"Mega" iceberg releases 152 billion tons of fresh water into ocean

When the massive A68A iceberg snapped off its ice shelf in July 2017, it was the sixth-largest iceberg on record. Now more than half of it is gone. 

A study published on January 10 in the journal Remote Sensing of Environment shows that the massive block of ice had broken off from Antarctica's Larsen Ice Shelf in 2017 and traveled northeast to South Georgia by 2021. The iceberg once measured roughly 5,719 square kilometers — nearly half the size of Connecticut — but it started to disintegrate once it arrived to the South Georgia island in the Atlantic Ocean. 

The European Space Agency described it as a "mega" iceberg, saying it stayed relatively the same size for the first two years of its life as it stayed in the cold waters of the Weddell Sea near the Antarctic Peninsula. Then it started its "epic" journey across the Drake Passage, ESA said, and everything changed.

As of January 2021, it had lost roughly 3,200 square kilometers, or more than half of its area. Now, it's a little bigger than Rhode Island.

Researchers from the University of Leeds, Centre for Polar Observation and Modelling and British Antarctic Survey studied the iceberg through satellite imagery and found that throughout those years of travel the iceberg became smaller as it broke apart and gradually melted. Over its three-and-a-half-year journey, it's estimated that the iceberg lost roughly 544 cubic kilometers of its ice, about a third of which was due to basal melting. 

In the time it's been around South Georgia, researchers found, the iceberg released roughly 152 billion tons of fresh water and nutrients into the ocean over the course of about three months. That amount of water could fill roughly 61 million Olympic-sized swimming pools. 

This significant loss could result in "potentially impacting the island's rich ecosystem," the study says. 

One of the concerns observers had was that the iceberg would collide with the seafloor near the island. Researchers found, however, that the closest the iceberg got to the island was about 38.5 miles offshore in December 2020. While A68A did not ground itself on the seafloor, researchers aid, it's likely that it did hit the floor in some of the shallower areas as it turned, and is believed to have affected "only a small area." 

It is possible, however, that other icebergs could end up grounded in the area in the future, which could potentially destroy organisms that reside on the seafloor . A grounded iceberg can also disrupt ocean currents and making it difficult for the island's penguins to feed in the sea, researchers said.

The study's lead author Anne Braakmann-Folgmann said in a statement that the berg released a "huge amount of melt water." She told CBS News that it's too early to say what the specific impact of A68A will be, but that generally, cold freshwater from icebergs changes the physical properties of ocean water around it, and releases nutrients that can "foster biological production." 

South Georgia and the South Sandwich Islands are a "haven for wildlife," according to their government, serving as home to roughly 5 million seals and 30 different bird species, a third of which are considered threatened or near-threatened. 

The waters surrounding the islands are also a critical area for migrating whales, fish and Antarctic krill populations, which according to the government, are a "key link" in the Southern Ocean food web. 

"In this case, the penguins, seals and whales feeding in the waters around South Georgia could benefit from more food availability," Braakmann-Folgmann said. "And especially the penguins and seals, who are raising their offspring on the island are dependent on food sources nearby." 

Researchers added, however, that the melting could potentially alter the ocean properties in a way that also impacts currents, which could, in the "worst case," divert krill, a crucial source of food for whales, away from the island. Studies on the matter are still ongoing.