Potential temperature, atmospheric mixing

There are a variety of potential explanations for carbonate mineral supersalurations that exceed uncertainties in the saturation indices of the pure, well-crystallized carbonates (about 0.1 SI units for calcite). As discussed earlier in this chapter, calcite supersaturation in surface-waters may result from a temperature increase, evaporation, and/or a loss in CO2 to photosynthesis or by exsolution to the atmosphere. Mixing of surface-waters or groundwaters can also produce a supersaturated mixture. The dissolution of more soluble gypsum causes calcite supersaturation in some groundwaters of the Floridan aquifer. 

Neutral atmosphere An atmosphere in which the potential temperature is constant with respect to height. Buoyant motion in a neutral atmosphere is negligible, but vertical mixing is not suppressed. Mixing will occur throughout the full depth of a neutral layer. 

Fig. 5.21. Seasonal fluctuations of (a) the mixed-layer depth, (b) TCO2, (c) NTCO2 (salinity-normalized total CO2, solid Une) and potential temperatinre (dashed line), (d) TA (solid hne) and salinity (dashed Une), (e) NTA (sahnity-normalized total TA), and (f) Fcoa (solid hne) and potential temperature (dashed hne) in the mixed-layer at the SEATS site from March 2002 to April 2003. The data points represent the averaged values of all samples measured in the mixed-layer from each cruise. The vertical bars indicate the analytical errors ( l

These developments follow theoretical advances built on vorticity theorems which are based on the conservation of both potential vorticity and potential temperature (i.e., entropy) on timescales for which friction, small-scale mixing, and diabatic heating can be ignored. IPV is a valuable atmospheric tracer which therefore shows the origin and predicted motion of atmospheric parcels indeed, it is the only such dynamical (as opposed to chemical) tracer. Since heating/cooling and friction act to alter the IPV, it is clear that careful representation of these plysical processes (i.e., parameterization ) in models and theories is crucial. 

---