The Breathing of the Atmosphere

Three dimensional representation of the global distribution of atmospheric carbon dioxide in the marine boundary layer assuming no variation with longitude. Data from the NOAA/CMDL Global Cooperative Air Sampling Network were used. The surface represents data smoothed in time and latitude. The contribution from the NOAA/CMDL South Pole Observatory flask sampling effort is shown inset as flask monthly means. The 10 degree latitude zone in which South Pole resides is highlighted. Principal investigators: Pieter Tans and Thomas Conway, NOAA/CMDL Carbon Cycle Group, Boulder, Colorado, (303)497-6678.

The total amount of carbon dioxide in the atmosphere results principally from the sum of globally distributed processes such as photosynthesis and respiration in the biosphere, deforestation, and the burning of fossil fuels and biomass. The oceans affect this total by drawing carbon dioxide from the atmosphere and depositing carbon in the bottom sediments.

Precise records of the concentration of atmospheric carbon dioxide are necessary for understanding (1) how it works as a greenhouse gas; (2) how it affects the flow of carbon from the biosphere through the atmosphere to the ocean; and (3) how it induces long-term climatic changes.

The atmospheric carbon dioxide concentration has been measured directly at Amundsen-Scott South Pole Station since the station opened in 1957 at the start of the International Geophysical Year. Since 1975, the NOAA Climate Monitoring and Diagnostic Laboratory has made continuous carbon dioxide measurements at the station as the southern anchor to their global monitoring network (highlighted in red in the diagram).

The diagram shows both the long-term global increase in the carbon dioxide concentration in the general upward tilt of the surface to the right with time and the annually recurring take-up of carbon dioxide by new growth (photosynthesis) in the annual wrinkles of the surface. The reversal of the seasons in the Northern and Southern Hemispheres appears as a 6-month shift for each maximum that occurs near the equator. The much greater variation in the Northern Hemisphere reflects the correspondingly greater land area.

The combined observations that carbon dioxide amounts at South Pole still vary annually and that each maximum follows a coherent yearly pattern show that atmospheric mixing occurs rapidly and that the turbulent mixing and distribution processes are efficient. While other observatories document the background state and chemical composition of Earth's atmosphere, South Pole Station's isolation from large-scale human activity makes it a vital component of the network because results obtained there set a global standard for clean air and are frequently compared to results from around the world.

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