5.1 Daily Ice Analysis Charts

5.1.1 Description

These 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 charts are meant to provide ice information for strategic planning for their activities during the next 24 hours.

Please note that there are significant differences between daily ice analysis charts and observed/image analysis charts:

• Frequency

Daily ice analysis charts are done on a daily basis during the season, whereas image analysis charts are done when images arrive for a particular operational area. Observed charts are generated whenever ice conditions are encountered either from ships, helicopters or aircraft.

• Detail

The other significant difference resides in the amount of detail on each chart. Observed and image analysis charts have more latitude regarding the amount of detail and information that can be placed on the product. Daily ice analysis charts will have less detail pertaining to ice areas and egg definitions. Consequently, daily ice analysis charts have a more generalized look compared to observed/ image analysis charts.

5.1.2 Method of Production

Daily ice analysis charts are computer-generated with the use of mapping and image analysis software. The system allows the forecaster to draw lines and place eggs, symbols, drift arrows, and ship positions.

The forecaster will use a variety of data sources such as NOAA AVHRR, GOES, SSMI, QUICKSCAT, ENVISAT and particularly RADARSAT, as well as the image analysis charts from these data. The field observation charts from ships, helicopter and aircraft provide ground truthing (See Figure 5.13). However on days when no data is available, or when the image analysis does not coincide with the valid time of the daily ice analysis chart (1800 UTC), the ice model from CIS can be used to advance ice to the valid time.

The Egg Code

There are some limitations on the use of the Egg Code for daily analysis charts. Later in this chapter, we will specifically outline the significant differences. For a complete version of the Egg Code, please see Chapter 3.

Figure 5.1: Elements of the Egg Code Used for Daily Ice Analysis Charts

Note: The symbols C_a C_b C_c and F_aF_bF_c correspond to S_aS_bS_c respectively.

Figure 5.2: Concentration(C)

Notes:

1. When only one ice type is present, the partial concentration shall not be indicated (see Example 1).
   
   
2. When only a trace of thinner ice is present with thicker ice, only the concentration of the thicker ice is indicated inside the egg; the thinner ice type will show as Sd (see Example 2).
   
   
3. When 2 or 3 ice types are present with more than 1/10 concentration, the partial concentration for each type will show inside the egg (see Example 3).

Figure 5.3: 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 type S_d, of which the concentrations are reported by C_a C_b C_c respectively.

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 Sea, Lake or River depending on where it forms. In Canada, the practice is to use the Lake Ice code 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. 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 4).

   S_d - stage of development of the thickest remaining ice types. It is the fourth stage present after S_a, S_b and S_c. Partial concentration must be at least 1/10 (see Example 4), except during the freeze-up period when a trace of new ice may be present (see Example 2).

   S_e - this stage of development will not appear on a daily ice analysis chart.

Table 5.1: Coding for Sea-Ice Stages of Development (S_o S_a S_b S_c S_d)

Description	Thickness	Code
New ice	< 10 cm	1
Grey ice	10 -15 cm	4
Grey-white ice	15- 30 cm	5
First Year ice	> 30 cm	6
Thin first-year ice	30- 70 cm	7
Medium first-year ice	70- 120 cm	1·
Thick first-year ice	> 120 cm	4·
Old ice		7·
Second-year ice		8·
Multi-year ice		9·
Ice of land origin
Brash		-

Table 5.2: Coding for Lake Ice Stages of Development (S_oS_aS_bS_cS_d)

Notes:

Figure 5.4: Form of Ice (F)

Floe Size corresponding to S_a S_b S_c

Table 5.3: Coding for Form of Ice (F_aF_bF_c)

Notes for Table 5.3:

1. Width refers to the maximum horizontal extent.
   
   
2. At least one code 8 must be used for fast or consolidated ice. When significant ice types are present and it is important to maintain their floe size, the younger ice type will be coded as fast ice (see Example 5).
   
   
3. Occasionally the stage of development of fast ice cannot be determined. The area shall be blackened-in to denote fast ice. Also when the area in question is very small or difficult to place a label, it can be blackened-in. For areas with a trace of old, second or multi-year ice embedded in fast ice, the area will be shaded-in in grey with an attached label or egg.
   
   
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 1).
   
   
5. When an area of ice has one particular ice type but varying floe sizes, the basic rule will be to represent the ice type that has the predominant concentration and use the corresponding floe size (see Example 6). An exception would be when there are a few giant old floes in a field of medium old floes (see Example 7).
   
   
6. Pancake floe size (code 0) will not appear on CIS charts. Since pancake ice floes implies new ice, the standard floe size when dealing with new ice at CIS is always X.
   
   

Coding and Symbology for Strips and Patches  

The symbol , placed at the bottom of the egg in Form of Ice section, indicates that the ice is in strips and patches and that the concentration within the strips and patches is represented by C (see Example 8).

In an area in which the ice is arranged in strips and patches and the ice floes are medium (code 4) or greater, the floe size shall be indicated by using two eggs. The floe sizes are indicated as normal in the first egg with the symbol placed between the first and second eggs. The symbol is repeated in the second egg beside the total concentration of the strips and patches (see Example 9).

In an area of ice in which some first-year or thicker ice type(s) is/are embedded as strips and patches, the strips and patches shall be indicated by the use of two eggs. The overall partial concentrations of the ice types are indicated in the first egg and the concentration within the strips and patches are indicated in the second egg. The symbol shall be placed between the two eggs and along with the total concentration in the second egg (see Example 10). Double eggs will be indicted with a leader line to the polygon in question.

Where there are isolated strips and patches of ice, of less than 1/10 concentration, located outside the main ice areas, the strip () symbol will be placed in the area of these strips. Usually these symbols are used to indicate ice in the final stage of melt.

5.1.2.1 Defining Polygons

The parsing of ice areas can be done in one of two ways:

1. By various ice types;
2. By concentration.

Note that only solid lines will be used to separate areas of different ice type/concentration (no dash lines).

1) Ice Type

Mandatory boundaries are required between new, grey, grey-white, first-year and old ice.

Please note that ice codes 2 (nilas ice, ice rind), 3 (young ice), 8 (first stage thin first-year ice) and 9 (second stage thin first-year ice) and X (undetermined or unknown) will not appear on any daily ice analysis charts from CIS.

For old ice, (7·, 8· and 9·) boundaries are required between areas with concentrations of:

• No old ice
• Trace of old ice
• 1 - 3/10
• 4 - 6/10
• 7 - 8/10
• 9 - 9+/10

old ice (7 · , 8 · and 9 · ) with a concentration of 4 tenths or more will be considered predominant.

When two ice types are present in equal concentration, the older/thicker type is considered predominant.

When three or more types are present in equal concentrations, the second oldest is considered predominant.

2) Total Concentration

In the case of total concentration, mandatory boundaries, shown as solid lines are required between areas of:

The total concentration is the first determining factor in defining ice boundaries. Partial concentrations of new ice are ignored when first-year or thicker ice is present.

5.1.2.2 Floe Size

Mandatory boundaries must also be placed between areas of predominantly medium floes or larger (code 4) and areas of predominantly small floes or smaller (code 3) when 6 tenths of thin first-year or thicker/older ice are present.

5.1.2.3 Discretionary boundary

In addition to the guidelines for mandatory boundaries, discretionary boundaries can also be used when sufficient data or knowledge of the ice regime has been verified by up-to-date reconnaissance flight, reports or satellite information. These boundaries are to be maintained on subsequent charts only if there is sufficient knowledge of the location, as provided by these data sources.

Discretionary boundaries should only be used in operationally sensitive areas, namely:

• Great Lakes: shipping routes
• Gulf of St. Lawrence: shipping routes
• Newfoundland: coastal waterway to Botwood
• Arctic: shipping routes

Ice type to consider:

When considering the use of a discretionary boundary, only first-year and old ice are considered, provided there is sufficient knowledge to supply this additional detail. The exception would be in the Great Lakes, where thick or very thick lake ice and areas of ridging should be considered for discretionary boundaries.

Ice Concentration of ice to consider:

Total ice concentration must be at least "close pack" (7 or 8 tenths of ice). New ice, as usual, is ignored when evaluating the total concentration.

Variance of the concentration to consider:

A discretionary boundary may be used if the partial concentration of the first-year or thicker (thick or very thick lake ice) ice varies by at least 3 tenths in a definable area within a mandatory polygon (see Examples 13 and 14).

5.1.2.4 Valid Time

Normally every daily analysis chart generated at the Canadian Ice Service has a valid time of 1800 UTC. The chart thus represents ice conditions at 1800 UTC.

5.1.2.5 Corrections and Amendments

When a correction or amendment is made to the chart, the abbreviation CCA or AAA will appear next to "ICE ANALYSIS/ANALYSE DE GLACES" at the top of the legend.

• A correction is required if an error appears on a chart (examples: C_t indicated 5/10, but should have read 8/10; the ice drift is missing; wrong date for an image in the legend).
• An amendment is warranted when a significant change in ice conditions in a certain area occurs (examples: C_t was put as 5/10 but a report indicated that the concentration was 9+/10; ice is reported in an area shown as open water).

5.1.2.6 Chart Legend

The legend is used on the daily ice analysis charts to describe the region, the valid time and date, what information the chart is based on and any warnings in effect. The information on the source data is to give the client an idea of what was used to prepare the chart, to give a general level of confidence. Only sources that made a significant contribution to the analysis will be indicated. Where possible, the time and the area covered by that source will be given.

Figure5.2: Example of Chart Legend

5.1.2.7 Deadlines

Deadlines may vary from chart to chart, and from season to season.

• Transmission

  As a general rule, at least one chart should be made ready for transmission from CIS at 1600 Eastern Standard Time (or Daylight Saving Time). However, in consultation with the CCG Ice Operations Centre(s), priorities regarding which chart to send out first will be determined on a daily basis, to ensure that the most operationally sensitive chart is first selected for transmission.

• Data reception and integration

  For information received from outside sources (CFR charts, CCG ship reports, etc.), a minimum of 2.5 hours before the transmission deadline is required to integrate it into the daily ice analysis chart. In most cases when the information arrives late, the forecaster will endeavour to integrate the information, especially if it is operationally sensitive. However, this may cause a delay in the delivery of the chart. The decision to process the information or not, for use in the chart, will be at the discretion of the forecaster in consultation with CCG ice operations office.

5.1.3 Dissemination of Charts

Upon completion of the analyses, daily ice analysis ice charts are disseminated electronically via a product delivery system. Clients will receive products via e-mail, fax or the internet. ISS and CCG clients have a special customised delivery system set up.

5.1.4 Symbols Used on Daily Ice Analysis Charts

Symbols for Dynamic Process

Indicates the direction and drift speed (in nautical miles per day) in the general area for the next 24 hours from the valid time of the daily ice analysis chart

Note
The drift arrow gives the direction and the number of nautical miles that ice, within 10 nm of the centre of the arrow, is expected to travel over the next 24 hours. Due to the influence of currents and winds, there can be large differences in the direction and speed of the ice even over areas within close proximity. This drift does not take into account the effect of land on the drift. When the arrow points towards land, there may be an increase in ice concentration and ice pressure along the coast.

Symbols for Defining Limits

Analysed edge or boundary
Bergy water boundary

Other Symbols Used

Ship reports	CGTF I5Z	Used to indicate the latest position and time of a Coast Guard ship (during last 24 hrs).
Bergy water		Symbol used to indicate bergy water conditions.
Ice-free		Symbol used to indicate ice-free conditions.
Ice island or Ice island fragment		Symbol used to indicate ice island or fragments
Open water		Stipple pattern used to indicate open water areas (less than 1/10).
Fast ice		Blackened area representing fast ice.
Strips and patches		Symbol used to indicate strips and patches of ice outside the ice edge.

Note
Some symbols may be displaced and have a leader line pointing to its actual location.

Figure 5.8: Black and White Daily Ice Chart

Figure 5.9: ISS Colour-Coded Daily Ice Chart

Figure 5.10: Exemple of Corrected/Amended Chart

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Last Updated: 2003-03-28

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