Iceberg Update: New Massive Icebergs Are Calved

May 5, 2000

Two new massive icebergs have broken off from the Ross Ice Shelf as a result of the movements of a much larger adjacent iceberg that was calved in March. Three additional icebergs have also broken off from the Ross Ice Shelf as a result of the gyrations of the giant iceberg, designated as B-15 by the National Ice Center. According to the National Ice Center, additional icebergs may continue to calve in the next few week s due to the ebb and flow of the ocean tides and the subsequent collisions of the larger icebergs with the ice shelf itself. The largest of the new bergs, designated as B-17, still is considerably smaller than B-15, which is about 4,250 square miles (11,000 square kilometers) or twice the size of Delaware. B-17 is approximately 960 square miles (2,480 square kilometers), and is already beginning to show signs of breaking up into smaller pieces. The second smaller iceberg has been designated as B-18. To the west of B-15, a separate iceberg called B-16 formed at about the same time as the giant iceberg and now appears floating out to sea. B-15 is also beginning to pull further away from the ice shelf.

This recent infrared satelite image clearly shows the new B-17 and B-18 icebergs and the smaller bergs which broke off from the Ross Ice Shelf due to the larger B_15 bumping against the ice sheet. The B-16 berg formed west of the giant B-15 in March. (Courtesy NOAA and the University of Wisconsin at Madison.)

This iceberg activity is not related to global warming, according to the National Science Foundation. Rather, it is "part of a normal process in which the ice sheet maintains a balance between constant growth and periodic losses." The mammoth B-15 iceberg was "calved," or broke off, from the main ice sheet about 200 miles east of the National Science Foundation's (NSF) McMurdo Station on March 20. Among the largest ever observed, it is expected to drift westward around the Antarctic for several years, eventually moving northward into the eastward-trending currents of the Southern Ocean.

Though B-15 is currently the largest iceberg known to exist, its size is eclipsed by an iceberg that was spotted in 1955 about 150 miles west of Scott Island inside the Antarctic Circle by the U.S.S. Glacier, the US Navy's most powerful icebreaker at the time. That iceberg was reported as 60 miles wide by 208 miles long, or about 12,000 square miles (31,000 square kilometers).

-- Eric McLamb

Also check out these sites:

• The National Ice Center
• University of Wisconsin Antarctic Projects Homepage