Freeze-up on the Beaufort Sea depends on the southern limit of the Arctic Pack, the multi-year ice, up to 4.5 meters thick, which moves depending on Arctic Ocean currents and wind patterns [1]. In late September, ice formation moves outward from multi-year floes. The average freeze-up date in Tuktoyaktuk between 1981 and 2010 was October 8, although across the Beaufort Sea region the freeze-up date has been shifting later by 6.5 days per decade [2, 3]. 

Spring thaw moves down Mackenzie in June, and open water develops in Kugmallit Bay. The fast ice across Kugmallit Bay and along the Tuktoyaktuk Peninsula fractures in late June to mid-July, depending on summer temperatures (which are themselves dependent on the location of the Arctic Pack – when northwesterly winds keep it closer to shore, the summer will be cold, and break-up will be delayed. The average break-up date in Tuktoyaktuk between 1981 and 2010 was June 18 [4]. In the Beaufort Sea region, the break-up date has been trending earlier by 2.7 days per decade [2].

Changes to the distribution of sea ice and length of the open water season will have important impacts on erosion and flooding, as well as seasonal temperatures, wildlife migration, and access to hunting and fishing areas [5,6,7, 8]. Since 1958, the annual sea ice cover over the Arctic has decreased and thinned, break-up begins earlier and freeze-up begins later in the year [9, 10, 11].

Climate change has a long-term impact on ice dynamics, by gradually changing spring and fall freezing and thawing conditions and thus lengthening the open-water seasons. However, human activities can also have short-term effects on sea ice. Prior to 1979, Kugmallit Bay froze clear across, with few drifting ice floes present in the fall [12]. However, ice-class ships coming in and out of port in Tuktoyaktuk began breaking up the forming ice during their transit, and ice blocks would float around and be pushed up on the shore by wind and currents creating pile-ups 3 to 5 meters high [11]. Unlike unmoving landfast ice, pile-ups have the potential to gouge the seabed and damage the shoreline and protection structures.