November 2022

Warming oceans raise sea level

This article is part of our series focused on the causes and consequences of a warming planet.

The world’s oceans are getting warmer. The warming is most obvious in the top layer of the ocean, but the extra heat has reached deeper waters than previously thought.

Physics tells us that water expands as it warms. We can see this when we fill our tea pot with water, put the pot on the stove, and turn the stove on. As the water warms, the water level in the tea pot rises, possibly overflowing. The same is true of the oceans. As the oceans warm, sea level rises.

This rise is especially relevant because over 90% of the heat in the atmosphere from the Earth’s warming goes into the oceans. Warming oceans account for as much as 50% of sea level rise.

In addition to sea level rise, warmer oceans affect weather patterns, cause more powerful tropical storms and can impact many kinds of sea life.

We know that continued emissions of greenhouse gases will result in further warming of the oceans and rising sea levels. But even if the world stops emitting greenhouse gases, the gases already in the atmosphere will keep the temperature of the atmosphere at a higher level causing the oceans to continue to warm over time. Scientists have found that even if we stop emitting greenhouse gases, sea levels will continue to rise for more than 1,000 years.

For example, when heating a tea pot of water, it takes a period of time for the water to become hot enough to make tea. On a much grander scale, the ocean will continue to warm as the atmospheric carbon dioxide blanket traps additional heat emitted by the warming earth.

Warmer oceans will impact us not only through rising sea levels,  but scientists are concerned that heat being stored in the oceans will eventually be released back into the atmosphere. Thus, committing earth to additional warming in the future, even if we end the emission of greenhouse gases.

figure 1 -- annual ocean heat content compared to average

See the Ag Decision Maker website for more from this series.

Don Hofstrand, retired extension agricultural business specialist,
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University


Don Hofstrand

retired extension agricultural business specialist
View more from this author
Reviewed by

Dr. Eugene Takle

retired professor emeritus Iowa State University