An iceberg 80 times the size of Manhattan could destroy a fragile South Atlantic ecosystem

One of the world’s largest icebergs is on a collision course with a South Atlantic island oasis, potentially threatening a rich ecosystem of wildlife including penguins, seals and krill.

The “A68a” iceberg, which broke off from Antarctica’s Larsen C Ice Shelf in July 2017, is currently cruising through open waters just a few hundred kilometers away from the British Overseas Territory of South Georgia.

If the 4,700 square kilometer (1,815 square mile) mass — greater than South Georgia itself — stays on its current path and reaches the island’s shores, scientists fear it could have a devastating effect on its wildlife populations for years to come.

Professor Geraint Tarling, Senior Biological Oceanographer at the British Antarctic Survey (BAS), told CNN that the iceberg could block seals and penguins from being able to access their normal feeding grounds at a time of year that is crucial for the colonies’ growth.

“If they have to make massive detours around the iceberg to make the same trip they normally would, they likely won’t be able to get back in time (to feed their young),” Tarling explained.

And because the iceberg is so huge, it could remain stuck on the island’s doorstep for years, potentially leading to catastrophic marine life population failure, he added.

Currently traveling at a speed of around 1 kilometer per hour, A68a could reach the British Overseas Territory in as little as three to four weeks if it travels in a straight line, Tarling said — though he explained that it was likely to take a more circuitous route.

South Georgia and the neighboring South Sandwich Islands (SGSSI) are home to approximately 5 million seals of four different species. Its surrounding waters serve as an important habitat for migrating whales and diverse fish populations, according to the local government.

As the iceberg moves closer to shore, it will “scour” the seafloor, killing off the diverse marine life that plays a critical role in balancing the global climate.

That’s because that marine life acts as a carbon sink. But if that wildlife is disturbed, the carbon will release into the water and ultimately into the atmosphere, Tarling explained, with the potential to “upset the balance for years to come.”

Scientists who have followed the A68a since it “calved” away from the Larsen C Ice Shelf more than three years ago say they are surprised by how intact it has stayed throughout its journey north.

Adrian Luckman, a glaciologist and professor of geology at  Swansea University told CNN that the “area-to-thickness ratio of A68a is approximately the same as a few sheets of copier paper stuck together, so it is remarkable that it has stayed pretty much intact despite over three years of drifting in the Southern Ocean.”

It has only been in the last year that the iceberg has picked up considerable pace, even acting as a positive fertilizing force as it makes its way through the ocean.

In open water, the iceberg is accumulating significant amounts of dust from the atmosphere that act as essential nutrients that open waters lack. But as soon as that mass hits the island’s shallow waters, it will have the opposite effect.

Shallow waters are already heavily fertilized and the iceberg’s excess fresh water and shading will prevent the growth of marine algae — the fuel that so much of that biodiverse marine life depends on.

While icebergs calving from glaciers is a natural process, the rate of melting and calving is getting faster.

The planet’s ice shelves are weakening due to human-induced warming of our oceans and atmosphere due to release of heat-trapping greenhouse gases.

CNN’s Amy Cassidy contributed to this report.