The Dynamic Nature of Arctic Ice and Its Formation

Key Insight

The Greenland ice cap, a continuous formation of compacted snow and trapped air, spans 1500 miles long, 450 miles wide, and up to 11,000 feet thick, its immense weight warping the island's center 1180 feet below sea level. Enormous sections calve into the sea, forming icebergs, predominantly from West Greenland's tidewater glaciers. Beyond icebergs, ice islands, originating from ice shelves along northern Greenland and Ellesmere Island, measure up to 300 square miles in extent but only 150 to 165 feet thick. These 'Fletcher’s Ice Island [T-3]' platforms, used for scientific research for up to 25 years, drift for decades before disintegrating.

Tabular icebergs, whole sections of tidewater glaciers, are even more massive, reaching 40 or 50 cubic miles in volume, making them the Northern Hemisphere's largest floating objects. Freshwater arctic ice also includes river ice, tundra lake/pond ice, and ground ice within permafrost, which influences 'patterned ground' and forms hemispherical mounds called pingos, like a cluster of 150 pingos near Toker Point, 3000 to 5000 years old. Sea ice, however, behaves less predictably, its crystalline structure initially incorporating brine, allowing it to bend under load before fracturing, unlike brittle freshwater ice that fractures suddenly.

Sea ice formation progresses from an oily film of crystals (frazil ice) to gray slush (grease ice), then an elastic layer of ice crystals (nilas), about an inch thick. Nilas, initially transparent, turns gray at approximately four inches, becoming 'young ice' or 'gray ice,' and finally 'first-year ice' when opaque. First-year ice can reach four to six feet thick by spring; if it survives summer, it becomes harder, blue-tinted 'second-year ice,' thickening to 10 to 12 feet over a few years. Multiyear ice, or 'polar pack ice,' can further develop into 'paleocrystic ice,' up to 50 feet thick in the open polar sea. Winds and currents profoundly sculpt sea ice into forms like pancake ice, finger-rafting, hummocks, and pressure ridges reaching 20 to 40 feet high, making smooth ice rare outside sheltered areas.