Climatide

I picked up the latest issue of National Geographic to check out their special feature on population growth (highly recommended reading, by the way) and got side-tracked by a short piece on ocean noise sporting some impressive graphics (this is National Geographic, after all). My favorite is this “heat map” of ship noise overwhelming right whale calls:

Images: C. W. Clark, Cornell Lab of Ornithology; W. Ellison, Marine Acoustics , Inc.; L. T. Hatch and D. Wiley, NOAA SBNMS; S. M. Van Parijs, NOAA NEFSC

The article includes some interesting factoids, like the fact that “on most days … the area over which whales in coastal waters can hear one another shrinks to only 10 to 20 percent of its natural extent” due to shipping noise. And it ends with a quick nod to efforts to budget ocean noise in Massachusetts Bay – a project I reported on a few years ago for WCAI. If you want to get a first-hand taste of the sounds involved, take a listen. Just one disclaimer – the volume of the animal and shipping sounds have been adjusted to allow you to hear the former without blowing out your eardrums with the latter.

• ListenOcean Noise Budget by Heather GoldstoneDownload

Back to the National Geographic article, there’s one caveat I have to point out: the article mentions that shipping is not only creating noise, it is altering the chemistry of the ocean to allow the noise to penetrate further. That refers to a complex physical-chemical phenomenon in which ocean acidification – the result of increasing amounts of carbon dioxide dissolving in the ocean – makes ocean water less resistant to sound waves. Scientists at Woods Hole Oceanographic Institution took a critical look at the idea earlier this year and found that, while it is sound in theory (sorry, couldn’t resist the pun), in practice, the effect is negligible.

That’s not to downplay the seriousness of the ocean noise issue. Scientists have found that Northern right whales are modifying their calling behavior – calling more loudly (presumably to be heard over the din), but less frequently (possibly out of exhaustion or sheer frustration). Given the importance of communication for feeding and reproduction, the long-term implications of ocean noise are unclear but concerning.