Major Iceberg Keeps Cracking As It Approaches South Georgia

A-68A before shedding the three new pieces. Copernicus Sentinel data (2020), processed by ESA, CC BY-SA 3.0 IGO

Back in 2017, The Larsen C ice shelf lost a huge iceberg. A-68, as it was dubbed, was 12 percent of the whole ice shelf, with a surface area of 5,800 square kilometers (2200 square miles). For two years, this one-trillion-tonne chunk of floating ice remained local and shed a piece (A-68B), but 10 months ago moved to open waters beyond Antarctica. It lost another portion (A-68C) in April.

Over the last seven weeks, the iceberg began to approach South Georgia Island. The risk of it coming aground is serious and threatens communities of penguins, seals, and many species that live on the seafloor. Over the last week, the iceberg experienced several further break-ups.

Last week, an 18 kilometer (11 mile) long fragment dubbed A-68D broke off the main body, which is now known as A-68A. This breakup was likely due to the iceberg hitting the seafloor, which is only 200 meters (656 feet) deep where it was. Major cracks followed suit across the iceberg, and on December 22, two more large fragments broke off; A-68E and A-68F.

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A-68A is now half the size it once was, but it and its newly formed fragments remain a present danger to the island as they continue to follow the currents of the ocean.

“The iceberg is going to cause devastation to the sea floor by scouring the seabed communities of sponges, brittle stars, worms and sea-urchins, so decreasing biodiversity. These communities help store large amounts of carbon in their body tissue and surrounding sediment. Destruction by the iceberg will release this stored carbon back into the water and, potentially, the atmosphere, which would be a further negative impact,” Professor Geraint Tarling, an ecologist at British Antarctic Survey, said in a statement.

“However, whilst we are interested in the effects of A-68a’s new arrival at South Georgia, not all the impacts along its path are negative. For example, when travelling through the open ocean, icebergs shed enormous quantities of mineral dust that will fertilise the ocean plankton around them, and this will benefit them and cascade up the food chain.”

The path of A-68 over the years. contains modified Copernicus Sentinel data (2020), processed by ESA; Antarctic Iceberg Tracking Database. CC BY-SA 3.0 IGO

All the recent fragments are currently being sloshed about by the Southern Antarctic Circumpolar Current Front. This is a fast-moving stream of water that moves around South Georgia, and could put the four icebergs on a northernmost trajectory.

The iceberg will be studied up close by a British Antarctic Survey mission starting next month.

[h/t: BBC News]

The iceberg over the last few weeks. contains modified Copernicus Sentinel data (2020), processed by ESA, CC BY-SA 3.0 IGO

 

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