Underwater ambient noise spectra and amplitude distributions are described for data recorded during late spring conditions under the ice in McMurdo Sound, Antarctica. The ice was fast to the shore and provided 10/10 cover at the time. While the ambient noise was characterized by intense biological activity a diurnal, nonbiological component became apparent during the three-day recording period. This component was found to be similar to that observed in Arctic measurements and attributed to surface cracking of the ice sheet under the influence of thermal stressing. In certain respects, however, this noise component was found to be different from its Arctic counterpart.