Sharks are adaptable predators found in diverse marine environments across nearly every major ocean basin. Their widespread distribution often leads to questions about whether any part of the global ocean is entirely devoid of their presence. While sharks are ubiquitous, there is one ocean where their populations are notably scarce and their diversity significantly limited.
The Ocean Where Sharks Are Absent
No ocean is completely without sharks. However, the Arctic Ocean is the ocean with the fewest sharks and the least diverse shark populations. While transient sharks may occasionally venture into its fringes, the central Arctic Ocean hosts very few resident shark species. The most notable exception is the Greenland shark (Somniosus microcephalus), a species uniquely adapted to the frigid environment. Other species, such as the Pacific sleeper shark, porbeagle, and salmon shark, are known to inhabit the northern Pacific and Atlantic fringes that border the Arctic, but their presence within the Arctic Circle is less common or seasonal.
Environmental Factors Limiting Shark Presence
The Arctic Ocean’s extreme environmental conditions significantly limit shark presence and diversity. Water temperatures are consistently low, often near or below the freezing point of saltwater (-1.8 degrees Celsius / 28.8 degrees Fahrenheit). While warmer Atlantic water flows into the Arctic at depths, it is typically separated from colder, less saline surface layers by a strong density gradient. Only a few specialized sharks, like the Greenland shark, can tolerate these perpetually cold conditions year-round, adapted to prevent freezing.
The Arctic Ocean also has unique salinity characteristics, with lower average salinity compared to other major oceans. This reduced salinity, particularly in surface waters, is due to significant freshwater influx from large rivers and extensive melting of sea ice. This creates a stratified water column where less dense, fresher water floats atop saltier, denser layers, hindering vertical mixing. This stratification and lower salinity can pose physiological challenges for many shark species adapted to more typical oceanic salinity levels.
The extreme cold and unique water stratification also directly influence prey availability, limiting shark presence. The harsh conditions and limited sunlight during much of the year restrict primary productivity and overall biodiversity in many parts of the Arctic. While certain areas experience seasonal algal blooms, the overall food web is less complex and abundant than in warmer oceans. This scarcity of suitable prey contributes to their limited numbers, though opportunistic feeders like the Greenland shark thrive by consuming available fish, seals, and carrion.