Iceberg dumps 132 billion tonnes of water into the ocean
After the world’s largest iceberg snapped off the Antarctic Peninsula in July 2017, it drifted north on a three-year death march, shedding an unfathomable amount of meltwater into the sea. Now, a recent study of the doomed iceberg, named A-68A, reveals just how much water the megaberg actually lost. Using observations from five satellites, the study authors calculated how much the iceberg’s area and thickness changed as it drifted north through Antarctica’s Weddell Sea and into the relatively warm waters of the Scotia Sea. While the berg headed towards South Georgia Island, iceberg A-68A lost more than 138 billion tonnes of fresh water in just three months, a mass equal to an incomprehensible volume of water that could fill more than 60 million Olympic-sized swimming pools. “This is a huge amount of meltwater, and the next thing we want to learn is whether it had a positive or negative impact on the ecosystem around South Georgia,” said Anne Braakmannfolgmann, a researcher at the Centre for Polar Observation & Modelling in the UK. “Because A-68A took a common route across the Drake Passage, we hope to learn more about icebergs taking a similar trajectory and how they influence the polar oceans.”
When A-68A broke off the Larsen C ice shelf in northern Antarctica in July 2017, it measured about 2,300 square miles in area. The berg ranked as the sixth-largest iceberg ever observed on Earth and the single largest iceberg floating through the ocean during its 3.5-year life span. A-68A bumped through the chilly Weddell Sea for about two years, moving north at a glacial pace. During this time, the iceberg barely melted and lost little volume.
Only when A-68A drifted north into the Scotia Sea did the real mass loss begin. Once there, the iceberg’s melt rate increased by nearly eightfold as the comparatively warm waters lapped away at the iceberg’s base and edges. For three months between November 2020 and January 2021, the iceberg reached its peak melt rate, losing more than 136 billion tonnes of ice in that period.
By April 2021, iceberg A-68A had completely melted away. Even with the iceberg having vanished into the sea, its impacts on sea life may not be over. A-68A dumped fresh water into the salty sea around South Georgia Island, along with nutrients that could boost biological production, such as plankton populations. This boost could have widespread impacts on local food chains, though whether that will be a positive or negative in the long term is unknown.