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NASA’s Carbon Sleuth Tracks Impact of El Niño


                                             NASA’s Carbon Sleuth Tracks Impact of El Niño

Data shows rise in global CO2 Concentrations: Increase due to the Land carbon cycle and decrease due to

                                                             the Ocean carbon cycle

Columbia, Maryland—October 12, 2017. A team of scientists from Universities Space Research Association (USRA), NASA, NOAA and National Center for Atmospheric Research (NCAR) announced today the results of their research on how the ocean and land carbon cycle responded during the 2015-16 El Niño.

The results, published this week in Science (http://science.sciencemag.org/content/358/6360/eaam577) along with other papers on NASA’s Orbiting Carbon Observatory -2 (OCO-2), showed an overall increase in atmospheric carbon dioxide concentrations following the strong El Niño event. While this increase in atmospheric CO2 concentrations has been well documented, this study used OCO-2 data to show the competing response from the ocean and the land carbon cycle; the ocean carbon cycle contributed to a slowdown in the growth of atmospheric CO2 concentrations but the land carbon cycle caused an increase that cancelled out the ocean signal.

Dr. Abhishek Chatterjee, from the Universities Space Research Association at NASA’s GFSC, and the lead author on the study noted, “During El Niño, there is a suppression of the upwelling of the tropical Pacific Ocean that typically brings carbon-dioxide rich water from the deep ocean to the surface. This reduced the normal release of carbon dioxide emissions from the ocean surface into the atmosphere. 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.”

The study attributes this increase to the response from the terrestrial component of the carbon cycle - a combination of enhancement in biomass burning emissions over Southeast Asia and Indonesia and reduction in biospheric uptake of CO2 over pan-tropical regions.

NASA’s Orbiting Carbon Observatory, OCO-2, which was launched on 2 July 2014, is designed to measure atmospheric carbon dioxide (CO2) with high precision and resolution. The global coverage provided by OCO-2 means that it closely monitored changes in global atmospheric CO2 concentrations during the 2015-2016 El Niño event. The team of researchers used observations from both OCO-2 and NOAA’s Tropical Pacific Observing System of buoys to confirm that the tropical Pacific Ocean played an early and important role in the response of atmospheric CO2 concentrations to the 2015-2016 El Niño event.

“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 Ocean,” said Chatterjee. The record uptick in atmospheric carbon dioxide that occurred in 2015 and 2016 would have been even greater without this decrease in tropical Pacific Ocean emissions.

El Niño and its cold counterpart La Niña, collectively referred to as the El Niño Southern Oscillation, or ENSO, are the dominant modes of tropical climate variability and spur a variety of anomalous weather patterns including floods and droughts around the globe. It also leaves an imprint on the global carbon cycle because both the ocean and the land carbon cycle respond to it. The high-density observations of CO2 from OCO-2 provided a valuable tool to partition these two responses, allowing the science community to better understand the impact of El Niño on atmospheric CO2 concentrations.