Sea Ice Outlook | Glossary

Glossary of Terms

Bergy Water

An area of freely navigable water in which ice of land origin is present.

Bottomfast Ice

Sea ice that is frozen to the seafloor.

Drift Ice

Ice that moves around on the ocean surface. It is pushed by winds, currents, or other forces.

First-Year Ice

Young floating ice, that has been developing no more than one year. It ranges in thickness from 0.3 to 2.0 meters (1 to 6.6 feet).

Ice Concentration

The amount of sea ice covering an area.

Marginal Ice Zone

A part of the seasonal ice zone that varies in width from 100 to 200 kilometers (62 to 124 miles) that extends from the ice edge into the ice pack. It is often characterized by variable ice conditions.

Melt Pond

A pool of melted snow and ice on the sea ice surface. Melt ponds are created during the summer melt season.

Multi-Year Ice

Ice that has survived at least one melt season.

Outlook Methods
Below is a list of the methods employed by Sea Ice Outlook researchers when calculating projections:
  • Modeling
    • A model is a mathematical representation of a real-world physical process. Scientists use models to simulate sea ice processes.
  • Heuristic
    • Heuristic methods represent a "rule of thumb" or trial and error approach toward problem solving based on discovery and experimentation.
  • Statistics
    • Statistics is a mathematical science pertaining to the collection, analysis, and interpretation of data. Using statistical methods, scientists can summarize data, identify patterns, and account for uncertainty in observations.
  • Modeling and Statistical
    • This method incorporates aspects of both modeling and statistics. A statistical model uses a set of math equations to describe the behavior of something in terms of random variables and probability.
  • Heuristic and Statistical
    • A heuristic and statistical method involves using a trial and error approach to solve a problem in conjunction with statistical analysis of real data.
Pack Ice

Ice that is not attached to the shoreline and drifts in response to winds, currents, and other forces.

Permanent Ice Zone

A region that is covered with sea ice all year.

Polyna (or Polynya, Polynia)

An area of open water surrounded by sea ice.


A deformation process in which one sheet of sea ice overrides another.

Remote Sensing

Remote sensing means viewing something from a distance. Scientists use satellites to collect a variety of remote data:

  • Visible
    • The light that our eyes detect is visible radiation from the sun, reflected off objects around us. "Whiter" objects (like ice) reflect more radiation than "darker" objects (like ocean water).
  • Infrared
    • Satellite sensors that measure infrared radiation infer the amount of heat emitted from an object at the earth's surface. Objects with an average earth temperature (roughly -50 to 50 degrees Celsius, or -58 to 122 degrees Fahrenheit) emit most of their energy in the infrared region.
  • Passive microwave
    • Objects at the earth's surface emit not only infrared radiation; they also emit microwaves at relatively low energy levels. When a sensor detects microwave radiation naturally emitted by the earth, that radiation is called passive microwave.
  • Active microwave
    • In addition to passively sensing emissions coming from objects on Earth, satellite sensors can also actively emit microwaves toward the earth's surface. These microwaves reflect off the surface and return to the sensors. This type of remote sensing is called active microwave, or radar.
      From The Encyclopedia of Earth website.
Sea Ice

Any form of ice found at sea which has originated from the freezing of sea water.

Sea Ice Maximum Extent

The amount of sea ice on the day of the year when the sea ice covers its largest area.

Sea Ice Minimum Extent

The amount of sea ice on the day of the year when the sea ice covers its smallest area.

Seasonal Ice Zone

An area of ocean that extends from the permanent ice zone to the boundary where winter ice extent is at a maximum.

Summer Minimum Extent

The permanent ice zone that remains in summer after all the melting has occurred.

Tidal Crack

A fracture in the landfast sea ice that coincides to the location where nearshore bottomfast ice or grounded pressure ridges transition to floating landfast ice. The crack emerges after tidal events in which changes in sea level cause the ice to break.

For a more complete Glossary of Terms, please visit the National Snow and Ice Data Center's Sea Ice Glossary at: ice.