ICE CHART SYMBOLOGY - EGG CODE
The World Meteorlogy Organization (WMO) system for sea ice symbology is more frequently
referred to as the "Egg Code" due to the oval shape of the symbol. A brief
description of the code follows.
Total Concentration
The total concentration (C) is reported in tenths and is the uppermost group.
Concentration may be expressed as a single number or as a range, not to exceed two tenths
(i.e., 3-5, 5-7)
Partial Concentrations
Partial concentration (Ca, Cb, Cc) are also reported in tenths, but must be reported as
a single digit. These are reported in order of decreasing thickness. That is, Ca is the
concentration of the thickness ice and Cc is the concentration of the thinnest ice.
Stages of Development
Stages of development (Sa, Sb, Sc, So, Sd) are listed using the following code in
decreasing order of thickness. These codes are directly correlated woth the partial
concentrations above. Ca is the concentration of stage Sa, Cb is the concentration of
stage Sb, and Cc is the concentrationof Sc. So is used to report a development with the
greatest remaining concentration that will not fit into the egg. If all partical
concentrations equal the total concentration and there is a Sd, Sd is considered to be
present in a trace amount. The following codes are used to denote stages of development
for sea ice.
| Stage of Development | Code Figure |
| New Ice-Frazil, Grease, Slush, Shuga (0-10 cm) | 1 |
| Nilas, Ice Rind (0-10 cm) | 2 |
| Young (10-30 cm) | 3 |
| Gray (10-15 cm) | 4 |
| Gray-White (15-30 cm) | 5 |
| First Year (30-120 cm) | 6 |
| First Year Thin (30-70 cm) | 7 |
| First Year Thin- First Stage (30-70 cm) | 8 |
| First Year Thin- Second Stage (30-70 cm) | 9 |
| Med First Year (70-120 cm) | 1. |
| Thick First Year (>120 cm) | 4. |
| Old-Survived at least one seasons melt (>2 m) | 7. |
| Second Year (>2 m) | 8. |
| Multi-Year (>2 m) | 9. |
| Ice of Land Origin |  |
The following codes are used to denote stages of development for fresh water ice:
| Stage of Development | Code Figure |
| New Ice (0 cm - 5 cm) | 1 |
| Thin Ice (5 cm - 15 cm) | 4 |
| Medium Ice (15 cm - 30 cm) | 5 |
| Thick Ice (30 cm - 70 cm) | 7 |
| First Stage Thick Ice (30 cm - 50 cm) | 8 |
| Second Stage Thick Ice (50 cm - 70 cm) | 9 |
| Very Thick Ice (70 cm - 120 cm) | 1. |
Forms of Sea Ice
Forms of sea ice (Fa, Fb, Fc) indicate the floe size corresponding to the stages
identified in Sa, Sb, and Sc respectively. The following codes are used to denote forms of
sea ice:
| Forms of Sea Ice | Code Figure |
| New Ice (0 cm - 10 cm) | X |
| Pancake Ice (30 cm - 3 m) | 0 |
| Brash Ice (less than 2 m) | 1 |
| Ice Cake (3 m - 20 m) | 2 |
| Small Ice Floe (20 m - 100 m) | 3 |
| Medium Ice Floe (100 m - 500 m) | 4 |
| Big Ice Floe (500 m - 2 km) | 5 |
| Vast Ice Floe (2 km - 10 km) | 6 |
| Giant Ice Floe (greater than 10 km) | 7 |
| Fast Ice | 8 |
| Ice of Land Origin | 9 |
| Undetermined or Unknown (Iceberg, Growlers, Bergy Bits) (Used for Fa, Fb, Fc, only) |
/ |
The following codes are used to denote forms of sea ice for fresh water ice:
| Forms of Sea Ice | Code Figure |
| Fast Ice | 8 |
| Belts and Strips symbol followed by the concentration of ice |
~F |
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Page last updated on 03 December, 1998 08:56 AM.