Impacts of hurricane Frances (2004) on vertical mixing and air-sea CO₂ exchange

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Abstract

[Truncated abstract] Recent research has suggested that global hurricanes release large amounts of CO2 from the ocean to the atmosphere during their passage, with CO2 effluxes comparable to the net local annual CO2 fluxes, but these estimates were based on arbitrary assumptions within the short “forced stage” of the hurricane passages. The factors controlling the air-sea CO2 exchange and the integrated impact of hurricanes on the annual carbon cycle are still unclear. Here we use in situ measurements, satellite observations and numerical models to investigate the mechanisms of the variation of partial pressure of CO2 in surface ocean water (pCO2 surf) and integrated air-sea CO2 exchange fluxes during and after the passage of Hurricane Frances (2004) over Caribbean Sea. The results suggest that the pCO2 surf variation is dominated by the changing sea surface temperature. The hurricane-induced vertical mixing brings cold, higher-CO2 water to the surface through water entrainment at the bottom of the surface mixed layer. The sea surface temperature cooling is the major reason for the decline of pCO2 surf, while the entrainment of higher-CO2 water partially offsets this decline. The spatial heat budgets reveal that during the hurricane passage not only the entrainment at the bottom of surface mixed layer but also the horizontal water advection are important factors determining the spatial pattern of sea surface temperature. At the free surface, the hurricane-induced precipitation contributes a negligible amount to the air-sea heat exchange, but the precipitation produces a negative buoyancy flux in the surface layer that overwhelms the instability induced by the loss of heat to the atmosphere.
Original languageEnglish
QualificationDoctor of Philosophy
Publication statusUnpublished - 2010

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