The largest iceberg in the world is moving at high speed

The images of the enormous iceberg A23a are going around the world. The iceberg floats in the Antarctic Sea towards the South Atlantic Ocean like a ghost ship without a driver. Its area is three times that of New York City or four times that of Berlin. Last week, the British research vessel “RRS Sir David Attenborough” passed the gigantic iceberg during its research trip to Antarctica. Water samples were taken from the sea surface along the route along which iceberg A23a moves.

The scientists want to know whether the iceberg supplies nutrients to the sea during its passage. Because that could lead to new ecosystems. “The iceberg is big enough to have an impact on the atmosphere and especially on the ocean,” says Nicolas Gruber, professor of environmental physics at ETH Zurich.

Consider physical changes such as the influence on temperature, but also on turbulence in the sea. The wind is also affected. Because the A23a covers an area of ​​4,000 square kilometers, vertical shifts occur in the ocean, which affect the availability of nutrients. “The melting iceberg itself also brings nutrients with it. Especially iron, which is scarce in the Southern Ocean. “This is all crucial for biological productivity,” says the ocean climate specialist. However, these are not permanent, but mainly temporary changes.

Some will interpret the broken iceberg as a signal of continued warming of the planet, the oceans and climate change. But that is not the case, says Gruber. “A23a broke down in the 1980s, at a time when ocean or global warming was still very small compared to today.” In 1986, the A23a broke away from the Filchner Ice Shelf, but remained attached to the seabed for the time being. The iceberg eventually beached itself in the Weddel Sea and remained there for more than thirty years. The first movements were observed in 2020, until A23a recently broke away from the seabed and is now moving relatively quickly with ocean currents towards the sub-Antarctic archipelago of South Georgia.

The size of the iceberg, which weighs almost a trillion tons, is extraordinary. “It is certainly one of the largest icebergs in the world, probably number 2 or 3. But extremely large ice sheets continue to break off from the Filchner ice sheet,” says ETH professor Nicolas Gruber.

This detachment after a long period of rest and the journey north makes the A23a so interesting for scientists, says Gruber. Because it is extremely rare for an iceberg of this size to be in motion. His path is therefore closely monitored. Maybe it will fall into pieces. However, if the A23a makes it past South Georgia undamaged and further north into South Africa, it could even become a problem for shipping traffic. (aargauerzeitung.ch)