Environment

Giant A-68 iceberg dumped 152 billion tonnes of freshwater into the sea

Giant A-68 iceberg dumped 152 ...
A satellite image of the giant iceberg A68, soon after it broke off from the Larsen C ice shelf
A satellite image of the giant iceberg A68, soon after it broke off from the Larsen C ice shelf
View 3 Images
A satellite image of the giant iceberg A68, soon after it broke off from the Larsen C ice shelf
1/3
A satellite image of the giant iceberg A68, soon after it broke off from the Larsen C ice shelf
A visualization of the amount of water released by the A-68A iceberg
2/3
A visualization of the amount of water released by the A-68A iceberg
A map of the journey of the A-68A iceberg
3/3
A map of the journey of the A-68A iceberg
View gallery - 3 images

The four-year saga of iceberg A-68 may be over, but its environmental impacts are still being assessed. A new study has calculated that the largest chunk, A-68A, released billions of tonnes of freshwater into the sea right near a marine nature reserve, which could have untold effects on the ecosystem.

In July 2017, A-68 broke off from the Larsen C ice shelf in Antarctica. Measuring 5,664 km2 (2,187 miles2), it was one of the largest icebergs ever recorded, and for about two years it floated around in the cold waters of the Weddell Sea, sticking close to the ice shelf. By early 2020 it had started drifting north into the open waters of the Drake Passage.

Later that year a large chunk designated A-68A was found to be on a collision course with the island of South Georgia, an important conservation site. The fear was that the iceberg would become lodged on the shallow seabed and potentially stay there for up to a decade, disrupting the feeding and breeding habits of the seals and penguins that call the island home.

A map of the journey of the A-68A iceberg
A map of the journey of the A-68A iceberg

Thankfully, the berg drifted away from South Georgia and broke into smaller pieces, and by April 2021 the fragments had become too small to track. But its very presence might still have had an effect on the region – specifically, how much freshwater A-68A released into the ocean as it melted.

To investigate, a new study used data from five different satellite missions to chart the changes in the iceberg’s area and thickness over time. The team calculated the changing area of the iceberg using optical imagery from the Copernicus Sentinel-3 and the Terra missions, and radar from Sentinel-1.

The CryoSat and ICESat-2 missions were able to measure the iceberg’s freeboard, which is its height above the sea surface. From this figure, the icebergs’s thickness can be determined, and, when combined with the area measurements, its entire volume can be calculated.

The team found that by the time A-68A reached the shallow waters around South Georgia, it only extended 141 m (463 ft) below the surface, narrowly avoiding getting lodged on the seabed which is around 150 m (492 ft) deep.

A visualization of the amount of water released by the A-68A iceberg
A visualization of the amount of water released by the A-68A iceberg

The researchers also estimated that A-68A released around 152 billion tonnes of freshwater into the sea near South Georgia. This can influence ocean circulation, the occurrence of plankton and the feeding habits of other animals in the area, but the team can’t be sure entirely what these effects may be like.

“This is a huge amount of meltwater, and the next thing we want to learn is whether it had a positive or negative impact on the ecosystem around South Georgia,” said Anne Braakmann-Folgmann, lead author of the study. “Because A-68A took a common route across the Drake Passage, we hope to learn more about icebergs taking a similar trajectory, and how they influence the polar oceans.”

The research was published in the journal Remote Sensing of Environment.

Source: ESA

View gallery - 3 images
9 comments
9 comments
vince
Fascinating. Hopefully all of Antartica will melt into the seas and raise sea levels 220 feet. Goodbye florida. Goodbye Washington, DC. Goodbye New Orleans. Goodbye NY. Goodbye Tokyo. Goodbye 30% of all sea shore cities. It's time mother nature to teach mankind a lesson since it won't listen to logic then let it rip.
Rustgecko
It all seems very dramatic until you give it some context. This iceberg melted over many years, it was suddenly "dumped". While the iceburg seems big by human scales, compared to the 1.3 billion cubic kilometres of sea water in the oceans, its a drop in the ocean. Furthermore, (apart from the Red Sea) the antarctic oceans are the saktiest in the world, and any meltwater is instantly mixed into the surrounding salty oceans.
It seems dramatic, but don't panic.
TechGazer
I'm sure this sort of thing has happened many times in the past. Some local species might have reduced numbers or even get wiped out, and others would expand into the new ecosystem and even develop into new variants. There is no 'correct' ecosystem; it's constantly changing. Even our civilization's dramatic alteration of the ecosystem is, from one perspective, 'natural', since our intelligence is the result of natural evolution.
AlbertoCellini
If it was already in the water then there is no problem,if it melts it also shrinks therefore the level of the sea will not raise.
Steve Barry
I’m sure that isn’t any more fresh water than a cyclone dumps every year.
FatFrass
This is a reason why countries should continue to use salt to treat icy roads. Everything will balance out...
Christian Lassen
Think of all that freshwater that got pulled out of the ocean (making it saltier) just to form that ice in the first place. It's going back home.
christopher
"positive or negative impact" ? It will be negative, because otherwise nobody will publish anything about it.
TpPa
It was part of an ice shelf already in the ocean, it did nothing by itself by breaking off and floating away and melting -zero