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WMO Legend - Sea Ice

WMO Total Concentration Colour Code Standard - Sea Ice

Colour RGB colour model Total concentration (definition from WMO Nomenclature)
alternative prime
white blue 000-100-255 Ice free
  blue 150-200-255 Less than one tenth (open water)
  green 140-255-160 1/10 - 3/10 (very open ice)
  yellow 255-255-000 4/10 - 6/10 (open ice)
  orange 255-125-007 7/10 - 8/10 (close ice)
  red 255-000-000 9/10 - 10/10 (very close ice)
  gray 150-150-150 Fast ice
  grayish 210-210-210 Ice shelf
  white with question marks 255-255-255 Undefined ice
Optional pink 255-175-255 7/10-10/10 new ice
  hot pink 255-100-255 9/10-10/10 nilas, grey ice (mainly on leads)


WMO Stage of Development Colour Code Standard - Sea Ice

Colour Stage of development (SoD) Thickness
alternative prime
white blue Ice free  
  blue <1/10 ice of unspecified SoD (open water)  
  pale pink New ice < 10 cm
  dark purple Grey ice 10-15 cm
  Grey-white ice 15-30 cm
  purple First-year ice (FY) >= 30 cm
  yellow FY thin ice (white ice) 30-70 cm
  olive green FY medium ice 70-120 cm
  green FY thick ice > 120 cm
  brown Old ice  
  orange Second-Year Ice  
  red Multi-Year Ice  
  gray Fast Ice of Unspecified SoD  
  grayish Ice shelf  
  Ice of undefined SoD  
  white with red triangles Drifting ice of land Origin (icebergs)  


Note: The following stage of development colour codes are part of the WMO colour code standard but are not depicted on the CIS chart products.

WMO Stage of Development Colour Code Standard – Sea Ice/additional codes

Colour Stage of development (SoD) Thickness
alternative prime
  lightpurp Dark nilas <= 5cm
  blue Light nilas > 5 cm
  pale pink Young ice 10-30 cm
  dark purple FY thin ice (white ice) first stage 30-50 cm
  FY thin ice (white ice) second stage 50-70 cm