Ice advection is a function of the atmosphere-ice and ice-ocean momentum stress and the sea surface gradient. The internal ice pressures and rheology are estimated using the Flato-Hibler viscous-plastic rheology as coded by Zhang and Rothrock, 1999. Due to the requirement that the surface type fractions don't vary over the surface flux calculation we calculate the ice velocities and ice-ocean momentum stress at the beginning of the calculation (in DYNSI), but the ice mass fluxes are not applied until afterwards (in ADVSI). The advection is done using the linear upstream scheme in the two horizontal directions. This code is turned on by using the ICEDYN_DRV ICEDYN modules instead of the ICEDYN_DUM module, and works with any ocean configuration.
In the fixed SST case, using the ice advection does not change the ice variables, but does allow the ice and energy convergences due to advection to be calculated, nad subsequently used in the the q-flux model. The q-fluxes need to be consistent with the ice advection, and so if ICEDYN_DRV ICEDYN is used in the spin-up, it must also be used in the q-flux model (and vice versa).