Quantification of Total Sublimation.

The quantification of sublimation was obtained from the vertical profiles of snowfall intensity. The difference between the maximum snowfall accumulation over the vertical column at a daily timescale and the near-ground accumulation is taken as a proxy for the total sublimation.

Fig. 2, for what concerns the models, is obtained by accumulating snowfall over the same period as when MRR data were available. The total sublimation ratio, shown in Fig. 4A, was obtained by accumulation over 1 y of data aggregated at the daily scale as explained below. For each day i and at each grid point, we calculated the maximum snowfall accumulation over the vertical column Cmaxi (in millimeters) and the total near-ground accumulation Cgri (in millimeters). The height levels vary slightly from profile to profile at the subdaily scale, as they result from the conversion of model levels to heights above ground that depend on the temperature and pressure at these levels. For this reason, they are linearly interpolated into a regular grid ranging from 10 to 4,500 m above ground for the sake of homogeneity. The analysis excludes all profiles that have a positive temperature in degrees Celsius to avoid the process of snow to rain conversion being confused with snowfall sublimation; 0.42% of the profiles over continental Antarctica are removed in this way, with maximum values becoming significant (up to 30%) at the lowest latitude of West Antarctica on the Antarctic Peninsula. The total sublimation ratio in Fig. 4C is obtained over N days as

The total sublimation in Fig. 4B for the period under analysis is given by the numerator of Eq. 1. Therefore, the estimation of sublimation is based on daily data. At subdaily scales, the contribution of sublimation can be even larger.