Leads /ˈliːdz/ are stretches of open water within fields of sea ice.[1] Leads are caused by movements of the ice due to wind, or to currents in the underlying water, and may open and close again within a brief period; alternatively they may remain open more or less permanently. The so-called "Big Lead", off the North Greenland coast, was discovered in 1906 by Robert Peary on his first (unsuccessful) North Polar trek, and was still there when he made his second attempt in 1909.[1]