World’s largest iceberg A23a resumes journey from Weddell Sea, Antarctica
The world’s largest iceberg A23a resumed its movement on December 13, 2024, after decades of being lodged on the seafloor.
Satellite imagery of Iceberg A23a recorded on December 13, 2024, showing its approximate dimensions of 74 x 59 km (40 x 32 nautical miles) at coordinates -42.12° latitude and -57.37° longitude in the Southern Ocean. The image shows the A23a's current position as it drifts northward. Image credit: US National Ice Center via Polar View, Sentinel-3 Mosaic, The Watchers
- The world’s largest iceberg, A23a, resumed its movement on December 13 after being trapped for decades on the Weddell Sea floor.
- Scientists are monitoring its northward drift toward South Georgia, where it is expected to fragment and release nutrients that can stimulate marine ecosystems.
- Research efforts aboard the RRS Sir David Attenborough have analyzed A23a’s impact on nutrient cycling, carbon balance, and marine biodiversity, providing valuable insights into polar processes.
The A23a iceberg spans an area of 3 800 km2 (1 465 mi2) and weighs nearly a trillion tons. It has broken free from its position near the South Orkney Islands and is now drifting through the Southern Ocean.
After being trapped in a Taylor Column, a rotating vortex of water near an underwater seamount, A23a had been spinning in place for approximately 8 months earlier this year.
The researchers from the British Antarctic Survey (BAS) confirmed on December 13 that the iceberg had finally freed itself and begun drifting northward.
The BAS reported that A23a is likely to follow the Antarctic Circumpolar Current, moving toward the sub-Antarctic island of South Georgia.
“It’s exciting to see A23a on the move again after periods of being stuck. We are interested to see if it will take the same route the other large icebergs that have calved off Antarctica have taken. And more importantly what impact this will have on the local ecosystem,” Dr. Andrew Meijers, an oceanographer at BAS, stated.
Decades of stability
The journey of A23a dates back to 1986 when it calved from Antarctica’s Filchner Ice Shelf. The weight of the iceberg, with an impressive thickness of 400 m (1 312 feet), caused it to become grounded on the seabed of the Weddell Sea, where it remained stationary for over 30 years.
The iceberg began to shift in 2020, but its progress was interrupted when it became ensnared in a Taylor Column in April 2024. This stationary period allowed scientists an opportunity to study the behavior and characteristics of large, grounded icebergs and their interaction with the surrounding marine environment.
The iceberg’s entrapment in the Taylor Colum shows the influence of oceanographic phenomena on its movement. The rotating water currents above the seamount prevented A23a from drifting freely, further delaying its journey northward. The iceberg’s immense size and draft made it particularly prone to such interactions. Its prolonged grounding allowed researchers to investigate the effects of its presence on the seabed, including scouring impacts on benthic ecosystems.
Scientists are examining its trajectory, now that it is moving once again. The iceberg is expected to fragment into smaller pieces and melt as it approaches the warmer waters of South Georgia. This natural process could influence the local marine ecosystem by releasing substantial amounts of nutrients that may support plankton blooms and other marine life.
Research on ecosystem impacts
Before the BAS December 2023 studies, research efforts in early 2023 also examined A23a’s behavior. Observations of “edge wasting” caused by warm water erosion provided important insights into its interaction with ocean currents.
Later, aboard the BAS’s RRS Sir David Attenborough vessel, researchers conducted studies in December 2023 to assess the iceberg’s impact on marine environments.
Laura Taylor, a biogeochemist involved in the study, focused on the ecological impact of such icebergs.
“We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas. What we don’t know is what difference particular icebergs, their scale, and their origins can make to that process,” Dr. Taylor explained.
Water samples were collected from areas surrounding A23a, during the expedition, including behind, adjacent to, and ahead of its path. These samples are being analyzed to understand how the iceberg contributes to nutrient enrichment and carbon cycling in the ocean. Initial findings suggest that such icebergs can alter the chemical composition of surrounding waters, with potential downstream effects on carbon sequestration and marine biodiversity.
Importance of monitoring icebergs
Large icebergs such as A23a are known to release nutrients like iron and nitrogen into ocean waters as they melt. The nutrients can stimulate phytoplankton growth, forming the base of marine food webs and supporting larger organisms. Understanding these processes is essential for evaluating their influence on ecosystems and global carbon cycles.
“We took samples of ocean surface waters behind, immediately adjacent to, and ahead of the iceberg’s route. They should help us determine what life could form around A23a and how it impacts carbon in the ocean and its balance with the atmosphere,” Dr. Taylor remarked.
The broader implications of such nutrient release extend to the global climate system. Phytoplankton blooms triggered by iceberg melt not only support marine ecosystems but also act as a carbon sink, offsetting some of the carbon emissions. The scale and efficiency of these processes remain areas of active research.
Focus in the future
Satellite monitoring and oceanographic surveys will continue tracking A23a’s progress and environmental impact, complemented by research efforts aboard the RRS Sir David Attenborough and other platforms.
The main focus areas include understanding how melting icebergs disperse nutrients to support marine biodiversity, examining their role in carbon exchange between the ocean and atmosphere, observing the formation of new marine ecosystems in their wake, and analyzing the long-term effects of grounded icebergs like A23a on benthic ecosystems.
References:
1 World’s largest iceberg A23a breaks free – BAS – December 13, 2024
Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.
Commenting rules and guidelines
We value the thoughts and opinions of our readers and welcome healthy discussions on our website. In order to maintain a respectful and positive community, we ask that all commenters follow these rules.