‘Serious threat’: giant iceberg on collision course with UK island

The world’s largest iceberg, known as A68a, is approaching the British Overseas Territory of South Georgia in the South Atlantic Ocean.

The iceberg has drifted about 4,000 km north from Antarctica to the large isolated island, which lies between the bottom of South America and South Africa.

The Antarctic ice giant is similar in size to the island, and there is a great chance that the iceberg could land and anchor off the coast of the wildlife refuge.

If that happens, it poses a serious threat to local seals and penguins.

The animals’ normal feeding routes could become blocked, preventing them from properly feeding their young.

And it goes without saying that all creatures living on the seafloor would be crushed where A68a landed, a disturbance that would take a long time to reverse.

“Ecosystems can and will recover, of course, but there is a danger that if this iceberg gets stuck it could be there for 10 years,” said Professor Geraint Tarling of the British Antarctic Survey.

“And that would make a huge difference, not just to the South Georgia ecosystem, but to its economy as well.”

The British Overseas Territory is a kind of graveyard for the largest icebergs in Antarctica.

These tabular giants rise from the white mainland in strong currents, only to have their keels caught in the shallow waters of the continental shelf surrounding the remote island.

Over and over, it happens. Huge ice sculptures that slowly fade at the sight of the earth.

A68a, which looks like a hand with an accusing finger, has been roaming this “iceberg alley” since it was liberated from Antarctica in mid-2017. It is now only a few hundred kilometers southwest of South Georgia.

More than twice the size of Stewart Island (1746 km2), the iceberg reaches more than 4200 km2 and weighs hundreds of billions of tons. But its relative thinness – a submerged depth of perhaps 200 meters or less – means that it has the potential to drift down to the South Georgia coast before anchoring.

“A nearby iceberg has massive implications for where land predators might forage,” Tarling said.

“When you talk about penguins and seals during the period that is really crucial for them, during the rearing of the cubs and chicks, the actual distance they have to travel to find food really matters. If they have to make a big detour, it means that they will not return to their young in time to prevent them from starving in the meantime. “

When another colossal iceberg, A38, landed in South Georgia in 2004, countless dead penguin chicks and baby seals were found on local beaches.

The British Antarctic Survey researcher is trying to organize resources to study A68a in South Georgia, in case it does its worst and lands in one of the key productive areas for wildlife and the local fishing industry.

The potential impacts are multifaceted and not all negative, he emphasizes.

For example, icebergs bring with them huge amounts of dust that will fertilize the oceanic plankton around them, and this benefit will cascade up the food chain.

Although satellite images suggest that A68a is on a direct path to South Georgia, it could still escape capture. Anything is possible, says the team’s mapping and remote sensing specialist Dr. Peter Fretwell.

“The currents should take it in what looks like a strange loop around the southern tip of South Georgia, before turning it along the edge of the continental shelf and backing northwest. But it is very difficult to say precisely what will happen. “

His colleague, Dr. Andrew Fleming, said a request was being sent to the European Space Agency for more satellite images, particularly of his pair of Sentinel-1 radar spacecraft.

This imaging scan works at wavelengths that allow them to see through the cloud, which means they can track the iceberg regardless of weather conditions.

“A68a is spectacular,” Fleming said. “The idea that it is still in a large piece is really remarkable, particularly given the huge fractures you see running through on radar images. I was hoping it was already broken.

“If you go around South Georgia and head north, it should start to break down. It will get to warmer waters very quickly, and the wave action, especially, will start to kill it.”