Imposed Sea surface conditions

The simplest ocean model is one where the sea surface temperature is read in from a file, either a fixed (annually repeating) climatology, or a transient (monthly varying) realisation based on observations or previous simulations. Monthly means and end of month values are read in and a quadratic approximation used to interpolate to the (fixed) daily value at every grid point. This is constructed to ensure that the monthly mean of the daily interpolated values is equal to the specified mean. Along with SST, the sea ice concentration is also a required field. This is interpolated similarly but is constructed so that the minimum and maximum values are respected. Sea ice thickness is also fixed in these cases, but given the lack of reliable global observations, we set this based on a local scaling to the sea ice concentration. However, if the sea surface conditions come from the output of a coupled model simulation, sea ice thickness can be provided as an input, by using the ZSI file, which is interpolated similarly.