SWEET Ontology Realm Cryosphere

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This zone usually occurs at higher elevations and generally overlaps the conversion of snow to glacial ice.

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Congelation ice usually forms through the fusion/coalescence of platelets into solid ice.

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Perennially and seasonally frozen ground can vary from being partially to extensively frozen depending on the extent of the phase change. It may be described as hard frozen ground, plastic frozen ground, or dry frozen ground, depending on the pore ice and unfrozen water contents and its compressibility under load.

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The composition of an ice core can be used to reconstruct past climates and climate change; typically removed from an ice sheet (Antarctica and Greenland) or from high mountain glaciers elsewhere.

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An ice shelf may grow hundreds of miles out to sea. Usually of great horizontal extent and with a level or gently undulating surface. Nourished by annual snow accumulation and also by the seaward extension of land glaciers. Limited areas may be aground. Ice shelves are much thicker than sea ice often filling embayments in the coastline of an ice sheet.. Currently, nearly all ice shelves are in Antarctica, where most of the ice discharged into the ocean flows via ice shelves. The mass balance of an ice shelf may have significant components of both gain and loss at the base. The seaward edge is termed an ice front. The calving of an ice shelf forms tabular icebergs and ice islands.

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In the United States, NOAA sea ice operations does not include superstructure icing as being sea ice. In sea ice operations however, sea ice is any form of ice found at sea which has originated from the freezing of sea water. It presents the main kind of floating ice encountered at sea. Except where it forms ridges, sea ice is up to a few metres thick, in which respect it differs from shelf ice. Sea ice may be discontinuous pieces (ice floes) moved on the ocean surface by wind and currents (pack ice), or a motionless sheet attached to the coast (land-fast ice). In brief, it forms first as lolly ice (frazil crystals), thickens into sludge, and coagulates into sheet ice, pancake ice, or into floes of various shapes and sizes. Thereafter, sea ice may develop into pack ice and/or become a form of pressure ice. Sea ice less than one year old is called first-year ice. Perennial ice is sea ice that survives at least one summer. It may be subdivided into second-year ice and multi-year ice, where multiyear ice has survived at least two summers.

Sea ice develops from young ice; thickness from 0.3 to 2 meters (1 to 6.6 feet). Sea ice be subdivided into thin first-year ice (white ice), medium first-year ice, and thick first-year ice. First-year ice is distinguished from older ice primarily by having a higher salinity. Undeformed first-year ice differs from older ice in that it is smoother and lacks refrozen melt ponds. Characteristically level where undisturbed by pressure, but where ridges occur, they distinguished by being larger, more angular, and more porous than multiyear ridges.

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