<p>A semi-analytical investigation of mass transmission in a horizontal porous fluid layer has been done. The impact of gravity modulation on a non-Newtonian viscoelastic fluid has been shown. A weakly nonlinear stability analysis using the perturbation approach is carried out to construct a real Ginzburg–Landau equation and determine the Sherwood number. A numerical solution of the real Ginzburg–Landau equation was obtained using MATHEMATICA software. The effects of the relaxation and retardation times of viscoelastic fluid on mass transfer have been discussed graphically. We established in this work that the rate of mass transmission can be efficiently regulated by correctly varying the frequency and amplitude of modulation. That substantial mass diffusion lowers mass transfer. In the present article, we discussed the outcomes for both the modulated and unmodulated scenarios. The main discovery is that the changes in gravitational acceleration over time considerably impact convection dynamics because they increase mass transfer and destabilize the system.</p>