flaw lead

A flaw lead is a navigable passage between floating pack and landfast ice. One side of the lead, the pack, is in more or less constant motion. The other side is motionless, a sheet of fast ice firmly attached to the shore or to an ice front, the seaward edge of an ice shelf. Fast ice may extend anywhere from a few feet to nearly two hundred miles from shore, and flaw leads are often temporary, their creation always subject to shifts in the direction of the wind. (Grounded or floating icebergs sometimes develop aprons of “fast ice,” but open water at the edge of such ice constitutes one of the floating pack’s many transitory “open leads.”) When a sheet of landfast ice rises more than six and a half feet above water, it can be reclassified as an ice shelf and it creates a special type of flaw lead. British explorer Robert Falcon Scott, sailing in the flaw lead of Antarctica’s Ross Ice Shelf, a mass of ice the size of France, described its ice front as “a relentless coast of high ice cliffs,” much of it more than one hundred feet high (and descending, he was unaware, hundreds of feet below his ship). In the Arctic, this type of flaw lead is rare. Far more common is the dynamic system of opening and closing flaw leads maintained by alternating on- and offshore winds, an unpredictable situation that makes navigating in the flaw leads dangerous—and frustrating.

Gretchen Legler