A Lee Wave Model for Deep-Sea Mudwave Activity

Mudwaves, with wavelengths up to 6 km and heights up to 100 m, are commonly found in the deep sea where steady, sediment-laden currents are present their internal structure suggests that they have migrated with time. Lee waves appear to be generated in the density gradient above the sinusoidal mudwave topography the near-bottom flow field associated with the lee waves creates a cross-wave asymmetry in bottom current velocity. A model of bottom flow and sedimentation rate for a transverse mudwave shows that preferential deposition occurs on the upstream flanks and the bed forms migrate upstream. The flow conditions for such lee waves are common in the deep sea therefore many mudwaves are probably active under present flow conditions. The model suggests that for a given wave, the ratio of downstream-upstream sedimentation rate varies primarily with flow velocity. Thus changes in this ratio, determined by seismic or sampling techniques, might be used to determine past variations in flow velocity. Reprints.