"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.

cbsnews.com