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Marine Functions in the Global Carbon Cycle

by Widiya

Since the 1970s, the overall sea has been a sink for anthropogenic CO2. But how much COis absorbed? What processes move it? How does it change in the future? To answer these questions, we first need to understand the function of the ocean in the carbon cycle or cycle globally.

Circulation of carbon in various forms of organic and inorganic, and carbon transport from the surface to the deep sea is built by physical and biological processes. These processes are commonly referred to as physical pumps (solubility pumps) and biological pumps. Both of these pumps act to increase the concentration of COin the ocean interior.

Physical Pump Cycle

Physical pumps are generated by slow reverse circulation and easier dissolution of COin cold water than in warm water. Dense and warm water types at high latitudes, especially in the North Atlantic and the Southern Ocean, absorb atmospheric CO2 before sinking (sinking) into the ocean interior.

This sinking water will be balanced by vertical transport (upwelling) in other parts of the sea. The water that rises to the top will warm up when it reaches the surface so that CO2 becomes less soluble and some of it will be released back into the atmosphere (through a process called outgassing). The net effect of these processes is pumping CO2 into the ocean interior.

Biological Pump Cycle

Carbon sequestration by phytoplankton, microscopic organisms that live on the surface of the sea that is exposed to sunlight and their exports to the interior and marine sediments are called biological pumps. Photosynthesis is the process by which phytoplankton take carbon. Photosynthesis rates are known as primary productivity. Phytoplankton is a machine for biological pumps.

Biological pumps play an important role in the ability of the ocean to absorb atmospheric CO2. Without photosynthesis at sea, atmospheric CO2 will be 1,000 ppm when compared to the current condition of 365 ppm. Conversely, if the biological pump functions with maximum efficiency, then the level of CO2 in the atmosphere will drop to 110 ppm.

Although important, so far biological pumps have not been widely measured. Much of the research has focused on expanding the understanding of biological processes, their variation in seasons, and the large-scale, climatic events that affect the functioning of these pumps. (Reference: Agus Setiawan, 2000, about marine biogeochemistry and global change, BPPT Environmental Technology Center, translated from IGBP Science No. 2).

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