The salinity of sea ice affects its physical and ecological properties. Here, a multilayer one-dimensional halo-thermodynamic sea ice model is used to simulate the vertical salinity profile of undeformed Arctic sea ice. The model successfully reproduces the desalination pattern observed in first-year (FY) and multi-year (MY) ice. The model can also be integrated with a prescribed, time-independent salinity profile. Substantial differences in the simulated mass balance and ice-ocean salt flux arise depending on the salinity. After 10 years into the simulation, the annual mean ice thickness is 2.85 m with the interactive halodynamic component, compared to 2.53 m (2.29 m) with a prescribed, time-independent, vertically varying (constant) salinity profile. Modelling sea ice salinity is especially important when sea ice is transitioning from a MY to FY ice regime. Thus including a halodynamic component in sea ice models would significantly improve simulations of future climate.