Aqueous solutions under thermal gradients feature thermodiffusion (Ludwig-Soret) and thermoelectric (Seebeck) effects, whereby the thermal fields build concentration and charge density gradients. Recently, it has been shown that thermal gradients induce polarization fields in water. We use non-equilibrium molecular simulations to quantify the thermoelectric Seebeck coefficient of alkali halide aqueous solutions. We examine the dependence of the coefficient on temperature and salt concentration and show that the thermal polarization of water plays a key role in determining the magnitude of the thermoelectric behavior of the solution.