Dear Tianhui,
The warnings you are getting sound similar to the ones you are reporting in the related forum post-- Question about Turbsim. However, if set the wind speed to practically zero, you should also disable wake and unsteady airfoil aerodynamic calculations in AeroDyn by setting WakeMod = 0 and AFAeroMod = 1. Alternatively, you can disable aerodynamic loads altogether by disabling AeroDyn, by setting CompAero = 0 in the OpenFAST primary (*.fst) input file.
The first part of your simulation appears to be related to a start-up transient, e.g, the tower deflecting as a result of the gravity load. I would not start post-processing the results until after this start-up transient diminishes. It may help to run a simulation without ice loads (without any load except gravity) just to assess the results and to quantify the length of the start-up transient before applying the ice loads. I start seeing the effect of the ice loads on the reaction load at the seabed (ReactFXss) at about 58 s into your simulation.
I hope that helps.
Best regards,