Ocean Effects of Limestone

Carbon Cycle

• Carbon dioxide, or CO2, from the atmosphere enters the ocean and dissolves. It combines with the water, H2O, and forms carbonic acid, H2CO3. This is one part of the carbon cycle. Plants in the ocean, such as algae, also take carbon dioxide from the atmosphere. Along with sunlight, the plants convert the carbon dioxide into carbohydrates that provide energy for the plants. The carbonic acid formed in the oceans continues the carbon cycle with a process called weathering.

Weathering

• Weathering involves a process of converting carbonic acid into calcium carbonate. Carbonic acid weathers rocks which produces bicarbonate ions. These ions combine with calcium and become calcium carbonate. This process yields limestone, which in effect is a storage unit for carbon. Layers of limestone accumulate on the ocean floor as a result of weathering.

CO2 Transformation

• The transforming of carbon dioxide in the oceans into limestone is a natural process. Scientists see this natural process as a means of eliminating carbon dioxide produced by humans. Greg Rau at the Lawrence Livermore National Laboratory has conducted experiments with limestone as a means of removing carbon dioxide from a natural gas power plant's flue stream. In the experiment, limestone converted up to 97 percent of the carbon dioxide into calcium bicarbonate, which is then stored in the ocean where it benefits marine life. This experiment, if converted to a large-scale production, speeds up the weathering process and eliminates excess carbon dioxide from the ocean.

Equilibrium

• The movement of carbon dioxide from the atmosphere to the ocean to limestone is part of nature's way of maintaining climate equilibrium. Too much carbon dioxide raises the Earth's temperature, while too little would cause lower temperatures. The amount of weathering varies in a manner to adjust the temperature through a slow process over a long period of years.