En-en adult card 17 increase in water temperature
Card #17: Increase in Water Temperature
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Oceans absorb 93% of the energy accumulated on Earth.
Their temperature has therefore increased, especially in the upper layers.
The water expands as it warms up.
Correction
Causes
Consequences
Explanation
The ocean is warming by only about a tenth of a degree at the surface and even less under water. Why so little when it absorbs 93% of the excess energy on Earth? This is because it is much larger than the atmosphere and it has a much greater calorific capacity.
To measure this, you need to remember that the ocean covers 71% of the Earth's surface and that it has a depth of 4000 m on average. The atmosphere extends over a greater height, but if brought it back to the same density as water, it would only be 10 m thick. (That's why we gain one atmosphere of pressure every 10 m when we dive.)
The water expands very little. How can warming the ocean by a tenth of a degree result in a rise in the water level? A first answer is that the ocean is 4000 m deep on average, so a very small expansion is enough to amount to a few centimeters. A more complete explanation is given in a practical sheet.