You might recall iceberg A68a, which gained some notoriety in 2017 after it detached from an ice shelf on the Antarctic Peninsula. It was one of the largest icebergs ever seen, measuring more than 100 miles long and 30 miles wide. It was hardly your typical iceberg.
An Extraordinary Iceberg Is Gone, but Not Forgotten
For a few years, the iceberg floated slowly through the icy Weddell Sea before gaining speed when it approached the Southern Ocean.
When we last heard from it, in 2020, it was approaching the South Atlantic island of South Georgia, much battered and diminished by a journey of more than a thousand kilometres.
Sadly, the old A68a is gone. It eventually did what all icebergs inevitably do last year, about 100 miles off South Georgia: it thinned so much that it broke up into microscopic bits and eventually floated off to nothingness.
A68a was Over 800 Feet Thick at its Thickest Point, But all But 120 Feet of that were Submerged.
Ecologists and others had worried that the iceberg would hit land close to South Georgia during its trip. It’s possible that prevented the numerous penguin and seal colonies from reaching their oceanic feeding areas.
That did not occur. According to new analysis, A68a probably only passed by a feature on the seafloor briefly before pivoting and continuing to travel till it broke apart.
But the investigation also discovered another potential threat from the iceberg to ecosystems around South Georgia. It melted from below, finally discharging a huge amount of fresh water into the sea close to the island as it passed through the relatively warm waters of the Southern Ocean into the South Atlantic.
The Influx of So Much Fresh Water could Harm Plankton and Other Organisms in the Marine Food Chain.
The researchers utilised satellite photos to track the iceberg’s shape and location during its journey. They were led by Anne Braakmann-Folgmann, a doctoral candidate at the Center for Polar Observation and Modeling at the University of Leeds in Britain.
It was named according to a convention established by the U.S. National Ice Center, which is a little less spectacular than the one used for storms, like previous enormous Antarctic icebergs.
The pictures demonstrated how the iceberg’s surface evolved over time. Using information from satellites that measure ice height, the researchers were also able to determine its thickness. When it split up, A68a was altogether more over 200 feet thinner, according to Ms. Braakmann-Folgmann.
A68a made its mark. The scientists estimated that melting in South Georgia caused the release of almost 150 billion tonnes of fresh water, and their findings were published in the journal Remote Sensing of Environment.
According to the experts, that is enough to fill an Olympic-size swimming pool 61 million times over; but, because the ice was already floating, its melting had no impact on sea level rise.
The water is not only fresh, not salty, but it also has a lot of iron and other nutrients in it. In order to ascertain the ecological effects of the iceberg and the meltwater, Ms. Braakmann-Folgmann is assisting a different team of researchers from the British Antarctic Survey.
The survey’s accompanying scientists were able to launch autonomous underwater gliders to collect water samples as the iceberg neared South Georgia.
On the island, they used monitoring devices on certain gentoo penguins and fur seals, to investigate whether the presence of the iceberg altered their foraging habits.
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Geraint Tarling, a biological oceanographer with the project, noted that preliminary findings from the tracking data revealed that the penguins and seals did not adjust foraging paths, as they might have had the iceberg blocked their way or harmed their prey.
The effects of the iceberg “are not as bad as we first anticipated,” Dr. Tarling said, “at least in the parts of the colonies that we watched.”
Dr. Tarling pointed out that there is still more data to be examined, particularly the water samples. According to him, a significant increase in surface freshwater could affect the variety of phytoplankton species that are readily available or interfere with phytoplankton growth at the bottom end of the food chain.
Complicating the analysis is that 2020, when the iceberg was nearing South Georgia, also occurred to be a poor year for krill, the small crustaceans that sit immediately above phytoplankton in the food chain. Thanks for reading our article An Extraordinary Iceberg Is Gone, but Not Forgotten.