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Carbon dioxide from Silicon Valley affects chemistry Monterey Bay

This map shows how carbon dioxide blows from land areas across Monterey Bay with morning land fires. Credit: Basic Image: Google Earth MBARI researchers recently estimated high levels of carbon dioxide in the air at sea from urban and agricultural areas, including Silicon Valley. In a new paper in PLOS ONE it is estimated that this previously unproblematic process could increase the amount of carbon dioxide that dissolves in coastal sea water by about 20 percent. Extending its calculations to coastal areas around the world, researchers estimate that this process could add 25 million extra tonnes of carbon dioxide to the ocean each year, which would represent about one percent of the ocean's total annual carbon dioxide uptake. This effect is not currently included in calculations of how much carbon dioxide enters the sea due to the burning of fossil fuels. Less than half of the carbon dioxide released by humans over the last 200 years has remained in the atmosphere. The rest has been absorbed in almost equal proportions of the sea and the soil's ecosystem. How fast carbon dioxide enters the sea in a particular area depends on a number of factors, including wind speed, water temperature and the relative concentrations of carbon dioxide in the surface water and in the air just above the sea surface. MBARI has measured the carbon dioxide concentrations in the air and seawater in Monterey Bay almost continuously since 1 993. But it was not until 2017 that scientists began to look…

This map shows how carbon dioxide blows from land areas across Monterey Bay with morning land fires. Credit: Basic Image: Google Earth

MBARI researchers recently estimated high levels of carbon dioxide in the air at sea from urban and agricultural areas, including Silicon Valley. In a new paper in PLOS ONE it is estimated that this previously unproblematic process could increase the amount of carbon dioxide that dissolves in coastal sea water by about 20 percent.

Extending its calculations to coastal areas around the world, researchers estimate that this process could add 25 million extra tonnes of carbon dioxide to the ocean each year, which would represent about one percent of the ocean’s total annual carbon dioxide uptake. This effect is not currently included in calculations of how much carbon dioxide enters the sea due to the burning of fossil fuels.

Less than half of the carbon dioxide released by humans over the last 200 years has remained in the atmosphere. The rest has been absorbed in almost equal proportions of the sea and the soil’s ecosystem. How fast carbon dioxide enters the sea in a particular area depends on a number of factors, including wind speed, water temperature and the relative concentrations of carbon dioxide in the surface water and in the air just above the sea surface.

MBARI has measured the carbon dioxide concentrations in the air and seawater in Monterey Bay almost continuously since 1

993. But it was not until 2017 that scientists began to look closely at the atmospheric data collected from seabed robots. “One of our summer interviews, Diego Sancho-Gallegos, analyzed the atmospheric carbon dioxide data from our research moorings and found much higher levels than expected,” MBARI Biological Oceanographer Francisco Chavez explained.

Chavez continued, “If these measurements had been aboard a ship, scientists would have thought that the extra carbon came from the ship’s engine exhaust system and would have discounted them. But our moorings and surface robots do not release carbon dioxide into the atmosphere.”

Early 2018 MBARI Research Assistant Devon Northcott began working on the data collection and analyzes hourly carbon dioxide levels in the air over Monterey Bay. He noticed another striking pattern-carbon dioxide concentrations peaked early in the morning.

Although atmospheric researchers had previously noticed early morning peaks in carbon dioxide levels in some cities and agricultural areas, it was the first time such peaks had been measured over seawater. The finding also opposed a common scientific assumption that concentrations of carbon dioxide across the sea areas do not vary greatly over time or space.

Northcott was able to track the sources of this extra carbon dioxide by using measurements made of a robot surface vessel called a Wave Glider that travels back and forth over Monterey Bay and makes measurements of carbon dioxide in the air and sea for weeks at a time.

Wave Gliders like this provided mobile platforms for measuring carbon dioxide in the air and the water in Monterey Bay. Credit: MBARI

“Because we had measurements from Wave Glider in many different places around the bay, Northcott explained,” I could use the Wave Glider position and the wind speed and the direction to triangulate the direction the carbon dioxide came from. “

The data suggested two main sources for the morning peaks of carbon dioxide – Salinas and the Santa Clara valleys. The Salinas Valley is one of California’s largest agricultural areas, and many plants release carbon dioxide at night, which may explain why there was more carbon dioxide in the air from that region. Santa Clara Valley [aka Silicon Valley] is a dense urban area where light winds and other atmospheric conditions early in the morning could concentrate carbon dioxide from cars and factories. Clara Valley south and then west through a gap in the mountains (Hecker Pass) and out over Monterey Bay.

“We had this evidence that the carbon dioxide came from an urban area” explained Northcott. “But when we looked at the scientific literature , there was nothing about air from urban areas that affect the coastal sea. People had thought of this, but no one had measured it systematically before. “

The researchers do not see this document as a final word, but as a” wake-up call “to other researchers.” This leads to many questions that we hope other researchers will examine, “Chavez said.” One of the first and most important things is to make detailed measurements of carbon dioxide in the atmosphere and the sea in other coastal areas. We must know if this is a global phenomenon. We would also like to get the atmospheric modeling community involved. “

” We have estimated that this can increase the amount of carbon dioxide entering the coastal water by about 20 percent, “says Chavez.” This can affect the acidity of seawater in these areas. Unfortunately, we do not have a good way to measure this increase in acidity because carbon dioxide takes time to enter the sea and the carbon dioxide levels vary dramatically in coastal waters. “

” There must be other pollutants in this city air that also affect the coastal ocean, “he added. said Chavez. “Hopefully, other researchers will see these results and want to know if this happens in their own backyards.”


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More information:
Devon Northcott et al, Influence of urban carbon dioxide emissions on sea flow and sea trout in nearshore waters, PLOS ONE (2019). DOI: 10.1371 / journal.pone.0214403
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Monterey Bay Aquarium Research Institute

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Silicon Valley carbon dioxide affects the chemistry of Monterey Bay (2019, April 23)
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