Interpreting ice charts: chapter 2


World Meteorological Organization Colour Code

Experts have long considered including colour coding for sea-ice charts in the World Meteorological Organization's "Sea Ice Nomenclature", but until recently this was considered optional.

However, the widespread use of electronic navigational information systems has brought about a definite need for colour coding on sea-ice charts. As a result, during the 2000-2001 period the International Ice Charting Working Group (International Ice Charting Working Group) prepared a draft colour standard consisting of two mutually exclusive colour codes based on:

  • total concentration; and
  • stage of development.

These proposed codes complement the existing World Meteorological Organization black and white ice symbols and are designed to be flexible.

Keys to Using and Understanding the World Meteorological Organization Colour Codes

There are two colour codes for use on sea-ice charts. They are based on:

  • total concentration: this code is used when concentration is highly variable but the stage of development is relatively uniform;
  • stage of development: this code is used when the stage of development is variable but the concentration is relatively uniform.

The two colour codes are mutually exclusive; only one should be used on a single chart.

  • Every chart should include a legend depicting the colour code used.
  • "Undefined Ice" is used when it is known that sea ice is in an area, but its characteristics are not known. This is different from "No Information", which indicates that nothing is known about the area.
  • No specific colour is assigned to areas of "No Information". Such areas should be clearly indicated on sea-ice charts-text annotation may be used where appropriate; an assigned colour within the code should not be used to indicate "No Information".
  • The use of colour codes does not rule out black and white hatching patterns or egg codes; egg codes may be used along with colours.
  • Other symbols may be used with the standard colours to depict special ice conditions under national practice.

Concentration Colour Code for Sea Ice

The World Meteorological Organization's colour code for total concentration is an international code that is intended for use when the stage of development is relatively uniform, but concentrations are highly variable (e.g. arctic summer). The legend for the use of the colour code is included on the chart. No colours are used to indicate differences in the ice stage of development.

World Meteorological Organization's Total Concentration Colour Code

Colour/
Pattern
Total concentration
 Blue Ice free
 White Ice free (Used at CIS)
 Light blue Less than one tenth (open water)
 Light green 1/10 - 3/10 (very open ice)
 Yellow 4/10 - 6/10 (open ice)
 Orange 7/10 - 8/10 (close ice)
 Red 9/10 - 10/10 (very close ice)
 Grey Fast ice
? ? ? ?
Undefined ice

Optional World Meteorological Organization's Total Concentration Colour Code

Colour Total concentration
 Light pink 7/10-10/10 new ice
 Pink 9/10-10/10 nilas, grey ice (mainly on leads)

*Areas of "No Information" are annotated accordingly

 

Stage of Development Colour Code for Sea Ice

World Meteorological Organization's Stage of Development Colour Code

Colour/
Pattern
Stage of Development Thickness
 Blue Ice Free  
 White Ice free (Used at CIS)  
 Light blue < 1/10 Ice (Open Water)  
 Light purple New Ice < 10 centimetres
 Purple Grey Ice 10-15 centimetres
 Pink Grey-white Ice 15-30 centimetres
 Yellow First-year Ice >=30 centimetres
 Light green Thin First-year Ice 30-70 centimetres
 Green Medium First-year Ice 70-120 centimetres
 Dark Green Thick First-year Ice > 120 centimetres
 Dark orange Old Ice  
 Orange Second-year Ice  
 Red Multi-year Ice  
 Grey Fast Ice of Unspecified Stage of Development  
? ? ? ?
Undefined Ice  
White with red triangle fill
Drifting Ice of Land Origin (icebergs)  

 

Note: The following stage of development colour codes are part of the World Meteorological Organization colour code standard but are not depicted on the Canadian Ice Service chart products.

 

Stage of Development Colour Code Standard for Sea Ice - Additional Codes

Colour
(prime)
Stage of Development (Stage of Development) Thickness
 Light pink Dark Nilas <=5 centimetres
 Pink Light Nilas > 5 centimetres
 Purple Young Ice 10-30 centimetres
 Light green Thin First-year Ice (white ice); First Stage 30-50 centimetres
 Green Thin First-year Ice (white ice); Second Stage 50-70 centimetres

 

Concentration Colour Code for Lake Ice

World Meteorological Organization's Total Concentration Colour Code for Lake Ice

Colour/
Pattern
Description
 White Ice Free
 Light blue Less than one tenth (open water)
 Light green 1/10 - 3/10 (very open ice)
 Yellow 4/10 - 6/10 (open ice)
 Orange 7/10 - 8/10 (close ice)
 Red 9/10 - 10/10 (very close ice)
 Grey Fast Ice of Unspecified Stage of Development
? ? ? ?
Undefined Ice

*Areas of "No Information" are annotated accordingly

 

Stage of Development Colour Code for Lake Ice

World Meteorological Organization's Stage of Development Colour Code for Lake Ice

Colour/
Pattern
Stage of Development Thickness
 White Ice Free  
 Light blue Ice of Unspecified Stage of Development (open water)  
 Light purple New Lake Ice < 5 centimetres
 Purple Thin Lake Ice 5-15 centimetres
 Pink Medium Lake Ice 15-30 centimetres
 Light green Thick Lake Ice 30-70 centimetres
 Green Very Thick Lake Ice > 70 centimetres
 Grey Fast Ice of Unspecified Stage of Development  
? ? ? ?
Undefined Ice  

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