How does ocean temperature affect air temperature?

Most of the Earth’s surface is covered by ocean.

Oceans have a moderating effect on Earth’s climate, helping to prevent extreme air temperatures. This is because water takes much longer than air to heat up and cool down. As about two-thirds of the planet’s surface is ocean, this has a profound effect on climate. Outside the equatorial regions, this vast body of water tends to store heat during the summer months and slowly release it during the winter. This is why coastal regions tend to have milder climates than areas far inland.

specific heat

Water takes longer to heat up and cool down, which impacts air temperature.

Specific heat is a measure of how much heat is needed to raise the temperature of a given amount of a substance by a given amount. This value is more than four times greater for water than for dry air or land. The earth heats up quickly and this heat is easily transferred to the air.

The air over land, however, also cools relatively quickly. In contrast, much more heat is needed to cause a similar rise in ocean temperature, and therefore the seas take much longer to warm up. Likewise, they take much longer to cool down. For this reason, in areas that experience seasons, the ocean tends to lag behind the land in terms of temperature.

effects on climate

As two-thirds of the planet’s surface is oceans, ocean temperature has a profound effect on climate.

This difference in specific heat affects temperature ranges on the seasonal and daily time scales. Days are cooler and nights are warmer in the oceans than on land. This affects coastal areas, keeping temperatures low during the day and preventing them from falling too low at night.

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On a micro scale, the effects of ocean temperature can easily be seen on the beach. Typically, beach air is a few degrees cooler than air just a few kilometers off the coast during the day. Likewise, at night, the air on the coast may not be as cool as inland. That’s why coastal areas like San Diego have one forecast for the beach and one for the interior. The effect can also be seen in the direction of the wind: normally, during the day the wind blows from the sea towards the land, where the heat makes the air rise, and vice versa at night.

Sea surface temperature can affect storm systems.

On a longer time scale, in summer the ocean temperature does not reach its maximum until sometime after the maximum length of day. Likewise, the minimum ocean temperature occurs sometime after the shortest day. This influences the Earth’s climate, creating a similar time span.

As the oceans warm, they release more water vapor into the air, increasing its humidity. This also affects the weather, as moist air takes longer to warm up and retains heat longer than dry air. Again, this has a moderating influence. Without oceans, temperatures would fluctuate much more dramatically, likely making conditions impossible for most life forms.

The extent to which the ocean influences the climate of the interior depends on the topography. Moist air from a warm ocean can help moderate weather for a considerable distance, but if forced up a mountain range, much of the moisture will condense, forming clouds and producing rain. On the other side of the strip, the air will have lost most of its moisture and the weather will tend to be more extreme.

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ocean currents

Equatorial regions receive more heat from the Sun than higher latitudes, and this difference in the degree of ocean warming leads to currents that circulate heat across the globe. These currents have a major impact on the climate of some parts of the world. Perhaps the best-known ocean current is the Gulf Stream, sometimes known as the North Atlantic Drift. This brings warm water from the Gulf of Mexico northward to northwestern Europe, where its effect can be seen by the contrast of winters experienced in this region with those of Eastern Europe. For example, Glasgow, Scotland often experiences mild, wet winters, while Moscow – at roughly the same latitude – experiences freezing conditions.

While this may be the most commonly cited example, ocean currents exist all over the world. Some are cold water currents, transporting cooler water from arctic areas towards the tropics. This reduces evaporation and moisture, leading to drier conditions with greater variations in temperature than normal in coastal regions. ENSO (El Niño / Southern Oscillation) is a periodic warming of part of the Pacific Ocean off the west coast of South America that has a major effect on the climate of the entire planet.

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