While monitoring the A68A Antarctic iceberg from space, scientists found that when it melted around South Georgia, Antarctica, it released a large amount of fresh water. According to a new study, when the giant iceberg A68A melts in 3 months of 2020/2021, 152 billion tonnes of fresh water – the equivalent of 20 Loch Ness or 61 million Olympic-sized swimming pools – enter the waters around South Georgia's sub-Antarctica.
In July 2017, the A68A iceberg broke off the Larsen-C ice shelf on the Antarctic Peninsula to begin its three-and-a-half-year, epic 4,000-kilometer journey through the Southern Ocean. With an area of 5,719 square kilometers, it is a quarter of the area of Wales, and was the largest iceberg on Earth at the time of formation and the sixth largest iceberg on record. Around Christmas 2020, the iceberg received widespread attention as it drifted worryingly off South Georgia, raising concerns that it could damage the island's fragile ecosystem.
Using satellite measurements, researchers from the Centre for Polar Observation and Modelling (CPOM) and the British Antarctic Survey (BAS) mapped how the area and thickness of the A68A iceberg changed throughout its life cycle. The authors suggest that the iceberg has melted during the drift, enough to avoid damaging the seafloor around South Georgia due to stranding. However, one side effect of the melting is the release of 152 billion tons of fresh water near the island – a disturbance that could have far-reaching implications for the island's marine habitat.
For the first two years of its life, the A68A had been close to Antarctica, barely experiencing melting in the cold waters of the Weddell Sea. However, since it began to cross the Drake Strait northward, it has crossed warmer and warmer waters and begun to melt. Overall, the iceberg has been reduced by 67 meters from its original thickness of 235 meters, and the rate of melting has risen sharply as the iceberg drifts in the Scott Sea around South Georgia.
Laura Grish, a geographic information systems and cartographer at BAS and co-author of the study, said: "The A68A is an absolutely fascinating iceberg, and we have been tracking it from its inception to its end. Frequent measurements allowed us to track every movement and rupture of this iceberg, which moved slowly northward, through Iceberg Alley, into the Scott Sea, and then it sped up to very close to South Georgia."