The largest iceberg in the world travels at high speed

The massive iceberg A23a is drifting across the northern tip of the Antarctic Peninsula at an unusually high speed. An ETH professor says whether climate change has caused drift.

Bruno Nellwulf/Media

Photos of the massive iceberg A23a are spreading around the world. The Antarctic sea iceberg is drifting toward the South Atlantic like a driverless ghost ship. It is three times the size of New York City or four times the size of Berlin. Last week, the British research ship RRS Sir David Attenborough passed the giant iceberg on its research trip to Antarctica. Water samples were taken from the sea surface along the path along which glacier A23a moves.

Scientists want to know if the iceberg is providing nutrients to the sea as it passes. Because this may lead to new ecosystems. “The iceberg is large enough to have an impact on the atmosphere and especially on the ocean,” says Nicola Gruber, professor of environmental physics at ETH Zurich.

These include physical changes such as the effect on temperature, but also on turbulence in the sea. Winds are also affected. Because A23a covers an area of ​​4,000 square kilometres, vertical shifts in the ocean occur, affecting the availability of nutrients. “The melting iceberg itself also brings with it nutrients. Especially iron, which is in short supply in the Southern Ocean. This is all crucial for biological productivity,” says the ocean climate specialist. However, these are not permanent changes, but temporary ones. in the first place.

No sign of climate change

Some will interpret the broken iceberg as a sign of ongoing global warming, oceans and climate change. But that’s not the case, Gruber says. “A23a exploded in the 1980s, at a time when ocean warming or global warming was still very small compared to today.” In 1986, A23a broke off the Filchner Ice Shelf, but remains stuck on the seafloor for the time being. The iceberg ended up stranded in the Weddell Sea and remained there for more than 30 years. The first movements were detected in 2020, until A23a recently broke away from the seafloor and is now moving relatively quickly with ocean currents towards the South Georgia island group located in sub-Antarctica.

The size of the iceberg, weighing nearly a trillion tons, is extraordinary. “It’s definitely one of the largest icebergs in the world, maybe No. 2 or 3,” says Nicola Gruber, a professor at ETH. “But very large ice sheets keep breaking off from the Filchner Ice Sheet.”

This separation after a long period of rest and journey north is what makes A23a interesting to scientists, Gruber says. Because it is very rare for an iceberg of this size to move. Therefore his route is closely monitored. Maybe it will fall apart into pieces. However, if the A23a manages to bypass South Georgia unscathed and then travels north into South Africa, it could become a problem for freight traffic. (aargauerzeitung.ch)