The Arctic Ocean is unique among the world’s oceans for many reasons. It is largely ice-covered (much of it year-round, the rest seasonally) and it is relatively isolated from the rest of the world’s oceans, much like the Mediterranean Sea. Follow the water as it enters and exits the Arctic Ocean.
- Cold and relatively less salty water enters the Arctic Ocean through the narrow Bering Strait between Alaska and Siberia.
- In winter, frigid winds from the icy Alaskan interior blast over the shallow Chukchi Sea. The cold air freezes seawater into sea ice and then pushes it out to sea, leaving new pockets of seawater available for freezing. This is the “ice factory,” which manufactures ice. When seawater freezes, it releases salt into surface waters. These cold, salty waters become denser and sink, spilling over the continental shelf into the western Arctic Ocean. They create a layer known as a halocline (from the Greek words for “salt” and “slope”). Halocline waters lie atop a deeper layer of saltier, denser—and warmer—waters that flow into the Arctic from the Atlantic Ocean. Why is the halocline important? There is more than enough heat stored in this Atlantic water to melt the polar ice cover from below.
- Once in the Arctic Ocean basin, the water is swept into a huge circular current—driven by strong winds—called the Beaufort Gyre. Mighty Siberian and Canadian rivers also drain into the circular current to create a great reservoir of relatively fresh water.
- Periodically, the winds shift and the circular current in the Beaufort Gyre weakens, allowing large volumes of fresh water to leak out and cross the Arctic in the Transpolar Current.
- The Arctic Ocean is largely isolated from the rest of the world ocean by land. The water exits the Arctic Ocean via several “gateways.” It can flow through the Fram Strait, between northeast Greenland and Svalbard Island, and then branch around either side of Iceland. It can flow around the west side of Greenland through Baffin Bay and out Davis Strait. It may also flow through a maze of Canadian islands and out Hudson Strait.
- Warmer, saltier surface water from the Atlantic penetrates the Arctic Ocean through Fram Strait and the neighboring Barents Sea; this is water which originally came from the Gulf Stream. Once in the Arctic, this water is cooled as it travels cyclonically (counter-clockwise) around the perimeter as a boundary current, finally exiting Fram Strait as a colder, fresher water mass (magenta arrow on map). This warm-to-cold conversion is a crucial component of the global ocean’s overturning circulation that helps maintain the earth’s climate.
This complex circulation system in the Arctic—which impacts the entire food web—is in a delicate balance. In recent years, scientists have documented changes in the Arctic system, including a dramtatic reduction in sea ice cover and a weakening of the Beaufort Gyre circulation system, that are attributed to climate change. The Arctic Ocean affects the way of life of not only the Arctic native peoples, but also those of us living “downstream,” in Europe and North America. As such, the Arctic Ocean, and the effect of changes that are taking place there, are the focus of intense study by oceanographers of all disciplines.
