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Most people picture icebergs like big floating boulders in the ocean. Maybe they might be as large as a house. The famous iceberg was big enough to sink the Titanic in 1912. However, most people don't really consider icebergs too deeply, beyond some memes about having more beneath the water than above it. Yet, icebergs, especially in the southern oceans, are becoming an increasing threat as the Antarctic ice sheets break apart thanks to climate change.The Biggest BergRight now, iceberg A23a is floating about 180 miles (~290 kilometers) off the coast of South Georgia Island in the South Atlantic Ocean. It turns out, A23a is the largest iceberg in the Earth's oceans today and has been at sea since 1986 when it broke off from the Filchner Ice Sheet. It measures almost 50 miles (80 kilometers) from west to east and has an area of almost 1,300 square miles. That's bigger than Rhode Island! Ships that have passed near A23a have estimated the iceberg to be ~1,300 feet (400 meters) thick. If the average amount of an iceberg above water is one-eight its total thickness, it sticks over 160 feet (50 meters) out of the ocean and holds ~320 cubic miles of water!This animated GIF shows the slow northward motion (and rotation) of Iceberg A23a in the South Atlantic Ocean over January 2025. Credit: NASA.A23a had been stuck in a current above a seamount north of Antarctica, but recently it broke free and is now drifting slowly northward, melting and breaking apart some as it goes towards South Georgia Island. Not many people live on South Georgia with a seasonal population of almost 30 (yes, 30) people who are mostly part of the British Antarctic Survey. It is likely most famous for being the island that Ernest Shackleton and his companions landed with the James Caird in 1916 after the loss of the Endeavor. The island itself is roughly the same size as New York's Long Island, but instead of people it is covered in glaciers and mountains.Ice in the WayAlthough South Georgia Island doesn't host many people, it does host abundant wildlife. Penguins, albatross, whales, seals and more frequent the island and the surrounding waters. The area was designated a wildlife protected area by the British government to help manage ecotourism to South Georgia Island to preserve this unique location into the future.Undated image of iceberg A23a taken by Landsat 9. Credit: US National Ice Center.However, if A23a continues northward, all that ice might disrupt life for all these animals on or near the island. The possibility exists for the iceberg to collide with the island, but a more likely scenario is A23a will break apart as it reaches warmer air and water. Yet, it could still inundate South Georgia Island with a massive volume of ice that could run aground on the shallow seabed around the island disrupting feeding grounds for birds, seals and other Antarctic wildlife as well as fishing grounds.This isn't the first time an iceberg has been on a collision course with the island. Back in 2020, another huge iceberg called A-68A was headed towards the island and got as close as 30 miles before it broke apart into smaller icebergs. A-68A was even bigger than A23a, reaching 100 miles across at its widest. Prior to A-68A, another large iceberg (A-43B) headed towards South Georgia Island in 2004, but it, too, broke apart and drifted around the island. Even if it does break apart, the influx of that much fresh water into the seas around the island could affect plankton and other microorganisms.Shrinking Ice CoverThe extent of Antarctica ice from 2023-2025 with a 10 year average, showing how the extent of ice is shrinking. Credit: US National Ice Center.With the increasing temperature on the planet, we should expect more large icebergs in the oceans as ice sheets at both poles break apart. Although it is tempting to think that the icebergs will harmlessly melt away, they can have very profound impacts on seaways. The US Coast Guard keeps track of the locations of icebergs in the northern oceans to keep ocean-going vessels safe from the fate of the Titanic. Moreover, as with South Georgia Island, the potential danger to ecosystems will increase as more of these monstrous chunks of ice break free. We'll just have to wait and see what A23a will do as it continues its northward journey.
