365 Days of Climate Awareness 63 - The Arctic Ocean

The Arctic Ocean is the body of water which spans the North Pole and extends down to roughly 60°N latitude, and is surrounded by North America, Asia, Scandinavia and Greenland. On average Arctic water is colder and fresher than in other oceans, because of high freshwater input from snow and ice melt and low evaporation. It is almost completely covered in ice during winter, but ice cover in summertime has been shrinking, with large stretches near land now open water. Though melting and freezing of sea ice does not affect global sea level, Arctic ice cover does affect regional dynamics and is an important indicator on the state of the climate.

Orthographic map of the Arctic Ocean.

Because the Arctic Ocean communicates with other ocean basins only through a series of relatively narrow straits, water circulates poorly and can become regionally very stratified. But the surface communicates pulses of comparatively fresh water, generally from the Pacific, with high rates of precipitation in its northeastern area, to the Atlantic, where significant evaporation occurs. Water also enters from the Atlantic, roughly ten times as much as from the Pacific, but it is denser and goes to the bottom.

As in the Antarctic region, phytoplankton photosynthesizing in the summer months are the basis of the food web, which includes a huge array of invertebrates, fish and mammals, both marine and terrestrial. Polar bears are gradually going extinct as the sea ice disappears and with it their opportunities to hunt.

Sea ice extent is a noisy signal, because it is responsive to many different influences, and global temperature is only one. Increased storm activity, pulses of water water from other basins, multi-year current variations. However, the year-to-year noise averages easily into a downward trend, where in the last 40 years summer ice cover has declined by more than 42%. The sensitivity of the cryosphere to climate, and the effect of air and ocean currents to transport heat from the equator to the poles, has made the arctic very important to climate science, not only displaying the effects of warming, but also providing evidence of the dynamics.

Tomorrow: the polar vortex.

Be well!