You may find this difficult to believe, but now that I’ve reviewed an entire year’s worth of data from Alaska’s Beaufort Sea I can say with great confidence (and no scientific evidence) that Marvin the Martian was in fact a bearded seal. If you don’t believe me I encourage you to listen to this sound and tell me that when he’s hanging out in his PJ’s on Mars that this isn’t exactly what’s coming out of our little Martian friend’s mouth.
While of course I’m being facetious, it is only to a point. The scary alien sound effects that have been ingrained in pop culture are made manifest in the Arctic soundscape. While the stoic images of starkly white sea ice may elicit feelings of cold noiselessness, underneath that sea ice it is loud.
In collaboration with the NOAA/PMEL a calibrated autonomous underwater hydrophone package (AUH) was deployed at the continental shelf break approximately 50 miles off the of the coast of Alaska in the Beaufort Sea. Using the AUH we were able to record continuously for an entire year (as my lab mate Amanda tweeted once she was done analyzing beluga calls “I’ve officially finished analyzing 8,760 hours of Arctic
#bioacoustics data”). For the acoustic buffs out there, the AUH was able to precisely record underwater ambient sound levels with 16 bits resolution (i.e., with 96 dB dynamic range) in the 10 Hz to 2,500 Hz frequency range. For the non-acoustics buffs out there this means that we could record sounds ranging from just below the low end of human hearing to about the pitch of a high whistle (think a little girl whistling Andy Griffith).
This was my first foray into Arctic acoustics, and I was properly daunted. My experience to this point has been strictly working on acoustics collected in Southeast Alaska that had concomitant visual observations. There were only three species my hydrophones were likely to detect- humpback whales, killer whales, and harbor seals. In the Arctic, however, there are many species (we detected bowhead whales, killer whales, humpback whales, beluga whales, ribbon seals, ringed seals, AND bearded seals). Furthermore the sound of the ice itself is deafening! It whistles, whines, creaks, groans, and pops- making this critical abiotic feature a character in its own right.
The Arctic is known to be visually “other-worldly” and I cannot emphasize enough how this is made manifest acoustically. For the spectrogram savvy this is a spectrogram of Marvin the Martia… I mean two bearded seals. FYI- this spectrogram was generated from the afore referenced sound file. For those less familiar with a spectrogram, a spectrogram is a visual representation of sound. Time is along the x-axis, and frequency (which we related to pitch) along the y-axis. The colors represent energy (or as we manifest, volume). The brighter the color the louder the sound. By generating spectrograms it allows researchers (like the PI’s, technicians, and of course grad students) here at ORCAA to classify caller species, to classify call types, and to gain a better understanding of who is utilizing the marine habitat and when. In the case of this Arctic data set I enlisted the advice of Arctic expert Kate Stafford at the University of Washington Applied Physics Lab to help me classify some of the more obscure files. She generously pointed me toward an excellent new publication which enabled me to compare the spectrograms that I was generating with those from known species.
Despite the many resources (publications, lab mates, experts in the field) I was still unable to identify all of the calls to species. Many calls were graded, others obscured by the sound of airguns (possibly more on the topic of airguns in the future), and still others vocalizations obscured by the sound of ice. Given that the goal of the project is to monitor long-term changes and trends in the Arctic underwater ambient sound field I understand that this is a cursory first pass at an incredibly rich data set. With as many hours as have yet to make their way into our lab I can’t help but imagine… who other than Marvin we might find there.