Arctic Lakes and Streams as Gas Conduits to the Atmosphere: Implications for Tundra Carbon Budgets

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Abstract
Arctic tundra has large amounts of stored carbon and is thought to be a sink for atmospheric carbon dioxide (CO 2 ) (0.1 to 0.3 petagram of carbon per year) (1 petagram = 10 15 grams). But this estimate of carbon balance is only for terrestrial ecosystems. Measurements of the partial pressure of CO 2 in 29 aquatic ecosystems across arctic Alaska showed that in most cases (27 of 29) CO 2 was released to the atmosphere. This CO 2 probably originates in terrestrial environments; erosion of particulate carbon plus ground-water transport of dissolved carbon from tundra contribute to the CO 2 flux from surface waters to the atmosphere. If this mechanism is typical of that of other tundra areas, then current estimates of the arctic terrestrial sink for atmospheric CO 2 may be 20 percent too high.