Forget Atmospheric Warming – Its the Ocean We Need to Worry About

August 13, 2015 – Whatever we are doing to the atmosphere by adding greenhouse gases will take centuries to repair. But the damage to the ocean makes these atmospheric perturbations look like a sideshow. That’s because the ocean is our biggest carbon sink and filling it with carbon dioxide (CO2) is changing the pH balance making it more acidic with consequences for the life that is dependent upon it.

In a recent study appearing in the journal Science, scientists measuring the cumulative impact of CO2 on the ocean predict by 2100 that pH levels will have fallen by 0.4, a 150% increase in ocean acidity since the mid-19th century when we first began keeping comprehensive records. For marine animals from corals to shellfish, and from fish to whales, acidification at this rate of change will have a negative impact. Animals dependent on shells and exoskeletons (crustaceans) when exposed to increasing acidification will likely become extinct. For other marine species acidification combined with ocean warming will alter seasonal behavior changing when spawning occurs and fertility rates. With extinction of crustaceans and zooplankton food sources will be impacted putting additional pressure on many marine species. Warmer oceans will alter migration patterns something already being observed off California where 43 fish species have been studied for almost six decades.

Extinction is the greatest threat posed by ocean acidification. The geological record supports this. The end of the Permian marks the greatest extinction event in the geological record. What caused it? Volcanic eruptions in Siberia 252 million years ago released CO2 in sufficient quantity to alter ocean pH levels. Known as the Siberian Traps, this catastrophic event unfolded over 60,000 years. The end of the Permian saw 95% die off of ocean species and 70% of species on land.

Will anthropogenic contributions of CO2 over two centuries produce the same results as found in the geological record?

A number of scientists think so. Some are calling for a “plan B,” using technology to get the CO2 out of the ocean and atmosphere. Sir Richard Branson is offering a $25 million U.S. prize to anyone who can demonstrate a method to suck CO2 out of the atmosphere and thereby to halt progressive ocean acidification.

Three years ago I wrote about an American businessman, Russ George, who dumped 100 tons of iron sulphate off the British Columbia coast in a personal geoengineering experiment. The end result was a temporary algae bloom that George argued would reduce ocean acidity. He believed if ramped up globally such a seeding effort would work. George is not alone in suggesting a technological fix. In addition to iron fertilization, some have proposed nitrogen fertilization. In both cases the geoengineers hope that resulting algae blooms will serve two purposes.

1. Create sufficient phytoplankton to draw CO2 from the surface water as well as from the immediate atmosphere above.
2. The biomass upon death will sink and the captured carbon will then become sequestered permanently in the deep ocean.

The seeding experiments such as the one George tried do not necessarily produce the intended results. Two such experiments to date have shown that expected phytoplankton growth is suboptimal with less than 30% of the ocean a suitable target. In addition the biomass created largely recycles the CO2 which gets re-released into the surface water and atmosphere.

Unintended consequences of this type seeding include:

• toxic algae blooms (red tides)
• changes in the species within the phytoplankton community impacting dependent species seeking food
• de-oxygenation of ocean water in proximity to the bloom upon its death
• increased releases of methane and nitrous oxide

In a new publication, Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration, scientists writing on behalf of the National Research Council have looked at a range of ocean geoengineering schemes and concluded that any attempt to add alkalinity to the ocean will have deleterious impacts.

States Sabine Mathesius, a lead author in a study published in the journal Nature Climate Change, “even if the CO2 in the atmosphere would later be reduced to the pre-industrial concentration, the acidity in the oceans could still be more than four times higher than the preindustrial level. It would take many centuries to get back into balance with the atmosphere.”

So what can be done?

Some scientists and engineers argue that removing CO2 from the air is the ocean’s panacea. But a recent computer simulation with a target removal rate of 5 gigatons of CO2 each year showed a marginal change in ocean acidity over 150 years. The exact number, a reduction in surface pH of 0.05. Of course such technology does not currently exist. Theoretically however if we were to develop it we would have to deploy thousands of units at a cost of as much as a trillion U.S. dollars.

Twenty marine scientists approaching the upcoming COP2015 meetings in Paris have come together to talk to policymakers so that they understand the consequences of not addressing ocean acidity in addition to climate change. They want to add ocean to atmospheric CO2 reduction targets. They argue that the 2 Celsius (3.6 Fahrenheit) atmospheric target limit needs to be accompanied by a sea surface temperature target of no more than 1.2 Celsius (2.16 Fahrenheit). They haven’t established a pH target because the science indicates the impact of current CO2 levels is already irreversible for the next several centuries. That means adaptation is the only strategy of choice.