Antarctica's A68a iceberg, the continent's sixth-largest in recorded history, is still floating more than a year after it broke off. It weighs about 1 trillion tons, is about the size of Maryland, and is mostly intact. However, the ice block just made a big and fatal turn.
- 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.
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
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.
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.