Sea-Ice Forcing Data
Recommendations are given below for specifying the detailed state of the sea ice at the beginning of the model integration. The strategy adopted to arrive at a reasonable initial sea-ice state for the coordinate experiment involves first initializing the sea-ice state in the manner specified below for January 1948, and then running the coupled sea-ice ocean model out for a period of five years, ending in January 1953. The sea-ice state for January 1953 is then used to initialize the coordinated-experiment run starting in January 1948 and running out to present.
The melting point of the sea-ice surface whether snow covered or not, is set to zero degrees Celsius:
The freezing point of the ocean surface is set according to a salinity-dependent formula (Millero, 1978):
Initial sea-ice concentration is set to 0.95 everywhere the surface temperature is within one degree of the salinity-dependent freezing point. The latter being determined from the temperature and salinity of the ocean surface waters as initialized using the PHC atlas.
For validation purposes, a variety of satellite-derived products of sea-ice concentration are available from NSIDC. For the period October, 1978, to December, 1996, the Nimbus-7 SMMR and DMSP SSM/I passive microwave data of daily and monthly archives is found here. For the period June, 1987, to present, the DMSP SSM/I daily and monthly polar grid archives are found here.
Initial sea-ice thickness is set to 2.0 m everywhere the surface temperature is within one degree of the salinity-dependent freezing point. The latter being determined from the temperature and salinity of the ocean surface waters as initialized using the PHC atlas.
Initial sea-ice velocity is everywhere set to 0.0 m/s.
There does not exist a sea-ice velocity validation data set for the time period corresponding to the coordinated spin-up experiment, i.e., during 1948-1978. Nonetheless, we can at least make use of the sea-ice velocity fields from the International Arctic Buoy Program (IABP), which span the time period 1979-1998, as a guide to the expected sea-ice velocity magnitudes, patterns, and variability.
Initial snow thickness over sea ice is everywhere set to 0.0 m.
Onset of Surface Melt
For validation purposes, an interannual data set (1979-1998) of "day of onset of melt" over the Arctic sea ice is available from the National Snow and Ice Data Center. An example of the data that display the onset of melt during 1979 is shown at right.