The air-sea flux of carbon dioxide

What is it about?

The ocean takes up at least one third of the additional carbon dioxide released to the atmosphere as a result of man's activities. The air-to-sea flux is most conveniently calculated at the ocean surface. Carbon dioxide in the upper ocean is measured by underway ships (ships of opportunity and research ships) while sea surface temperatures are measured from satellites. Though the ships also measure sea temperature, these measurements are generally inferior in quality and quantity. Very accurate temperatures are required for the calculation of the flux of carbon dioxide. Analogous issues are related to salinity, though their effects are generally less substantial. An objective method is required to make the best use of the measurements in calculating air-sea fluxes of carbon dioxide. This paper explains the issues involved and describes a solution.

Featured Image

Why is it important?

Existing calculations of the sea-to-air flux of carbon dioxide contain errors related to incorrect handling of temperature and salinity. Two errors are especially important. Firstly, recent estimates have omitted the true effect of a temperature difference across the "thermal skin of the oceans". Secondly, there is a regionally and seasonally varying discrepancy between ship-based temperatures and satellite-measured temperatures ( http://www.ocean-sci.net/11/519/2015/ ) and that discrepancy leads to errors in maps of the air-sea flux of carbon dioxide. Those and other errors can be eliminated by following the solution proposed in the new paper. The effect is to considerably increase the estimate of the contemporary global sea-to-air flux of carbon dioxide; and by implication, increase estimates of the uptake of anthropogenic carbon dioxide by the ocean.