Twice the size of Greater London: World's largest iceberg sets sail

The world's largest iceberg, A23a, which had been trapped in the Weddell Sea for over 30 years, is now moving northward towards the Southern Ocean. On Friday, the British Antarctic Survey (BAS) announced that it is now being carried further north, according to reports by The Independent.

Iceberg A23a boasts an area of approximately 3,900 square kilometers (1,500 square miles), making it more than twice the size of Greater London and 40 times the area of the city of Lisbon. Its impressive dimensions include a thickness of 400 meters (1,212 feet), almost twice as tall as Spain's tallest building, Torre de Cristal, which is 249 meters tall, as reported by Diario AS.

Originally separating from Antarctica in 1986, A23a became anchored on the seabed of the Weddell Sea, where it remained static for over three decades. The depth of the iceberg caused its lower part to become grounded on the seabed, preventing it from moving with ocean currents.

In 2020, A23a began its slow journey northward after remaining motionless due to its depth, which caused it to ground on the seabed. Its movement was delayed when it became trapped in a Taylor Column—a rotating water phenomenon that traps large objects in currents above a seamount—causing it to spin in place, as reported by WION. In the spring of 2023, it was observed rotating around itself near the South Orkney Islands, according to BBC News.

After breaking free from the Taylor Column, A23a has embarked on a new journey across the Southern Ocean. Scientists anticipate that it will continue its journey following the Antarctic Circumpolar Current, which moves one hundred times more water than all the rivers on the planet. This current is likely to drive it towards the sub-Antarctic island of South Georgia, as reported by The Independent.

Researchers are closely monitoring iceberg A23a's movement to understand its influence on the environment and potential impact on the local ecosystem. Dr. Andrew Meijers from the British Antarctic Survey expressed excitement about A23a's movement, stating, "It's exciting to see A23a on the move again after periods of being stuck," according to The Independent. He noted that scientists are particularly interested in whether it will follow the same route taken by other large calved icebergs from Antarctica.

Biogeochemist Laura Taylor, also from the British Antarctic Survey, is studying the ecological impacts of iceberg A23a. "We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas," she explained, as reported by The Daily Galaxy. "What we don't know is what difference particular icebergs, their scale, and their origins can make to that process," Taylor added.

The RRS Sir David Attenborough vessel is actively studying A23a's impact on the surrounding environment. By collecting seawater samples from areas ahead, adjacent to, and behind the iceberg's path, researchers hope to assess its effects on ocean productivity, nutrient availability, and biodiversity.

As A23a drifts northward, it is expected to encounter warmer waters near South Georgia Island, causing it to break into smaller icebergs and eventually melt completely. The melting process is expected to take time but will have important ecological consequences. The nutrients released by melting icebergs can support plankton blooms and create thriving ecosystems in surrounding waters.

Satellite images have shown that large chunks are already falling off A23a into the sea, with some fragments the size of football fields, according to Diario AS.

While some may immediately turn to blame global warming for A23a's breaking off from the Antarctic mainland, experts note that not everything can be attributed to it. "Iceberg A23a comes from a part of Antarctica that is still very cold, where the calving of large ice blocks is natural," reported Diario AS. In other parts of Antarctica, warmer conditions have triggered whole-shelf collapse, producing a large number of icebergs.

A positive aspect of A23a's melting is that it will release mineral dust that was trapped inside when it was part of a glacier. In the open ocean, this dust becomes a source of nutrients for the organisms that form the base of ocean food chains, according to Daily Express.