5.5 Colour Coding Ice Charts

Colours are used to enhance ice charts for presentations and briefings. The codes allow users to make a quick assessment of the general ice conditions and to visually follow trends. It is important to remember that the colours alone cannot be used for navigation decisions and that more detailed ice information is contained within the Egg Code. There are four colour codes in use at CIS, since each code displays the ice in different ways.

5.5.1 Standard CIS Colour Code or ISS Colour Code

The Standard CIS Colour code is intended to assist navigation decisions in ice infested waters. It represents the severity of the ice conditions and is somewhat similar to a traffic light. Colours are used to identify ice concentrations of significant ice.

5.5.1.1 Colours used in Standard CIS Colour Code

Total amount of ice thicker than 15 cm (grey-white ice or thicker)

white (white) less than 1/10 of ice >15 cm but at least 1 tenth of thinner ice types present
green (green) 1 to 3 tenths of ice >15 cm
yellow (yellow) 4 to 6 tenths of ice >15 cm
orange (orange) 7 to 8 tenths of ice >15 cm
red (red) 9 to 10 tenths of ice >15 cm
purple (purple) 5 to 10 tenths old ice (takes precedence over the other colours)
If there are other ice types present, the following symbols would be added to the above colours
blue star (blue star) 1/10 or more of new ice (less than 10 cm). Would not be visible if equal or greater amount of grey ice is present.
red star (red star) 1/10 or more of grey ice (10 to 15 cm). Would not be visible if there was also 9 tenths of ice grey-white or thicker.
purple slash (purple diagonal dashed lines) 1 to 4 tenths old ice. Would be visible in addition to blue or red stars.
In addition, the following colours are used:
light blue (light blue) open or bergy water (less than 1/10 total ice of any thickness)
grey or black (grey or black) areas of land fast ice of any thickness

5.5.2 Internal Quality Assurance (QA) Colour Code

The QA colour code is used internally to help identify total concentration and thickest ice types within the polygons. Colour is used to identify the stages of ice development and patterns are used to identify ice concentration.

5.5.2.1 Colours used in Internal QA Colour Code

The pattern of the predominant ice colour is determined by the total concentration of the ice. Total concentration is calculated by adding the partial concentrations. The exception is when first year ice or older is present, any new ice is not included in the calculation of the total concentration.

horizontal lines horizontal lines 1 to 3 tenths total concentration
vertical lines vertical lines 4 to 6 tenths total concentration
diagonal lines diagonal lines 7 to 8 tenths
solid black solid colour 9 to 9+ tenths
hatched white hatched white background 10 tenth compacted ice
hatcehed grey hatched grey background 10 tenths land fast ice that is coded with an egg

The colour of the predominant ice displays the most common type of ice present. Again, new ice is ignored if first year ice or greater (or older or thicker) is present. The other exception is that old ice is considered predominant if there are 4 tenths or more present.

yellow (yellow) New ice
orange (orange) Grey ice
blue (blue) Grey-white ice
pink (pink) Thin first-year ice
red (red) Medium first-year ice or combined all stages of first-year ice
purple (purple)Thick first-year ice
brown (brown) Old ice

The second pattern and colour will be the determined by the partial concentration of the second most common ice type. The rules for determining this ice type are:

The patterns and colours used for the second ice type are:

blue star stars less than 1 tenth concentration
horizontal lines horizontal lines 1 to 3 tenths concentration
vertical lines vertical lines 4 or 5 or 6 tenths concentration
yellow (yellow) New ice
orange (orange) Grey ice
blue (blue) Grey-white ice
pink (pink) Thin first-year ice
red (red) Medium first-year ice or combined all stages of first-year ice
purple (purple) Thick first-year ice
brown (green)Old ice (colour changes from what it is as a predominant colour so that it is more visible)
In addition, other colours that may be seen on the charts are:
light blue (light blue) open water (less than 1/10 sea ice, no ice of land origin)
blue (medium blue) Bergy water (less than 1/10 sea ice, and less than 1/10 iceberg concentration).
white (white) less than 1/10 of ice >15 cm but at least 1 tenth of thinner ice types present
black (black) Small areas of land fast ice or any thickness.

5.5.3 WMO Colour Code for Concentration

The WMO 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.

Table 5.4: WMO Total Concentration Colour Code

Colour RGB colour model Total concentration
Alternate Used at CIS
ice free alternate ice free 000-100-255 Ice free
  Less than one tenth (open water) 150-200-255 Less than one tenth (open water)
  1/10 - 3/10 140-255-160 1/10 - 3/10
  4/10 - 6/10 255-255-000 4/10 - 6/10
  7/10 - 8/10 255-125-007 7/10 - 8/10
  9/10 - 10/10 255-000-000 9/10 - 10/10
  Fast Ice 150-150-150 Fast ice
  Undefined ice (unknown type and amount) 255-255-255 Undefined ice (unknown type and amount)
Optional
  7/10 - 10/10 new ice 255-175-255 7/10 - 10/10 new ice
  9/10 - 10/10 nilas 255-100-2555 9/10 - 10/10 nilas or grey ice (mainly on leads)
Areas of No Information are annotated accordingly

Table 5.5: WMO Total Concentration Colour Code for Lake Ice

Colour Description
ice free alternate Ice Free
Less than one tenth (open water) < 1 Tenth Ice
1/10 - 3/10 1 - 3 Tenths Ice
4/10 - 6/10 4 - 6 Tenths Ice/td>
7/10 - 8/10 7 - 8 Tenths Ice
9/10 - 10/10 9 - 10 Tenths Ice
Fast Ice Fast Ice of Unspecified Stage of Development
Undefined ice (unknown type and amount) Undefined ice
Areas of No Information are annotated accordingly

5.5.4 WMO Colour Code for Stage of Development

The WMO colour code for stage of development is an international code that is intended for use when the concentration is relatively uniform, but the stage of development is highly variable (e.g. Atlantic winter). The legend for the use of the colour code is included on the chart. No colours are used to indicate differences in the concentration of the ice.

Table 5.6: WMO Stage of Development Colour Code

Colour RGB colour model Stage of Development
Alternate Used at CIS
ice free alternate ice free 000-100-255 Ice free
  Less than one tenth (open water) 150-200-255 ≪ 1/10 Ice (open water)
  New Ice 240-210-250 New Ice
  Grey Ice 135-060-215 Grey Ice
  Grey-White Ice 220-080-235 Grey-White Ice
  First-Year Ice 255-255-000 First-Year Ice
  Thin First Year Ice 155-210-000 Thin First Year Ice
  Medium First Year Ice 00-200-020 Medium First Year Ice
  Thick First Year Ice 000-120-000 Thick First Year Ice
  Old Ice 180-100-050 Old Ice
  Second-Year Ice 255-120-010 Second-Year Ice
  Multi-Year Ice 200-000-000 Multi-Year Ice
  Fast Ice of Unspecified State of Development 150-150-150 Fast Ice of Unspecified Stage of Development
  Ice of Undefined Stage of Development 255-255-255 Ice of Undefined Stage of Development
  Icebergs 255-255-255 Drifting Ice of Land Origin (Icebergs)


Table 5.7: WMO Stage of Development Colour Code - Lake Ice

Colour Description Thickness
ice free alternate Ice Free  
Less than one tenth (open water) Ice of Unspecified Stage of Development (open water)  
New Ice New Lake Ice < 5 cm
Grey Ice Thin Lake Ice 5 - 15 cm
Grey-White Ice Medium Lake Ice 15 - 30 cm
1/10 - 3/10 Thick Lake Ice 30 - 70 cm
4/10 - 6/10 Very Thick Lake Ice > 70 cm
Fast Ice Fast Ice of Unspecified Stage of Development  
Undefined ice (unknown type and amount) Undefined ice