The amount and type of sea ice present, and the total minimum area it covers during the summer season, impacts human activity and biological habitat. Lying at the interface between ocean and atmosphere, it is influenced by the temperature of the air and the water, as well as by surface winds and ocean currents. In turn, the presence or absence of sea ice has a profound impact on the water below it and the air above it.
Between 1968 and 2020, summer sea ice area in the Northern Canadian Waters declined at a rate of 7.5% per decade (Source: Environment and Climate Change Canada (2020) Climate Research Division). Arctic sea ice is very sensitive to climate change because of the sea ice-albedo feedback that influences how much solar radiation is absorbed into the sea ice-ocean system. Research has shown that the loss of Arctic sea ice is a very significant contributor to the recent amplification of Arctic temperature change compared to the global average.
Changes in the amount of sea ice, the location of ice edges and the timing of seasonal ice formation and melt have complex, cascading ecosystem impacts. Sea ice decline results in a loss of wildlife habitat, as it serves as hunting platforms for polar bears and as resting grounds and nursery areas for walruses and seals. Algae that grow on the underside of sea ice are also important to the marine food supply. Duration of open-water season, and ice formation and breakup dates are also of high importance for maritime transportation and shipping planning.
Sea ice is described by the area it covers, its thickness, its age, and its movement with the winds and ocean currents. This chapter will focus on three of those characteristics:
- Sea ice concentration (the fraction of ocean covered with sea ice)
- Sea ice thickness (or volume/mass)
- Sea ice drift