One-fifth of carbon entering coastal waters of eastern North America is buried

April 11, 2018

Coastal waters play an important role in the carbon cycle by transferring carbon to the open ocean or burying it in wetland soils and ocean sediments, a new study shows.

The team, led by Raymond Najjar, professor of oceanography in Penn State's College of Earth and Mineral Sciences, constructed the first known carbon budget of the eastern coast of North America from the southern tip of Nova Scotia, Canada, to the southern tip of Florida. They tracked the flows of organic and inorganic carbon into and out of coastal waters.

There has been considerable research into the Cycling of carbon in the open ocean and on land has been the focus of much research, but coastal waters, which border the two areas, have "fallen through the cracks," Najjar said.

"Coastal waters have a whole set of issues that are difficult to grapple with, such as the tides affecting certain areas twice a day, and this has made it difficult to incorporate this area into quantitative models," he said. "We recognized there was a gap there and thought we should develop a carbon budget so we could see what we know and don't know."

Models are the primary way scientists predict future carbon dioxide levels in the atmosphere, which in turn tell us how much the global surface temperature may rise from the greenhouse effect. This new research helps to establish how coastal waters influence atmospheric carbon dioxide levels and, in turn, climate.

Najjar began this research in 2012 and has since partnered with 29 other scientists who specialize in various aspects of coastal oceanography. The team gathered data from dozens of published studies to quantify how much carbon enters, exits and is transformed within coastal waters of eastern North America. They report in Global Biogeochemical Cycles that, of the carbon entering coastal waters from rivers and the atmosphere, about 20 percent is buried while 80 percent flows out to the open ocean.

The study subdivided coastal waters into tidal wetlands, estuaries and continental shelf waters. Tidal wetlands and estuaries, despite being the smallest ecosystems in the study domain at 2.4 percent and 9 percent of the area, respectively, buried the majority of the region's carbon, the team found. Tidal wetlands buried 42 percent of the carbon in the study and estuaries buried 38 percent, for a total of 80 percent of carbon burial in coastal waters.

Najjar believes this is due to the relatively shallow depth of water in tidal wetlands and estuaries, as well as the fact that rivers bring life-sustaining nitrogen to these ecosystems.

"The way carbon gets buried usually starts with photosynthesis, through which carbon dioxide is converted to organic material in the form of plankton, marsh grass, mangroves, or sea grass," he said. "Eventually that material dies and settles to the bottom. But continental shelf waters are deeper than tidal wetlands and estuaries, so there is more time for bacteria and other animals to consume this dead matter before it can get buried."

Carbon burial is an important metric when it comes to predicting future atmospheric carbon dioxide levels because, once carbon is in the sediments, it has the potential to remain there and not contribute to the greenhouse effect. However, the fragility of the coastal zone, Najjar said, could be cause for concern.

"As sea level continues to rise and disturb the coasts, some of the buried carbon could be respired and released to the atmosphere in the form of carbon dioxide," he said.

The team used the mass balance approach for their calculations, which assumes that the total amount of carbon going into a system equals the amount leaving a system. Carbon cycling within coastal waters is complex and the team sought to identify how carbon flows into and out of tidal wetlands, shelf waters and estuaries. The team compiled data from many studies and for the first time synthesized observations and numerical model output to develop a cohesive view of the carbon cycle in a large coastal region. The scientists also identified carbon fluxes where further research would be needed to reduce uncertainties, including the exchange of carbon between shelf waters and the open ocean.
-end-
Najjar is now working with scientists to create a carbon budget that includes the Gulf of Mexico, as well as a carbon budget of the western North American coast.

Penn State researchers on the study include Maria Herrmann, Department of Meteorology and Atmospheric Science, and Elizabeth Boyer, Department of Ecosystem Science and Management. Other collaborators include Richard Alexander and Kevin Kroeger, U.S. Geological Survey; David Burdige, Margaret Mulholland and Richard Zimmerman, Old Dominion University; David Butman, University of Washington; Wei-Jun Cai, University of Delaware; Elizabeth Canuel, Marjorie Friedrichs and Pierre St-Laurent, Virginia Institute of Marine Science of the College of William & Mary; Robert Chen, University of Massachusetts Boston; Rusty Feagin and Audra Hinson, Texas A&M University; Peter Griffith, Antonio Mannino and Sergio Signorini, NASA Goddard Space Flight Center; James Holmquist, Smithsonian Environmental Research Center; Xinping Hu, Texas A&M University-Corpus Christi; Michael Kemp, University of Maryland Center for Environmental Science; Leigh McCallister, Virginia Commonwealth University; Wade McGillis, Lamont Doherty Earth Observatory at Columbia University; Cynthia Pilskaln, University of Massachusetts Dartmouth; Joseph Salisbury, University of New Hampshire; Hanqin Tian, Auburn University; Maria Tzortziou, the City College of New York and Columbia University; Penny Vlahos, University of Connecticut; and Aleck Wang, Woods Hole Oceanographic Institution. NASA and the National Science Foundation funded this research.

Penn State

Related Atmosphere Articles from Brightsurf:

ALMA shows volcanic impact on Io's atmosphere
New radio images from ALMA show for the first time the direct effect of volcanic activity on the atmosphere of Jupiter's moon Io.

New study detects ringing of the global atmosphere
A ringing bell vibrates simultaneously at a low-pitched fundamental tone and at many higher-pitched overtones, producing a pleasant musical sound. A recent study, just published in the Journal of the Atmospheric Sciences by scientists at Kyoto University and the University of Hawai'i at Mānoa, shows that the Earth's entire atmosphere vibrates in an analogous manner, in a striking confirmation of theories developed by physicists over the last two centuries.

Estuaries are warming at twice the rate of oceans and atmosphere
A 12-year study of 166 estuaries in south-east Australia shows that the waters of lakes, creeks, rivers and lagoons increased 2.16 degrees in temperature and increased acidity.

What makes Saturn's atmosphere so hot
New analysis of data from NASA's Cassini spacecraft found that electric currents, triggered by interactions between solar winds and charged particles from Saturn's moons, spark the auroras and heat the planet's upper atmosphere.

Galactic cosmic rays affect Titan's atmosphere
Planetary scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed the secrets of the atmosphere of Titan, the largest moon of Saturn.

Physics: An ultrafast glimpse of the photochemistry of the atmosphere
Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

Using lasers to visualize molecular mysteries in our atmosphere
Molecular interactions between gases and liquids underpin much of our lives, but difficulties in measuring gas-liquid collisions have so far prevented the fundamental exploration of these processes.

The atmosphere of a new ultra hot Jupiter is analyzed
The combination of observations made with the CARMENES spectrograph on the 3.5m telescope at Calar Alto Observatory (Almería), and the HARPS-N spectrograph on the National Galileo Telescope (TNG) at the Roque de los Muchachos Observatory (Garafía, La Palma) has enabled a team from the Instituto de Astrofísica de Canarias (IAC) and from the University of La Laguna (ULL) to reveal new details about this extrasolar planet, which has a surface temperature of around 2000 K.

An exoplanet loses its atmosphere in the form of a tail
A new study, led by scientists from the Instituto de Astrofísica de Canarias (IAC), reveals that the giant exoplanet WASP-69b carries a comet-like tail made up of helium particles escaping from its gravitational field propelled by the ultraviolet radiation of its star.

Iron and titanium in the atmosphere of an exoplanet
Exoplanets can orbit close to their host star. When the host star is much hotter than our sun, then the exoplanet becomes as hot as a star.

Read More: Atmosphere News and Atmosphere Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.