When an oceanic thermal front is under the influence of an atmospheric high-pressure system, differences in atmospheric mixing height across the front exist, mainly because of the gradient in the sea-surface temperature (SST). To study and estimate these differences, an analytical model based on a basic thermodynamic equation is devised. The model states that ΔH=KΔT, where ΔH and ΔT are the difference in the mixing height in meters and SST in degrees Celsius across the front, respectively, and K (in m/0C) is related to the entrainment coefficient, wind speed, transfer coefficient for sensible heat flux, local change of the potential temperature in the mixed layer, advection due to winds, and radiative processes due to clouds. On the basis of pertinent field experiments conducted over the Gulf Stream, in the Korea Strait, and over the Alboran Sea, the composite value of K is found to be approximately 38 m/0C. The limitation of using a constant K is discussed.