Scientists: Global warming has already changed oceans

Scientists: Global warming has already changed oceans

By Les Blumenthal | McClatchy Newspapers


WASHINGTON — In Washington state, oysters in some areas haven't reproduced for four years, and preliminary evidence suggests that the increasing acidity of the ocean could be the cause. In the Gulf of Mexico, falling oxygen levels in the water have forced shrimp to migrate elsewhere.

Though two marine-derived drugs, one for treating cancer and the other for pain control, are on the market and 25 others are under development, the fungus growing on seaweed, bacteria in deep sea mud and sea fans that could produce life-saving medicines are under assault from changing the ocean conditions.

Researchers, scientists and Jacques Cousteau's granddaughter painted a bleak picture Tuesday of the future of oceans and the "blue economy" of the nation's coastal states.

The hearing before the oceans subcommittee of the Senate Commerce Committee was expected to focus on how the degradation of the oceans was affecting marine businesses and coastal communities. Instead, much of the testimony focused on how the waters that cover 70 percent of the planet are already changing because of global warming.

Ocean acidification or diseases that thrive in acidified, oxygen-depleted seawater could be responsible for oysters not reproducing in Washington state, said Brad Warren, who oversees the ocean health and acidification program of the Sustainable Fisheries Partnership in Seattle. A federal study found that two-thirds of larval blue crabs died when exposed to acidity levels like those currently measured off the West Coast, he said.

Federal studies also found acidity levels in the North Pacific and off Alaska are unusually high compared to other ocean regions. The high acidity is already taking a toll of such tiny species as pteropods, which are an important food for salmon and other fish.

more...

http://www.mcclatchydc.com/226/story/69751.html

It's happening.

for fishing and other ocean-related industries and for the nation's coastal communities. Taken together, the ocean and coastal economies, including the Great Lakes, provide more than 50 million jobs and make up nearly 60 percent of the nation's economy."

Someone is concerned about the "economic toll"... great. Well, if "economic toll" carries more impact with capitalists than "mass starvation" maybe that's good thing. It makes me ill.

Why is the acidity increasing? Increased CO₂ will increase acidity, but the increases we've seen in ambient CO₂ would not raise the acidity appreciably. Increasing temperature certainly will reduce gas solubility (most importantly O₂) but increasing temps will also decrease CO₂ solubility and actually decrease acidity.

There's clearly a problem here, but I'm not understanding what the cause is supposed to be.

http://www.planetark.com/dailynewsstory.cfm/newsid/26065/newsDate/16-Jul-2004/story.htm

"An international team of scientists found that oceans have taken in about 118 billion metric tons of carbon dioxide from human activities between 1800 and 1994, accounting for nearly a third of their long-term carrying capacity.

These findings could pose a long-term risk for marine organisms, such as corals, which have greater difficulty in forming their outer shells as carbon dioxide levels increase, researchers found.

"There is a price to pay in this process, and that is with living organisms," said Richard Feely, a marine chemist with the National Oceanic and Atmospheric Administration, the lead author on one of the studies."

The volume of the oceans is 1.4 billion km³. Assuming that the CO₂ is distributed uniformly, that equates to a change in concentration of 1.9 micromolar. To obtain this change, it would require a 15% drop in CO₂ pressure from today's ambient levels. Translating to pH, today's pH as a result of CO₂ is pH 5.62; and 15% decrease in CO₂ would result in pH 5.66, or an increase of only 0.04 pH unit.

Again, I don't see it. What's the source of the acidity?

I haven't focused on it, but I believe most of the readings are of surface water. Vertical mixing is extremely slow (on the order of 10K years in and some cases) between the temperature and density/salinity boundaries. I couldn't even guess at the volume of water being affected, but perhaps, if we assume the numbers above are legitimate, it could be estimated by using the observed ph readings and the estimated amount of dissolved CO2. What volume of water would balance the equation?

CO₂ is absorbed at the surface, but it then takes anything from centuries to millenia (depending on location) for the ocean to 'turn over' and bring the CO₂ to the bottom: Waves churn the top 200 meters or so, but below that you're waiting on currents.

Meanwhile, the top layers - where most of the interesting stuff happens - gets more and more acidic.

Edit: Ahh, Kris beat me to it, but counting on my toes I reckon you've got at most 62 million km³ to play with. It's actually less, since some of it isn't 200+m deep, but I don't have a figure for how much.

In 1800, the CO₂ in the atmosphere was 280 ppm. The current level is 380 ppm. In sea water, 280 ppm corresponds to a pH of 5.69. Current levels would generate a pH of 5.62.

So, no assumptions about distribution, volumes, turnover. The change in CO₂ is simply not enough to cause radical acidification. What did?

You've got the degree of change in pH about right (8.18 to 8.1), and for us it not a big deal (directly). But if you're a coral depending on calcium carbonate saturation (which in turn is dependent on pH) it can be a problem: Your skeleton is slowly dissolving rather than slowly building, and if you've spent 10 million years not evolving a mechanism to cope with that, you're in trouble.

Light reading on carbonate chemistry & acidification at http://www.ipsl.jussieu.fr/~jomce/acidification/paper/Orr_OnlineNature04095.pdf for the curious.

Remember, this is a process that's only just starting to take effect, and there's a huge amount of hysteresis in the cycle so it's not going away any time soon. We've only just started this particular roller-coaster.

200 meters from the surface. It is here where the acidification will do the most damage, as that's where most of the life is. so the volume to be considered is much smaller than the total volume of the oceans.

Since dispersion through different depths is slower that allows the concentration to build up much faster in the top 200 meters - where most of the the life is.

http://www.scienceclarified.com/Mu-Oi/Ocean-Zones.html

The pelagic realm

In the region of the pelagic zone from the surface to 660 feet (200 meters), phytoplankton (algae and microscopic plants) live. They are the primary producers of the ocean, the lowest level on the oceanic food web. They use the process of photosynthesis to provide food for themselves and for higher organisms.

On the next level upward in the pelagic food web are the primary consumers, the zooplankton (microscopic animals). They feed on phytoplankton and, in turn, become food for larger animals (secondary consumers) such as sardines, herring, tuna, bonito, and other kinds of fish and swimming mammals. At the top of this food web are the ultimate consumers, the toothed whales.