Ice Cover Classification

In order to understand ice formation and the types of ice in the Great Lakes, the NOAA Great Lakes Environmental Research Laboratory (GLERL) and the U.S. Coast Guard use Synthetic Aperture Radar (SAR) data from the NOAA CoastWatch Great Lakes Node to monitor six different types of ice, ice thickness, and ice cover. This risk assessment tool is known as the Ice Condition Index (ICECON). The U.S. Coast Guard uses ICECON to identify areas that require ice breaking operations and ship transit assistance. These ice breaking operations allow government and commercial ships to travel through the Great Lakes unobstructed.

Satellite SAR Ice Type ICECON Scale

Example Ice Types
ThicknessColorImpacts to Vessels
0Calm Water
(or below noise floor)
0″BlueNo Ice present or imminent.
1New Lake Ice<2″GreenMinimum ice concentrations and thickness, Does not present hindrance to commercial navigation.
2Pancake Ice2″ – 6″YellowLight Ice conditions present. Still open water areas. May be some hindrance to less ice-capable ships.
3Consolidated Flows6″ – 12″OrangeLight-to-moderate ice conditions present. Less ice-capable ships may need icebreaker assistance for transit and /or be at risk for damage.
4Lake Ice w/patchy
crusted snow
Up to 28″Moderate-to-Heavy Ice conditions present. All Commercial ships may require ice breaker assistance for transit.
Up to 9-11m
RedHeavy-to-extreme ice conditions. All transits require icebreaker escort. Approaching or exceeds capabilities of light icebreaker assets. Increased risk of damage to vessels.