Drift ice

Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.). Unlike fast ice, which is 'fastened' to a fixed object, drift ice is carried along by winds and sea currents, hence its name. When drift ice is driven together into a large single mass (>70% coverage), it is called pack ice. Wind and currents can pile up that ice to form ridges up to several metres in height. These represent a challenge for icebreakers and offshore structures operating in cold oceans and seas. The icebreaker Kontio, which has become stuck in drift ice while towing a cargo ship in pack ice in the northern Baltic seaIce floes / pack iceSatellite image of drift ice in the Arctic Ocean around Wrangel IslandDrift ice in the Sea of OkhotskAboard the Aurora icebreaker in the Sea of Okhotsk Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.). Unlike fast ice, which is 'fastened' to a fixed object, drift ice is carried along by winds and sea currents, hence its name. When drift ice is driven together into a large single mass (>70% coverage), it is called pack ice. Wind and currents can pile up that ice to form ridges up to several metres in height. These represent a challenge for icebreakers and offshore structures operating in cold oceans and seas. Drift ice consists of ice floes, individual pieces of sea ice 20 metres (66 ft) or more across. Floes are classified according to size: small – 20 metres (66 ft) to 100 metres (330 ft); medium – 100 metres (330 ft) to 500 metres (1,600 ft); big – 500 metres (1,600 ft) to 2,000 metres (6,600 ft); vast – 2 kilometres (1.2 mi) to 10 kilometres (6.2 mi); and giant – more than 10 kilometres (6.2 mi).