10:45 AM - 12:15 PM
[ACG44-P03] Distribution and seasonality of double-diffusive convection in the subsurface North Pacific Transition Zone
★Invited Papers
Keywords:the North Pacific Transition Zone, double diffusion, front, density compensation, mode water, water mass modification
The North Pacific Transition Zone is a region between the Subarctic front and the Subarctic boundary, and it is the boundary zone between the cold and fresh subarctic water and the warm and saline subtropical water. One of the characteristics of this region is that the horizontal gradient of density is small due to the compensating contributions of the horizontal gradients of temperature and salinity to the density change.
Saito et al. (2011) showed that a flow with vertical sheer across the temperature and salinity front that compensates for density changes tends to produce a temperature and salinity stratification in the subsurface layer where salt-finger type convection is likely to occur. Furthermore, their results suggest that the vertical mixing by salt fingering may be responsible for the large-scale transformation of Transition Region Mode Water with subarctic characteristics into Central Mode Water with subtropical characteristics. Double diffusive convection is vertical convection that occurs when the density field is stable but either the temperature or salinity one is unstable, due to the difference in diffusion coefficients between heat and salinity. Salt-finger convection occurs when the water column is stabilized by temperature stratification, and diffusive type convection occurs when it is stabilized by salinity stratification. In the transition zone where subarctic and subtropical water meet, double diffusive convection may also play an important role in heat and salt redistribution and nutrient and CO2 transport through vertical mixing and water mass transformation.
In this presentation, we would like to discuss the results of the distribution and seasonal changes in the double-diffusive layers in the North Pacific Transition Zone, using individual profile data and gridded climatological data from Argo floats.
Saito et al. (2011) showed that a flow with vertical sheer across the temperature and salinity front that compensates for density changes tends to produce a temperature and salinity stratification in the subsurface layer where salt-finger type convection is likely to occur. Furthermore, their results suggest that the vertical mixing by salt fingering may be responsible for the large-scale transformation of Transition Region Mode Water with subarctic characteristics into Central Mode Water with subtropical characteristics. Double diffusive convection is vertical convection that occurs when the density field is stable but either the temperature or salinity one is unstable, due to the difference in diffusion coefficients between heat and salinity. Salt-finger convection occurs when the water column is stabilized by temperature stratification, and diffusive type convection occurs when it is stabilized by salinity stratification. In the transition zone where subarctic and subtropical water meet, double diffusive convection may also play an important role in heat and salt redistribution and nutrient and CO2 transport through vertical mixing and water mass transformation.
In this presentation, we would like to discuss the results of the distribution and seasonal changes in the double-diffusive layers in the North Pacific Transition Zone, using individual profile data and gridded climatological data from Argo floats.