Cloud

160 km

Fig. 4.4. NOAA-9 satellite infrared image of the 154 km long iceberg B-9 on 9 November

1987, four weeks after its separation from the eastern front of the Ross Ice Shelf. Several other bergs up to 20 km long that calved at the same time can be seen between B-9 and the ice shelf. These had drifted as far west as Ross Island (approximately 600 km) by March 1988 whereas B-9 was only 150 km west-north-west of its calving site at that time. By May

1988, B-9 was close to the north-eastern boundary of the Ross Sea at the edge of the continental shelf along which flows a strong north-west setting current. This image, obtained by U.S. Navy scientists at McMurdo Station, was supplied by the Antarctic Research Center at Scripps Institution of Oceanography.

front of the ice shelf (Anonymous, 1987b) (Fig. 4.4). The iceberg contained about 1,100 km3 of ice which is many times the average annual production of the Ross Ice Shelf. The former Bay of Whales feature was destroyed during the calving but a new indentation was formed some 40 km further east and a similar distance south of the old ice front. It is possible that such a large and sudden mass loss could affect the dynamics of the ice shelf upstream of the calving site.

Minor calving occurs more frequently, probably many times each year. Jacobs et al. (1986) considered that such calving has been most prevalent west of 178°E. About 0.3-0.4 km yr1 appears to calve off this 200 km length of the ice front (including minor attrition) which represents probably less than 10 km3 yr1 (from Fig. 4.3). Averaged over the whole ice front, recent calving before September 1987 appears to have totalled much less than the estimated 150 km3 yr1 required to maintain a stationary ice front assuming realistic melt rates (Doake, 1985; Jacobs et al., 1986). Clearly, the ice front does not maintain a precise equilibrium position.

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