Arctic Ecology and the Fundamental Role of Snow and Ice

Key Insight

The Arctic Ocean, often considered the least understood of the world's seas, is ecologically unique. Its waters are relatively sterile, not primarily due to cold or lack of light, but because of their vertical stability, which prevents the essential upwelling of inorganic salts like phosphates, nitrates, and silicates necessary for rich life in sunlit layers. This results in a low number of plankton species and small populations, indicative of the ocean's 'youth as well as its sterility.' Oceanographers categorize the Arctic into five regions based on species distribution, including perpetually ice-covered abyssal zones and brackish coastal areas influenced by massive river outflows, such as the Lena River, which discharges more meltwater than any other Northern Hemisphere river.

Despite low productivity, arctic marine life is fundamentally structured around a spring bloom of epontic phytoplankton, supporting a food web including herbivorous zooplankton, carnivorous zooplankton, various crustaceans, and fish like polar and arctic cod. Sea ice, while blocking 99 percent of sunlight to active water layers, crucially insulates creatures from extreme winter cold and has profoundly shaped their evolution. For terrestrial life, snow is as essential as rainfall or sunlight in other biomes; it provides stable platforms for animals to browse, acts as a barrier for migrating birds, offers cover and insulation for species like ermine and ptarmigan, and creates contours for predator-prey dynamics. Snow also dictates behaviors like hibernation for ground-dwelling squirrels.

Ice, considered an extreme form of snow by ecologists, similarly alters landscapes and affects animal lives profoundly. The type and quality of sea ice are critical for arctic marine mammals: seals and walrus depend on ice floes as platforms for resting, molting, birthing, and protection from predators like orcas. Ice acts as a 'winter highway' for migrating muskoxen, caribou, polar bears, and arctic foxes. Polynyas, persistent areas of open water maintained by specific wind, current, and tide patterns, are vital winter refuges and spring staging grounds for various marine mammals like walrus and bearded seals, and seabirds such as black guillemots and eiders, despite the challenging conditions for food webs.