See also:

Old Crow River Ice-free Period
 
Temperatures at Old Crow
 
Peel River Ice Bridge

Arctic Borderlands Ecological Knowledge Co-op

What is happening?

• This graph shows the length of the ice-free period observed for the Porcupine River near the U.S./Canada border.
• There is year to year variation in the dates of the ice-free period, but no clear trend in the timing or length of the ice-free period.
• In 2007, the ice-free period started May 23rd, which was about 5 days later than average. The date of freeze-up was about five days earlier than average so that the overall length of the season was about 9 days shorter the average based on the last 21 years.

Why is it happening?

• The timing of winter freeze and spring break-up depends on weather conditions in the river basin in fall, winter and spring. Long-term trends in these weather conditions can be expected to affect the river's ice conditions.

Why is it important?

• Timing of spring break-up and of winter freeze affects nesting waterfowl, river crossing and travel conditions for people and migrating animals, and conditions in the river such as growth of algae.
• The length of the ice-free season affects summer habitat for animals using open running water.

Technical Notes

• The ice-free period of the river is defined as the period during which ice formation does not affect river flow by more than 5% compared to flow during open water conditions. Thus, the break-up and freeze-up times presented here reflect the final stage of ice break-up and first stage of ice freeze-up on the river.
• The data presented here are from the Porcupine River near the U.S./Canada border, and were obtained from Water Survey, Environment Canada. Dates of the ice-free period for 1991 were estimated from data recorded for the Porcupine River at Old Crow.