GLOBAL WARMING is usually blamed for melting glaciers and icebergs, and rightly so in many cases. But in the fjord off the Greenland town of Narsaq, and elsewhere on the island, a melting glacier is not an unusual sight. During the summer, rising temperatures polish and hollow out the giant frozen floats, often creating fantastic formations. This window to Narsaq thus does not necessarily forebode a flooded globe.