Guest Post by Willis Eschenbach
I’m a long-time ocean devotee. I’ve spent a good chunk of my life on and under the ocean as a commercial and sport fisherman, a surfer, a blue-water sailor, and a commercial and sport diver. So I’m concerned that the new poster-boy of alarmism these days is sea-water “acidification” from CO2 dissolving into the ocean. Heck, even the name “acidification” is alarmist, because sea water is not acid, nor will it every be. What we are seeing is a slight reduction in how alkaline the sea water is.
There is a recent and interesting study in GRL by Byrne et al., entitled “Direct observations of basin-wide acidification of the North Pacific Ocean“. This study reports on the change in ocean alkalinity over a 15 year period (1991-2006) along a transect of the North Pacific from Hawaii to Alaska. (A “transect” is a path along which one measures some variable or variables.) Here is the path of the transect:
Figure 1. Path (transect) used for the measurement of the change in oceanic alkalinity.
I love researching climate, because there’s always so much to learn. Here’s what I learned from the Byrne et al. paper.
The first thing that I learned is that when you go from the tropics (Hawaii) to the North Pacific (Alaska), the water becomes less and less alkaline. Who knew? So even without any CO2, if you want to experience “acidification” of the ocean water, just go from Hawaii to Alaska … you didn’t notice the change from the “acidification”? You didn’t have your toenails dissolved by the increased acidity?
Well, the sea creatures didn’t notice either. They flourish in both the more alkaline Hawaiian waters and the less alkaline Alaskan waters. So let’s take a look at how large the change is along the transect.
Changes in alkalinity/acidity are measured in units called “pH”. A neutral solution has a pH of 7.0. Above a pH of 7.0, the solution is alkaline. A solution with a pH less than 7.0 is acidic. pH is a logarithmic scale, so a solution with a pH of 9.0 is ten times as alkaline as a solution with a pH of 8.0.
Figure 2 shows the measured pH along the transect. The full size graphic is here.
Figure 2. Measured ocean pH from the surface down to the ocean bottom along the transect shown in Figure 1.
The second thing I learned from the study is that the pH of the ocean is very different in different locations. As one goes from Hawaii to Alaska the pH slowly decreases along the transect, dropping from 8.05 all the way down to 7.65. This is a change in pH of almost half a unit. And everywhere along the transect, the water at depth is much less alkaline, with a minimum value of about 7.25.
The third thing I learned from the study is how little humans have changed the pH of the ocean. Figure 3 shows their graph of the anthropogenic pH changes along the transect. The full-sized graphic is here:
Figure 3. Anthropogenic changes in the pH, from the surface to 1,000 metres depth, over 15 years (1991-2006)
The area of the greatest anthropogenic change over the fifteen years of the study, as one might imagine, is at the surface. The maximum anthropogenic change over the entire transect was -0.03 pH in fifteen years. The average anthropogenic change over the top 150 metre depth was -0.023. From there down to 800 metres the average anthropogenic change was -0.011 in fifteen years.
This means that for the top 800 metres of the ocean, where the majority of the oceanic life exists, the human induced change in pH was -0.013 over 15 years. This was also about the amount of pH change in the waters around Hawaii.
Now, remember that the difference in pH between the surface water in Hawaii and Alaskan is 0.50 pH units. That means that at the current rate of change, the surface water in Hawaii will be as alkaline as the current Alaskan surface water in … well … um … lessee, divide by eleventeen, carry the quadratic residual … I get a figure of 566 years.
But of course, that is assuming that there would not be any mixing of the water during that half-millennium. The ocean is a huge place, containing a vast amount of carbon. The atmosphere contains about 750 gigatonnes of carbon in the form of CO2. The ocean contains about fifty times that amount. It is slowly mixed by wind, wave, and currents. As a result, the human carbon contribution will not stay in the upper layers as shown in the graphs above. It will be mixed into the deeper layers. Some will go into the sediments. Some will precipitate out of solution. So even in 500 years, Hawaiian waters are very unlikely to have the alkalinity of Alaskan waters.
The final thing I learned from this study is that creatures in the ocean live happily in a wide range of alkalinities, from a high of over 8.0 down to almost neutral. As a result, the idea that a slight change in alkalinity will somehow knock the ocean dead doesn’t make any sense. By geological standards, the CO2 concentration in the atmosphere is currently quite low. It has been several times higher in the past, with the inevitable changes in the oceanic pH … and despite that, the life in the ocean continued to flourish.
My conclusion? To mis-quote Mark Twain, “The reports of the ocean’s death have been greatly exaggerated.”
[UPDATE] Several people have asked how I know that their method for separating the amount of anthropogenic warming from the total warming is correct. I do not know if it is correct. I have assumed it is for the purposes of this discussion, to show that even if they are correct, the amount is so small and the effect would be so slow as to be meaningless.
[UPDATE] WUWT regular Smokey pointed us to a very interesting dataset. It shows the monthly changes in pH at the inlet pipe to the world famous Monterey Bay Aquarium in central California. I used to fish commercially for squid just offshore of the aquarium, it is a lovely sight at night. Figure 4 shows the pH record for the inlet water.
Figure 4. pH measurements at the inlet pipe to the Monterey Bay Aquarium. Inlet depth is 50′ (15 metres). Light yellow lines show standard error of each month’s measurements, indicating a wide spread of pH values in each month. Red interval at the top right shows the theoretical pH change which the Byrne et al. paper says would have occurred over the time period of the dataset. Photo shows kids at the Aquarium looking at the fish. Photo source.
There are several conclusions from this. First, the sea creatures in the Monterey Bay can easily withstand a change in pH of 0.5 in the course of a single month. Second, the Byrne estimate of the theoretical change from anthropogenic CO2 over the period (red interval, upper right corner) is so tiny as to be totally lost in the noise.
This ability to withstand changes in the pH is also visible in the coral atolls. It is not widely recognized that the pH of the sea water is affected by the net production of carbon by the life processes of the coral reefs. This makes the water on the reef less alkaline (more acidic) than the surrounding ocean water. Obviously, all of the lagoon life thrives in that more acidic water.
In addition, because of the combination of the production of carbon by the reef and the changes in the amount of water entering the lagoon with the tides, the pH of the water can change quite rapidly. For example, in a study done in Shiraho Reef, the pH of the water inside the reef changes in 12 hours by one full pH unit (7.8 to 8.8). This represents about a thousand years worth of the theoretical anthropogenic change estimated from the Byrne et al. paper …
The sea is a complex, buffered environment in which the pH is changing constantly. The life there is able to live and thrive despite rapidly large variations in pH. I’m sorry, but I see no reason to be concerned about possible theoretical damage from a possible theoretical change in oceanic pH from increasing CO2.