Manual of Ice (MANICE): chapter 3

Chapter 3: Observed Ice Charts

• 3.1: Preparation of Ice Charts
• 3.2: Dissemination of Aerial Ice Charts
• 3.3: Dissemination of Shipboard Ice Charts
• 3.4: The Egg Code
• 3.5: Symbols Used on Ice Charts
• 3.6: Supplementary Procedures for Indicating Total Concentration
• 3.7: Colour Coding Ice Charts
• 3.8: Examples of the Use of the Egg Code

This chapter deals with basic procedures for preparing and transmitting ice charts. Ice charts are of importance to icebreaker captains, commercial shipping interests and fishing vessels to assist them in finding the easiest passage through the ice or to avoid the ice when feasible to do so. The data on the chart is of vital importance to ice forecasters, serving as the basis for:

• ice hazard warnings
• preparation of daily ice analysis chart
• short- and long-range ice forecasts and seasonal outlooks
• preparation of regional ice charts

3.1 Preparation of Ice Charts

Time and care are necessary to prepare ice charts. Details and precision are of the utmost importance.

3.1.1 Drawing Procedures

Ice charts are drawn directly on a computer screen using Geographical Information Systems software. This software has been developed specifically for the Coast Guard to allow precise observation and quick transmission of data.

It is beyond the scope of this manual to describe this particular software in detail. It is sufficient to know the precision of observation is greatly increased by the use and integration of the Global Positioning System (GPS). The usefulness of the data is enhanced by the automatic verification of all coding and final preparation of charts.

Data will generally be transmitted in the form of electronic files and distributed by Canadian Ice Service to clients. Maps of observed data will also be produced by Canadian Ice Service and made publicly available.

3.2 Dissemination of Aerial Ice Charts

Data (in the form of electronic files or charts) is of special importance to the ice forecasters and analysts and ships operating in or near the areas observed during the reconnaissance mission. Files are updated continuously while airborne and sent frequently. Partial files, rough copies and final copies of charts may be sent in-flight to the Canadian Ice Service, the appropriate Coast Guard ice offices and Coast Guard ships as necessary.

After the termination of the reconnaissance mission, the Ice Service Specialist will transmit the completed and corrected data to the Canadian Ice Service for distribution.

3.3 Dissemination of Shipboard Ice Charts

An Ice Service Specialist serving on icebreakers equipped with appropriate communication equipment should relay their ice information (even if incomplete) before 1800 UTC to Canadian Ice Service. Upon completion of the duty day, a second transmission is recommended. The data should be sent in the form of an electronic file via cellular phone, landline or satellite link depending on what is practical and available.

If it is not possible to transmit an electronic file, then a map could be printed and send by facsimile.

3.4 The Egg Code

The basic data concerning concentrations, stages of development (age) and form (floe size) of ice are contained in a simple oval form. A maximum of three ice types is described within the oval. This oval and the coding associated with it, are referred to as the "Egg Code". To indicate ice observations interpreted from radar imagery, the oval shall be omitted.

In the following figures and tables where ranges are shown for thickness, floe sizes or other dimensions, a report coinciding with the end point of a range shall be coded as the higher value.

The following is a summary diagram of the Egg Code. This code conforms to international convention and shall be used in coding all visual sea ice and lake ice observations without exception.

The symbols C_aC_bC_c and F_aF_bF_c correspond to S_a S_b S_crespectively.

There are some minor additions to the egg code symbology that are Canadian practice. In Canada, to enable the reporting of additional ice classes, especially during freeze-up and break-up, C_d S_e and F_e can be used. This should not be a common occurrence.

The following pages describe the specific details and rules for completing each level of information within the egg.

3.4.1 Concentration (C)

Total concentration (C_t ) of ice in the area reported in tenths and partial concentrations of thickest (C_a), second thickest (C_b), third thickest (C_c) and fourth thickest (C_d) ice in tenths.

Notes:

1. Less than 1/10 (i.e. traces) shall not be reported within the oval except to describe open water (see Example 1, section 3.8).
2. C_d shall only be included when S_d and S_eare reported (see Example 2, section 3.8).
3. When S_d is used and C_d is omitted, C_d equals C_t-(C_a+C_b+C_c) (see Example 3, section 3.8).
4. When only one ice type is present, the partial concentration shall not be indicated (see Example 4, and Example 5, section 3.8).
5. When one ice type is present with a trace of a thinner type, only total concentration of the major ice type shall be indicated (see Example 5, section 3.8 ).

3.4.2 Stage of Development (S)

Stage of development of thickest (S_o), second thickest (S_a), third thickest (S_b) and fourth thickest (S_c) ice and the thinner ice types S_d and S_e, of which the concentrations are reported by C_aC_b C_c C_drespectively.

Notes:

1. Reference to thicker ice should be understood to mean older ice and conversely, thinner ice to mean younger ice types.
2. Ice is designated as Sea, Lake or River Ice depending on where it forms. In Canada, the practice is to use lake-ice coding to report ice in the Great Lakes and the St. Lawrence Seaway. Elsewhere, including the St. Lawrence River east of Montreal, sea-ice coding is used for stages of development.
3. S_a, S_b and S_c shall have concentrations of at least 1/10, except when C_t is zero (see Example 1, section 3.8).
4. Reporting of S_a, S_b and S_c should generally be restricted to a maximum of three significant classes. In exceptional cases further classes may be reported as follows:
   • S_o- Stage of ice development thicker than S_a, but having a concentration less than 1/10 (see Example 6, section 3.8).
   • S_d- Stage of development of the thickest remaining ice types (if more than one type remains). It is the fourth stage present after S_a, S_b and S_c.
   • S_e- Shall only be reported when a thinner ice type remains after S_d. Partial concentration of S_e is obtained by subtracting partial concentrations (C_aC_bC_cC_d) from total concentration (C_t) (see Example 2, section 3.8).
5. When S_e is not present,S_d may be a trace of ice (see Example 6, section 3.8).
6. Concentration shall not be indicated for S_o and S_e(see Example 2, section 3.8, and Example 6, section 3.8).
7. Concentration shall not be indicated for S_d when S_eis not present (see Example 3, section 3.8, and Example 5, section 3.8).

Table 3.1: Coding for Sea-Ice Stages of Development (S_oS_aS_bS_cS_dS_e)

Table 3.2: Coding for Lake-Ice Stages of Development (S_oS_aS_bS_cS_dS_e)

Notes for Tables 3.1 and 3.2:

3.4.3 Form of Ice (F)

Floe Size corresponding to S_aS_bS_c S_d and S_e (when S_dand S_eare greater than a trace).

Notes

1. World Meteorological Organization International procedures also permit reporting of F_pand F_s as the primary and secondary forms of all the ice without reference to stage of development.
2. It is Canadian practice to report F_aF_b F_c as predominant floe sizes of S_a S_bS_crespectively. This makes it necessary, when only S_a and S_bare present, that F_a and F_bshall be followed by a dash (-) where F_c would normally appear (see Example 7, section 3.8)

Table 3.3: Coding for Forms of Ice (F_aF_b F_c F_d F_e)

Notes for Table 3.3

1. Width refers to the maximum horizontal extent.
2. At least one code 8 must be used for fast or consolidated ice. Other ice types embedded may retain their floe size (see Example 9, section 3.8).
3. Occasionally the stage of development of fast ice cannot be determined. The area shall be blackened-in to denote fast ice (see Table 3.9).
4. New sea ice does not have a definite form; therefore, when this stage of development occurs as S_a, S_b or S_c, the symbol X shall be used to designate floe size (see Example 4, section 3.8).
5. Floe size is not included for S_o, S_d and S_eif the concentration of these ice types is less than 1/10. Otherwise floe sizes for S_d and S_e are optional.
6. If there is a significant variation in floe sizes in an area containing only one particular ice type, the ISS may enter the applicable floe-size Categories in the lowest part of the oval reserved for floe size. The largest floe-size category shall be put on the left side within the oval, followed by the other applicable floe sizes. In this case, the partial concentrations listed (C_a C_b C_cC_d) would match the partial concentration of floe sizes, instead of different ice types.

3.4.4 Coding and Symbology for Strips and Patches

The symbol, placed at the bottom of the oval in the section reserved for Form of Ice, indicates that the ice is in strips and patches; the concentration within the strips and patches is represented by C.(see Example 11, section 3.8).

When strips and patches are observed in open-water areas, the symbol shall be placed to denote the position of the strips and patches. If the ice in the strips and patches is of the same composition as that inside an adjacent ice edge, no oval is required. If the ice in the strips and patches is of a different composition, an oval shall be used with an arrow or arrow(s) to the strips-and-patches symbol(s). To avoid confusion, the strip symbol must be included with the total concentration (see Example 10, section 3.8).

In an area where the ice is arranged in strips and patches and the ice floes are medium or greater, the floe size shall be indicated by using two ovals. The floe sizes are indicated as normal in the first oval, with the symbol placed between the first and second ovals. The symbol is repeated in the second oval beside the total concentration of the strips and patches (see Example 12a, section 3.8).

An alternate way of reporting the same situation as above:

In an area where the ice is arranged in strips and patches and the ice floes are medium or greater, the floe sizes shall be indicated as normal. Both the total concentration and the concentration within the strips will be placed in the space reserved for C_t, with the symbol between them. When this option is used, C_a C_b C_c and possibly C_d refer to the total concentration and not the concentration within the strips. For example, C_t can be reported as 29 meaning the total concentration is 2 tenths with strips of 9 tenths and the partial concentration(s) shall equal 2 tenths (see Example 12b, section 3.8).

In an area of ice where some thicker ice type(s) is (are) embedded as strips and patches, these shall be indicated by the use of two ovals. The overall partial concentrations of the ice types are indicated in the first oval and the concentrations within the strips and patches are indicated in the second oval. The symbol shall be placed between the two ovals and along with the total concentration in the second oval (see Example 13, section 3.8).

3.4.5 Coding for Brash

If 1 tenth or more of brash is present, it will always be C_a .

If brash is present, S_a will always be a dash (-), otherwise the normal table is to be used.

Brash is already indicated in the table as 1, therefore F_a= 1 confirms the dash (-) for S_a.

Four digits (VKMT) shall be added below the oval to indicate the thickness concentration breakdown of the brash that is present. Table 3.4 (below) shows the thickness Categories for agglomerated brash. The breakdown shall be entered going from right (T) to left (V). In the case where there is no thickness for thin but there are entries for medium, thick and very thick a zero (0) shall be placed in the thin column. This also holds true for medium (M) and thick (K) regardless of the combination (see Example 14, to Example 17, section 3.8).

Table 3.4: Thickness Categories for Brash (VKMT)

3.5 Symbols Used on Ice Charts

3.5.1 Symbols for Dynamic Processes

Symbols for Dynamic Processes

3.5.2 Symbols for Openings in the Ice

Symbols for Openings in the Ice

3.5.3 Symbols for Topographical Features

Symbols for Topographical Features

3.5.4 Symbols for Ice Thickness

Examples:

When more than one measurement has been taken, both mean and maximum thicknesses are reported, as shown below:

30/40

3.5.5 Coding for Stage of Melting

Stage of melting

Table 3.5: Coding for Stage of Melting (ms)

3.5.6 Coding and Symbology for Snow Cover

Coding and Symbology for Snow Cover

Table 3.6: Coding for Snow Depth (s)

3.5.7 Coding and Symbology for Ice of Land Origin

Triangular symbol shown:

nn=number, see following Table 3.7
yy=day of month of sighting

Table 3.7: Number of Bergy Bits/Growlers or Icebergs (nn)

Table 3.8: Symbology for Ice of Land Origin

Notes

Tabular iceberg indicated by adding a horizontal line through any of the symbols as shown in the following example. These symbols can be combined with a number, if exact numbers are known.

Example:

For further detail on reporting ice of land origin, see Chapter 4.

3.5.8 Symbols for Defining Limits

Symbols for Defining Limits

3.5.9 Supplementary Coding for Radar Observations

Relative Roughness

Note:

Areas showing no radar return shall be indicated NIL ECHO.

3.6 Supplementary Procedures for Indicating Total Concentration

In order to facilitate readability of the chart, ice-covered areas may be hatched according to total ice concentration. The hatching symbology (developed by World Meteorological Organization) may be applied to all areas of ice concentration or only to some of them. Whenever hatching is applied, the hatching symbols as shown in Table 3.9 shall be used. No International Rules are given for the thickness of the hatching lines; the thickness may be the same throughout all hatched areas or may vary in the sense that the thickest lines are used for areas of thicker ice. It is Canadian practice not to hatch ice charts except for total concentrations less than 1/10th.

Table 3.9: World Meteorological Organization Symbols For the Hatching of Total Concentration of Ice

Note

Presence of new ice can be indicated by the following symbols scattered throughout area affected:

3.7 Colour Coding Ice Charts

3.7.1 Introduction

For several years, the Ice Service Specialists have been applying a colour code to ice information charts for the Canadian Coast Guard operations in the St. Lawrence River and the Gulf of St. Lawrence. This has proven to be quite beneficial to individuals making transportation decisions based on these information products. More recently, we have modified and expanded this colour code for application in all coastal waters of Canada, including the Arctic.

3.7.2 The Colour Code

This colour code is intended to assist navigation decisions in ice infested water. It is loosely based on the concept of a traffic light where green represents proceed, yellow represents caution and red represents danger. The objective of the colour code application is to enable a person to quickly assess general ice conditions. A ship sailing in a given area can easily assess the general ice conditions and hence qualify the difficulty or ease to either navigate through easily, or to reduce speed or to stop the ship.

However, this does not consider the other variables such as winds, currents or ship design which are important considerations in any ice navigation decision. The most detailed ice information continues to reside in the ice egg codes.

3.7.3 How to Interpret the Code

The following text is intended to assist an individual interpret the colour presentation.

Open or Bergy Water

Areas of open water or bergy water are coloured blue.

Open or bergy water

Presence of Ice

For ice concentration of one tenth or greater, the ice type must be separated into two categories: less than 15 centimetres and greater than 15 centimetres thickness:

Ice Types Thicker than 15 centimetres

The colour for a given ice area will be determined by the total concentration of the ice types thicker than 15 centimetres and is represented by the following list:

Colour code for ice types thicker than 15 centimetres

Presence of Old Ice

The presence of old ice (multi-year ice) is indicated by the colour purple, and is represented by the following list:

Presence of Fast Ice

The presence of fast ice, regardless of the thickness is always black or grey.

or

Ice Types Thinner than 15 centimetres - No Colour Assigned in Background

Ice less than 15 centimetres in thickness is indicated by a star code and the colour of the stars is determined by the predominance between grey ice (10 to 15 centimetres) and new ice (0 to 10 centimetres), and is represented by the following list:

Ice Types Thinner than 15 centimetres - Colour Assigned in Background

Secondary ice types with less than 15 centimetres in thickness are indicated by a star code and the colour of the stars is determined by the predominance between secondary grey ice (10 to 15 centimetres) and secondary new ice (0 to 10 centimetres), and is represented by the following list:

The star code is placed over top of the background colour. In the case of 9 to 10 tenths of ice (red background) and predominance of ice thickness between 10 and 15 centimetres (red stars), there is only one colour which can be represented: red. The result of red stars on a red background is red.

3.8 Examples of the Use of the Egg Code

3.8.1 Various Ice Type and Concentration Combinations

3.8.2 Strips and Patches

3.8.3 Brash