Second APO Workshop
Scripps Institution of Oceanography, La Jolla, California, U.S.A.
18-20 September 2015


APO, or Atmospheric Potential Oxygen, is a tracer conservative with respect to land biospheric carbon and oxygen exchanges [Stephens et al., 1998], which can be used to gain valuable insight into, and provide constraints, on a wide range of biogeochemical applications [Keeling and Manning, 2014; Ishidoya et al., 2012; Nevison et al., 2012; Tohjima et al., 2012; Rödenbeck et al., 2008; Battle et al., 2006; Gruber et al., 2001; Keeling et al., 1998].


o The first APO Workshop was held in 2004, at the Max Planck Institute for Biogeochemistry, Jena, Germany, hosted by Martin Heimann. Eleven years passed until the second APO Workshop, held at the Scripps Institution of Oceanography, La Jolla, California, U.S.A., over 3 days from 18-20 September, 2015, hosted by Ralph Keeling. There were 28 oral presentations given, and much engaging, lively discussion amongst the 33 participants.


The goal of the APO Workshop was to bring together members of both the modelling and observational communities to discuss topics related to APO, such as how to use APO data to improve understanding of ocean biogeochemical processes and carbon cycling.  The meeting addressed both observational needs and methods, as well as applications.  We hope that new research endeavours and new collaborations will bear fruit as a result of the Workshop.


Below you can find links to the Workshop abstracts, agenda, and PDFs of the presentations.








Friday, 18th September  
Mark Battle Zonal APO Gradients in the Equatorial Pacific
Yasunori Tohjima Spatiotemporal variability in APO in the western Pacific region observed from the NIES's observing network
Yassir Eddebbar ENSO-driven variability of air-sea fluxes of oxygen: Observations and mechanisms
Britton Stephens Global scale airborne and ship based observations of atmospheric potential oxygen
Cynthia Nevison Evaluating CMIP5 ocean biogeochemistry and Southern Ocean carbon uptake using APO: Present day performance and future prediction
Shinji Morimoto Temporal variations of δ(O₂/N₂) and Atmospheric Potential Oxygen (APO) observed at Syowa Station, Antarctica
Shigeyuki Ishidoya Time and space variations of Atmospheric Potential Oxygen over the Western Pcific observed by using a cargo aircraft C-130H
Sara Mikaloff-Fletcher Oxygen gradients across the Pacific Ocean: Resolving an apparent discrepancy between atmospheric and ocean observations and models
Laure Resplandy Constraints on meridional oceanic heat transport from combined measurements of atmospheric potential oxygen
Keith Rodgers Sensitivity of the seasonal and intraseasonal variations of APO over the Southern Ocean to wind stirring
Christian Rödenbeck Using atmospheric O₂/N₂ data to estimate the variability of ocean biogeochemistry
Andrew Manning The "GOLLUM" O₂ intercomparison programme: Latest results and next steps
Saturday, 19th September  
Gordon Brailsford Atmospheric oxygen observations from New Zealand
Sander van der Laan Is climate change affecting the biotic pump of the Pacific Ocean?
Valerie Livina

Tipping point analysis of atmospheric oxygen concentration

Thomas Barningham A preliminary investigation into the detection and attribution of carbob cycle processes from APO observations at Baring Head, New Zealand
Daisuke Goto Continuous measurements of APO at Ny-Ålesund, Svalbard
Jonathan Bent Assessing ocean biogeochemical models with high-resolution airborne observations of atmospheric oxygen over the Southern Ocean
Manfredi Manizza Testing ocean biogeochemical models with atmospheric potential oxygen (APO) and Ar/N₂ ratio
Charlotte van Leeuwen Continuous and flask observations of atmospheric δO₂/N₂ and CO₂ at Lutjewad station, the Netherlands, and Mace Head station, Ireland
Penelope Pickers First continuous shipboard measurements of atmospheric O₂, CO₂ and APO from meridional Atlantic Ocean transects
Roberta Hamme Semi-continuous measurements of Ar/N₂, O₂/N₂, and CO₂ at the Scripps pier
Markus Leuenberger APO variations in Central Europe obtained at the Jungfraujoch Research Station, Swizerlandin comparison to a combined record of Scripps La Jolla and Alert values
Lingxi Zhou Determination of the changes in atmospheric AR/O₂ and O₂/N₂ by using GC-TCD
Sunday, 20th September  
Ralph Keeling Grand challenges for atmospheric O₂/N₂ and Ar/N₂ measurements
Prabir Patra Can O₂/N₂ measurements help to constrain global total fossil fuel emissions
Penelope Pickers Quantifying fossil fuel CO₂ from continuous measurements of APO: a novel approach
Charlotte van Leeuwen Detection of CO₂ leaks from Carbon Capture and Storage (CCS) sites with combined atmospheric CO₂ and O₂ measurements



Battle, M., S. Mikaloff Fletcher, M. L. Bender, R. F. Keeling, A. C. Manning, N. Gruber, P. P. Tans, M. B. Hendricks, D. T. Ho, C. Simonds, R. Mika, and B. Paplawsky, Atmospheric potential oxygen: New observations and their implications for some atmospheric and oceanic models, Global Biogeochemical Cycles, 20, doi:10.1029/2005GB002534, 2006.
Gruber, N., M. Gloor, S.-M. Fan, and J. L. Sarmiento, Air-sea flux of oxygen estimated from bulk data: Implications for the marine and atmospheric oxygen cycles, Global Biogeochemical Cycles, 15 (4), 783-803, 2001.
Ishidoya, S., S. Morimoto, S. Aoki, S. Taguchi, D. Goto, S. Murayama, and T. Nakazawa, Oceanic and terrestrial biospheric CO2 uptake estimated from atmospheric potential oxygen observed at Ny-Ålesund, Svalbard, and Syowa, Antarctica, Tellus Series B-Chemical and Physical Meteorology, 64, doi:10.3402/tellusb.v64i0.18924, 2012.
Keeling, R. F., and A. C. Manning, 5.15 - Studies of Recent Changes in Atmospheric O2 Content, in Treatise on Geochemistry (Second Edition), edited by Holland, H. D., and K. K. Turekian, pp. 385-404, Elsevier, Oxford, 2014.
Keeling, R. F., B. B. Stephens, R. G. Najjar, S. C. Doney, D. Archer, and M. Heimann, Seasonal variations in the atmospheric O2/N2 ratio in relation to the kinetics of air-sea gas exchange, Global Biogeochemical Cycles, 12 (1), 141-163, 1998.
Nevison, C. D., R. F. Keeling, M. Kahru, M. Manizza, B. G. Mitchell, and N. Cassar, Estimating net community production in the Southern Ocean based on atmospheric potential oxygen and satellite ocean color data, Global Biogeochemical Cycles, 26, doi:10.1029/2011gb004040, 2012.
Rödenbeck, C., C. Le Quere, M. Heimann, and R. F. Keeling, Interannual variability in oceanic biogeochemical processes inferred by inversion of atmospheric O2/N2 and CO2 data, Tellus Series B-Chemical and Physical Meteorology, 60 (5), 685-705, doi:10.1111/j.1600-0889.2008.00375.x, 2008.
Stephens, B. B., R. F. Keeling, M. Heimann, K. D. Six, R. Murnane, and K. Caldeira, Testing global ocean carbon cycle models using measurements of atmospheric O2 and CO2 concentration, Global Biogeochemical Cycles, 12 (2), 213-230, doi:10.1029/97GB03500, 1998.
Tohjima, Y., C. Minejima, H. Mukai, T. Machida, H. Yamagishi, and Y. Nojiri, Analysis of seasonality and annual mean distribution of atmospheric potential oxygen (APO) in the Pacific region, Global Biogeochemical Cycles, 26, doi:10.1029/2011gb004110, 2012.


Alex Etchells 2021