The Antarctic waters are certainly not quiet – and yet many whale species feed there throughout the summer months!

It’s a little known fact that the sound of calving/cracking/colliding Antarctic icebergs can be recorded on seabed acoustic loggers deployed on the edge of Australia’s continental shelf several thousand kilometres away.  If the sound travels that distance, what must their intensity be at source?

Professor Alexander Gavrilov of Curtin University Centre for Marine Science and Technology (CMST) has estimated the source level of these sounds at “220 dB to nearly 250 dB re 1uPa at 1m” (J Hughes, pers. comm. 2013).  To get a “feel” for these sounds the interested reader can access  playbacks of a variety of Antarctic Ice Sounds recorded at the Alfred Wegener Institute PALAOA listening station.

Listen to the audio and spectral clips entitled “Break-off from the ice shelf” and “Colliding icebergs”.  It is remarkable how the former looks and sounds like a series of pulses in a seismic survey.

The sound of colliding icebergs is, of course, very intense but, as we all know, many whale species (we’ve seen them on TV being hunted with icebergs in the vicinity!), including true blue whales, southern right whales and humpback whales feed totally unaffected by sounds in Antarctic waters during the summer months when such noises are at their most intense.

Further evidence of the intense sounds generated by the break-up of ice-bergs and ice-shelves can be found in the recent paper by Robert Dziak et al entitled “Life and death sounds of Iceberg A53a”.

If that iceberg created sounds which “averaged ~ 220 dB-rms re 1 μPa @ 1 m, yielding a total energy flux density of 252 dB μPa2-sec over the ~ 20 minute duration of the entire sequence” one can only imagine what intensity the peaks were!  Fig 1C in the paper provides an indication of the intensity of the peaks.

One is left to wonder why, if whales show such tolerance to and are unaffected by intense natural sounds when they are feeding in the Antarctic (which just happen to be at similar frequencies and intensities to seismic survey sounds) they are considered by some to be less tolerant to and adversely affected by similar sounds when they visit Australian waters.

Advertisements

Trackbacks

  1. […] whales feed in Antarctic waters during the summer months and are obviously not disturbed by the sounds of calving/colliding icebergs which are similar in intensity and frequency to seismic […]

  2. […] on this site, the sound of a breaching humpback whale is the same as a seismic pulse at 68m and the sounds of calving/colliding icebergs are similar to seismic sounds at 1m. In addition, blue whales vocalise at 180-190 dB re 1 […]

  3. […] cetaceans successfully live in noisy environments for significant lengths of the year can also be found in Antarctic waters where the sounds of calving/cracking/colliding icebergs are as intense as and at similar […]

  4. […] noisy place as a result of biological sounds (vocalisations, breaching, etc) and natural sounds (cracking/colliding icebergs, earthquakes, lightning strikes, etc).  Thus, species living in the ocean have evolved over […]

  5. […] to the contrary showing that whales live in a noisy ocean where there are natural sounds such as calving/colliding icebergs and sounds from their own activities that are similar in intensity, frequency and periodicity to […]

  6. […] summarising how seismic sounds compare with other typical sounds in the ocean. For example, the sounds of calving/colliding icebergs generate sounds of similar loudness, frequency and periodicity and whale calls and breaches are at […]

  7. […] case, biological and other natural sounds, including their own vocalisations, their breaching and icebergs calving/colliding (in their feeding grounds!) are as loud as seismic sounds!  Why has the humpback population on the […]

  8. […] 1. Greenpeace claim: “These blasts are nearly as loud as the nuclear bomb dropped over Hiroshima“.  This is surely a deception of the most serious form as it ignores the facts and science.  As can be seen in an article already published on this website, drawn from readily available information, comparing seismic sounds with typical sounds in water (and air), a typical seismic source is approximately 230dB whereas an atomic explosion is 248dB in air BUT 310dB in water.  Thus, an atomic explosion such as Hiroshima, is more than 8192 times louder than a typical seismic pulse.  This is very different from Greenpeace NZ’s claim that seismic pulses are “nearly as loud” as atomic explosions.  Furthermore, seismic sounds are no different from many common natural sounds in the ocean, including humpback breaching and the sound of calving/colliding icebergs. […]

  9. […] us why.  Much of this science, such as other sounds in the ocean, the sounds of breaching whales, Antarctic ice sounds, the reaction of cetaceans to seismic sounds, attenuation of sound in water, etc, is covered in […]

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: