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Small pictorial glossary of sea ice terms and evolution*

 

 

I. Ice growth

Agitated conditions
Calm conditions

Frazil ice: small spicules and platelets freely suspended in the water column

Nilas:
• dark nilas
(<0.05 m thick)
• light nilas
(0.05-0.1 m thick)


Aggregation of crystals at sea surface



Ice growth

Grease ice: aggregations of frazil into surface layer

Young ice:
• grey ice (0.1-0.15 m)
• grey-white ice (0.15-0.3 m)


Ice growth in a wave field

Pancake ice: consolidation of frazil into larger units



Further thickening
and ageing

 

First-year, white ice



Survival of
at least one summer

Old ice (second- and multiyear)

 

 

 

II. Ice deformation

Convergent regimes
Divergent regime

Rafting (mostly confined to thin ice)

Crack



Pressure ridge formation (mostly confined to thicker ice)

Lead

Polynya

 

 

 

III. Ice evolution and melting

Snow deposition and flooding
Melting

Snow deposition

Surface melt puddles


Depression of ice surface be-
low sealevel


Complete melting of floes

Flooding and snow-ice formation

Rotten ice

 

 

* All terms comply with sea-ice nomenclature of World Meteorological Organisation (1985). Figure is based on chart shown in Eicken (1995) which in turn relied heavily on Weeks (1976).

Last update: August 15, 1999
Responsible: Hajo Eicken
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