Early Results from ORCAS: The O2/N2 Ratio and CO2 Airborne Southern Ocean Study (Invited Presentation)

The Southern Ocean currently absorbs a significant amount of human emitted CO2, but the future behavior of this sink is uncertain.  Sparse observations and complex interacting physical and biological processes limit our understanding of biogeochemistry and climate feedbacks at high southern latitudes.  The ORCAS campaign was designed to add new observational constraints on summertime fluxes and controlling processes for carbon dioxide and oxygen with unprecedented spatial coverage over the Southern Ocean.  We conducted a series of 19 flights totaling ~100 research hours over a period of 6 weeks in January-February 2016 with the NSF/NCAR Gulfstream V (GV) aircraft over diverse biogeochemical regions adjacent to the southern tip of South America and the Antarctic Peninsula.  The atmosphere was sampled from the surface to 12 km and over a latitudinal range from 35 to 75 S.  Measurements were made of O2, CO2, and ~100 related trace and reactive gases (such as N2O and CO) as well as hyperspectral remote sensing of the ocean surface.  We will discuss preliminary results from the campaign, including the successful implementation of Lagrangian flights, observational constraints of Southern Ocean fluxes of O2 and CO2, measurement tests of modeled O2:CO2 ratios, and validation of space-based measurements of CO2 made by the Orbiting Carbon Observatory 2 (OCO-2) over high southern latitudes.