SEA
1.Seeding ocean with iron
Sea sequesters significant amount of carbon. While there is about 7500 million carbon in atmosphere, there is 35 trillion in the ocean. Especially, the main role of trapping carbons is oceanophyte. Photo plankton including alga store CO2 as organic matters through the photosynthesis. These organic matters fall from sea surface to deep ocean by gravity and are used as food of top predator. During this process, some of them are emitted to the atmosphere by respiration, but most of them sink to bottom of sea as a shape of stools or debris. Sea is actually perfect carbon storage. There is an opinion that we should supply some nutrients for plant growth to activate this function. Nitrogen, iron, and phosphorous are composition elements of coastal plant. Among them, iron is trace element of the sea. Plant tissue is made by reacting 1 Fe and 100,000 C. If we provide iron for the sea fully, a huge amount of carbon can be sequestered during a process of oceanophyte. Fe fertilization experiments are conducted about 12 times from 1994 for 15 years. However results aren’t consistent. In 2006, Tokyo research team in japan did research on burying steel slug to a coast, and the amount of seaweed increase 8 times for 8 months. Also the area buried iron is absorbed CO2 5.5 kg/km2․year. But another experiment had no effect. Because there is a few silicic acid that is essential for diatom in the sea. Besides, it can have bad effects on ocean ecosystem.
2.Weathering on ocean
There is a process of sequestering CO2 as mineral form in the ocean. This takes place when rain combines with carbon dioxide or an organic acid to form a weak carbonic acid which reacts with calcium carbonate (limestone) and forms calcium bicarbonate. The melted 2 CO2 molecules in the sea combine with Ca2+ and form limestone. This process is called as weathering. Carbonates combine with 1 carbon atom, and they are more soluble than silicate minerals. It's clear that weathering process has significant effect on absorbing CO2. Also, this idea will be a little harmful, because it makes small change of pH than direct injecting. Also limestone control pH of the ocean and prevent from acidation. And dissolved limestone has CO2 in sea, but it emits CO2 to atmosphere. However this process requires a long time. There is another method that seeds bicarbonate directly, but it can be that the reaction is very slow and weak if bicarbonate doesn't sink to the bottom fully.
3.Seawater spray
Salt particle is useful for forming cloud. Because it is familiar with water and adheres to water vapor. So, some geo-engineers suggest that seawater sprays for making clouds. Clouds will be good device that reflects sunlight. If the problems occur, we will just turn off this spray. And salt particles in the atmosphere fall down as rain or scatters there, so it doesn't make problem. Besides we can control amount of water vapor. Still, salt particles are made on the sea, but they form in various time and the degree of development is different depending on waters. Scientists say that if we use this idea, we can get appropriate cooling effect. Professor Stephen Salter designs a ship for this idea. The ship gets energy by rotating cylinder and this energy is used to work motor that pumps seawater.
4.Bright water
This theory was suggested by Russell Seitz. Bright Water theorizes that pumping tiny bubbles into the ocean will brighten the ocean, thus helping the earth to cool down. As bubbles in the water are what makes it more reflective, putting these tiny bubbles into the ocean should lower the temperature of the water and the earth. Microbubbles are made by using ships or putting compressed air into the ocean. These are smaller than natural ones and about 2 μm. According to the simulation results, as water albedo was doubled by bubbles, temperature decreased over 3℃. Besides, bubbles protect water resources by reducing evaporation from the river and lake. However, it's impossible to apply to large area over 1km2. To inject bubbles to Whole Ocean, 1000 wind generators are required. Bubbles can't be sustained for a long time. So it may not work because of bursting.
5.Ocean pumps
James loverock of 'gaia theory' suggests a physical method that pump up water of bottom. The idea is to tether millions of vertical pipes across the oceans to pump nutrient-rich deep water to the surface. These waters would fertilize the growth of algae, which in turn fix carbon dioxide. The pipes, reaching to depths of 200 meters, would have flap valves at the bottom operated by the energy of waves, which would push deep water up the pipe. Research team said that flap valves can work without extra electricity supply. Actually, a wave-driven 'ocean up-welling system' to absorb CO2, very similar to what Lovelock and Rapley are proposing, is currently being developed by a company called Atmocean, based in Santa Fe, New Mexico. Atmocean estimates that a pump-driven up-welling system, if deployed across 80% of the world's oceans, could help bring down to the ocean floor an additional 2bn metric tonnes of carbon per year, potentially doubling the ocean's annual rate of CO2 sequestration. The company has developed floating tubes, 3 meters in diameter and 300 meters long, that it claims can do just this. There are the opposites. “The concept is flawed,” says Scott Doney, a marine chemist at WHOI. He says it neglects the fact that deeper waters with high nutrients also generally contain a lot of dissolved inorganic carbon, including dissolved CO2. Bringing these waters to the lower pressures of the surface would result in the CO2 bubbling out into the air. So contrary to the desired effect, the scheme could result in a net ‘ out-gassing’ of CO2, he warns. “There is no technological fix for this problem,” he says. Also if there are up-welling in some regions, sinking motions appear in others. In other words, it can have CO2 reducing effect locally, there is still no way of global effect due to balancing all around the world.
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