icebergs

An iceberg is a large piece of freshwater ice that has broken off from a glacier or ice shelf and is floating in open water. Most icebergs originate in the polar regions, especially Greenland and Antarctica, and they can be found in the North Atlantic and surrounding seas as well as the Southern Ocean. Icebergs vary greatly in size, from small blocks called growlers or bergy bits to massive tabular icebergs that can extend several kilometers across. The majority of an iceberg's mass is submerged underwater, with roughly 90% of its volume below the surface; only about 10% is visible above water.

Icebergs are categorized by shape as well as size: tabular icebergs have flat tops and edges, pinnacled icebergs have spires, and wedges are large triangular blocks. They form when glacial ice fractures and calves from outlets such as tidewater glaciers or ice shelves.

In the ocean, icebergs drift with currents and winds and gradually melt. They can remain afloat for months or years, eventually fragmenting into smaller pieces such as growlers. Icebergs pose hazards to ships and offshore structures; the International Ice Patrol monitors their drift to provide warnings, a practice prompted by historical incidents including the sinking of the Titanic in 1912.

Ecologically, iceberg melt contributes fresh water to the ocean and can locally reduce salinity, influencing marine ecosystems and, on longer timescales, ocean circulation near polar regions.