Sea Ice Symbols Fact Sheet

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Two International Egg Code Eggs

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 cm1
Nilas;Ice Rind< 10 cm2
Young Ice10-30 cm3
Grey Ice10-15 cm4
Grey-white Ice15-30 cm5
First-year Ice30 cm6
Thin First-year Ice30-70 cm7
Medium First-year Ice70-120 cm1.
Thick First-year Ice> 120 cm4.
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 m1
Ice cake2 - 20 m2
Small floe20 – 100 m3
Medium floe100 – 500 m4
Big floe500 – 2000 m5
Vast floe2 – 10 km6
Giant floe> 10 km7
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


WMO Concentration Colour Code - Sea Ice
 WhiteIce Free
 Blue< 1 Tenth Ice
 Green1-3 Tenths Ice
 Yellow4-6 Tenths Ice
 Orange7-8 Tenths Ice
 Red9-10 Tenths Ice
 GreyFast Ice
 White with question mark fillUndefined Ice
 Pink7 Tenths New Ice
 Dark pink9+-10 Tenths Nilas, Grey Ice **

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.

WMO Stage of Development Colour Code - Sea Ice
 WhiteIce Free 
 BlueOpen Water 
 PinkNew Ice< 10 cm
 Dark purpleGrey Ice10-15 cm
 PurpleGrey-White Ice15-30 cm
 YellowFirst-Year Ice>= 30 cm
 Light greenThin First-Year Ice30-70 cm
 GreenMedium First-Year Ice70-120 cm
 Dark greenThick First-Year Ice120 cm >
 BrownOld Ice 
 OrangeSecond-Year Ice 
 RedMulti-Year Ice 
 GreyFast Ice 
 White with question mark fillUndefined Ice 
 White with red triangleIcebergs 

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