Featured picture: The long journey of the iceberg A-68A

Iceberg A-68A
Iceberg A-68A south of the South Orkney Islands. (Image: NASA Earth Observatory)

Three years ago, this 150-kilometer iceberg broke off the Larsen C ice shelf in the Antarctic – since then it has drifted through the Southern Ocean. At the moment, however, he seems to be stuck in a kind of vortex that slowly turns it around its axis.

In July 2017 the time had come: For months, an ever longer, 100-meter-wide crack had formed in the Antarctic Larsen-C ice shelf, now this crack also separated the last connection. As a result, a 5,800 square kilometer piece of ice broke off – this corresponds to around twelve percent of the total area of ​​this ice shelf. The resulting table iceberg weighed around a trillion tons and was one of the largest ever observed.

This A-68A baptized table iceberg is now around three years old – and is still in surprisingly good shape, as can be seen from this image of the MODIS instrument from NASA’s Terra satellite. It shows A-68A about 230 kilometers south of the South Orkney Islands (top right in the picture). This icy colossus has already covered a distance of around 800 kilometers from its birthplace in the Larsen-C Ice Shelf.

However, his journey was not exactly straightforward: in his first year at sea, the iceberg covered only 45 kilometers because the currents kept drifting it back and forth. The A-68A collided several times with rocky outcrops and peninsulas along the West Antarctic peninsula. Only then did the Tafeleisberg get into a steady north current, which then drove it further into the south ocean.

In the past few weeks, however, the A-68A seems to have come to a standstill again: As current satellite images show, the giant iceberg is almost on the spot and is slowly turning around its own axis. Researchers suspect that the iceberg has landed in a whirlpool, a local circular current. “We have seen this with other icebergs downstream from the West Antarctic Peninsula,” explains Christopher Readinger U.S. National Ice Center. “Then they seem to start turning out of the blue.”

When the journey for A-568A continues is still unclear. But the researchers are certain that it will soon get out of the vortex into the strong Antarctic circumpolar current. This will then drive the iceberg relatively quickly further north into the South Atlantic – one of the large iceberg “cemeteries” in the South Ocean. Because in the warmer water of this sea region, the icebergs melt, break and finally dissolve.

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