“It doesn’t make any sense to try to conquer ice,” Peter Høeg has a character say in his novel Smilla’s Sense of Snow. “I can feel how the sea wants to close us in, how it’s merely because of a coincidental, passing constellation of water, wind, and current that we’re allowed to continue.” Such is the mercurial nature of leads—openings in the ice through which boats and larger vessels can navigate. There is irony in the word, for it suggests a direction one might follow; but leads, short or long, jagged or straight, narrow or wide, often close abruptly, as abruptly as they open— and even if they remain open, they might soon freeze over. Dynamic systems of leads connected to areas of nearshore open water called polynyas permit more light to enter the water, thus stimulating photosynthesis. Like leads, some polynyas may be temporary. (Submariners use the term skylight for polynyas that have recently frozen over, and call an ice canopy full of such polynyas “friendly ice.” “Hostile ice” is thick, tight, unrelieved.) Leads provide not only channels for vessels but also breathing space and migratory routes for whales and seals, hunting grounds for polar bears, feeding grounds for sea ducks and alcids, and, occasionally, access for all to open water at the ﬂoe edge. Large leads provide dramatic passage for large ships; it is the small leads, however, kayak-size and smaller, that are so vital to wildlife and indigenous culture. Leads also permit the ocean itself to “breathe.” This transpiration of heat between the ocean and the atmosphere sometimes creates sea smoke or rising water vapor, or, one might say, the ocean’s breath.