7 Oceans and Climate
Learn how exchanges between the ocean and atmosphere regulate climate, store heat and carbon, and connect climate change to changes in ocean conditions and marine ecosystems.
Exchanges between ocean and atmosphere
The ocean and atmosphere continually exchange heat, water, and momentum. Sunlight warms the sea surface, and the ocean transfers heat to the air through direct heat exchange and evaporation. Evaporation supplies moisture for clouds and precipitation, while winds transfer momentum to the sea surface and help drive currents.
Currents move warm and cool water between regions, influencing winds, rainfall, and regional temperatures. For example, warm surface currents can carry tropical heat toward higher latitudes and moderate nearby coastal climates.
Heat and carbon storage
Water has a high capacity to store heat, so the ocean absorbs and retains much of the excess energy trapped by greenhouse gases. Since the 1970s, it has taken up more than of the excess heat added to the climate system by human activities. Currents and mixing carry some of this heat below the surface, delaying its release to the atmosphere. This moderates the pace of atmospheric warming, although the stored heat can persist for a long time.
The ocean also takes up carbon dioxide from the air. Some dissolves in seawater, and some is converted into dissolved forms such as bicarbonate. Phytoplankton absorb carbon through photosynthesis, and some of this organic matter sinks into deeper water. Circulation and sinking water help transport carbon from the surface to the deep ocean, where it can remain for centuries or longer. This combined chemical uptake, biological activity, and water circulation is often described as the ocean’s .
Climate regulation and
By storing and redistributing heat and carbon, the ocean slows and shapes climate change. Its role is not simply a one-way buffer: it can also return heat and carbon dioxide to the atmosphere. For example, warmer water holds less dissolved , so warming can weaken ocean uptake or promote release.
The rate of exchange also depends on winds, currents, and how readily surface water mixes with deeper water. These interactions are climate because they can strengthen or weaken the original change.
Ocean responses to climate change
Continued greenhouse-gas emissions are warming the ocean. Warmer seawater expands and contributes to sea-level rise; melting glaciers and ice sheets add further water to the ocean. Warming can also increase , the layering of water with different temperatures and densities. This makes vertical mixing more difficult and can affect the movement of heat, nutrients, oxygen, and carbon.
The ocean’s uptake of human-produced carbon dioxide changes seawater chemistry and lowers pH, a process called . Warming and stronger layering can also reduce oxygen availability in some waters. —periods of unusually high ocean temperature—can stress marine life. Together, these changes affect ecosystems and the people who depend on them.