Ocean surface waves propagating through sea ice are scattered and dissipated. The net attenuation occurs preferentially at the higher frequencies, and thus the spectral bandwidth of a given wave field is reduced, relative to open water. The reduction in bandwidth is associated with an increase in the groupiness of the wave field. Using SWIFT buoy data from the 2015 Arctic Sea State experiment, bandwidth is compared between pancake ice and open water conditions, and the linkage to group envelopes is explored. The enhancement of wave groups in ice is consistent with the simple linear mechanism of superposition of waves with narrowing spectral bandwidth. This is confirmed using synthetic data. Nonlinear mechanisms, which have been shown as significant in other ice types, are not found to be important in this data set.