Giant Iceberg Breaks in Two

The massive BiSA iceberg, which has blocked part of the entrance to McMurdo Sound for three years, causing inconvenience to both humans and penguins, has at last begun to break up. In October 2003, following a major storm, satellite photos showed a widening jagged crack developing across the elongate, 160 km long tabular iceberg, and Iceberg B15J, the ninth large fragment of the original BiS iceberg, was spawned.

Satellite photographs showed the massive BiS iceberg (295 km by 37 kin) breaking off the Ross Ice Shelf in March 2000 to be become the world's largest iceberg.

After drifting west, the berg subdivided and the largest fragment, BiSA, still the size of Jamaica, became partly grounded against Ross Island (see Antarctic Vol 19, nos 3 & 4, p. 143).

Its grounded position almost opposite the Drygalski Ice Tongue prevented the annual break out of sea ice from McMurdo for two seasons, which caused the ice to thicken. This made it harder for US icebreakers, even at the end of the season, and last year resulted in fuel having to be piped across the sea ice to McMurdo for the first time. Penguin colonies have also come under threat from the iceberg because it meant that more distance had to be covered between the nest and open sea, leading to exhausted birds and starved chicks.

After being battered by storms and waves for three years and tugged by coastal currents, the split across BiSA was expected eventually" across "some inherent weakness" in the iceberg, said Mike Williams of New Zealand's National Institute of Water and Atmospheric research (NIWA). The two fragments have twisted slightly, but "they are still grounded on the Ross Sea floor by their weight," he said.

In November US researchers planted a weather and global positioning tower on the BiSA fragment so that it could be more easily tracked. The title of world's largest iceberg now passes to C19A (5,659 square kin), which drifted out of the Ross Sea and along the coast of Wilkes Land, and is currently floating somewhere near Commonwealth Bay.

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