More of those big bergs: where are they now?

A massive iceberg of about 5000 km2, designated B22, broke away from the Thwaites Glacier in West Antarctica in March 2002. In the previous November, iceberg B21, about 700 km2, calved from the neighbouring Pine Island Glacier. Such events are part of the natural process of extension of the glacier tongues and their reduction through iceberg calving, but they have left the tongues at the shortest extent observed for these glaciers.

In another part of West Antarctica, along the east coast of the Antarctic Peninsula, more than 3000 km2 of the Larsen ‘B’ Ice Shelf disintegrated over a few weeks in February and March 2002, producing several large icebergs and thousands of smaller fragments. Unlike the calving of B21 and B22, this event is clearly associated with climatic warming in the Peninsula region (see ‘Antarctic ice and the global climate system', p 3). The flotilla of icebergs has joined the group of massive icebergs that calved from the Ronne Ice Shelf two years ago, and which are still moving slowly north along the Peninsula (see Antarctica: satellites give the big picture).

In East Antarctica, the massive icebergs that calved from the Ross Ice Shelf in early 2000 An iceberg the size of Jamaica continue their slow progress around the coast. The largest remaining section of B15 (B15A) and iceberg B16, still next to Ross Island, have caused major changes in the movement and breakup of sea ice in that region, reduced biological productivity of surface waters and wrought havoc on local penguin colonies (see story below), as well as seriously affecting shipping to and from McMurdo station. Other Ross Ice Shelf icebergs have now drifted together close to the coast near Mertz and Ninnis Glaciers, where many could run aground, joining others accumulating over the past 20 years. One large section, B15D, has passed the Mertz Glacier Tongue and continues moving around the coast to the west.

Neal Young, Antarctic CRC and AAD