论文部分内容阅读
Air-sea gas exchange is modulated through an O (100 m) oceanic boundary layer,which hosts multiple small-scale processes that directly influence the water properties and yet cannot be resolved in current climate numerical models.One particular area that has a dearth of information is the tens of meters immediately below the mixed layer,which is characterized by sharp temperature and density gradients.The effects of physical processes in the upper thermocline,notably gas exchange with deeper layers,play an important role for the geochemical cycle of carbon and yet are poorly understood.The Canadian SOLAS Northeast Pacific mooring at OWS Papa,active from September 2002 to June 2006,was designed to study air-sea exchange in the oceanic boundary layer for an region subject to high wind inputs and seasonal cycles of vertical stratification.Since June 2004,the addition of an Acoustic Doppler Current Profiler to the mooring line has allowed for measurements of velocity shear in the thermocline.Using the mooring data combined with density estimates compiled from Argo floats,we derive first estimates of dissipation below the mixed layer for OWS Papa at different periods during 2005.Vertical diffusivity estimates below the mixed layer have average values of 10?5 m2 s?1 and increase to near 10?4 m2 s?1 during periods of high shear/ low stratification.These results are in apparent contrast to a ’background diffusivity’ often used in 1-D mixed layer models.A simple numerical model is then used to explore the effect of this parameter on the dissolved gas budget.This work was supported by grants from the Natural Science and Engineering Research Council of Canada (NSERC) and the Canadian Foundation for Climate and Atmospheric Science (CFCAS) as well as governmental contributions from Environment Canada and Fisheries and Oceans Canada as part of Canadian SOLAS.