurance ship, researchers discovered hundreds of fish nests arranged in particular patterns.

    A remotely operated vehicle (ROV) investigating the seafloor in Antarctica’s Western Weddell Sea found over 1,000 circular nests making up a large geometric neighborhood. The discovery sheds light onto the unique ecosystems thriving in Earth’s most extreme environments and carries significant implications for conservation efforts.

    A dynamic fish community

    The nests (the divots in the sand pictured in the image below) belong to a species of rockcod known as the yellowfin notie and were located in an area previously covered by a 656-foot-thick (200-meter) ice shelf. Some were arranged individually, while others were in curves or clusters. It even turns out yellowfin notie are orderly homekeepers—while the surrounding seafloor was covered in plankton detritus, each nest was clean.

    The yellowfin notie nests. © Weddell Sea Expedition 2019

    The researchers describe the fish community as a mix of cooperation and self-interest in a study published today in Frontiers in Marine Science. A parent fish would have guarded each nest, but the arrangement of the nests themselves also played a defensive role. The nest clusters represent the “selfish herd” theory, which suggests that individuals in the center of a group are safer than those on the margins. According to the researchers, the isolated nests likely housed larger and stronger fish who were better suited to protecting their nests.

    Following the footsteps of Endurance

    Researchers found the fish neighborhood during the Weddell Sea Expedition 2019, which aimed to conduct research near the Larsen Ice Shelf and find the wreck of Sir Ernest Shackleton’s ship. Endurance was crushed by pack ice in 1915 before it got swallowed by the sea. Miraculously, the entire crew survived the misadventure.

    Endurance Sinking
    Endurance sinking in the ice. © Frank Hurley, Public domain, via Wikimedia Commons

    The same perilous conditions that upended Shackleton’s undertaking over 100 years ago prevented the 2019 expedition aboard South African polar research vessel SA Agulhas II from locating his ship—that happened in 2022. Nonetheless, the team found a peculiar habitat associated with ice shelves, a crucial formation involved in ice flow and sea level rise.

    In the wake of A68 iceberg

    Antarctica’s borders are laced with floating ice shelves that hold back the flow of glaciers. When ice shelves are lost, glaciers flow freely into the ocean, raising sea levels. The Larsen Ice Shelf is in West Antarctica, and it’s so long that researchers refer to its various sections as Larsen A, B, C, and D. In 2017, a giant chunk of Larsen C broke off and turned into one of the world’s largest icebergs. Called the A68 iceberg, it measured 2,240 square miles (5,800 square kilometers) at its peak.

    The team was able to explore previously inaccessible areas of the seabed with an ROV and autonomous underwater vehicles (AUVs) in the wake of the ice shelf’s splitting. Their subsequent discovery of the fish nests indicates that the area hosts an unusual and vulnerable habitat vital to biodiversity with important ramifications for conservation, given that their study joins a host of other research supporting the proposal to formally designate the Weddell Sea as a Marine Protected Area.

    More broadly, the paper represents further evidence that life finds a way even in the most inhospitable of regions.

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    Margherita Bassi

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  • The World’s Biggest Iceberg Is Finally Crumbling

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    Just months ago, the world’s largest iceberg weighed about a trillion tons and covered an area nearly the size of Anchorage, Alaska. Now it’s less than half that—and rapidly disappearing.

    In recent weeks, massive chunks of ice measuring up to 250 square miles (400 square kilometers) have sloughed off the ‘megaberg’ known as A23a. Smaller pieces float freely in the surrounding waters too, many of them still big enough to threaten ships.

    The iceberg’s disintegration has reduced its total area to 683 square miles (1,770 square kilometers), according to an Agence France-Presse analysis of satellite images captured by the European Union Earth observation monitor Copernicus. It could disappear completely within weeks.

    Andrew Meijers, a physical oceanographer from the British Antarctic Survey, told AFP that A23a was “breaking up fairly dramatically” as it drifted further north. “I’d say it’s very much on its way out…it’s basically rotting underneath,” he said. “The water is way too warm for it to maintain. It’s constantly melting.”

    End of the line

    This could mark the end of A23a’s 40-year-long journey, which started when the iceberg broke off Antarctica’s Filchner Ice Shelf in 1986, according to the U.S. Geological Survey. It remained grounded on the bottom of the Weddell Sea for more than 30 years before detaching and beginning its slow drift northward in 2020. Over the next four years, A23a followed the Antarctic Circumpolar Current on a path known as “Iceberg Alley” and then became trapped in an ocean vortex near the South Orkney Islands in April 2024.

    After finally breaking free eight months later, the iceberg resumed its journey north. In March, it ran aground near the Southern Ocean’s South Georgia Island, sparking fears that it could disrupt large colonies of penguins and seals. Fortunately, it dislodged in May, drifting around the island and northward again.

    As A23a has encountered huge waves and increasingly warmer waters, it’s been crumbling into the ocean. Losing half its size in a matter of months is staggering, but most icebergs never make it this far from the frigid waters of Antarctica, Meijers said. “This one’s really big so it has lasted longer and gone further than others,” he explained.

    Still, A23a is shrinking faster than new ice can form. “I expect that to continue in the coming weeks, and expect it won’t be really identifiable within a few weeks,” Meijers said. It’s unclear how much water this megaberg contained at its peak, but the similarly sized A68a dumped more than 1 trillion tons of fresh water into the ocean during its lifetime.

    A warning sign

    Contrary to popular belief, melting icebergs—even giants like A68a and A23a—don’t raise global sea levels. That’s because they’re already floating in the ocean. However, their rapid disappearance is a clear sign of rising global temperatures, which do contribute to sea level rise by accelerating glacial melt.

    Recent research estimates that Antarctica’s ice sheet could raise global sea levels 11 inches (28 centimeters) by 2100, and potentially more if we surpass certain warming thresholds. That said, much remains unknown about the processes that underlie accelerated sea level rise. Despite uncertainties in future projections, the disappearance of Antarctic behemoths like A23a serves as a stark reminder of how rapidly humans are reshaping this critical region.

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    Ellyn Lapointe

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