Icebergs are found primarily in two regions: the North Atlantic Ocean (off the coasts of Greenland and eastern Canada) and the Southern Ocean surrounding Antarctica. Smaller numbers also appear in the Arctic waters near Alaska, Norway, and Russia. The vast majority of the world’s icebergs, by both number and size, originate from Antarctica’s ice shelves and glaciers.
The North Atlantic
The North Atlantic is where most people picture icebergs, largely because this is the shipping corridor where the Titanic sank in 1912. These icebergs calve from glaciers along Greenland’s western and eastern coasts, then drift south on ocean currents through Baffin Bay and the Labrador Sea. Many reach the Grand Banks off Newfoundland, Canada, where they cross into major shipping lanes.
Greenland produces an estimated 10,000 to 15,000 icebergs per year, though only a fraction survive the journey south far enough to threaten ships. The peak iceberg season along Canada’s east coast runs from February through August, with the highest concentrations typically appearing between March and July. The International Ice Patrol, established after the Titanic disaster, monitors this region year-round and issues warnings to vessels.
North Atlantic icebergs tend to be irregular in shape, often jagged and tall relative to their width, because they break off from narrow glaciers squeezed between mountain valleys. They rarely exceed a few hundred meters in length, though even “small” icebergs, classified as 14 to 50 feet above the waterline and up to 200 feet long, can weigh tens of thousands of tons.
The Southern Ocean Around Antarctica
Antarctica is the world’s largest iceberg factory. Its massive ice shelves, some the size of small countries, periodically release flat-topped “tabular” icebergs that dwarf anything found in the north. The Amundsen Sea is the most iceberg-productive sea in Antarctica, though large icebergs calve from ice shelves all around the continent. The highest concentrations of ice mass accumulate near giant icebergs longer than 18.5 kilometers (about 11.5 miles), as well as in front of ice shelves that shed smaller icebergs almost continuously.
Southern Ocean icebergs can be enormous. The largest ever recorded, designated B-15, broke off the Ross Ice Shelf in 2000 and measured roughly 295 kilometers long, about the size of Jamaica. These tabular icebergs float in the circumpolar current and can drift for years, sometimes traveling thousands of kilometers before melting. Fragments regularly reach as far north as 40°S latitude, occasionally entering shipping lanes between South America, South Africa, and Australia.
Unlike the seasonal pattern in the North Atlantic, Antarctic icebergs are present year-round. However, large calving events are unpredictable, and the total number of icebergs in the Southern Ocean fluctuates significantly from year to year based on when major ice shelves break apart.
Other Arctic Waters
Beyond Greenland, smaller icebergs calve from glaciers in the Canadian Arctic Archipelago, Svalbard (north of Norway), Franz Josef Land, and other Russian Arctic islands. These icebergs generally stay in high-latitude waters and rarely drift into heavily trafficked areas, so they receive less attention. Alaska’s tidewater glaciers, particularly in places like Glacier Bay, also produce icebergs, though most are relatively small and remain confined to fjords and coastal waters.
How Icebergs Are Classified by Size
Not every chunk of floating ice qualifies as an iceberg. NOAA uses a standardized classification system that ranges from the smallest fragments to enormous floating platforms:
- Growlers: Roughly the size of a truck or grand piano, extending less than 3 feet above the sea surface. They occupy about 60 square feet of surface area and are notoriously hard to spot on radar.
- Bergy bits: Medium to large fragments rising 3 to 15 feet above the waterline, covering 300 to 900 square feet.
- Small icebergs: 14 to 50 feet high, 47 to 200 feet long.
- Medium icebergs: 51 to 150 feet high, 201 to 400 feet long.
- Large icebergs: 151 to 240 feet high, 401 to 670 feet long.
- Very large icebergs: Over 240 feet high and more than 670 feet long.
These measurements only describe what’s visible above water. Roughly 80 to 90 percent of an iceberg’s mass sits below the surface, which is why even a “small” iceberg represents a serious hazard.
Why Location Matters
The two main iceberg zones differ in important ways. North Atlantic icebergs are a direct navigation hazard because they drift into some of the busiest shipping lanes in the world. They’re smaller but harder to predict, and the fragments called growlers can be nearly invisible to both radar and the naked eye in rough seas.
Southern Ocean icebergs pose less risk to shipping simply because fewer vessels travel through those waters, but they play an outsized role in ocean ecology. As they melt, they release iron and other nutrients locked in glacial dust, fertilizing the surrounding water and triggering blooms of microscopic algae. A single large tabular iceberg can influence ocean productivity across hundreds of square kilometers.
Climate change is shifting the picture in both hemispheres. Greenland’s glaciers have accelerated their calving rates over the past two decades, and several of Antarctica’s largest ice shelves have thinned or collapsed entirely. The Larsen B ice shelf on the Antarctic Peninsula disintegrated in 2002, and sections of the Thwaites and Pine Island glaciers in the Amundsen Sea are losing ice at increasing rates. These changes mean more icebergs entering the ocean, at least in the near term, until the source glaciers and ice shelves are depleted.