Inquiry on Calculation of SKT and SST Over Sea Ice-Covered Grid Points in ERA5 Data

I wonder how the skin temperature (SKT) and sea surface temperature (SST) are calculated for grid points with sea ice coverage? For SST, does it represent the temperature of only the open water portion of the grid point (if the grid point is partially covered by sea ice), or does it include any assumptions or adjustments due to the presence of sea ice?