Profile measurements from a meteorological mast installed in the middle of a sea ice floe in the Bothnian Bay allowed the skin roughness parameter and drag to be computed. Radiosonde and pibal profiles at the same location enabled the large-scale stress and roughness parameter to be estimated by the geostrophic departure method. The generally significant form drag contribution appears to depend also on thermal stability. These results are compared with the predictions from a model of Arya (1975) as a function of sea ice surface features statistics. The qualitative agreement is good, but uncertainty in the numerical values is considerable.