Global average of air-sea CO2 transfer velocity from QuikSCAT scatterometer wind speeds

The absolute calibration of the relationship between air-sea CO2 transfer velocity, k, and wind speed, U, has been a topic of debate for some time, because k global average, < k >, as deduced from Geochemical Ocean Sections Study oceanic C-14 inventory has differed from that deduced from experimental k-U relationships. Recently, new oceanic C-14 inventories and inversions have lead to a lower < k >. In addition, new measurements performed at sea in high-wind speed conditions have led to new k-U relationship. Meanwhile, quality and sampling of satellite wind speeds has greatly improved. The QuikSCAT scatterometer has provided high-quality wind speeds for more than 7 years. This allows us to estimate the global distributions of k computed using k-U relationships and temperature-dependent Schmidt numbers from 1999 to 2006. Given the difficulty of measuring in situ wind speed very accurately, we performed a sensitivity study of the < k > uncertainty which results from QuikSCAT U uncertainties. New QuikSCAT-buoy U comparisons in the northern Atlantic Ocean and in the Southern Ocean confirm the excellent precision of QuikSCAT U (RMS difference of about 1 m s(-1)), but it is possible that QuikSCAT overestimates wind speeds by 5%, leading to a possible overestimation of k derived with quadratic relationships by 10%. The < k > values obtained with two recent experimental k-U relationships are very close, between 15.9 and 17.9 cm h(-1), and within the error bar of k average deduced from the new oceanic C-14 inventory.


CO2 transfer velocity, QuikSCAT, CARIOCA

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Boutin J., Quilfen Yves, Merlivat L., Piolle Jean-Francois (2009). Global average of air-sea CO2 transfer velocity from QuikSCAT scatterometer wind speeds. Journal of Geophysical Research ( JGR ) - Oceans. 114 (C04007). 1-14.,

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