Learn about Henry's Law
As formulated in 1803 by William Henry, Henry’s law states "At a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid." In other words, at a given temperature a gas will dissolve into a liquid to a degree that is determined by the balance between the undissolved gas and the and the dissolved gas in the liquid.
Let’s take a look at Henry’s law:
Where k is a constant for each gas that can be looked up on a table, though when the temperature of a system changes so does the constant value of k. Pgas is the partial pressure of the gas in the parcel, and Cx is the concentration of the gas in the liquid solution. The concentration of the the gas in solution (solute) is directly proportional to the partial pressure of the gas above the liquid.
Carbon dioxide molecule
Let’s first consider how the process happens on a chemical level. Carbon dioxide (CO2) is made up of one oxygen atom and two carbon dioxide atoms. The atoms share the electron, but unevenly; the oxygen side of the molecule has a slight negative charge. CO2 (Figure 1) is a linear, symmetrical, molecule with a slight negative charge on either end, which is why it is a (weak) non-polar molecule.
Water, H2O, is made up of two hydrogen atoms and one oxygen atom (Figure 2). Again, the atoms share electron, but not evenly. This uneven sharing of electrons give water molecules a slight positive charge near the two hydrogen atoms and a slight negative charge near the oxygen atom, which is called a polar molecule.
The positive charge, or electron rich, area of the water molecule attracts the negative charge, or electron deficient are of the carbon dioxide molecule allowing it to go into solution.
To dissolve in the water, the CO2 molecule must pass through the air-water surface, where the CO2 molecule gain an outer shell of the H2O molecule. This process transfers the molecule from the gaseous state to an aqueous solution.
Any parcel of gas, or air for example, contains a mixture of gases, each of which has a partial pressure that contributes to the total sum of the pressure. The higher the concentration of a gas outside of the liquid, or partial pressure, the more gas of that gas will be able to go into solution.
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Gas solubility is temperature dependent, gas can dissolve more readily in colder liquids. If you leave an opened bottle of soda on the counter it soon goes “flat”, or all of the CO2 leaves the solution, however if you leave your opened bottle of soda in the refrigerator, it will not go flat as quickly. This is because, even at the same pressure, the colder temperature allow for the gas to stay in the solution longer.
This is also true for ocean temperature and the solubility of gases such as CO2. As discussed earlier, the colder the temperature is the more CO2 can be dissolved, or colder ocean water can dissolve more CO2 than warm ocean water. So in theory, colder water towards the poles can take up more CO2 than warmer equatorial waters. (Figure in Folder)
Scientists are concerned that increased CO2 in the atmosphere could creates a positive feedback loop, a cycle in which the effects of a change in a system increase the magnitude of the change. For example, if ocean temperatures warm CO2 could be released from solution, increasing the atmospheric concentrations leading to further heat trapping mechanisms, or at least slowing the rate of uptake by the oceans. The cycle continues to warm the atmosphere and the ocean.