Pancake ice is a form of

sea ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's o ...

that consists of round pieces of ice with diameters ranging from 30 centimetres (12 in) to 3 metres (9.8 ft) and thicknesses up to 10 centimetres (3.9 inches), depending on the local conditions. It forms as a result of wave action on slush or ice rind.

Characteristics

Pancake ice features elevated rims formed by piling of

frazil ice Frazil ice is a collection of loose, randomly oriented ice crystals millimeter and sub-millimeter in size, with various shapes, e.g. elliptical disks, dendrites, needles and of an irregular nature. Frazil ice forms during the winter in open-wate ...

or slush onto the edges of pancakes when they collide, both due to random bumping into each other and because of periodic compressions at

wave trough A crest point on a wave is the maximum value of upward displacement within a cycle. A crest is a point on a surface wave where the displacement of the medium is at a maximum. A trough is the opposite of a crest, so the minimum or lowest point in a ...

s. These rims are the first indication of the onset of the formation of the pancake ice from less consolidated forms of ice.

Formation

Pancake ice forms in conditions of high wave activity, in contrast to other types of sea ice formed under calm conditions. Pancake ice can form in two processes: (1) on water covered to some degree in slush, shuga or

grease ice Grease ice is a very thin, soupy layer of frazil crystals clumped together, which makes the ocean surface resemble an oil slick. Grease ice is the second stage in the formation of solid sea ice after ice floes and then frazil ice. New sea ice ...

, or (2) from breaking of ice rind, nilas or even

gray ice Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed o ...

in agitated conditions. If the waves are strong enough, pancakes can raft over each other, creating an uneven top and bottom surface on the ice. At this point, the pancake ice will fuse together and amalgamate into an

ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...

. This ice sheet will continue to grow over the winter. This process increases pancake ice's resilience, resulting in

characteristic length In physics, a characteristic length is an important dimension that defines the scale of a physical system. Often, such a length is used as an input to a formula in order to predict some characteristics of the system, and it is usually required by ...

scales less than ocean wavelengths and causing waves passing through pancake ice not to scatter.

Examples

Arctic Ocean

A notable example of pancake ice occurs in the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...

, where a new prevalence of pancake ice is occurring, particularly along the ice edge, as a result of increasing Arctic wave activity.

References

External links

Definition of pancake ice
from the

Canadian Ice Service The Canadian Ice Service (CIS) is a division of the Meteorological Service of Canada (MSC), and a branch of Canada's Department of the Environment. The CIS is the leading authority for information about ice in Canada's navigable waters. Ice affect ...

Large 'ice pancake' forms on cold river in Braemar

BBC News BBC News is an operational business division of the British Broadcasting Corporation (BBC) responsible for the gathering and broadcasting of news and current affairs in the UK and around the world. The department is the world's largest broadc ...

Sea ice {{antarctica-stub