Thank you for the great clarification @spencerwong!
I believe that the 1.5 hour vs 1 hour ice/ocean timestep difference between OM2 and ESM respectively is what is causing the subsurface differences I see. I have tried to remedy this by changing the ice_ocean_timestep = 3600 from 5400s in &accessom2.nml but that didn’t fix the subsurface biases. I am not sure if the time lag between atmos/ice and ice/ocean coupling is the same between ESM and OM2 though? @sofarrell might know more? and @dougiesquire about where else DT needs to change in OM2 to match ESM? Cheers!