The gigantic iceberg A68 dumped more than 1.5 billion tons of fresh water into the ocean every day at the height of its melt.
To put this in context, it is about 48 times the amount of water used daily by all Brazilians (considering that each Brazilian consumes 154 liters of water daily, totaling around 32 million tons per day).
The A68 was, for a short time, the biggest iceberg in the world.
It covered an area of ​​nearly 6,000 km.2 when it broke free from Antarctica in 2017. But by early 2021, it had already disappeared.
A trillion tons of ice have melted.
Researchers are currently trying to assess the impact the A68 has had on the environment.
And a team led by the University of Leeds reviewed all the satellite data to calculate the dimensions of the gigantic iceberg as it traveled north from Antarctica, across the Antarctic Ocean and into the South Atlantic.
This allowed the group to assess the varying melt rates during the three and a half years that the iceberg was in existence.
One of the key periods was towards the end, as the A68 approached the warmer climates of the British Overseas Territory of South Georgia.
For a time, there were fears that the giant block could run aground in the shallow waters around it, blocking the routes of millions of penguins, seals and whales.
But that never happened because, as the team can now show, the A68 lost enough depth to remain afloat.
“It looks like it briefly touched the continental shelf. That’s when the iceberg made a turn and we saw a small piece break. But it wasn’t enough to bring down the A68,” Anne Braakmann-Folgmann of Leeds told BBC News.
“And I think you can see why in the thickness estimates,” said Andrew Shepherd, co-author of the study. “At that height, the keel of the iceberg was 141 m on average, and the bathymetry (depth) charts in the area showed 150 m. In the end, it was close.”
By April 2021, the A68 had broken into countless small fragments that could not be tracked. But its impacts on the ecosystem will be much longer-lived.
Giant, or flat-topped, icebergs are now recognized to have considerable influence wherever they pass.
The melting of these huge chunks of fresh water will alter local currents. And all the iron, other minerals and even organic matter picked up throughout their lives and later released into the ocean will go into biological production.
The British Antarctic Survey was able to place some robotic gliders in the vicinity of the A68 to monitor conditions before the ice mass completely broke apart.
The data retrieved from these and other instruments, while not yet fully analyzed, reveal some interesting features, according to biological oceanographer Geraint Tarling.
“We think there is a very strong signal in the changing flora of the phytoplankton species around A68, and also in the actual deposition of material in the deeper parts of the ocean. The particle sensor on the glider was picking up some very strong signals of deposition coming of the iceberg,” he told BBC News.
Details of the A68’s shape change and freshwater flows are contained in an article published in the journal Remote Sensing of Environment.
.
