WMO Ice Concentration
symbols used on ice charts

Ice chart pattern Total Ice concentration
  Blackened area representing fast ice.
  Fast ice.
  9 to 10 tenth.
  7 to 8 tenth.
  4 to 6 tenth.
  1 to 3 tenth.
  Less than 1 tenth.

WMO Ice Concentration
symbols used on ice charts

Ice chart symbol Ice concentration and type
  Ice free.
  Icebergs but no, or under 1/10,
sea ice.
  New sea ice.
  Strips and paches of ice.
  Few icebergs.
  Many icebergs
  Few Growlers
  Many Growlers