Sea of Okhotsk

The Sea of Okhotsk is a marginal sea located in the northwestern Pacific Ocean. It is a large body of water surrounded by several distinct landmasses. To the east lies the Kamchatka Peninsula of Russia. The Kuril Islands form its southeastern border. To the south is the Japanese island of Hokkaido. The large island of Sakhalin and the Siberian coast define its western and northern edges. This sea is vital for marine life and global ocean patterns.

Geography and depth define the physical structure of this sea. The Sea of Okhotsk has a mean depth of 591 meters. Its maximum depth reaches 3,380 meters. It connects to the Sea of Japan through two main routes. One route is the Sakhalin Gulf and the Gulf of Tartary to the west. The other is the La Pérouse Strait to the south. The northeast corner of the sea is known as the Shelikhov Gulf. The sea takes its name from the port of Okhotsk. That port was named after the Okhota River.

Seasonal changes create a unique biological engine in these waters. In winter, cold air from Siberia forms sea ice in the northwest. This process is influenced by the Amur River. The river pours large amounts of freshwater into the sea. This freshwater lowers the salinity, or salt content, of the upper layers. Lower salinity can raise the freezing point of the surface water. As sea ice forms, it expels salt into the deeper layers of the ocean. This creates heavy, salty water that sinks toward the bottom. This sinking water carries oxygen and nutrients toward the deep sea. These nutrients support an abundant variety of sea life.

Many islands exist within the Sea of Okhotsk. Some are very large, like Sakhalin and Hokkaido. Most islands are located in coastal waters or within the Kuril Islands chain. Iony Island is unique because it sits in open waters. Most of these islands are uninhabited by humans. This makes them perfect breeding grounds for animals. Seals, sea lions, and various seabirds live there. Large colonies of crested auklets also use these islands for nesting.

History shows a long period of exploration and shifting control. The Okhotsk culture and Ainu people lived in this region long ago. European explorers began arriving in the 1600s. Vassili Poyarkov and Ivan Moskvitin visited the sea in 1639 and 1645. The Dutch captain Maarten Gerritsz Vries charted parts of the coast in 1643. Later, Vitus Bering led an expedition that mapped the entire coast starting in 1733. Political boundaries changed after 1945. The Soviet Union occupied the Kuril Islands after World War II. Today, Japan still claims the southern Kuril Islands.

Modern environmental changes are affecting the sea's ecosystem. The Sea of Okhotsk has warmed in some areas by 3°C since preindustrial times. This warming is happening three times faster than the global mean. Higher temperatures inhibit the formation of sea ice. This change also shifts where fish populations live. For example, the salmon catch on the northern Japanese coast fell by 70% in the last 15 years. Meanwhile, the Russian chum salmon catch has quadrupled.

Economic resources like fishing and energy are also important. The sea is rich in shellfish, crabs, and many fish. A central area called the Peanut Hole is a site for large pollock catches. In 2013 and 2014, the United Nations ruled that this area belongs to Russia's continental shelf. The sea also contains significant energy reserves. Scientists have identified 29 zones for oil and gas accumulation. These reserves include 1.2 billion tons of oil and 1.5 billion cubic meters of gas. However, working in these waters can be dangerous. In 2011, the drilling rig Kolskaya sank during a storm.