EOL Seminar Series: Britton Stephens

Oceanography among the clouds and terrestrial ecology a thousand miles from land: The power of global-scale airborne observations 
Britton Stephens
National Center for Atmospheric Research

The total amounts of biological productivity in a given year in the world’s oceans and on land are fundamental properties of Earth system health that are poorly constrained by satellite and surface measurements. Likewise, our understanding of the distribution of anthropogenic carbon sinks among the Southern Ocean, tropical forests, and northern hemisphere temperate and boreal ecosystems—an important diagnostic of future carbon-climate feedbacks—is limited by sparse observations and uncertainties in atmospheric transport. Over the past decade, measurements of atmospheric CO2, O2, and related tracers on global-scale airborne research campaigns have enabled new insights into these carbon cycle questions. By measuring gradients and integrated signals from the surface to the lower stratosphere, nearly pole to pole, and in all seasons, we can overcome the data sparseness and transport limitations, because airborne measurements are representative of large zonal scales and column means less sensitive to model vertical mixing biases. The HIAPER Pole-to-Pole Observations (HIPPO, 2009-2011), O2/N2 Ratio and Airborne Southern Ocean (ORCAS, 2016), and Atmospheric Tomography (ATom, 2016-2018) campaigns are enabling new estimates of 1) the growing season net flux (GSNF) of CO2 with the Northern Hemisphere land biome, 2) the partitioning between northern extratropical and tropical forest carbon sinks, 3) the seasonal net outgassing (SNO) of O2 by the ocean in both hemispheres, and 4) the Southern Ocean CO2 sink. These estimates show that GSNF has increased by > 50% over the past 60 years, that intact tropical forests are a major sink for anthropogenic carbon, that SNO is surprisingly balanced between the hemispheres, and that the seasonal variability in Southern Ocean CO2 exchange is much greater than previously thought. I will present these results and discuss new opportunities for making global-scale aircraft observations a more routine part of the future climate observing system.  

Tuesday, 27 February 2018, 3:30 PM
Refreshments 3:15 PM
NCAR-Foothills Laboratory  3450 Mitchell Lane
Bldg 2 Large Auditorium (Rm1022)


Room Number: 
Will this event be webcast to the public by NCAR|UCAR?: 
Announcement Timing: 
February 22, 2018 to February 27, 2018
Calendar Timing: 
Tuesday, February 27, 2018 - 3:30pm to 4:30pm