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Image: christopher pala

Toil and trouble

Kilo Moana scientists are at the fore of acidification research

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Cover image for Apr 21, 2010

With Second Mate Kim Krueger at the controls, the Kilo Moana slows to a crawl as a dot on a screen shows it inching toward the Holy Grail of ocean acidification. Known as Station ALOHA, it is here that the effects of the changing chemistry of the atmosphere have been observed on the world’s oceans with the most precision.

But there is nothing to see: it’s simply a point in the open ocean at the center of a circle six nautical miles across where scientists have been measuring 40 chemicals, notably carbon dioxide, for two decades. The ship glides to the spot, located at 22° 45’ North, 158° West, about 115 km north of Honolulu. Krueger stops the electric motors and switches on a computer that manages the propellers and rudder to keep the ship within two feet of its position over the ocean bottom three miles below.

On the afterdeck, Vic Polidoro, a tall, lanky marine technician with wraparound sunglasses, a red life jacket and a white hard-hat, holds a rope stabilizing the yellow tubing frame called a rosette. The rosette holds 24 gray bottles, each three-feet-long, that open on both ends. Working seamlessly with the crane operator, he eases the package into the ocean at the end of a cable that contains a wire connected to a half-dozen sensors. After the initial splash, the package is lowered at a speed of 200 feet per minute to a point just above the ocean floor.

In a cubicle a few yards away, Fernando Santiago-Mandujano, a University of Hawaii physical oceanographer, peers at a computer screen as the rosette descends, noting the densities of the different layers of water it traverses. An hour and 20 minutes later, the rosette stops just short of the bottom and the first bottle is closed, locking in water that last saw the surface 1,000 years ago. As the rosette is slowly winched up, Santiago-Mandujano closes the other 23 bottles at different depths. The operation will be performed 20 times on this four-day cruise, though most of the time the rosette only goes to about 1,000 meters.

Once the bottles have been lifted out of the sea and onto the Kilo Moana’s spacious afterdeck, Research Associate Dan Sadler of the University of Hawaii takes less than a liter and measures its pH, dissolved inorganic carbon and alkalinity.

More than a dozen ships have taken turns at coming to this spot every month, measuring the different characteristics of the ocean at different depths, since October 1988, when the RV Moana Wave took the first samples. Station ALOHA–which scientists insist stands for A Long-Term Oligotrophic Habitat Assessment–was chosen because it sits near the center of the world’s biggest and most stable body of water and is just a day’s sail from Honolulu. A sister site, where temperature and salinity data has been collected since 1988 under the same program, is 53 miles south of Bermuda.

Since then, recalls Jeff Snyder, a burly UH electronics technician who was on that first cruise, the project “has just gotten bigger and bigger.” So big, in fact, that in 2008 the Kilo Moana served as the platform for the first attempt to use a wave pump to remove carbon dioxide from the atmosphere and sequester it on the sea floor.

“When the program was founded, there was no clear understanding of just how much of the carbon dioxide (the main greenhouse gas causing global warming) emitted into the atmosphere had been absorbed by the ocean,” Sadler says. “The atmospheric record could only account for about half of it, and that led us to look more closely at the intake by the ocean. This would allow detailed examination of physical and biogeochemical processes that underlie how the ocean at various times absorbs or emits carbon dioxide.”

As the speed and extent of the ocean’s acidification became apparent, says David Karl, a professor of oceanography at the University of Hawaii and co-founder of the HOT program (Hawaii Ocean Time-series) who participated in the founding of the program, having Station ALOHA a mere 400 kilometers from the Big Island’s Mauna Loa observatory that’s home to the so-called Keeling Curve–the world’s longest time series of carbon dioxide in the atmosphere–has increased its value. The observatory is located at an altitude of 11,145 feet. “This is the only place where we can compare the two longest records in close proximity,” says Karl.

ALOHA PROGRAM

The ALOHA program was started none too soon: Humans are now releasing 30 billion tons of carbon dioxide from burning oil and coal, and another 7 million tons from deforestation, according to Ken Caldeira of the Carnegie Institution’s Department of Global Ecology. One-third of our total production, which started around 1800 with the industrial revolution, has now been absorbed into the sea, according to a study published in March in Science. As a result, the oceans’ average pH (it varies depending on depth and location) has gone from 8.2 to 8.08, which, because it’s a logarithmic scale, is a 30 percent decrease. And a fifth of that came in just the 20 years since the ALOHA measurements began.

“The problem began when we reached 320 parts per million [of carbon dioxide in the atmosphere] in the early 1980s,” says Ove Hoegh-Guldberg, a coral biologist at the University of Queensland, Australia. “In the Great Barrier Reef, the calcification rate has slowed 15 percent since 1990.” Because cold waters absorb more atmospheric pH than warm waters, the sharpest drop in pH has been in the polar oceans. “The amount of krill in the southern ocean is 10 percent today what it was 30 years ago,” he adds, though acidification is only one of several possible culprits.

On a sheltered spot just behind one of the Kilo Moana’s two bows is an instrument that records the carbon dioxide in the air. On a recent afternoon, it registered 386 parts per million. Many researchers believe that by mid-century, when it reaches 560 parts per million, or double what it was in 1800, the shells of marine organisms will start dissolving in some parts of the ocean. One paper, published in March in Geophysical Research Letters, asserts that that will happen pretty much everywhere by 2050 if the effects of global warming are added to the equation. For instance, even short periods of unsually warm water cause corals to reject the algae with which they live symbiotically and as a result the corals will turn white and often die, a phenomenon called coral bleaching. “By the time it reaches 560 parts per million, all coral reefs will cease to grow and start to dissolve,” asserts lead author Jacob Silverman of Hebrew University.

In a paper published in Science in December 2007, lead author Hoegh-Guldberg brings in more factors, like bleaching and competition and concludes that the decline will start even earlier, when the CO2 in the atmosphere is at 450 parts per million, probably in 25 years.

“Very few corals will survive this century and they will be in very bad shape,” adds Caldeira of Carnegie. “Acidification’s effect on corals is easy to predict because they’re the architecture of the ecosystem, “ he adds. “We also know that acidification makes it harder for shellfish to reproduce and contributes to asphyxiation of fish and squid, but it’s much harder to predict what effect that will have on the whole marine ecosystem.”

That’s because the past, it turns out, provides few insights to the future: Tomorrow’s ocean will be aqua incognita.

Gregory Ravizza, a geologist at the University of Hawaii, says that 55 million years ago, the atmosphere took in 2,000 billion tons of CO2 over 10,000 years, warming Earth by 5 degrees Celcius. This period is being intensely studied because it brought a rate of global warming similar to the present one.

The good news, he says, is that it brought no major mass extinction like the one that knocked out the dinosaurs 65 million years ago. The bad: “The world then was a much warmer place and had been for a long time,” he says. “The huge ice sheets that dominate the poles today were absent and Earth’s biosphere was radically different. The coral reef ecosystems we know did not begin to develop until after 34 million years ago, when a major ice sheet grew on Antarctica.”

But for the past 700,000 years at least, we’ve had a glaciation about every 100,000 years, with ice sheets covering the temperate zones for thousands of years and then melting back to pre-industrial conditions. “Industrialization happened at the hottest point of the cycle, which means that life on Earth today is much less prepared for more heat than it was 55 million years ago,” Ravizza says.

THE BIG DIFFERENCE

The problem isn’t the atmospheric carbon dioxide alone: until the appearance of the Antarctic ice, carbon dioxide levels in the air may have reached 2,000 parts per million, yet the ocean at the times appears to have been rich in fauna and flora, albeit quite different from today’s. “The climate had been quite stable for tens of millions of years, so life had ample time to adapt,” says Ravizza.

The big difference with today is we’re emitting more carbon dioxide than ever before and much faster, scientists agree. “We have about 5,000 billion tons of fossil fuels that we could burn in the next few centuries, and if we do, we’ll add more carbon dioxide to the atmosphere than was released in more than 5,000 years 55 million years ago,” says Richard Zeebe, an oceanographer at the University of Hawaii. “We will have mass extinctions and disruptions because the ocean and the sediments are the main buffers and their ability to absorb carbon dioxide is very slow.” In other words, we are emitting carbon dioxide 10,000 times faster than the planet can absorb it, Hoegh-Guldberg says.

“The rate of change now is 1,000 times faster than in all of the ice ages that we’ve had in the past million years,” he says, with oscillations between 280 parts per million to 200 parts per million in each 10,000-year cycle. “Sure, today we have mussels and oysters that live in much more acidic water in lakes, but they’ve had millions of years to adapt.”

Since 1988, University of Hawaii scientists have been measuring the chemistry of the ocean near Oahu. Last year, they reported their results in a publication of the National Academy of Sciences that showed how the acidity of the ocean has steadily risen as it absorbed carbon dioxide from the air. This ocean acidification process is harmful to many forms of life, including corals and organisms that have bones or shells. On Sunday, their paper, one of 3,700 published by the academy last year, will receive the academy’s 2009 Cozzarelli Prize for physical and mathematical sciences, considered one of America’s top two honors for a single paper. “We’ve been working hard on this for over 20 years, going out every month, and it’s satisfying to see that it’s been recognized as something useful,” said co-author Daniel Sadler this week. “This is a global problem and Hawaii should be proud that we’re leading the charge on defining the impact of acidification on the ocean, which is a big part of people’s lives here.”