After the world’s largest iceberg snapped off of 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 new study of the doomed iceberg (named A68a) reveals just how much water the infamous mega-berg actually lost and how that could impact the local ecosystem for generations to come.
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. There, while the berg appeared to be headed for a direct collision with South Georgia island, iceberg A68a lost more than 152 billion tons (138 billion metric tons) 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, according to the study authors.
“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,” lead study author Anne Braakmann-Folgmann, a researcher at the Centre for Polar Observation and Modelling in the U.K., said in a statement. “Because A68a 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 iceberg A68a broke off of the Larsen-C ice shelf in northern Antarctica in July 2017, it measured about 2,300 square miles (6,000 square kilometers) in area roughly large enough to hold the five boroughs of New York City five times over. 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.
A68a bumped through the chilly Weddell Sea for about two years, moving north at a (pardon the expression) glacial pace. During this time, the iceberg barely melted and lost little volume, the researchers said.
Only when A68a drifted north into the Scotia Sea did the real mass-loss begin. 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 150 billion tons (136 metric tons) of ice in that period.
Scientists feared that the still-massive iceberg would smash head-on into South Georgia island, a British overseas territory that’s home to large penguin and seal populations. Unlucky animals could have been crushed to death in the collision, while countless others could have lost access to their regular feeding and foraging routes, Live Science previously reported.
Fortunately, A68a never made landfall near the island but, the new study shows, it came perilously close. According to the team’s research, the iceberg collided briefly with the seafloor near South Georgia however, A68a had thinned so much by that point that it didn’t get stuck. By late December 2020, the iceberg began cracking into pieces, further reducing the risk to South Georgia’s animal populace.
By April 2021, iceberg A68a had completely melted away. In total, the icy object lost about 1 trillion tons (900 million metric tons) of ice in just over three years.
Even with the iceberg having vanished into the sea, the impacts on South Georgia island and the surrounding sea life may not be over, according to the study authors. As A68a dumped fresh water into the salty sea around the island, it also dumped nutrients that could boost biological production, possibly altering the types of plankton that thrive there. This boost could have widespread impacts up the local food chain, the researchers said though whether that will be a positive or negative in the long-term is yet to be seen.
The study was accepted for publication in the March 1 issue of the journal Remote Sensing of Environment.
Originally published on Live Science.
livescience.com, 23 January 2022