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The Yellow Sea

Ara Bike Path
Learn about the Yellow Sea, the water body on Korea's western coastline.

The Ara Bike Path begins on the edge of the Yellow Sea (황해; map; West Sea). Gaze westward. When the tide ebbs, you’ll see a vast muddy expanse surrounding Yeongjong Bridge (영종대교; map) and Yeongjong Island (영종도; map) where Incheon International Airport hums.

A picture of a bike and the Ara West Sea Lock Certification Center
The Ara Bicycle Path begins on the edge of the Yellow Sea, whose muddy flats feed birds migrating as far Australia.


Ever wonder where the name “Yellow Sea” comes from? Year-round westward winds swipe sediment from China’s Gobi Desert and deposit thin sheets of yellow sand atop the sea’s waves as it crosses towards the Korean peninsula.

East Sea vs. West Sea

Two seas lie dominate South Korea’s coasts. The East Sea, or Sea of Japan, in the east. And the West Sea, or Yellow Sea, in the west.

Not only are the seas located on opposite sides of the country, but their topographies and characteristics are inverted.

Let’s compare.

  • Average depth:
    • East Sea: 1,530 meters (5,020 ft)
    • West Sea: 44 meters (144 ft)
  • Deepest point: 
    • East Sea: 3,742 meters (12,277 ft)
    • West Sea: 152 meters (499 ft)
  • Size:
    • East Sea: 1.05 million km2 (25th in the world)
    • West Sea: 380,000 km2 (51st in the world)
  • Appearance:
    • Deep waters and circulating currents keep the East Sea clear and blue.
    • Winds that blow over China’s Gobi Desert pick up and deposit yellow sand on the West Sea’s waves. Hence: “Yellow Sea.”
  • Topography:
    • The East Sea features many continental shelves and deep basins.
    • The West Sea is shallow and flat. When its tide recedes, the coastal regions become the world’s largest mudflats. Migratory birds stop along them to feed on critters trapped in the exposed sea’s underbelly. 
  • Temperature:
    • The East Sea’s three distinct water layers create wider variations in temperature: 5~20°C (41~68°F).
    • The West Sea’s shallow waters warm easier and create a more stable temperature 12~18°C (54~64°F).

The Yellow Sea Birds

The Yellow Sea doesn’t just support marine life. When water recedes, it becomes the world’s largest tidal mudflats. It may look like an endless expanse of bland, brown goop. But it teams with life, facilitating an awe-inspiring display of endurance and perseverance.

Come spring and fall, this muddy underbelly becomes a major stop for migratory birds on the East Asian–Australasian Flyway. Tens of millions of birds fly non-stop as much as 9,600 kilometers (6,000 mi), from as far away as Australia and New Zealand.

Once they reach the Yellow Sea, they land and eat. They jab their beaks into the sticky mud and root around for worms, mollusks, and shrimp wriggling just underneath. 

During the migratory season, waves of birds pause for a few days and gorge their shrunken organs. They double their body weight to prepare for the next 8,000 kilometers (5,000 mi) leg of their journey up to the thawing tundras of Siberia and Alaska.

From the Ara Bike Path’s starting point, you might spot a spoon-billed sandpiper grabbing a tiny crab from the dank dredges of the Yellow Sea’s mudflats at low tide. Or a red-crowned crane resting before continuing its annual migration marathon.