Results from a seven year study by the National Oceanographic and Atmospheric Administration show that the rate of acidification in the Pacific ocean is twice the global average. The study, led by Emily Osborne of NOAA, used fossil remains to determine the pH levels of the California current for the past 100 years.
In 2013, Osborne gathered core samples from the Santa Barbara Basin containing the fossilized shells of foraminifera, a type of plankton. Many marine organisms, including foraminifera, depend on calcium carbonate, a chemical compound present in seawater, to develop their shells.
Carbon dioxide absorbed from the atmosphere reduces the concentration of carbonates in the ocean, consequently affecting pH levels. Thus, by measuring the shell thickness of the plankton from her samples, Osborne was able to observe the change in pH over the course of a century.
“I started looking at the lowest, oldest parts of core and worked my way to top,” she told The Oregonian. “It was crazy to see visually how the shell changed throughout the core.”
Her measurements paint a bleak picture. Since 1895, shell thickness has gone down by 20 percent, suggesting a 0.21 decline in pH, more than twice the global average decline of 0.09. Chemical analysis of the shells revealed the presence of carbon from greenhouse gases.
She also found that pH levels were affected by weather patterns like the Pacific Decadal Oscillation and El Niño.
“We now know that the Pacific Decadal Oscillation can intensify or alleviate (ocean acidification) in this region. For those large swings to also have a human imprint, it’s going to make the extremes more extreme.”
By Brandon Urey