This presents how the calls of the Humback whale would appear in modern SOSUS technology displays.
The top reveals a wider frequency range than is normally observed in SOSUS operation, but that is because it has been sped up by a factor of ten to allow the calls (normally sub-sonic) to be heard in sound recordings. This, then, suggests that the LOFARgram is not of live data, but of a sped-up recording.
If you apply a divide by ten to the left scale, we are back to the conventional LOFARgram display covering from 0 Hz to 50 Hz.
SOSUS technologists saw these waveforms for years, and were unable to determine their origin. Further complicating matters were that these noises moved. Because the early stages of SOSUS was called Project Jezebel, these noises were tongue-in-cheek attributed to the Jezebel monster.