The Existential Imperative: Ocean Thermal Energy Conversion

A 2006 study led by Michael Behrenfeld, at Oregon State University suggested warming oceans produce less phytoplankton. It outlined as well the importance of this finding by pointing out this basic form of plant life are the base of the ocean food chain and absorb substantial amounts of carbon from the atmosphere. They do this by converting the carbon to organic matter by photosynthesis giving off oxygen in the process.

It has been suggested our atmosphere contained no oxygen before cyanobacteria, which are a form of phytoplankton, came into existence about 2.45 billion years ago and that all forms of phytoplankton continue to produce about half of our planet’s oxygen.

The Behrenfield study found that between 1999 to 2004, some regions of the oceans experienced a phytoplankton decline of as much as 30% and that globally about 190 million tonnes of carbon per year were not absorbed due to this decline.

The 2006 models predicted that the loss of plankton due to warming in the mid-latitudes would be reversed near the poles, where researchers expect to see a rise in productivity. They did not however expect that this rise would counter the loss of plankton from the tropical region.

A 2010 paper, “Global phytoplankton decline over the past century” by Daniel G. Boyce et al. reinforced the 2006 finding and postulated the reason for the phytoplankton decline, which was estimated at close to one percent per year since 1950, was thermal stratification of the oceans. “The plants need sunlight from above and nutrients from below; and as it becomes more stratified, that limits the availability of nutrients,” said Boyce.

Thermal stratification is the same phenomena that makes the generation of power in a heat engine possible with ocean thermal energy conversion. And the movement of surface heat to a depth of 1000 meters to produce power would lessen the thermal stratification and produce convection that would bring the nutrients phytoplankton require back to the euphotic zone.

A more recent paper, A Global Pattern of Thermal Adaptation in Marine Phytoplankton by Mridul Thomas et al. estimated that by 2090 as much as one third of tropical species of phytoplankton will be forced by ocean warming to migrate towards the poles, adapt, or die.

Unfortunately a recent article in The Economist suggests that global warming may make the northernmost ocean less productive, not more so and again the main reason is stratification of the ocean. In this case however it is caused by less dense melt water from the icecap sitting on the surface.

The article concludes by stating, “A warming Arctic will not, in other words, be full of fish. It will simply be an ice-free version of the desert it already is.”

There is no reason to conclude why the Antarctic would be any different.

According to NASA, the poles are warming faster than the rest of the planet (creating density stratification) largely as a result of energy in the atmosphere being transported through large weather systems.

A paper “Artificial Upwelling for Environmental Enhancement” by a group from the University of Hawaii and Florida Atlantic University pointed out, ”The prospect of global climate warming will only mean more intense and frequent hurricanes, as they do not form in the North Atlantic when the monthly mean temperature is less than 26.8C.” (The oceans have accumulated over 90 percent of the heat attributable to climate change and Hurricane Sandy was powered by sea surface temperatures 3C above normal.)

“Hurricanes form in warmer waters and dissipate when incurring a temperature drop of 2C. Thus, if a mechanism can be found to lower the temperature of the ocean surface in those areas of the Atlantic, Pacific, and Indian Oceans where hurricanes/typhoons are normally generated, it is possible that the frequency or severity of them can be minimized, if not entirely eliminated.”

As was suggested in the Hawaii/Florida paper and by Ray Schmitt, Woods Hole Oceanographic Institution, “Assessing the potential of Ocean Thermal Energy Conversion(OTEC)”, OTEC is the mechanism by which hurricanes can be minimized, if not eliminated.

Schmitt and Gerard Nihous of the University of Hawaii also have estimated OTEC has the potential to produce as much as 24-25 terawatts of power, whereas the world currently operates on about 16 terawatts.

The research cited above as well as the damage caused by recent storm activity suggests there are vital reasons for us to be doing this.