Ocean Acidification- The Evil Twin

The oceans contain some of our greatest biodiversity and most productive areas in terms of biomass produced. But ocean life depends on fragile interconnected food webs and has small tolerances to changes in environmental conditions. Today however our  oceans’ ever-increasing absorption of CO₂, coupled with warming from Climate Change is triggering large changes, changes that  may lead to a collapse in our ocean’s  ecosystem. 

Every second of every day mankind emits over 2,700,000 pounds of anthropogenic CO₂. About 30% or 24 million tons per day of this CO₂ is absorbed by our oceans causing large, easily understood and catastrophic changes.  To understand  Climate Change one needs College Physics 101. For Ocean Acidification a high school chemistry text showing the absorption of a gas in water as a function of the gases  atmospheric partial pressure and water temperature will suffice .

Once absorbed in the ocean CO₂ combines with water to form Carbonic Acid and a constantly changing mix of Bicarbonate and Hydrogen Ions according to the following formulas, the ratio of each of these ingredients is determined by additional items such as ocean temperature and alkalinity. 

 CO_{2 (aqueous)} + H₂O        H₂CO₃ (Carbonic Acid)             HCO₃^-(bicarbonate)+ H⁺                 

Thus the result of increased absorption of CO₂ will  be the increase in hydrogen ions making the ocean more acidic. Acidification is measured using the pH scale which ranges from zero (acidic) to fourteen (basic) with water having a pH of 7. Past CO₂ emissions have already resulted in a decrease in ocean pH from 8.2 to under 8.1 as shown in Figure 1. 

The red line in Figure 1. Is the “Keeling Curve” showing the increase in Atmospheric CO₂, the blue line shows the corresponding increase in dissolved CO₂ in the ocean while the green line shows the decrease in Ocean pH (an increase in acidity). A decrease from 8.2 to 8.1  may not seem like much but as the pH scale is logarithmic it represents an increase in ocean hydrogen ion concentration of about 30%, in the last 200 years .

This change, faster than any known change in acidification including the change during past mass extinctions[1] is occurring in an environment that is intolerant to changes and cannot adapt in short time frames. Note that the term “Acidification” doesn’t mean the ocean is acidic, it is merely a shift towards acidity. But this fine point is lost on animals who are adapted to a pH of 8.2.

This increase in H+ ions has a major effect on ocean life. Note in the equation above that one result of increasing CO₂ absorption is a bicarbonate ion and an H⁺ ion. The H⁺ ion obviously increases the acidity changing the ocean environment, but the ocean has a way of reducing or “buffering” this increase. The extra H⁺ ion can combine with an existing carbonate ion to form an additional bicarbonate ion removing the H⁺ ion and decreasing the rate of increase in acidity. This effect is called carbonate buffering. 

Unfortunately this reduction of Carbonate Ions has an additional large effect on some ocean life: animals that make shells from Calcium Carbonate. As the Carbonate concentration in the ocean decreases so does the concentration of Calcium Carbonate. Deprived of Calcium Carbonate many of these animals will be unable to form shells and die.

This description correctly describes what is happening, but it doesn’t convey the true impact. Animals such as Krill, coccolithophores, pteropods, foraminifera, the very basis of the food web, will begin to dissolve and they will die- what follows isn’t hard to imagine. Figure 2 shows the 45-day one-way journey of a Pteropod through ocean water of the acidification levels in 2100 if we continue our current CO₂ pollution.

Figure 2 Pteropod at expected acidification levels in 2100 see http://www.pmel.noaa.gov/co2/story/What+is+Ocean+Acidification%3F

This is not a scientific hypothesis, it is fact; simply search the web for “Oysters, Oregon, Acidification” and you will find that about 85% of the commercial oyster crop in and Oregon (and Washington) has failed due to the larva being unable to form shells in the acidified water as the acidity and CO₂ levels alter their shell formation. Given the speed at which this change is happening not only oysters, but many other species will be unable to adjust, and we face massive changes and extinctions in ocean life. Lobsters in Maine are moving North due to warming and very young lobsters are having trouble forming shells due to acidification. Decreasing Carbonate levels is clearly a problem, but it is worse than a simple decrease in saturation the decrease reduces the areas of the  oceans where these creatures can survive.

Shelled animals make their shells from one of two forms of Calcium Carbonate; Calcite or Aragonite. Both Calcite and Aragonite have an interesting property, the solubility of both increases with pressure, thus, the deeper you go the higher the solubility. 

If you were to take a journey on a deep diving submersible vehicle you would notice that there were seashells on the ocean floor down to a certain depth, below that depth the shells disappear. Why? The increased solubility at increasing depths. Above a certain depth (the “Saturation Line”) the solubility is low and if Carbonite saturation is greater than the solubility, shells will not dissolve, the water cannot absorb any more Carbonate. , Below the “Saturation Line” depth, the water becomes  unsaturated as the solubility has increased due to the  increased pressure, and shells thus dissolve.

Figure 3  Saturation profile at 7.5 concentration                   Figure 4. Saturation profile at 6.5 Concentration  

Figures 3 and 4 graphically portray what happens as depth increases. Assume hypothetically that the Calcium Carbonate concentration in the ocean is 7.5 units as shown in Figure 3 (not the real units) . Assume the Ocean can only dissolve 5 units of Calcium Carbonate at the surface (right hand scale in Figure 3.). At the surface there is more Calcium Carbonate (7.5)  than can be dissolved (5.0) so Calcium Carbonate will precipitate out and fall to the seafloor until the concentration reaches 5.0. 

As we descend the solubility increases, eventually we come to the “Saturation Line”  the depth where the increased solubility (7.5) will dissolve all the Calcium Carbonate (7.5). Below this point ,as the solubility continues to increase, the water is unsaturated, no calcium carbonate is found on the seafloor and shells falling from above will dissolve.

Now consider Figure 4 which shows the effects of acidification decreasing the Calcium Carbonate concentration as explained above. Assume the  Calcium Carbonate  in the ocean has decreased  from 7.5 to 6.5 units. On the righthand scale the saturation line moves upwards from 7.5 to 6.5.  One of the main effects of ocean acidification will be the calcite and aragonite saturation lines continually moving upward as their concentration decrease. This upwards movement will decrease  the vertical range of carbonate shelled creatures until finally the saturation line reaches the surface. 

The effects of Ocean Acidification will eventually be felt worldwide but will first be observed on a large scale in Polar Regions as CO₂ is more soluble in cold water. Studies show that if we continue to emit CO₂ at the projected rate the entire Polar Regions, some of the most productive areas in the ocean will become unsaturated by 2100. 

Figure 5, from NOAA, shows the projected aragonite saturation depths for 2020, 2040 and 2090. 

As shelled creatures  at the base of the food webs disappear catastrophic changes in the oceans biosphere that we cannot hope to predict will also occur. But even this isn’t the end of the story the decrease in shelled creatures also drives positive feedbacks for climate change. In the atmosphere one of the main paths for CO₂ removal and fixation is photosynthesis in plants. In the oceans several other paths exist.

For millions of years we have had a balance as the oceans have absorbed CO₂ from the atmosphere while at the same time gaining Calcium from surface runoff from dissolved rocks thus reaching an equilibrium. This balance, another instance of the “Goldilocks Planet” resulted in the right amount of Calcium Carbonate in the Ocean’s which allowed shelled creatures to make shells. 

When these shelled creatures died they sank along with carcasses from other sea life such as fish taking their calcium and their carbon with them allowing he ocean to absorb more CO₂. If these creatures cannot form shells one of the main pathways for ocean absorption and sequestration of CO₂ will be destroyed meaning more CO₂ will remain in the atmosphere increasing the rate of warming.

Ocean acidification alone is catastrophic, but climate change is also wreaking havoc in the oceans. Climate change deniers constantly (and desperately) pointed out (before 2016) that atmospheric heating had slowed in the last decade and they were right. Climate Scientists concurrently  pointed out “wait till an El Nino year. Unfortunately for deniers (and human kind) 2016 was an El Nino year and atmospheric temperatures skyrocketed.

NASA measurements however (not theories deniers, measurements) showed that the total energy captured by the earth didn’t slow down during the period of low atmospheric temperature rise. The earths’ total outgoing radiation is about 0.6 watts/m² less than the incoming radiation and the difference is growing (for the earth to remain in thermal balance it must be zero). When summed up over the earth’s total surface area this equates to the energy of over three  World War II Nuclear Weapons  being added to our environment EVERY SECOND. 

But the question remains; “Where was the heat going during the last decade, if it wasn’t going into the atmosphere?

The First Law of Thermodynamics is on sufficiently sound footing to dictate that if that energy is not going into the atmosphere it has got to be going somewhere else; in fact studies show that up to 90% of the heat was going into the oceans and melting ice. The Greenland Ice Sheet alone is losing about 279 billion tons of ice annually.[2] (need reference to last great melting day) This statistic is staggering but its’ implications are even worse. It takes 80 Calories per gram to melt ice but only 1 calorie per gram to heat water 1⁰C and about 0.23⁰C to heat air. As the ice disappears  the heat currently absorbed by ice will be directed at air and water. The heat required to melt one gram of ice (80 calories)  will then raise 80 grams of water  or 347 grams of air 1⁰C

While ocean acidification alone will cause massive changes to the ocean’s ecosystem Climate induced heating will only hasten the process putting even more stress on already stressed organisms. Studies show that we could lose 90% of our coral reefs in this century. Currently the combined stress from warming and acidification are beyond the capability of many orgasms to adapt. As the British Royal Academy pointed out in a paper on Climate Change, ““In such a 4°C world, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world.”  

Either climate change or ocean acidification alone mandates that we reduce CO₂ emissions but together they present an overwhelming mandate to act now, forcefully and quickly. 

Like climate change ocean acidification is happening here and now. Further there are no alternative hypotheses from wonderland like those that exist among climate change deniers as to why Ocean Acidification is happening. If you know the partial pressure of CO₂ in the atmosphere and the temperature of the water then you can look up the dissolved CO₂ in a table and calculate the resulting pH, it’s that simple.

Most of our grandchildren will never see a coral reef, they will live in a world where the one billion people who depend on the sea as their primary source of protein will, if lucky, be displaced if not, be starving. They will live in a world of barren oceans, catastrophic climate change induced weather and mass population displacement, in short, they will live in a “hellish future.” 

Our grandchildren will live in their world because we live in our world, a world where short-term rationalization trumps overwhelming scientific consensus, a world where “tomorrow” seems to be a perfectly good strategy, a world where deniers contribute to support junk science to sow doubt but in sowing doubt they also reap certainty, the certainty as to the world their grandchildren will live in.

In his farewell address at West Point General Douglas MacArthur said, “The Long Gray Line has never failed us. Were you to do so, a million ghosts in olive drab, in brown khaki, in blue and gray, would rise from their white crosses thundering those magic words: Duty, Honor, Country.” Today we are failing the long multicolored line of humanity, we are leaving them twin environmental disasters fueled by our quest for short-term gain. . 

For our grandchildren Sarah Conner had it right; “The future is not set, there is no fate but what WE make.” If your grandchildren could beam back to our boardrooms and political venues from their twilight in 2100 their overriding question would be, “Why? Why did you destroy our Future?” 

What is our answer to the question? Our (their) future depends on it. Finally, what are you doing about it? What rationalizations is your company making to justify its’ continued CO₂ emissions? 

“You must be the change you want to see.” Gandhi

By Charles E. Bayless

[1] http://earthobservatory.nasa.gov/Features/CarbonCycle/page5.php

[2] http://www.nasa.gov/vision/earth/lookingatearth/greenland_slide.html