Iceberg B-15 was the largest iceberg ever recorded by area. It measured about 295 kilometers by 37 kilometers (159 nautical miles by 20 nautical miles), with a surface area of 11,000 square kilometers (3,200 square nautical miles). This size is similar to the island of Jamaica. B-15 broke off from the Ross Ice Shelf in Antarctica in March 2000. It later split into smaller icebergs, with the largest piece named B-15A. In 2003, B-15A moved away from Ross Island into the Ross Sea and traveled north. It eventually broke into smaller icebergs in October 2005. In 2018, a large part of the original iceberg was moving northward, located between the Falkland Islands and South Georgia Island. As of August 2023, the U.S. National Ice Center (USNIC) still tracked one remaining piece of B-15 that met the size requirement for tracking (70 kilometers or 20 square nautical miles). This iceberg, B-15AB, measured 20 kilometers by 7 kilometers (11 nautical miles by 4 nautical miles). As of 2021, it was grounded near the coast of Antarctica in the western part of the Amery region.
History
In the final weeks of March 2000, Iceberg B-15 broke off from the Ross Ice Shelf near Roosevelt Island, Antarctica. This event happened along existing cracks in the ice shelf. The iceberg measured about 295 km by 37 km (159 nmi by 20 nmi), with a surface area of 10,915 km² (3,182 sq nmi). Scientists believe the large piece of ice separated as part of a natural cycle that happens every 50 to 100 years. Between 2000 and 2003, Iceberg B-15 split into several pieces, the largest of which, B-15A, covered 6,400 km² (1,900 sq nmi) of ocean.
In November 2003, after separating from B-15J, B-15A moved away from Ross Island into the Ross Sea. In December 2003, a small, knife-shaped iceberg called B-15K (about 300 km long) broke off from B-15A and began drifting northward. By January 2005, ocean currents guided B-15A toward the Drygalski Ice Tongue, a 70-kilometer-long (40 nmi) extension of the David Glacier, which flows through the mountains of Victoria Land. A few kilometers from the ice tongue, the iceberg became stuck on a shallow underwater mountain before continuing north. On April 10, 2005, B-15A collided with the ice tongue, breaking off the tip of the ice tongue. The iceberg was not damaged by the collision.
Iceberg B-15A continued drifting along the coast, moving away from McMurdo Sound. On October 27–28, 2005, the iceberg ran aground near Cape Adare in Victoria Land, creating earthquake-like signals detected as far as the Amundsen-Scott South Pole Station. It then broke into smaller pieces, with the largest still named B-15A (now about 1,700 km² or 500 sq nmi). Three other pieces were named B-15P, B-15M, and B-15N. B-15A then moved farther north and broke into more pieces, which were spotted by air force patrols on November 3, 2006. On November 21, 2006, several large pieces were seen 60 km (30 nmi) off the coast of Timaru, New Zealand. The largest measured about 1.8 km (1 nmi) long and rose 37 meters (120 ft) above the ocean.
As of 2018, four pieces large enough to track remained, each at least 70 km² (20 sq nmi) in size. One piece, B-15Z, measured 19 km by 9 km (10 nmi by 5 nmi) and was located in the southern Atlantic Ocean, about 280 km (150 nmi) northwest of South Georgia Island. As it moved north, it melted faster. Most icebergs do not survive this far north.
By 2020, only two large pieces remained. B-15aa, a piece from B-15Z, was drifting east of South Georgia Island in the South Atlantic. B-15ab remained near sea ice along the coast of Antarctica south of Africa. In 2021, B-15ab became the last piece tracked by the US National Ice Center, still grounded near Antarctica.
Effects on Antarctic ecology
On January 29, 2001, scientists from the University of Chicago and the University of Wisconsin placed weather and GPS tools on Iceberg B-15A. This was the first time researchers had studied an iceberg using these methods. The information collected helped scientists learn more about how large icebergs move through the waters of Antarctica and other areas.
On April 10, 2005, Iceberg B-15A hit the Drygalski Ice Tongue, causing a section of the ice tongue that was 8 square kilometers (2 1/4 square nautical miles) to break off. Maps of Antarctica had to be updated to show this change.
B-15A blocked ocean currents and winds that usually help break up sea ice during the summer of 2004–2005 in McMurdo Sound. It also made it harder for ships that bring supplies to three research stations to travel through the area. Scientists were worried that the iceberg could cause a major drop in the number of Adélie penguins because the distance parent penguins had to travel to reach their chicks increased. Weddell seals and skuas, which also live in McMurdo Sound, might have been affected as well.
On October 21, 2005, a large storm in the Gulf of Alaska created a wave that traveled across the Pacific Ocean. This wave may have caused B-15A to break into many pieces on October 27, 2005. The wave moved 13,500 kilometers (7,300 nautical miles) from Alaska to Antarctica over six days. Scientists are studying this event to understand how weather in one place can affect other parts of the world and to learn more about global warming.
A more detailed study in 2010 showed that the iceberg’s breakup was mainly caused by repeated contact with underwater features near Cape Adare, Victoria Land.