This true-color image, acquired by the Enhanced Thematic Mapper Plus on NASA’s Landsat 7 satellite on December 4, 2002, shows part of Antarctica’s Luitpold Coast, roughly 77.3 degrees south and 33.7 degrees west, just east of the Filchner Ice Shelf. Immediately off the coast is an expanse of land-fast sea ice—sea ice frozen to the coast. Northwest of that is thinner, less permanent sea ice. The raised areas of ice within the land-fast sea ice are icebergs that likely broke off a large slab of land-based ice and drifted seaward before encountering shoals that held them in place.
On the land-fast sea ice, in between two icebergs, is a light brown stain. Land-based ice, such as glaciers, can contain dirt or other debris that discolors it. Sea ice, however, has no excuse for such a stain. In this part of the world, only one thing can turn so much once-pristine ice brown: bird guano. In fact, the BAS researchers explained, looking for guano stains is more reliable than looking for actual penguins since the birds’ tuxedo colors might simply blend in with the shadows on the ice. By locating penguin droppings, the BAS team identified 38 emperor penguin colonies along the Antarctic coast. Although some breeding colonies occur on more ephemeral sea ice, many breeding grounds occur on semi-permanent, land-fast sea ice, which is the case here.