Sinks Remove Carbon Dioxide From The Air
January 12, 2011
By WeatherBug Meteorologist, Fred Allen
The carbon cycle is a delicate balance of sinks and sources between the atmosphere and ocean. Young forests, agricultural land and colder oceans remove carbon dioxide from the atmosphere, acting as a carbon sink, and storing it away. Since the turn of the industrial revolution in the 1800s, the biggest greenhouse gas, carbon dioxide, has increased nearly 30 percent, affecting the carbon cycles balance.
Forests play a key role in the carbon cycle, as it acts as a natural carbon sink. A young forest composed of growing trees, absorbs carbon dioxide and acts as a sink reservoir. Meanwhile, mature forests made up of a mix of various aged trees as well as dead and decaying matter which emit carbon dioxide, may be carbon neutral. Forests hold a vast amount of carbon that otherwise would be released as carbon dioxide into the atmosphere.
Soils act as a direct carbon sink reservoir, more so than vegetation and the atmosphere combined.
Methods that significantly enhance carbon sequestration include no-till farming, residue mulching, cover cropping, and crop rotation, all of which are more widely used in organic farming than in conventional farming. Because only 5 percent of U.S. farmland currently uses no-till and residue mulching, there is a large potential for carbon sequestration. Furthermore, a conversion to pastureland, particularly with good management of grazing, can sequester even more carbon in the soil.
Aside from the forests and soils impact on creating carbon dioxide, oceans, lakes and rivers act as one of the largest carbon absorbers or sinks on Earth. The role as a sink for carbon dioxide is driven by two processes, the solubility pump and the biological pump. Solubility, which is the ability of a liquid to accept a gas, is what makes water a vital carbon sink. With nearly 70 percent of the Earth's surface covered by water, its solubility greatly impacts the carbon cycle.
The interaction of carbon dioxide between the ocean and atmosphere is directly related to salinity and temperature. The salinity influences the types of plants and organisms that grow in water, as well as define the world's ocean circulations. The changes with temperature and salinity cause sinking and rising of water masses, which contribute to global changes as more saline waters are less likely to dissolve carbon dioxide.
Colder waters at higher latitudes absorb carbon dioxide. This water sinks, storing the greenhouse gas for hundreds of years. The water circulates from the poles to the tropics, where it becomes warmer and releases the stored carbon dioxide into the atmosphere.
Other ocean currents begin in the tropics and flow toward the poles. Take the Gulf Stream for instance. It is a warm ocean current that parallels the East Coast and heads toward higher latitudes. The warm water in this current originates near the Bahamas, where it is heated and releases carbon dioxide into the atmosphere. The same water flows north, where it cools down and absorbs carbon dioxide. In addition, plants that grow in the ocean also absorb additional carbon dioxide.
The greatest source of atmospheric carbon is manmade. Humans impact the carbon cycle through combustion of fossil fuels, which may include oil, coal, or natural gas. Fossil fuels were formed very long ago from plant or animal remains that were buried, compressed, and transformed into oil, coal, or natural gas. The carbon is said to be "fixed" in place and essentially locked out of the natural carbon cycle. Humans, by burning fossil fuels, have unlocked this carbon, adding it to the nature's carbon cycle and affecting its balance.
Unfortunately, this manmade extra carbon dioxide that is released into the atmosphere is the subject of considerable debate and its possible effect in enhancing the greenhouse effect. In contrast, forests, soils and oceans if managed properly, will be effective carbon sinks for many years to come. The balance of the carbon cycle through the land, ocean and atmosphere is delicate and the proper management of both its sources and sinks will be important going forward.
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