Antarctica’s large iceberg has made a fatal turn toward warmer waters

A photo of Antarctica’s
A-68 iceberg in September 2017.

Joshua
Stevens/NASA Earth Observatory; USGS

• A Maryland-size iceberg broke off Antarctica in July 2017.
• More than year later, iceberg A68a had floated a few
  dozen miles away from its birthplace.
• But A68a just made a fateful turn and should now wander
  north, where it will eventually break up and melt.
• The process may take a few years, though some large
  icebergs survive for
  decades.

One of the largest icebergs ever documented is still mostly
intact more than a year after it
broke off Antarctica, despite losing a
big chunk and having its northern flank smashed to bits.

However, a recent turn may prove fateful in speeding the
Maryland-size ice block toward its inevitable doom.

Iceberg A68, or A68a as it’s sometimes called (to denote it’s now
the parent of smaller icebergs), calved from Antarctica’s Larsen
C ice shelf in July 2017. It’s hard to say exactly when A68 was
born due to limited satellite coverage and thick cloud cover, but
it happened last year between July 10 and 12.

Scientists at the time estimated iceberg A68 to be about 1,000
feet thick and weigh 1.1 million tons — roughly the mass of

20 million Titanic ships.

Satellites in space have kept watch on the iceberg as it floats
in the Weddell Sea a few dozen miles off the ice shelf on the
Antarctic Peninsula. It’s lost about a city’s worth of area from
repeatedly smashing and grinding into the nearby ice shelf,
according to a blog post published in July by the
Project Midas research program.

However, a new animation shared by Adrian Luckman, a glaciologist
at Swansea University and a member of Project Midas, reveals that
strong winds have rotated the 100-mile-long ‘berg 90 degrees.

“Until recently, the iceberg was hemmed in by dense sea ice in
the East and shallow waters in the North around Bawden Ice Rise,”
Luckman wrote in a blog post on Wednesday,
adding that A68 has since rotated into the Weddell Sea. “Here it
is much more free to begin moving away and be carried further
North into warmer waters.”

Luckman put it more succinctly in a tweet on Monday: “Iceberg
A68 is on its way,” he said.

The time-lapse animation below comes by Luckman and was made
using Sentinel satellite image data. It shows part of the
Antarctic Peninsula from March 12, 2017 through September 3,
2018. You can see a huge crack in the Larsen C ice shelf creep
north until the iceberg completely breaks off in July 2017, then
begin a clockwise turn in August 2018.

What will eventually happen to iceberg A68

Red
lines illustrate the paths of previous Antarctic
icebergs.

NASA
Scatterometer Climate Record Pathfinder;
ESA

Antarctic icebergs calve naturally as snow piles up, forming
ultra-dense ice that gravity then drags toward the ocean.

From there, a predictable yet erratic story plays out.

Most icebergs that calve from the Antarctic Peninsula get caught
up in wind and water currents that drag them clockwise around the
Southern Ocean as they move north.

Scientists can’t be sure where iceberg A68 will ultimately float,
though some think it could drift more than
1,000 miles north to the Falkland Islands. The largest ‘bergs
can even reach South Georgia and the South Sandwich Islands
before vanishing.

Martin O’Leary, a researcher at Swansea University and Project
Midas,
said on Reddit last year that A68 could take a couple of
years to drift that far. Then it could be many years before it
completely melts. A68’s recent turn into the open Weddell Sea may
now accelerate that timeline, though.

In the case of B15, the second-biggest iceberg in recorded
history, the process has taken nearly two decades. B15 snapped
off Antarctica’s Ross ice shelf in 2000. It had a surface area of
4,200 square miles — twice that of A68. Today it’s drifting in
warm waters near South Georgia.

St.
Andrews Bay on South Georgia Island.

Shutterstock

Warmer air causes surface melt that “works its way through the
iceberg like a set of knives,” Kelly Brunt, a glaciologist at
NASA’s Goddard Space Flight Center, said in a NASA Earth Observatory post in October 2017.
“This is often the end of the life cycle of a lot of Antarctic
icebergs.”

Scientists continue to study and debate
what caused A68 to break off, including the role of climate
change driven by human activity.

“To me, it’s an unequivocal signature of the impact of climate
change on Larsen C,” Eric Rignot, a glaciologist at NASA JPL,

told CNN in July 2017. “This is not a natural cycle. This is
the response of the system to a warmer climate from the top and
from the bottom. Nothing else can cause this.”

This story has been updated with new information. It was
first published on July 10, 2018.