Physical oceanographers have lately made the sound of wave crashing a diagnostic tool for tracking and predicting changes in ocean chemistry and biology. In June of 2019, I met with atmospheric chemist Kim Prather at the University of California in San Diego, where she and a crew of colleagues and students seek to reproduce in a 33-meter-long wave tank at the Scripps Institution of Oceanography the shapes, substance, and sound of breaking waves, with an eye and ear to understanding the climatological effects of sea spray, which aerosolizes elements into the air (see Stokes et al. 2013; see also Deane et al. 2017). Sea spray is made largely of particles of sodium chloride, but, in areas like the coast of California, where the atmosphere is dosed with nitrogen dioxide from car exhaust — a gas that, fused with water vapor, becomes nitric acid — sea spray also often turns up heavily laden with sodium nitrate. The spume and spit from crashing waves thus offers what Prather calls a “chemical signal” of anthropogenic climate change. The beat goes on: crashing wave bubbles contain a range of organic materials — from lipids in small bubbles to heterotrophic bacteria in the larger bubbles. Understanding how biochemical matter gets into the atmosphere requires knowing the size of bubbles in sea spray, or, more exactly, the statistical distribution of different sizes of bubbles. How can that be assayed?

One answer is through machine-aided hydrophonic listening. Prather and her colleagues place hydrophones in their wave tanks as well as off the San Diego coast, coupling these with signal analyzers. Coalescing, splitting, oscillating, and bursting bubbles make sounds — resonances, noise spikes — that can be arrayed by frequency and therefore arranged into a sound spectrum (see Deane and Stokes 2002, Graham 2002). Here’s an example from one of Prather’s papers:

Figure from Stokes et al. 2013 of “Spectrum of the voltage output from a miniature hydrophone (ITC 1089d) mounted approximately 5 cm from the end of … [a] plunging sheet” of water.

 

That information, in turn, can be used to make assessments about the size of the biochemical entities that crash, splash, and aerosolize into the air just above waves. If there are synthetic chemical microfluids floating on the surface of the sea — like detergent or soap derivatives used to clean up after oil spills — that makes the bubbles sound different, too (see Deane 2013). In my conversation with her, Prather told me that, “if you listen to a bubble pop in salt water versus water loaded with surfactants, it sounds different.” As T.G. Leighton of the Institute of Sound and Vibration Research the U.K.’s University of Southampton argues, it is also possible to engage in “monitoring the transfer of greenhouse gases between atmosphere and ocean using the sounds of breaking ocean waves” (2014). Bubble acoustics here can be used as a tool for following, but also predicting climate change effects on the ocean.

Here is another example of what the sound of breaking waves might disclose about climate:

This is a recording of a breaking wave courtesy of Grant Deane, a research oceanographer at Scripps and colleague of Prather’s who is an expert in bubble acoustics, particularly as applied to climate change. Indeed, Deane is the key bubble acoustician informing much of the research I discuss above. In this sound file —recorded in the summer of 2014 in the shallow waters on the northern shore of Hornsund Fjord, Southwestern Spitsbergen, the largest island in the Svalbard archipelago — we hear bubbles exploding out of ice, and, at about 13-15 seconds in, the sound of a breaking wave. The bubble spectrum profile of this breaking wave, along with other such instances, can be assayed for information about how quickly ice is falling off of glaciers (for additional information, see Deane et al. 2014).

What is often described and experienced in everyday life as wave noise becomes, listening oceanosonically to such dynamics as these, scientific sound, meaningful. Bubble sounds, in this framework, become proxies for processes to come. The sound of waves in decoalescence come to be apprehended by scientists as a sonic and semiotic herald of climate-changed sea states, and perhaps even of Anthropocene oceans.

To be sure, wave sound has long overflowed — for musicians, poets, and many, many others — with meaning (Helmreich 2018). Consider the Lac Seul First Nation (Anishinaabe) artist Rebecca Belmore’s “Wave Sound,” a series of horn-shaped ear trumpets pointed at the sea off the coasts of Canada, a series that, as Natalie Loveless has suggested (this issue), seeks to tune auditors to the sounds of changing seashores. Or think, following Christina Sharpe, who writes of “the transverse waves of the wake” (2016: 57) of Atlantic slave ships, of how waves might murmur with death, with the continuing and echoing water weather of dispossession, colonialism, and the Plantationocene. The new sounds of waves, scientifically audited, may then be heard as a grim harmony to what Peter Sloterdijk (2016) has named as today’s time of foam — a time during which public and private spheres along with the form of the globe have decoalesced, not into utopian heteroglossia of vitally fusing and fissioning bubbles, but into the form of a long-in-the-gathering dystopic resonance.

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Image credit: False color side-view image of a breaking wave (left to right), with warm colors indicating intense bioluminescence from dinoflagellates caught up in the wave. These organisms’ bioluminescence is here used as a proxy for shear stress, a measure of turbulent energy dissipation. Figure 2 from Deane, Grant B., Dale Stokes, and Adrian H. Callaghan. 2016. “Turbulence in Breaking Waves.” Physics Today 69(10): 86-87. Used with kind permission of authors.

Stokes, M. D., G. B. Deane, K. Prather, T. H. Bertram, M. J. Ruppel, O. S. Ryder, J. M. Brady, and D. Zhao. 2013. “A Marine Aerosol Reference Tank System as a Breaking Wave Analogue for the Production of Foam and Sea-spray Aerosols.” Atmospheric Measurement Techniques 6: 1085–1094.