The world’s largest iceberg is A-23A. The iceberg regained that title on May 26, 2021 when iceberg A-76 broke off two smaller icebergs, A-76B and A-76C.
How big is Iceberg A-23A?
Iceberg A-23A current has an area of 40 x 32 nautical miles (3,460-square-kilometers or 1,240-square-miles) per the U.S. National Ice Center. That makes Iceberg A-23A roughly the size of the US state of Rhode Island.
Origins of Iceberg A-23A
Iceberg A-23A first calved from the Filchner–Ronne Ice Shelf, an Antarctic ice shelf fronted by the Wedell Sea. When icebergs calve, or break loose, from an ice shelf they will either float on the ocean surface or become grounded, or stuck, on the seafloor.
Route of Iceberg A-23A
After breaking off from the ice shelf iceberg A-23A spent decades grounded on the seafloor of southern Weddell Sea. In the early 2020s, Iceberg A-23A finally broke loose from the seafloor and started its journey across the Southern Ocean.
Ocean currents, eddies, tides, and wind all play a role in determining the route an iceberg takes. In general, most icebergs float along a route known as “iceberg alley.” According to NASA, more than 90% of icebergs that calve in the Antarctica region enter the Weddell Gyre off East Antarctica, veer north towards the Antarctica Peninsula. These enters then drift through the Drake Passage into warmer South Atlantic waters where they eventually melt.
Since its migration from the Weddell Sea, Iceberg A-23A has moved 2,000 kilometers (1,200 miles) north. Scientists have used satellite imagery to track the movement of this and other icebergs.
Where is Iceberg A-23A?
Iceberg A-23A is currently grounded off the coast of South Georgia island. Located about 100 kilometers (60 miles) off South Georgia, the iceberg is stuck in a shallow underwater shelf off the coast of the remote Antarctic island in the South Atlantic Ocean.
Since grounding in early March, the iceberg has lost about 360 square kilometers (140 square miles) in area due to fragmentation. Satellite imagery of Iceberg A-23A shows thousands of smaller pieces of ice in the ocean. Some of these fragments of ice are large. The largest fragment was named Iceberg A-23C by the US National Ice Center after it broke off from Iceberg A-23A around April 11, 2025. Iceberg A-23C currently has an area that measures 11 x 14 nautical miles.
The breaking off of Iceberg A-23C and other fragments is known as “edge wasting.” This fragmentation is triggered by warmer waters and weather destabilizing the outer edges of the iceberg. With Iceberg A-23A moored in the South Atlantic Ocean at nearly 55°S latitude, this is well outside the frigid conditions further south that allowed the iceberg to maintain its enormous size after calving from the ice shelf off the coast of Antarctica.
Previous world’s largest iceberg
May 20, 2021: A new iceberg temporarily took the crown as the world’s biggest iceberg. When it calved, Iceberg A-76 was about the size of the state of Rhode Island with an area of 1,667 square miles (4,320 square kilometers) and about 106 miles (170 kilometers in length) and 15.5 miles (25 kilometers) wide.
As with previous icebergs in the area that have calved. A-76 gets its name from the quadrant in Antarctica where it was calved. Iceberg A-76 was calved from the western side of the Ronne Ice Shelf, located in the Weddell Sea, in Antarctica.
The British Antarctic Survey first identified the iceberg, which was then confirmed by the US National Ice Center using Copernicus Sentinel-1 imagery.
This Sentinel-1 imagery shows Iceberg A-76 calving from the Ronne Ice Shelf on May 16, 2021. The outline of the Spanish island of Majorca shows the relative size of the floating iceberg.
Timelapse imagery of A-76 calving
A timelapse shows a crack forming in the Ronne Ice Shelf and A-76 calving between May 11 and May 16, 2021.
Losing the title as the world’ largest iceberg
June 2021: The iceberg had broken apart into three distinct chunks (A-76A, A-76B, and A-76C) by May 26, 2021, reducing its size and result in losing its status as the world’s largest iceberg. Iceberg A-76A at the time of its calving was measuring “73 nautical miles on its longest axis and 14 nautical miles on its widest axis” per the U.S. National Ice Center.
In December of 2020 Iceberg A-68A Was the World’s Biggest Iceberg
In July of 2017, a piece of ice the size of Delaware broke off of Antarctica’s Larsen C ice shelf. When an iceberg breaks off from glacier’s terminus (the lowest end of a glacier) it is called calving.
At the time of its split, Iceberg A-68A measured 5,800 square kilometers (2,200 square miles), making it the world’s largest iceberg.
Tracking Cracks in the Larsen C Ice Shelf
Larsen C is a floating platform of glacial ice found on the east side of the Antarctic Peninsula. Researchers had been tracking a crack that formed on the fourth largest ice shelf in Antarctica with satellite data. In 2014, a crack that had formed on Larsen C suddenly accelerated leading to the eventual birth of Iceberg A-68A in 2017.
This video shows the growth of the crack in the Larsen C ice shelf from 2006 to 2017 as captured by imagery from NASA/USGS Landsat satellites.
How are Icebergs Named?
Iceberg A-68A was named by the US National Ice Center which explains that icebergs are named based on the Antarctic quadrant in which they are signed:
A = 0-90W (Bellingshausen/Weddell Sea)
B = 90W-180 (Amundsen/Eastern Ross Sea)
C = 180-90E (Western Ross Sea/Wilkesland)
D = 90E-0 (Amery/Eastern Weddell Sea)
The number after the letter is a sequential number assigned to the iceberg. Iceberg A-68 therefore, is the 68th iceberg to have been recorded as formed in that Antarctic quadrant.
Letters starting with B after the iceberg’s name indicate any icebergs that have calved from the parent iceberg. Iceberg A68-A has calved two smaller icebergs so far since it broke off from Larsen C: Iceberg A68-B and Iceberg A-68C.
Iceberg A-68A now measures (151 kilometers) 94 miles long and 48 kilometers (30 miles) wide.
Using Satellites to Track the Movement of Iceberg A-68A
Researchers have continued to use satellite technology to track the movement of Iceberg A-68A as it moves in a northerly direction.
In the three years since Iceberg A-68A was calved, it has drifted towards South Georgia, a remote island in the southern Atlantic Ocean. NASA researchers used data from the Antarctic Iceberg Tracking Database to map the path of Iceberg A-68A.
The iceberg has moved over time with the ocean currents, with the path of the iceberg swirling in a circular path due to oceanic eddies. Iceberg A-68A has followed the path of more than 90% of icebergs as it passed through “Iceberg Alley”, a section of the Atlantic Ocean that reaches from the Antarctic Peninsula to Chile.
Researchers are continuing to monitor the path of Iceberg A68-A to see if it will get stuck in the shallow waters around South Georgia, actually strike the island, or float just past it. If the Iceberg gets stuck on or near the island, it can have a negative impact by blocking the foraging routes of the seals and penguins that hunt on and near South Georgia Island.
References
Antarctic iceberg data. (n.d.). U.S. National Ice Center Home. https://usicecenter.gov/Products/AntarcIcebergs
Brasher, B. R. (2020, April 24). Iceberg B-68C press release. U.S. National Ice Center Home. https://usicecenter.gov/PressRelease/IcebergA68C
Essary, F. M. (2021, May 26). Iceberg A-76 Calves into A-76A, A-76B, and A-76C as it slowly moves away from the Ronne Ice Shelf. U.S. National Ice Center Home. https://usicecenter.gov/PressRelease/IcebergA76A_B_C
Hansen, K. (2020, November 16). Iceberg A-68A nears South Georgia. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/147535/iceberg-a-68a-nears-south-georgia
Viñas, M. J., & Hansen, K. (2017, July 12). Antarctic ice shelf sheds massive iceberg. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/90557/antarctic-ice-shelf-sheds-massive-iceberg
This article was originally published December 9, 2020 with updated information
References
Hansen, K. (2021, June 3). Sizing up a tabular iceberg. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/148388/sizing-up-a-tabular-iceberg
Hansen, K., & Shuman, C. (2022, March 19). March of the icebergs. NASA Earth Observatory. https://earthobservatory.nasa.gov/images/149592/march-of-the-icebergs
