NOAA observing buoys validate findings from NASA’s new satellite for measuring carbon dioxide

NOAA, NASA measure carbon dioxide over tropical Pacific Ocean during El Niño

The strong El Niño event of 2015-2016 provided NASA and NOAA an unprecedented opportunity to test the effectiveness of the newest observation tool to measure global atmospheric carbon dioxide concentrations -- NASA’s Orbiting Carbon Observatory-2 satellite or OCO-2. 

Observations of carbon dioxide concentrations over the tropical Pacific from the satellite were validated by data from NOAA’s Tropical Pacific Observing System of buoys, which directly measure carbon dioxide concentrations at the surface of the ocean. 

Both observing systems showed that in the early months of the El Niño, during the spring of 2015, outgassing of carbon dioxide over the tropical Pacific Ocean significantly declined by 26 to 54 percent. “This response is consistent with what we expect from a theoretical understanding, and comparable to what the NOAA data suggests,” said Richard Feely, senior scientist at NOAA’s Pacific Marine Environmental Laboratory, who is a co-author of a new study appearing today in Science. 

Measuring carbon dioxide

This cross section shows NASA's new satellite measuring atmospheric carbon dioxide over the tropical Pacific Ocean during the El Niño as NOAA's observing buoy takes direct measurements at the ocean's surface. NASA/NOAA

The research is part of a series of studies to better understand the growth of carbon dioxide concentrations in the global atmosphere using the new NASA satellite.  The studies show how various regions contribute to those emissions or serve as sinks, absorbing carbon dioxide emissions at different times. 

Initially the warming waters of El Niño suppressed the tropical Pacific Ocean’s upwelling that typically brings carbon-dioxide rich water from the deep ocean to the surface. This reduced the normal release of carbon dioxide from the ocean surface into the atmosphere. This decrease -- during the 2015 El Niño -- was observed both in the satellite and buoy data. 

But once the El Niño event began to affect tropical land ecosystems, from August 2015 onwards, the satellite data show a consistent rise in global atmospheric carbon dioxide concentrations. This is compatible with observations of atmospheric carbon dioxide. 

El Niño-driven weather had begun to warm and dry out the tropics, limiting the ability of forests and other vegetation to absorb carbon dioxide. The drying and warming tropics also triggered increased fires, adding more carbon dioxide to the atmosphere. 

“The OCO-2 observations clearly show that the delayed response from the land quickly offset any initial decline in carbon dioxide emissions from the tropical Pacific,” said Abhishek Chatterjee, Ph.D., NASA scientist and lead author. 

OCO-2 is NASA’s first satellite designed to measure atmospheric carbon dioxide with the precision, resolution, and coverage necessary to quantify regional carbon sources and sinks.

For more information, please contact Monica Allen, director of public affairs for NOAA Research, at 301-734-1123 or monica.allen@noaa.gov