Serendipitous measurements of deep internal wave signatures are evident in variations in the descent rates of certain Deep Argo floats (Deep SOLO models), which oscillate around a slow decrease with increasing pressure (and density). Averaged from 1000 dbar to the seafloor (using 10070 profiles that extend to at least 3000 dbar, and sometimes as deep as 6000 dbar) the mean of vertical velocity variances corresponds to a sinusoidal wave amplitude of about 0.007 dbar s^-1. The distribution of variances is skewed towards larger values. They also exhibit notable regional variations among and within some deep ocean basins, with generally larger variances in regions of rougher topography or stronger deep currents. Dominant vertical wavelengths estimated from Morlet wavelet transform power spectra range from 393 to 1572 dbar, most frequently 786 and 935 dbar. Vertical wavelengths are weakly anticorrelated with bathymetric roughness, expectedly since shorter wavelengths should be found near generation regions.