GPS doesn’t work when trying to locate anything under the ocean surface because radio signals cannot penetrate seawater. So today, when research scientists want to track a whale, a Great White Shark, or other wildlife, they tag it. When the tagged creature surfaces or is caught the location is then transmitted to a satellite. Fishers that come across tagged wildlife are compensated when they return the tags to the researchers who created them.
WHOI has been working on sonic communication systems since World War Two, originally to find enemy submarines and the locations of mines, while helping to hide American marine assets. Emulating how whales communicate, scientists discovered a water layer between approximately 600 and 1,200 metres (2,000 and 4,000 feet) that could channel low-frequency sounds and transmit them over long distances. They dubbed this layer SOFAR, an acronym for what is now known as the Sound Fixing and Ranging channel.
How does the SOFAR channel work? The ocean is multilayered determined by water temperatures, salinity and pressure. Sound reacts differently in its different layers, speeding up in warmer water and slowing down in colder dense water. But in between the warm and the cold layers lies SOFAR bounded by what essentially is a ceiling and floor. Sounds within the SOFAR channel bounce back on forth between the warm water ceiling and cold dense floor and can be channelled horizontally allowing for sonic communication over hundreds of kilometres before becoming attenuated.
WHOI is deploying buoys throughout the ocean that transmit a 32-second location signal twice a day. They call these signals “pongs” as opposed to “pings” which are used by naval sonar. Pongs transmit at a low frequency of 300 Hertz, as opposed to pings at 18 Kilohertz.
With pongs being transmitted from multiple locations, it becomes possible to triangulate the location of any device with an onboard receiver.
The ocean is full of listening and sampling devices. The ARGO Program alone represents a constellation of thousands of instrumentation packages drifting with the currents and moving up and down through various water layers while gathering enormous amounts of data on temperature, salinity, and composition.
Although SOFAR was originally a classified naval secret, in the 1990s it was made accessible for scientific research. And now it is being used by universities and companies to deploy increasingly smaller submersibles, and tags that can be applied to a range of marine wildlife and more.
Researchers are tagging swordfish and have revealed previously unknown behaviours. For example, this species spends much of its day in water 800 metres (2,650 feet) deep, but at night it rises near the surface. An ecologist at WHOI believes the behaviour conforms with warm water eddies where the species’ food can be found.
In another application, SOFAR is being used to track carbon in the ocean. A University of Rhode Island researcher has developed Minions, tiny underwater floats designed to monitor marine organic matter as it drifts down from the surface to the depths. Understanding the mechanism could become a guide for projects seeking to permanently sequester carbon in the ocean’s deepest parts.
As more buoys and devices are deployed, the world’s oceans will become as wired as the surface of our planet is today, but this time instead of satellite-based GPS, it will be a sonic network.
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At the time of the Torrey Canyon the operator, British Petroleum, had just invented dispersant detergents which were liberally dumped onto the wreck, and even rolled off the Welsh cliffs onto the polluted beaches and rocky shore. Since then fossil fuel and marine shipping companies have come up with all kinds of technology to attempt to break up oil spills on the surface of our oceans. The industry’s oil spill response documents include the latest in dispersants, booms, and skimmers and what works best in cold or warm water, in rough seas, and in windy conditions or calm.
Conventional thinking today says that when an oil spill occurs, it spreads fast with some of the discharge evaporating, and microbes digesting the rest. There is no reference to the role sunlight plays. That is an oversight.
New research published in the last week from, the Woods Hole Oceanographic Institute, Cape Cod, Massachusetts, suggests that oil spills need to be treated differently in the presence of sunlight. The multi-authored article entitled, Partial Photochemical Oxidation was a Dominant Fate of Deepwater Horizon Surface Oil, describes a previously unknown phenomenon.
Sunlight exposure over several days chemically altered 50% of the oil contained within the Deepwater Horizon slick making chemical dispersants less effective. The sunlight played no part in evaporation and so the oil remained on the surface unresponsive to the dispersants that were being dumped into the Gulf. In the end, the oil had to be skimmed up but not before it damaged the biodiversity along the Louisiana coast and in the Gulf.
It appears no one in the fossil fuel and chemical industry had observed this phenomenon before, that sunlight photo-oxidizes compounds to the molecules contained in oil, and binding more oxygen to them altering their makeup. And the longer the oil sat on the surface the greater degree of oxidation.
Within the over three months from the Deepwater oil spill start to the well being capped, almost 500 million barrels entered the water of the Gulf with most of it floating to the surface. There the oxygen contained within oil molecules reacted to sunlight in less than five days.
So why is this important?
Today oil spill response teams prepare and practice using fresh, not weathered oil. They don’t look at how they need to alter their response based on sunlight conditions. But looking back at the Deepwater Horizon case, it is clear that dispersants used today are largely ineffective on photo-oxidized oil. That means we need to invent new dispersants or develop new oil cleanup techniques. And during training crews need to test photo-oxidized oil with boom, skimmer and absorption technology to see if these tools are impacted negatively. Still to be done is an accurate calculation of the photo-oxidizing process subject to different environments, whether cold or warm water or in rough seas.
For Canada, which hopes to build a pipeline from Alberta’s oil sands to a cold water port on the British Columbia coast, testing of the photo-oxidizing effect on heavy synthetic crude, the product being shipped to Asian markets, needs to be done to update spill response standards. This should be part of the environmental due diligence currently underway, and before we witness tanker traffic increases from 5 to 34 per month in the narrow channels linked to the Burnaby. British Columbia, oil terminal.
