The world’s largest iceberg has been engaged in unusual behavior in recent months that has left some glaciologists dizzy.
Four years ago, A23a, the world’s most massive iceberg, managed to free itself after more than three decades spent anchored to the Antarctic sea floor.
Now, after striking out on its maiden voyage into open waters, satellite imagery of the gigantic iceberg has revealed something odd: the huge ice formation appears to be spinning in circles.
The Spinning Era of the World’s Largest Iceberg
“The A23a megaberg is in its spinning era,” read a statement posted to the official Instagram channel of the British Antarctic Survey (BAS).
“These dance moves down ‘iceberg alley’ are part of the iceberg’s long, melty journey into warmer waters,” the statement read, emphasizing the iceberg’s massive size.
“[T]his is the biggest iceberg in the world, around the size of Cornwall or Rhode Island,” the posting read.
According to the BAS, A23a began its journey last December and is following a track similar to that of other massive icebergs drifting in the Earth’s southernmost ocean waters.
The BAS statement confirmed that A23a has been spinning for over a month now on the opposite side of South Scotia Ridge from the location of its icy cousins, A76 and A68a.
A23a was initially attached to the Filchner Ice Shelf, which it broke away from in 1986. Although A23a remained attached to a sandbank for many decades after its separation, in 2020, it finally became free and began to drift to sea.
Although spinning along its oceanic course, A23a has not undergone any significant changes in shape. However, several smaller fragments of ice reportedly have broken free and are also moving on a northeasterly course ahead of the iceberg.
Currently, the BAS says the spinning behemoth is continuing its rotations several hundreds of miles from its departure point on the Antarctic Peninsula. The iceberg’s progress has been charted since its departure by satellite imagery provided by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, which captured the large iceberg during its northward trek earlier this year (see image above).
As its icy dance continues, the BAS continues to monitor the iceberg’s movements, which it says are maintaining a rotation of about 15 degrees daily.
So why is the world’s largest iceberg spinning in the first place?
Trapped in a Taylor Column
The cause underlying the iceberg’s dizzying movements lies in what is called a Taylor column, which arises from the Coriolis effect, a phenomenon that causes the deflection of objects relative to their position in the Earth’s hemispheres. Taylor columns result from the perturbation of rotating fluids by a solid object, giving rise to the formation of columns that run parallel to the axis of rotation. Under these conditions, objects that move parallel to this axis within a rotating fluid will have a greater drag force exerted against it.
In the case of A23a, the influence of the Taylor column conditions has essentially captured it within an oceanic vortex, which induces its current spinning movement.
A23a’s spin may also represent the most significant real-world example of such phenomena ever observed in nature.
Presently, scientists are uncertain about how frequently Taylor columns naturally form in the ocean and how often icebergs become trapped by such vortex-like phenomena.
Despite showing no signs of significant structural changes or breakage, A23a is shrinking as it gradually melts while drifting through the ocean, a factor that could influence its spin as it continues its journey through Earth’s Southern Ocean.
Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.