Canadian marine warning program: chapter 4

Ice Warnings

• Rapid Closing of Coastal Leads Warnings
• Ice Pressure Warnings
• Special Ice Warnings

Ice Warnings are issued by the Canadian Ice Service (CIS), which is a specialized forecast centre within Environment Canada that deals specifically with providing information about ice in Canada’s navigable waters. Ice Warnings are included in the Ice Forecast bulletins issued by the CIS and are conveyed using the keywords “in effect.” 

Ice Warnings are designed to alert mariners to hazardous ice conditions that have already developed, or are forecast to develop, either locally or throughout the entire marine area under the warning. Ice Warnings are issued for specific ice conditions (Rapid Closing of Coastal Leads and Ice Pressure) and non-specific ice conditions (Special Ice) which may be hazardous to navigation or marine operations.

Rapid Closing of Coastal Leads Warnings

Rapid Closing of Coastal Leads Warnings are issued when the forecast combination of winds and ocean currents will result in the movement of pack ice rapidly closing any open waterways, known as leads, along the affected coastal sections.

Coastal leads can become blocked by six tenths or more of greywhite or older ice within a 12-hour period. Rapid Closing of Coastal Leads Warnings are relevant to all marine interests and can be issued for all coastal marine areas that have an ice forecast.

Ice Pressure Warnings

Ice Pressure Warnings are issued when a prolonged period of strong winds are forecast, which would cause ice pressure within the ice pack or along the coast.

Strong ice pressure could cause ships to lose the ability to navigate freely and could push ships towards potentially hazardous areas.  Ice Pressure Warnings are relevant to all marine interests and can be issued for all marine areas that have an ice forecast.

Special Ice Warnings

All other non-specified ice conditions that may warrant a warning being issued will be covered in a Special Ice Warning. Special Ice Warnings are relevant to all marine interests and can be issued for all marine areas that have an ice forecast.

A Special Ice Warningis issued for ice conditions that may be hazardous to marine operations. For example, a Special Ice Warning may be issued when ice is in an area at a time when ice is not usually there.