Sea Ice Symbols Fact Sheet

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Diagram of the components of the egg code: total and partial concentration, stage of development and forms of ice. See description below for details.

Row A

Total concentration: the ice coverage of an area determined by its concentration and expressed in tenth (in this example, 9/10)

Row B

Partial concentration: the break-down of the total ice coverage expressed in tenths and graded by thickness. The thickest starting from the left and in this example, 1/10 is the thickest.

Row C

Stage of development: the type of ice in each of the grades, determined by its age, that is 1/10 is medium first-year ice (1. ), 6/10 is grey-white ice (5) and 2/10 is new ice (1). Trace of old ice is represented on the lefthand side (outside the egg) by the number 7.

Row D

Floe Size: the form of the ice determined by its floe size for each section. In this example, big floes (5) for medium first-year ice (1. ); small floes (3) for grey-white ice (5); and undetermined, unknown or no form floes (x) for new ice (1).

Note: When an ice type has a dot (.) every other value to the left of it is also considered to have a dot.

Description of column E, F, G, H, and I in the Egg Code

ETrace of ice thicker/older then Sa
GSecond thickest
HThird thickest
IAdditional groups

Sea Ice Symbols

 White background with pointsOpen Water
  White background with solid linesIce Free
 White background with solid lines and triangleBergy Water
 Solid backgroundFast Ice

Stage of Development (SoSaSbScSdS e)

New Ice< 10 centimetres1
Nilas;Ice Rind< 10 centimetres2
Young Ice10-30 centimetres3
Grey Ice10-15 centimetres4
Grey-white Ice15-30 centimetres5
First-year Ice30 centimetres6
Thin First-year Ice30-70 centimetres7
Medium First-year Ice70-120 centimetres1.
Thick First-year Ice> 120 centimetres4.
Old Ice 7.
Second-year 8.
Multi-year 9.
Ice of Land Origin  Ice of land origin symbol
Undetermined/Unknown X

Floe Size (FaFbFc)

Pancake ice 0
Small ice cake; brash ice< 2 metres1
Ice cake2 - 20 metres2
Small floe20 – 100 metres3
Medium floe100 – 500 metres4
Big floe500 – 2,000 metres5
Vast floe2 – 10 kilometres6
Giant floe> 10 kilometres7
Fast Ice 8
Icebergs* 9
Undetermined, unknown or no form X
Strips (concentration = C)  Symbol for Ice in strips

Concentration of Ice

 Open water - < 1/10< 1/10Open Water
 Very open drift -1-3/101-3/10Very open drift
 Open drift - 4-6/104-6/10Open drift
 Close pack/drift - 7-8/107-8/10Close pack
 Very close pack - 9/109/10Very close pack
 Very close pack - 9+/109+/10Very close pack
 Compact/Consolidated ice -10/1010/10Compact / Consolidated ice


World Meteorological Organization's Total Concentration Colour Code

PatternTotal concentration
 BlueIce free
 WhiteIce free (Used at CIS)
 Light blueLess than one tenth (open water)
 Light green1/10 - 3/10 (very open ice)
 Yellow4/10 - 6/10 (open ice)
 Orange7/10 - 8/10 (close ice)
 Red9/10 - 10/10 (very close ice)
 GreyFast ice
? ? ? ?
Undefined ice

Optional World Meteorological Organization's Total Concentration Colour Code

ColourColour descriptionTotal concentration
 Light pinkLight pink7/10-10/10 new ice
 PinkPink9/10-10/10 nilas, grey ice (mainly on leads)

Areas for which no information is known are identified accordingly.

* Colour is based on total ice concentration.

** The optional colour indicating 9+-10 tenths of nilas or grey ice indicates level ice, mainly on leads; it is not used for ice broken into brash or ice cakes or for concentrations less than 9+ tenths.

World Meteorological Organization's Stage of Development Colour Code

Stage of DevelopmentThickness
 BlueIce Free 
 WhiteIce free (Used at CIS) 
 Light blue< 1/10 Ice (Open Water) 
 Light purpleNew Ice< 10 centimetres
 PurpleGrey Ice10-15 centimetres
 PinkGrey-white Ice15-30 centimetres
 YellowFirst-year Ice>=30 centimetres
 Light greenThin First-year Ice30-70 centimetres
 GreenMedium First-year Ice70-120 centimetres
 Dark GreenThick First-year Ice> 120 centimetres
 Dark orangeOld Ice 
 OrangeSecond-year Ice 
 RedMulti-year Ice 
 GreyFast Ice of Unspecified Stage of Development 
? ? ? ?
Undefined Ice 
White with red triangle fill
Drifting Ice of Land Origin (icebergs) 

Areas for which no information is known are identified accordingly.

Colour is based on stage of development of predominant ice.

See also: Lake Ice Symbols Fact Sheet