En-en adult card 17 increase in water temperature

Card #17: Increase in Water Temperature

Causes		Consequences
Energy Budget		Disruption of the Water Cycle Sea Level Rise Marine Biodiversity Cyclones

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.

Explanation

The ocean is warming by about a tenth of a degree at the surface and even less at depth. Why is this happening when it absorbs 93% of the excess energy on earth? This is because it is much larger than the atmosphere. It has a much greater calorific capacity.

To measure this, you have to remember that the ocean covers 71% of the earth's surface and that it has a depth of 4000m on average. The atmosphere extends over a greater height, but if we brought it back to the same density as water, it would only measure 10m (that's why we gain one atmosphere of pressure every 10m 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 4000m deep on average, so a very small expansion is enough to make a few centimetres. A more complete explanation is given in a practical sheet.