The research helps establish how coastal processes influence atmospheric carbon dioxide levels and, in turn, climate.
Cycling of carbon in the open ocean and on land has been the focus of much research, but lead author Raymond Najjar says intervening coastal waters have “fallen through the cracks.” Najjar is a professor of oceanography in Penn State’s College of Earth and Mineral Sciences.
“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,” Najjar says. “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.”
Planning for the research project began during a workshop at VIMS in 2012. Since then, the study’s 30 authors have gathered data from dozens of published studies to quantify how much carbon enters, exits, and is transformed within the study area’s coastal waters. They report in Global Biogeochemical Cycles that about 20 percent of the carbon entering coastal waters from rivers and the atmosphere is buried, while 80 percent flows out to the open ocean.
“Efforts like this help fill gaps in knowledge and inspire further research to help refine carbon budgets for the region,” Canuel says.
Indeed, Friedrichs and St. Laurent have already began follow-on work to resolve one of the biggest uncertainties in the recent study— the magnitude of carbon flow between large estuaries like Chesapeake Bay and the waters of the continental shelf, and how this may have changed over the past century.
Canuel and her students likewise continue efforts to develop high-resolution measurements of carbon transferred across the marsh-estuary interface.
“Despite advances in many aspects of the carbon cycle,” she says, “how tidal wetlands and estuaries modify exchanges among land, ocean, and atmosphere remains one of the biggest unknowns.”
The researchers also recognize that their recent budget exercise is not static.
“We know that many of the processes we’ve quantified are already undergoing change,” Friedrichs says. “With growing atmospheric CO2 concentrations, increasing global temperatures, and rising seas, what will this budget look like in 2100? Or even in 2050?” [Read more…]