Drift Ice/Pack Ice
Term used in a wide sense to include any area of ice, other than fast ice, no matter what form it takes or how it is disposed. When concentrations are high, "pack ice" is normally used. When concentrations are less, "drift ice" is normally used.

Ice Cover
The ratio of an area of ice to the total area of water surface within some large geographic locality.

Concentration
The ratio expressed in tenths ( /10 ) describing the area of the water surface covered by ice as a fraction of the whole area. Total concentration includes all stages of development that are present; partial concentration refers to the amount of a particular stage or of a particular form of ice and represents only a part of the total.

• Consolidated Ice: Floating ice in which the concentration is 10/10 and the floes are frozen together.
• Compact Ice: Floating ice in which the concentration is 10/10 and no water is visible.
• Very Close Pack/Drift: Floating ice in which the concentration is 9/10 to less than 10/10.
• Close Pack/Drift: Floating ice in which the concentration is 7/10 to 8/10, composed of floes mostly in contact with one another.
• Open Drift: Floating ice in which the concentration is 4/10 to 6/10, with many leads and polynyas. Floes generally not in contact with one another.
• Very Open Drift: Ice in which the concentration is 1/10 to 3/10 and water dominates over ice.
• Open Water: A large area of freely navigable water in which ice is present in concentrations less than 1/10. No ice of land origin is present.
• Bergy Water: An area of freely navigable water in which ice of land origin is present. Other ice types may be present, although the total concentration of all other ice is less than 1/10.
• Ice Free: No ice present. If ice of any kind is present, this term shall not be used.

Openings in the Ice:

Fracture

Any break or rupture through very close pack ice, compact ice, consolidated ice, fast ice or a single floe resulting from deformation processes. Fractures may contain brash ice and/or be covered with nilas and/or young ice. Their lengths may vary from a few metres to many kilometres.

Fracture Zone
An area which has a great number of fractures. Fractures are subdivided as follows:

Crack
Any fracture of fast ice, consolidated ice or a single floe which may have been followed by separation ranging from a few centimetres to 1 m.

Flaw
A narrow separation zone between floating ice and fast ice, where the pieces of ice are in a chaotic state. Flaws form when ice shears under the effect of a strong wind or current along the fast ice boundary.

Lead
Any fracture or passage-way through ice which is navigable by surface vessels.

Polynya
Any non-linear shaped opening enclosed by ice. May contain brash ice and/or be covered with new ice, nilas or young ice; sub-mariners refer to these as skylights.

Ice Edge
The demarcation at any given time between open water and sea, lake or river ice whether fast or drifting.

Ice Boundary
The demarcation at any given time between fast ice and floating ice or between areas of ice of different concentrations, types and/or floe sizes.

Status:   User: Guest  Group: Guest

Last Updated: 2003-03-19

Print Format      Home      Important Notices