DEH CHO DRUM - A Great Slave Helicopter positions the ice breakup teepee on the ice at the Mackenzie River at Fort Simpson. The teepee is used to time when breakup occurs. Photo courtesy of Sean Whelly A Great Slave Helicopter positions the ice breakup teepee on the ice at the Mackenzie River at Fort Simpson. The teepee is used to time when breakup occurs. Photo courtesy of Sean Whelly