Figure 15. A diagram showing different thickness elements of a floating ice cover. These are as follows: the height above sea level of a hummock h_hum, of the snow surface h_sn, and of the ice surface h_i; the distance below sea level (draft) of the ice-water interface at a specified location Z_i, and of a hummock keel Z_t; and the thickness of the snow cover H_sn.