Guest Post by Willis Eschenbach
The British tabloid “The Guardian” has a new scare story about what is wrongly called “ocean acidification”. It opens as follows:
Pacific Ocean’s rising acidity causes Dungeness crabs’ shells to dissolve
Acidity is making shells of crab larvae more vulnerable to predators and limiting effectiveness in supporting muscle growth
The Pacific Ocean is becoming so acidic it is starting to dissolve the shells of a key species of crab, according to a new US study.
Sounds like the end of times, right? So let me start with a simple fact. The ocean is NOT acidic. Nor will it ever become acidic, except in a few isolated locations. It is alkaline, also called “basic”. The level of acidity/alkalinity is expressed on the “pH” scale, where neutral is 7.0, alkaline is from 7 to 14, and acidic is from 0 to 7.
Figure 1. The pH scale, running from the most acid at the bottom, through neutral in the middle, and up to the most alkaline at the top.
From the chart, the ocean has a pH of around 8 (although as we’ll see, that conceals great variation).
And from my high school chemistry class in titration, I know that adding a small amount of an acid to a basic solution, or adding a small amount of a base to an acidic solution, is called “neutralization” for a simple reason. It moves the solution toward neutral.
When carbon dioxide (CO2) dissolves in rainwater or in the ocean, it makes a weak acid. And adding that weak acid to the ocean will slightly neutralize the ocean. How much? Well, by the year 2100, if you believe the models, it is supposed to move the pH of the ocean from around 8 all the way down to around … wait for it … a pH of 7.92. In other words, a slight neutralization.
So why is it called “ocean acidification” rather than “ocean neutralization”? Sadly, because “acidification” sounds scary. We see this in the story above, where the opening line is:
“The Pacific Ocean is becoming so acidic it is starting to dissolve the shells of a key species of crab, according to a new US study.”
Well, no, that’s not true at all. The ocean is not acidic in the slightest. It is slightly less alkaline. Using “acidification” rather than “neutralization” lets us convince people that impossible things are happening. Consider the following restatement of their opening sentence.
“The Pacific Ocean is becoming so neutral it is starting to dissolve the shells of a key species of crab, according to a new US study.”
Huh? The Pacific Ocean is becoming so neutral that it’s starting to dissolve things? Say what?
Alarmism run wild.
Here’s another important and counterintuitive fact about pH. Living creatures deal with acidic substances much better than we do with alkaline substances. Look at Figure 1 above. We regularly consume quite acidic things. Grapes and orange juice are at a pH of three. Lemon juice has a pH of two, very acidic, five pH units below neutral. And at six pH units below neutral, with a pH of just one is … our own stomach acid.
But we don’t eat many things that are more alkaline than a pH of about 10, things like cabbage, broccoli, and artichoke. And while our stomachs happily tolerate a pH of one, we are badly burned by bleach, at the opposite end of the pH scale.
Next, the required disclaimer. I have a personal stake and a personal passion regarding this subject. I live on the West Coast of the US in the very area they’re discussing, and I fished commercially in these waters for many years. So I know a few things about the local oceanic ecosystems.
With that as prologue, the new Guardian scare story is based on a scientific study called “Exoskeleton dissolution with mechanoreceptor damage in larval Dungeness crab related to severity of present-day ocean acidification vertical gradients“ … the “ocean acidification” BS strikes again. Heck, it gets its own cute little acronym, “OA”, as in the portion of the abstract below:
Ocean acidification (OA) along the US West Coast is intensifying faster than observed in the global ocean. This is particularly true in nearshore regions (<200 m) that experience a lower buffering capacity while at the same time providing important habitats for ecologically and economically significant species.
Now, I can’t find any reference in the study for the idea that somehow the US West Coast is acidifying faster than the global ocean. In fact, we have very little pH data for the global ocean.
But we do have some data. One most informative graphic gives us a look at a slice of the ocean from top to bottom and from Hawaii to Alaska. Over a 15-year period, scientists traveled that route, periodically stopping and sampling the pH from the surface to the seafloor. I discussed that “transect” in my post “The Electric Oceanic Acid Test“. Here’s the ocean cross-section with its original caption.
Inset at lower left shows the area studied. Click to expand. Graphic Source
Now, there are several fascinating things about this graphic. The first is the wide range of pH in the ocean. We tend to think of it as all having about the same pH, but that’s far from true. Around Hawaii (top left of the chart), the pH is about 8.05. But at a couple of hundred metres under the surface off the coast of Alaska (top right), the ocean is at a pH of 7.25. This pH is what hysterical scientists and the Guardian would call “MUCH MORE ACIDIC!!”, but is properly called “approaching neutral”.
Next, where is the most sea life in this chart? Why, it’s off the coast of Alaska, my old fishing grounds, which is replete with plankton, herring, salmon, sharks, flounders, whales, and every kind of marine creature. They flourish in those “MUCH MORE ACIDIC”, aka “more neutral”, ocean waters.
Finally, sea life thrives at every pH in the graphic. There are fish and marine creatures of all kinds at every pH level and every area in the graphic, top to bottom and Hawaii to Alaska. They are not tied to some narrow band where they will die if the pH changes by a tenth of a pH unit over a hundred years.
So please, can we get past this idea that a slight, slow neutralization is going to kill every poor creature in the ocean? Alkalinity is a problem for sea creatures, not acidity. It’s why so many of them are covered by a coating of slime or mucus—to protect them from the alkaline seawater. Fun Fact—if you want to dissolve a fish (or a human), use lye (pH 14), not sulfuric acid (pH 1) … but I digress.
Moving on, I wrote before about the pH measurements at the intake pipe of the Monterey Bay Aquarium in a post entitled “A Neutral View of Oceanic pH“. In that post, it was obvious that the long-term trend in pH at the Monterey Bay Aquarium was smaller than the trend at the “H.O.T.” deepwater location off of Hawaii. Here’s the graph from that post showing the difference:
Figure 2. Surface pH measurements from HOT open ocean and Monterey Bay upwelling coastline. The Hawaii data shows both measured pH (black) and pH calculated from other measurements, e.g. dissolved inorganic carbon (DIC), total alkalinity, and salinity. You can see the higher pH around Hawaii that was visible in the previous Figure.
Sadly, the web page containing the Monterey Bay pH dataset has become some kind of unknown Japanese web-page. Fortunately, I kept the data. And I was also able to find further pH data which starts just after my old data, although it appears that the calibration of the pH sensors is slightly changed in the new set. In any case, I’ve put both datasets in one graph, with separate linear trendlines for the two datasets.
Figure 3. Twenty-five years of monthly average pH measurements at the inlet pipe that delivers 2.5 million gallons (9.5 million liters) of seawater per day to the Monterey Bay Aquarium. Two separate datasets were used. The entrance of the pipe is at a depth of 50 feet (15 metres). The size of the projected pH drop by the year 2100 using RCP6.0 is shown by the top-to-bottom size of the “whiskers” in white at the upper right.
The neutral pH of 7.0 is down at the bottom, a ways below the data. Note that the long-term trend of the average pH value of the water is about the same in both datasets, and that the trend is quite small compared to the projected slight neutralization by the year 2100.
And more to the point, that projected pH decrease by 2100 of 0.08 pH units is dwarfed by the daily change in the pH. Heck, it’s smaller than the size of the monthly change in the pH. The standard deviation of the daily change in pH is 0.6 pH units, and the standard deviation of the monthly change is 0.1 pH units.
Why is the pH changing so fast on the West Coast of the US? It all has to do with coastal upwelling. Varying winds along the coast cause deep, cold, CO2-rich, more neutral water to come to the surface in varying amounts, changing the pH literally overnight.
Figure 4. The mechanical action of the winds blowing southward along the West Coast of the US causes the upwelling of CO2-rich more neutral water from the ocean depths. Image Source NOAA
And that constantly-changing pH is why I find these claims about oceanic creatures here on the West Coast of the US being killed off or badly injured by some trivially small slow change in pH to be totally unbelievable. Every living being in the ocean along this coast undergoes much, much larger pH changes from one day to the next than they will see over the next century.
There’s one more dataset that I have to add to this before turning to the study itself. The study actually takes place up in the area near Seattle. So what is the oceanic pH up there doing?
Turns out it is very hard to find long-term pH measurements in that area. The best that I’ve been able to find are an intermittent series of measurements from an offshore buoy on the coast of Washington near the Strait of Juan de Fuca, a lovely part of the planet that I battled through a while back. Here’s where the La Push buoy is located:
Figure 5. The yellow square shows the location of the “La Push” offshore buoy. The Strait of Juan De Fuca is the blue channel leading into the land. Seattle and Tacoma, Washington are below the inner end of the Strait. Vancouver Island, Canada, is on the north side of the Strait.
It appears that the buoy is brought in when the weather gets very rough, because there is a gap in the data each winter. Here’s the La Push buoy data, to the same scale as the Monterey data above.
Figure 6. Daily surface pH records at the La Push, Washington offshore buoy. The background is an offshore island near La Push.
Once again, we see the same situation. The pH changes are much larger than the size of the projected change between now and the year 2100. And while I wouldn’t put much weight on the trend line because of the gaps in the data, it’s quite possible that the trend is actually becoming slightly more alkaline.
How can it become more alkaline? Remember that along this coast, the swings in the pH, and the average pH itself, are not direct functions of CO2 levels. Instead, they are determined by the instantaneous and average strength of the wind. If there is more wind, more of the deeper, more neutral waters come to the surface to lower the surface pH, and vice versa.
And lest you think that such swings in pH are limited to this coast, here’s some data from around the planet.
Figure 7. pH values and variations from different oceanic ecosystems. Horizontal black “whiskers” show the range of the pH values. The size of the expected slight neutralization by the year 2100 according to RCP6.0 is shown by the red whiskers at the top. Ischia South Zone, the site that goes the lowest in pH, is on the side of a volcano that is constantly bubbling CO2 through the water. DATA
Let me close by looking at the study itself, at least as much as I can bear. I’ll discuss a few quotes. The first line of their “Highlights” says:
Coastal habitats with the steepest [vertical] ocean acidification gradients are most detrimental for larval Dungeness crabs.
There’s no such thing as a “vertical ocean acidification gradient”. There is a vertical pH gradient, as you would expect with upwelling deeper CO2-rich water hitting the more alkaline surface waters with less CO2. But this is a natural condition that has existed forever and has nothing to do with “OA”. And they present no evidence to show that the gradient will change significantly in the future.
Next, in their conclusions they say:
Like dissolution in pteropods, larval dissolution observed in Dungeness crab is clear evidence that marine invertebrates are damaged by extended exposure to strong present-day OA-related vertical gradients in their natural environment.
However, they present no evidence that past “OA”, or mild oceanic neutralization, has had any effect on the “vertical gradients in the natural environment”. The vertical gradients in pH off of the coast are a function of the upwelling, which in turn is a function of the wind, which is constantly changing. They don’t have long-term data for the vertical pH gradient. Instead, they went on a two-month cruise, took some samples, and extrapolated heavily. We don’t even know if they’d have found the exact same “dissolution” a hundred, fifty, or twenty-five years ago. Or perhaps the dissolution was particularly bad during that particular two-month period in that particular small location. This should not surprise us. One reason that so many marine creatures spawn hundreds of thousands of larvae is that many, perhaps most, of them will drift into inhospitable conditions and die for any one of a host of reasons—problems with salinity, turbidity, pH, predators, temperature, the list is long.
Finally, this paper does prove one thing—that Neptune, the trident-wielding god of the ocean, definitely has a sense of humor. Here’s the ultimate irony.
They couldn’t see the parts of the crab larvae that they wanted to examine because those parts are covered by the “epicuticle”, the outer layer of the hard carapace that surrounds the larva. So they first had to dissolve the epicuticle in order to get access to what they wanted to study. Here’s their description of the problem and the solution. (The “megalopa” are a stage of the larval form of the crabs).
The carapace epicuticle, which otherwise overlies the crystalline layer and makes dissolution observations impossible, was removed from each megalopa prior to analysis. This was accomplished using sodium hypochlorite, which efficiently removes the epicuticle but does not damage the crystalline layers underneath, even at high concentrations.
Care to take a guess at the pH of the 6% solution of sodium hypochlorite, which is what they used to dissolve the carapace epicuticle?
It has a pH of 11 or more, almost at the very top of the scale in Figure 1, very strongly alkaline.
So it no wonder that Neptune is laughing—they’re all up in arms about “acidification” dissolving the crab carapaces … but in the event, they’re using an alkaline solution to actually dissolve the crab carapaces.
Ain’t science wonderful?
It’s clear today, and from my house perched high up on a hill six miles (ten km) from the coast, I can see a small bit of the very part of the ocean that we’re discussing. It’s foggy down there and it’s clear up here, as is often the case. And right out there, millions of marine creatures are happily going about their lives as the pH gyrates up and down every hour, every day, and every month.
If a slight oceanic neutralization were going to injure them as we are franticosolemnly assured at every opportunity by the bad boffin boys and the popular press, those oceanic inhabitants would all have died long ago.
My very best to everyone on a sunny winter day,
PS: After early years of having to point out that “No, I didn’t say that, I said nothing like that”, I’ve taken to asking those who comment to quote someone’s exact words that you are going to discuss. This avoids endless misunderstandings and arguments.