World’s biggest iceberg spins in ocean trap

The world’s largest iceberg, known as A23a, is captured on a rotating oceanic vortex north of Antarctica that could keep it from melting for years


1 1986: A23a calves off Filchner Ice Shelf, but quickly becomes grounded on sea floor

2 2022: Berg loses grip and starts moving across Weddell Sea

3 Apr 2024: A23a crosses into Antarctic Circumpolar Current – instead of heading towards warmer waters, it is trapped in Taylor Column, a massive rotating cylinder of water


ANTARCTICA

1 2 3
Filchner-Ronne Ice Shelf
Mar 2022
Weddell Sea
South Orkney
Current position
Antarctic Peninsula


Taylor Column: As current meets obstruction on seafloor, under right conditions, it can
separate into two distinct flows, generating mass of rotating water between them

In this instance, obstruction is 100km-wide bump on ocean bottom known as Pirie Bank

A23a: Rotating anti-clockwise by around 15 degrees per day

Berg has area of 3,600 sq km – twice the size of Greater London

Antarctic Circumpolar Current
South Orkney Islands
Pirie Bank
Rotating water
100km 60 miles


Sources: BBC, NASA, British Antarctic Survey
Pictures: IBCSO
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