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FAST ICE EDGE

McMurdo Sound is covered by sea ice for 10-11 months of the year. Fast ice is sea ice which forms and fastens to the coastline; the boundary between fast ice and open ocean is the fast ice edge. The fast ice edge is dynamic; sea ice cracks form and enlarge while ice floes (large relatively flat pieces of sea ice) break off. Drifting ice crunches up against the fast ice edge piling up angular ice blocks. Emperor and Adelie penguins can be seen in small groups taking rest breaks between group fishing excursions. Predators are on the prowl for penguin prey. In this photo, killer whales Orcinus orca cruise in a pack along the McMurdo Sound fast ice edge looking for penguin prey. Leopard seals Hydrurga leptonyx also hunt along the fast ice edge. In mid-November when this photo was taken, the fast ice edge joined Ross Island at Cape Royds; Mt Erebus is in the background.



The diver looks up at a sharp vee in the fast ice edge and sees swimming Emperor penguins. Emperor penguins swim in groups to increase their safety from predators. Emperor penguins eat fish, squid, and euphausid and amphipod crustaceans which they dive and pursue to capture at speeds up to 3.4 meters per second.

1: The Penguins, Spheniscidae. TD Williams. Oxford : Oxford University Press, 1995. pp.152-160

Text ©Peter Brueggeman. Photographs ©Norbert Wu. Photographs may not be used in any form without the express written permission of Norbert Wu. Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?