After remaining grounded for more than 30 years, the world’s largest iceberg, A23a, has begun drifting into the Southern Ocean. This massive iceberg, which is almost twice the size of Greater London and weighs almost a trillion tons, broke off from Antarctica’s Filchner Ice Shelf in 1986. Since then, it has been stuck on the seabed near the South Orkney Islands in the Weddell Sea. It began its slow movement northward in 2020.
“It is exciting to see A23a moving again after being stuck for some time. We are interested to see whether it will take the same path that other large icebergs have taken that have broken away from Antarctica. And more importantly, What impact will this have on Earth’s local ecosystems,” said Dr Andrew Meares, an oceanographer with the British Antarctic Survey.
A23a trip
The journey of Iceberg A23a has been marked by fascinating scientific events. A23a was freed from Antarctica in 1986 but remained trapped in the bottom mud of the Weddell Sea for 30 years. It remained a stable “ice island” until 2020 when it finally began flowing again. Slowly at first, then it accelerated northwards and began moving towards warm air and water.
For several months, the iceberg was trapped in a rare marine phenomenon known as a Taylor Column, where swirling water over a seamount held it in place. This unusual phenomenon caused the A23a to veer in one spot, delaying its rapid flow northwards.
As A23a continues on its journey, it is projected to follow the Antarctic Circumpolar Current in the Southern Ocean. This current is likely to carry the iceberg towards the sub-Antarctic island of South Georgia. Once it reaches this region, A23a will encounter warm water, which will eventually cause it to break into smaller icebergs and subsequently melt.
Biogeochemist Laura Taylor, who was aboard a research ship, hoped scientists would be able to study the impact the melting and breaking of the giant iceberg A23a would have on the surrounding ecosystem.
“We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas,” Ms Taylor said.
“We don’t know what difference particular icebergs, their scale, and their origin might make to that process. We took samples of ocean surface water behind, right next to, and ahead of the iceberg’s path. They determined that “should help us understand what life might form around A23a and how this affects carbon in the ocean and its balance with the atmosphere,” she said.
