The largest iceberg in the world has broken free — and is on the move

With a surface area about 30 times larger than the area of ​​Lisbon (or twice that of the island of Madeira), A23a is the largest iceberg on the planet. After breaking free from the Filchner-Ronne ice shelf in 1986, this year it stopped and was left spinning in a vortex. Now, it’s on the move again.

The frozen colossus is now moving through the Antarctic seas, after spending the last few months going in circles.

His first decades of freedom were anticlimactic: A23a was anchored to the bottom of the sea.

Until finally, in 2020, it began to advance towards the Southern Ocean, only to run out of water at the beginning of this year.

These specific oceanic vortices are known as Taylor columnscaused by the presence of underwater mountains. The resulting circulating currents may make it difficult to release most icebergs, but in fact the A23a achieved it.

Having escaped the imprisoning Taylor column, the A23a, with a mass of one billion tonscould advance to the next phase of a journey that scientists continue to follow closely.

“It’s exciting to see the A23a in motion again after periods in which he was imprisoned”, says the oceanographer Andrew Meijersdo British Antarctic Survey (BAS).

These periods include more than three decades of immobilization in the Weddell Sea, trapped by its own size and weight on the ocean floor. A23a’s halted progress has significantly slowed its melting.

At the end of last year, the mega-iceberg moved againfollowed by ESA’s Copernicus Sentinel-1 satellite. At the same time, scientists were able to observe A23a more closely, collecting samples from the surrounding waters.

We know what icebergs can do a huge difference at the levels of carbon and nutrients in water as they melt, which in turn affects food chains and aquatic life beneath the waves.

“We are interested in seeing will follow the same path than the other large icebergs that broke off Antarctica,” says Meijers. “And, most importantly, which the impact it will have on the local ecosystem“.

The team predicts that winds and currents carry the A23a to the Southern Ocean, following the Antarctic Circumpolar Current. This will take you closer to an area known as “iceberg alley,” which tends to be where the biggest icebergs end up.

As it heads towards the island of South Georgia, A23a is expected to reach warmer waters and melt faster. This means that everything picked up from the rocky bottom of the ocean and all the dust accumulated on its surface will be released into the water.

Taking into account its scale, it is difficult to predict the consequences of the thaw of A23a, but previous studies have shown that increased iron from melting glaciers can increase phytoplankton levelsfor example, retaining part of the CO₂ da atmosfera

All of this has to be weighed against the potentially catastrophic downsides of major melting at the poles – downsides that include sea ​​level rise and habitat loss for the animals that live in and around these glaciers.

A new one, published this month in Naturehas also just linked the decrease in Antarctic sea ice to the increase in ocean storms.

“We know that these giant icebergs can provide nutrients to water that they cross, creating thriving ecosystems in areas that would otherwise be less productive,” he says. Laura TaylorBAS biogeochemistry.

“What we don’t know is the difference what certain icebergs, their scale and their origin can do to this process”, concludes the researcher.