Current and temperature records sampled at 1-minute resolution reveal powerful internal waves on the Weddell Sea continental shelf. Packets of up to six solitary waves with leading soliton amplitudes >200 m and vertical velocities > 0.15 m/s were observed at tidal frequencies, causing large vertical displacements of sound scattering layers. Breaking of large amplitude internal waves in the shallower portions of the eastern Antarctic Peninsula and eastern Weddell Sea shelf may be an important up to now overlooked source of mixing with important repercussions on pelagic production and coupling with the filter-feeding benthos, explaining recent observations of rapid sponge growth.