Sea of Japan

The Sea of Japan is a marginal sea in East Asia.

It is located between the Japanese archipelago and the mainland of the Russian Far East. To the west lies the Korean Peninsula. The sea is bounded by Sakhalin island to the north. It is separated from the Pacific Ocean by the Japanese islands. This location makes it a nearly enclosed body of water.

Like the Mediterranean Sea, it has almost no tides. This is because it is so isolated from the open ocean.

The sea's water balance depends on specific connections. It connects to neighboring seas through five shallow straits. These include the Strait of Tartary, La Pérouse Strait, Tsugaru Strait, Kanmon Straits, and the Korea Strait. The Korea Strait consists of the Western Channel and the Tsushima Strait. These straits are mostly shallow, often 100 meters deep or less. This shallowness limits water exchange with the Pacific Ocean. Consequently, the sea has lower salinity and less faunal diversity than the open ocean. However, the seawater has high levels of dissolved oxygen. This leads to high biological productivity in the region.

The sea has three distinct underwater basins. The Japan Basin is in the north and is of oceanic origin. It is the deepest part of the sea. The Yamato Basin sits in the southeast. The Tsushima Basin, also called the Ulleung Basin, is in the southwest. The Tsushima Basin is the shallowest, with depths below 1,000 meters.

The sea's shape is somewhat like a carrot. It is wide in the south and narrows toward the north. The surface area is about 970,000 square kilometers. The maximum depth reaches approximately 3,700 meters. The coastline is very long, and Russia owns the largest portion.

Geological history shows how the sea formed. During the Early Miocene, the Japan Arc began to form.

At that time, the Sea of Japan began to open. The northern and southern parts of the Japanese archipelago separated. During the Miocene, the sea continued to expand. Later, the formation of high mountain ranges in northeast Japan occurred. The eastern margin may host a subduction zone. This zone is responsible for large earthquakes in 1940, 1964, 1983, and 1993. The formation of the straits also changed animal migrations. The Tsugaru and Tsushima straits formed first. They stopped elephants from migrating into the Japanese islands 2.6 million years ago. The La Perouse Strait formed much later, between 60,000 and 11,000 years ago. This closed the path for mammoths moving to northern Hokkaidō.

Exploration of the sea has a long history. For centuries, the sea protected Japan from land invasions. Many explorers mapped these waters in the 18th and 19th centuries. Russian expeditions mapped Sakhalin and the Japanese islands between 1733 and 1743. In the 1780s, Jean-François de Galaup traveled through the strait named after him. Other explorers include William Robert Broughton and Adam Johann von Krusenstern. In the mid-1800s, American, Canadian, and French whaleships cruised the sea.

They primarily targeted right whales. As those numbers declined, they began catching humpback whales. They also attempted to catch blue and fin whales. Between 1847 and 1892, many vessels entered via the Korea Strait. They often exited through the La Pérouse Strait.

Economic activities in the region are significant. Because of the high biological productivity, fishing is the dominant activity. Shipments across the sea have been moderate due to political issues. However, shipping is steadily increasing. This growth is driven by expanding East Asian economies. The sea also features various underwater ridges. The Yamato Ridge is made of volcanic rocks like granite, rhyolite, andesite, and basalt. Other ridges include the Okujiri, Sado, Hakusan Banks, Wakasa, and Oki ridges.

There is an ongoing naming dispute regarding this sea. The name "Sea of Japan" is the dominant term in English. Japan asserts this name has been used internationally since the early 19th century. In contrast, South Korea argues that "East Sea" was used historically. They request that "East Sea" be used alongside "Sea of Japan." North Korea advocates for the name "East Sea of Korea."

Even the International Hydrographic Organization (IHO) has dealt with this. Their previous standard, S-23, used "Japan Sea." The IHO is now developing a new digital standard called S-130. This new system will use unique identifiers for maritime areas instead of names.