Marine research at CNR
observatory in Florence, Italy. During the cruise, regions with both high and low biogenic activity were encountered. The results described above clearly show that the exchange of CO2 at the air-sea interface are mainly determined by the turbulence conditions. In particular it was shown that above a certain threshold (0.25 m·s−1 ) for the friction velocity the fluxes can be significant. During the cruise this condition was satisfied for about half time. The observed CO2 fluxes are into the ocean and they are of the order of 1 µmol·m−2 · s−1 at most. This is of the same order of magnitude as those measured by [14], 0.3-0.6 µmol·m−2 · s−1 . Measured acetone fluxes show a significant relationship with biogenic activity. Although the uncertainty is very high due to the very low signal to noise ratio, positive acetone mean fluxes of the order of 1×10−5 µmol·m−2 · s−1 , comparable to the results of [8], have been clearly observed in bloom areas, whereas near zero or negative acetone fluxes have
been measured in the other areas. The order of magnitude of the sink in the oligotrophic ocean area is in general agreement with the sink reported in literature [3], who measured values ranging between -1 and -10 µmol·m−2 · day−1 . Both our measurements and those of [3] have shown that the acetone fluxes are very small, quite close to the sensitivity of the current experimental methods. In conclusion, the source strength over the bloom seems comparable to the sink over the oligotrophic ocean. Bloom areas, however, represent circa 1% of the global ocean surface and therefore most of the ocean will be a sink and the estimated sink will not be significantly offset by the bloom source assuming that the bloom measured here is representative of all bloom/active areas. The flux from the phytoplankton rich region would have had to have been circa 100 times larger than the oligotrophic flux to offset the uptake elsewhere.
References [1] D.J. Jacob and et al. Atmospheric budget of acetone. Journal of Geophysical Research-Atmospheres, 107(D10):10.1029, 2002. [2] H.B. Singh et al. Analysis of the atmospheric distribution, sources, and sinks of oxygenated volatile organic chemicals based on measurements over the Pacific during TRACE-P. Journal of Geophysical Research-Atmospheres, 109(D15S07):10.1029, 2004. [3] C.A. Marandino, W.J. De Bruyn, S.D. Miller, M.J. Prather, and E.S. Saltzman. Oceanic uptake and the global atmospheric acetone budget. Geophysical Research Letters, 32:L15806, 2005. [4] S. Taddei, P. Toscano, B. Gioli, A. Matese, F. Miglietta, F. P. Vaccari, A. Zaldei, T. Custer, and J. Williams. Carbon Dioxide and Acetone Air-Sea Fluxes over the Southern Atlantic. Environmental Science and Technology, 43:5218–5222, 2009. [5] J. Williams, R. Holzinger, V. Gros, X. Xu, E. Atlas, and D.W.R. Wallace. Measure-
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