SeaWiFS The Meaning of Ocean Color The Role of Phytoplankton The Carbon Absorbing Oceans

The Carbon Cycle How do phytoplankton control carbon? How do the ocean and atmosphere interact? Make a Greenhouse The concentration of carbon dioxide in the atmosphere has changed in the past hundred years. QUICK FACTS The ability for a given area to produce Carbon is measured in terms of its productivity. The productivity of a natural shallow estuary (small river) is similar to that of highly productive land crops. - Estuaries, sugarcane and sorghum all produce between 500 and 1250 grams of Carbon per square meter per year. - The productivity for the open ocean is similar to that of deserts and grasslands on land, between 40 and 80 grams of Carbon per square meter per year. - An ocean upwelling zone, or deep estuary, is as productive as the same area in rain forests, moist crops and intensive agriculture. They all produce between 150 and 500 grams of Carbon per square meter per year. How do the ocean and atmosphere interact? Differences in the heating and cooling rates of land and ocean affect air circulation. Land and water temperatures rise and fall at different rates because land absorbs and loses heat faster than water does. During the day, hot air rises and is replaced by cooler air. This small-scale circulation is called a sea breeze, and usually starts three or four hours after sunrise, reaching its peak by early afternoon. At night, the land is cooler than the water because the land has given up its heat to the atmosphere. The cool air flows over the warmer water and rises as it is warmed. This circulation is called a land breeze, and usually starts to form in the late evening. It reaches its peak intensity near sunrise. Without the Earth's atmosphere, our planet would become extremely cold and barren of life. The atmosphere consists of nitrogen (about 78 percent) and oxygen (about 21 percent). The other one percent consists mostly of argon, carbon dioxide, and several "trace" gases such as neon and helium. Like the glass roof and walls of a greenhouse, the Earth's atmosphere keeps its surface much warmer than it would be without the "greenhouse effect." How? Energy from the sun arrives as short-wavelength radiation (light), while the Earth emits long-wavelengeh (infrared) energy back into space. The hotter an object is, the shorter the wavelength of the radiation it emits. The short-wavelength sunlight easily penetrates the atmosphere and warms the Earth. However some of the long-wavelength energy emitted from the Earth is absorbed by the atmosphere before it escapes into space. Carbon dioxide, water vapor and other gases in the atmosphere are responsible for absorbing escaping long-wavelength energy. Thus, the Earth keeps some of the heat that would otherwise have been lost to space. The concentration of carbon dioxide in the atmosphere has changed in the past hundred years. Before the Industrial Revolution, carbon dioxide levels stayed nearly stable for thousands of years. Since human beings developed a fossil-fuel- based global economy and lifestyle, the amount of atmospheric carbon dioxide has increased dramatically. This increase means that less long- wavelength energy emitted from the Earth can escape to space. Many scientists believe this can lead to a gradual warming of the Earth, but others believe that different factors counteract this warming effect. For example, cloud cover reflects sunlight before it ever reaches the Earth, thus reducing the amount of sunlight that reaches the Earth's surface. Studying these processes is difficult, because they are complicated. Ocean color information provides one of the many tools scientists use to try to find what changes are occurring, and how they may affect us.

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