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December 17, 2019 03:30 am

California Coastal Waters Rising In Acidity At Alarming Rate, Study Finds

An anonymous reader quotes a report from Los Angeles Times: Waters off the California coast are acidifying twice as fast as the global average, scientists found, threatening major fisheries and sounding the alarm that the ocean can absorb only so much more of the world's carbon emissions. A new study led by the National Oceanic and Atmospheric Administration also made an unexpected connection between acidification and a climate cycle known as the Pacific Decadal Oscillation -- the same shifting forces that other scientists say have a played a big role in the higher and faster rates of sea level rise hitting California in recent years. El Nino and La Nina cycles, researchers found, also add stress to these extreme changes in the ocean's chemistry. This study, published Monday in the journal Nature Geoscience, came up with a creative way to confirm these greater rates of acidification. Researchers collected and analyzed a specific type of shell on the seafloor -- and used these data to reconstruct a 100-year history of acidification along the West Coast. The study analyzed almost 2,000 shells of a tiny animal called foraminifera. Every day, these shells -- about the size of a grain of sand -- rain down onto the seafloor and are eventually covered by sediment. Scientists took core samples from the Santa Barbara basin -- where the seafloor is relatively undisturbed by worms and bottom-feeding fish -- and used the pristine layers of sediment to create a vertical snapshot of the ocean's history. The more acidic the ocean, the more difficult it is for shellfish to build their shells. So using a microscope and other tools, the research team measured the changes in thickness of these shells and were able to estimate the ocean's acidity level during the years that the foraminifera were alive. Using these modern calibrations, the scientists concluded that the waters off the California coast had a 0.21 decline in pH over a 100-year period dating back to 1895 (the lower the pH, the greater the acidity, according to the logarithmic pH scale of 0 to 14). This is more than double the decline -- 0.1 pH -- that scientists estimate the ocean has experienced on average worldwide.

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