Question

How do oceans absorb CO2?

Answer 1

1) Differences in pressure between the air and the ocean cause carbon dioxide to be exchanged and 2) algae and phytoplankton absorb carbon dioxide.

Explanation:

The ocean can absorb carbon dioxide (`"CO"_2`) in 2 ways: diffusion from the atmosphere and through photosynthesis in plankton and algae.

Carbon dioxide moves between the atmosphere and the ocean by molecular diffusion: a difference between `"CO"_2` pressure in the atmosphere and ocean causes `"CO"_2` to be exchanged (source). The `"CO"_2` moves from the air to the water, when the atmospheric pressure of `"CO"_2` is higher. The `"CO"_2` is dissolved in the ocean because it is soluble.

The solubility of carbon dioxide varies based on salinity and temperature of the water and there is a finite amount that the water can absorb. The colder the water, the more `"CO"_2` can be dissolved.

The solubility of `"CO"_2` in water is demonstrated in the video below.

Another way in which the ocean absorbs `"CO"_2` is through some of its lifeforms. Phytoplankton and algae both photosynthesize in the ocean. They both consume `"CO"_2` using sunlight and release `"O"_2`.

For more information:

1. The Ocean Carbon Cycle
2. Carbon Dioxide in the Ocean and Atmosphere
3. The Marine Carbon Cycle Video