Scientists Publish 37-Year Record of Ocean Acidification off Southern California

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For the first time, oceanography scientists at UC San Diego’s Scripps Institute have published nearly four decades’ worth of dissolved carbon dioxide measurements off Southern California. The measurements show a small but consistent trend Ocean acidityA process characterized by a decrease in ocean pH over time due to absorption of carbon dioxide.2) from the atmosphere.

Since the early 1980s, ocean carbonate chemistry samples have been collected by California Cooperative Ocean Fisheries Research.Calcofi) program established in 1949 to investigate the decline of sardine populations in the California area. In a new studyScripps Oceanography researchers presented 37 years of measurements from CalCOFI Line 90 Station 90 (Station 90.90), a measuring site located 450 kilometers (280 miles) off the coast of San Diego. The team’s findings were published Nov. 3 in the Nature-related journal Communications Earth and Environment.

The measurements from Station 90.90 constitute the oldest known inorganic carbon observations in the Pacific Ocean. While measurement at the site continues to this day, the study lists quarterly measurements collected from 1984 to 2021, with a funding gap from 2002 to 2008. Specifically, the data shows that the seawater in the study area is becoming more acidic with a pH decrease of 0.0015 per year.

“We’re tracking a climate signal in the ocean,” said Scripps Oceanography marine chemist Todd Martz, one of the lead authors on the paper. “Fewer than 10 places in the world have a similar time series, which highlights the importance of publishing the findings.”

Ocean acidification is a global threat due to its negative effects on organisms such as corals and shellfish. As the water becomes more acidic, these organisms have trouble building their shells, or coral structures, and scientists worry about the impact on marine ecosystems.

Thanks to decades of research efforts to monitor the level of ocean acidification Charles David Keelingpioneer Scripps Oceanography geochemist The keeling curve – Global atmospheric CO daily record2 Attention. In 1983, Keeling CO2 Seawater bottles collected by the CalCOFI program and played a key role in establishing dissolved CO2 Measurements at two other hydrographic stations near Bermuda (BATS) and Hawaii (Hot), which continues to this day.

The ocean time series shows the same trend of increasing CO2 It is known as the “Ocean Killing Curve” which includes a total of eight stations.

“The ocean killing curve has been measured and reported by other programs around the world, but station 90.90 is one of the oldest stations. And Here in our backyard, it’s never been published — until now,” Martz said.

Eight stations around the world measure ocean carbonate chemistry, creating a time series known as the “Ocean Killing Curve.” This is the world’s longest time series of seawater inorganic carbon, measured in Bermuda (BATS); Another popular site near Hawaii (Hot); And CalCOFI station 90.90 – the oldest station in the Pacific Ocean, published for the first time in a new study.

Study leader and recent Scripps Oceanography PhD graduate Willie Wolf took on the task of analyzing the backlog of samples, extracting data to retrieve all past measurements, and consolidating all the data to show observed trends.

“It was exciting to turn a room full of bottles into a tool for scientific discovery,” says Wolff, now a postdoctoral fellow at the University of Virginia. “It’s an amazing collection of data, and it just took someone taking the time to complete the analysis and bring it to light.”

Wolfe helped carry the project across the finish line, but he notes that he was the last runner in a very long rerun race started by Keeling. The success of the project is due to the efforts of many CalCOFI team members, marine scientists and laboratory technicians who have diligently maintained the 90.90 station over the years.

Sterile seawater reference samples prepared in the Andrew Dixon Laboratory of Scripps Marine Chemistry.

The study’s co-author, Scripps Oceanography marine chemist Andrew Dixon, is a key member of the project. In the early days, he worked closely with Keeling to develop a standardized system for measuring carbon dioxide in the ocean. A careful process involves collecting seawater samples at specific depths, using sterilization methods to prevent contamination, and adhering to best practices while waiting for the bottles to be analyzed in the laboratory.

In the year Following Keeling’s passing in 2005, Dixon’s lab took over monitoring and analysis of measurements at Station 90.90. Longtime Scripps Oceanography researcher Guy Emanuel played a key role in the analysis, as well as Other seawater sampling efforts led by Dixon Lab To the wider ocean science community.

The data from Station 90.90 is now publicly available, and the authors hope it will help the research community improve regional models and data products aimed at monitoring carbon and CO fluxes in the ocean.2 Through the air-sea interface.

The authors of the study say that direct measurements of long-term trends in the ocean are rare, because it is difficult to separate the trend signal from the surrounding noise. Establishing a trend It can take years or even decades to “see” a trend in the data.

“It’s important to set baselines, even if they’re not immediately newsworthy. “Much of oceanography and science is built on these long-term records, because without them we can’t tell if something has changed,” Wolff said. “We need to know what the past was like – to know whether the present is different – and to make predictions about the future.”

In addition to Martz, Wolf and Dixon, the study was co-authored by Scripps Oceanography scientists Ralph Gorick and Mark Ohman.

Measurements for the study were supported by various funding sources, including the National Science Foundation (California Current Ecosystem Long-Term Ecological Research, award OCE-16-37632), the NOAA Climate Program Office, and currently through the NOAA Ocean Acidification Program.

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