There is growing concern over a collosal iceberg on a collision course with the British territory of South Georgia, a largely uninhabited South Atlantic island of roughly the same size. 

Measuring 158 kilometers long (98 miles) and 48 kilometers wide, A68a — as the iceberg is called — is believed to be the biggest currently in the southern ocean, and one of the largest on record. 

As the iceberg has moved closer to the island over the past weeks, aerial images have shown it breaking up. This has sparked concern over the impact of freshwater from the melting ice on local marine life. 

"This is basically an area that's completely thriving with wildlife," Geraint Tarling, a professor with the British Antarctic Survey (BAS), told DW. "The island has globally significant populations of penguins and seals ... Enormous numbers that if they were not there anymore, there would be severe declines in quite a few species."

Scientists are due to set off for the region next month on the research ship RRS James Cook to assess the impact on local biodiversity. The waters around the island are home to recovering populations of humpback and blue whales. South Georgia is also home to one of the largest numbers of albatrosses in the world.

Two underwater robotic gliders will be used to get as close to the iceberg as possible to measure water temperature, salinity and plankton concentrations. 

'Iceberg graveyard'

Scientists had expected A68a to shatter after breaking off from the Larsen C ice shelf on the east coast of the Antarctic peninsula in summer 2017. 

According to the European Space Agency (ESA), the icy giant has lost at least two large chunks during its long journey, prior to which it was roughly twice the size of Luxembourg. 

Although A68a would be the biggest to hit the island, it would not be the first in the region named the "iceberg graveyard." In 2004, a smaller iceberg grounded a few kilometers from land. 

What is particularly concerning about this one is not only its size but its shallow shape, explained Tarling. According to ESA, the iceberg is only a few hundred meters thick.

"This one has the potential to go right on the shore and really block those [animal] colonies from getting to their food sources and coming back to get the food back to their pups and chicks.” 

In addition to preventing access to foraging paths to offshore food sources for penguins, seals and albatrosses, it could also disrupt conditions for marine algae at the base of the food chain, said Tarling. "And if that's not there, then everything that depends on it can't thrive either.”  

The iceberg could also impact creatures on the ocean's floor, he added, many of which store carbon in their bodies and secure it in the seabed. "If this is scoured, it gets churned up, it goes back into the water column and then goes back into the atmosphere potentially.”   

Currents will decide iceberg's path

While still traveling through the water, icebergs of A68a's size can also have a positive environmental impact through the meltwater they produce, said Grant Bigg, professor in earth systems science at the University of Sheffield in northern England.

Bigg said the icebergs can release plumes of material, sometimes hundreds of kilometres long, which contain iron, picked up while the ice moved over land before reaching the ice shelf. This can fertilize the ocean and support organisms such as phytoplankton.

If the iceberg, which has already traveled an estimated 1,600 kilometers, continues on a direct trajectory at its current speed of one kilometer per hour, BAS predict it could arrive at the island between late December and early January. 

"It's too large to really do anything about it," said Bigg. "It's a case of waiting and seeing, and hoping the currents will send it around the south [of the island] or break it up."