Why the Ocean Doesn't Freeze Like the Great Lakes

The science behind why salt water freezes at a lower temperature than fresh water.

Jan. 28, 2026 at 11:31am

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While the Great Lakes around major Midwest cities often freeze over in the winter, the Atlantic Ocean around Delaware does not. This is because ocean water has a higher salt content than fresh water, which disrupts the water molecules and makes it harder for the water to freeze. Additionally, the ocean's currents prevent the water from freezing, even in colder temperatures.

Why it matters

Understanding the science behind why salt water freezes at a lower temperature than fresh water is important for understanding the different freeze patterns between the ocean and large freshwater lakes. This knowledge can help people better prepare for and respond to winter weather conditions in coastal areas.

The details

Salt water freezes at 28.4 degrees Fahrenheit, which is roughly 4 degrees cooler than the freezing point of fresh water at 32 degrees. The salt in ocean water disrupts the water molecules, making it harder for them to form the solid structure needed for ice to form. Additionally, the constant currents in the ocean prevent the water from staying still long enough to freeze, even in cold temperatures.

  • In Delaware, winter temperatures range from average highs in the 40s to lows in the upper 20s.

The players

Great Lakes

A group of five large freshwater lakes in North America, located between the United States and Canada.

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The takeaway

The key difference between the ocean and the Great Lakes when it comes to freezing is the salt content. While the Great Lakes can freeze over in the winter, the Atlantic Ocean around Delaware is unlikely to do so unless there is an extremely strong cold wave, due to the disrupting effect of salt on water molecules and the constant ocean currents.