Giant iceberg dumps 152 billion tons of fresh water off island

And that can have far-reaching consequences…

Remember Iceberg A-68? This iceberg broke off the Larsen C Ice Shelf in July 2017 and embarked on an epic journey across the Southern Ocean. However, researchers were a little concerned when A-68 appeared to be on a collision course with the sub-Antarctic island of South Georgia. Fortunately, it ended with a sizzle. Although it now appears that the iceberg has caused quite a stir. He has flooded the waters around the island with tens of billions of tons of fresh water.

For years the iceberg bobbed around and moved further and further north. In December 2020, the clump of ice then threatened to move alarmingly close to the island of South Georgia. Researchers were not convinced. Because if A68 were to stay on its current course, the iceberg could get stuck in the shallow waters off the coast of South Georgia. Not only would this damage the ecosystem on the seafloor, but it could also make life miserable for penguins and seals living there, blocking the path of these animals trying to hunt for food.

Fresh water

In the end, the story came to a screeching halt. An extremely strong current around South Georgia fortunately prevented a catastrophic coastal collision. But that doesn’t mean the danger was over. At the same time, the iceberg slowly melted away and broke into several pieces. It means that quite a bit of fresh water flowed into the surrounding ocean at the time. And now scientists are coming up with the straight forward numbers.

melt

Using satellite measurements from five different satellite missions, scientists have mapped how the iceberg’s surface area and thickness changed over its life cycle. By combining all the satellite measurements, the scientists were able to calculate how the iceberg’s volume changed and thus how much freshwater eventually ended up in surrounding waters. This shows that in the first two years of its life, while still in the cold waters of the Weddell Sea close to the original ice shelf, A-68 lost little ice. However, as the clump of ice began its heroic journey, it sailed through increasingly warming waters and slowly began to melt.

152 billion tons

In total, the famous iceberg, which was initially 235 meters thick, has become no less than 67 meters thinner. The researchers found that the melt rate increased notably when the iceberg entered the Scotia Sea, near the island of South Georgia. Ultimately, A-68 dumped a whopping 152 billion tons of fresh water near the island.

Visualization of the amount of freshwater dumped into surrounding waters by Iceberg A-68. That corresponds to a cube of about 5.3 x 5.3 above Manhattan in the American city of New York. Image: CPOM/ESA/Google basemap

This could have far-reaching consequences for the marine life around the island. That’s because melting icebergs not only dump meltwater, but also nutrients as they languish. This process affects the local ocean circulation and affects the prevailing ecosystems.

Effects

The waters around South Georgia are considered one of the most biologically rich places on Earth. The area is home to more marine species than the Galapagos and is one of the largest marine protected areas in the world. Moreover, many animal species in polar regions are highly adapted to their environment. Therefore, melting icebergs can have a major impact on the phytoplankton, which is at the bottom of the food chain. This, in turn, could affect krill – which eat phytoplankton – and be eaten by seals, penguins and whales.

The exact impact of the 152 billion tons of freshwater seeping into the waters around South Georgia is still largely unknown. “This is really an enormous amount of meltwater,” said researcher Anne Braakmann-Folgmann. “The next thing we want to learn is whether it has had a positive or negative impact on the ecosystem.”