Airborne measurements of oxygen concentration from the surface to the lower stratosphere and pole to pole

Stephens, Britton B.; Morgan, Eric J.; Bent, J. D.; Watt, A.; Shertz, Stephen; Daube, Bruce C.

doi:10.5194/amt-2020-294

Cited by 7 publications

(16 citation statements)

References 31 publications

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“…During these flights, measurements were made of greenhouse gasses and related tracers. CO 2 mole fractions were measured using three different in situ instruments and two whole air samplers: the Harvard Quantum Cascade Laser System (QCLS, Santoni et al., 2014), the Harvard Observations of the Middle Stratosphere (OMS, Daube et al., 2002) instrument, the National Center for Atmospheric Research (NCAR) Airborne Oxygen Instrument (AO2, Stephens et al., 2021), the National Oceanic and Atmospheric Administration (NOAA) Portable Flask Packages (PFP, Sweeney et al., 2015), and the NCAR/Scripps Medusa Whole Air Sampler (Stephens et al., 2021). For our analysis, we used the recommended CO2.X variable, which is derived primarily from QCLS measurements with calibration periods gap‐filled using OMS measurements, reported as part per million dry air mole fractions (Wofsy et al., 2017).…”

Section: Methodsmentioning

confidence: 99%

Evaluating Northern Hemisphere Growing Season Net Carbon Flux in Climate Models Using Aircraft Observations

Loechli

Stephens

Commane

et al. 2023

Global Biogeochemical Cycles

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Understanding terrestrial ecosystems and their response to anthropogenic climate change requires quantification of land‐atmosphere carbon exchange. However, top‐down and bottom‐up estimates of large‐scale land‐atmosphere fluxes, including the northern extratropical growing season net flux (GSNF), show significant discrepancies. We developed a data‐driven metric for the GSNF using atmospheric carbon dioxide concentration observations collected during the High‐Performance Instrumented Airborne Platform for Environmental Research Pole‐to‐Pole Observations and Atmospheric Tomography Mission flight campaigns. This aircraft‐derived metric is bias‐corrected using three independent atmospheric inversion systems. We estimate the northern extratropical GSNF to be 5.7 ± 0.3 Pg C and use it to evaluate net biosphere productivity from the Coupled Model Intercomparison Project phase 5 and 6 (CMIP5 and CMIP6) models. While the model‐to‐model spread in the GSNF has decreased in the CMIP6 models relative to that of the CMIP5 models, there is still disagreement on the magnitude and timing of seasonal carbon uptake with most models underestimating the GSNF and overestimating the length of the growing season relative to the observations. We also use an emergent constraint approach to estimate annual northern extratropical gross primary productivity to be 56 ± 17 Pg C, heterotrophic respiration to be 25 ± 13 Pg C, and net primary productivity to be 28 ± 12 Pg C. The flux inferred from these aircraft observations provides an additional constraint on large‐scale gross fluxes in prognostic Earth system models that may ultimately improve our ability to accurately predict carbon‐climate feedbacks.

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Section: Methodsmentioning

confidence: 99%

Evaluating Northern Hemisphere Growing Season Net Carbon Flux in Climate Models Using Aircraft Observations

Loechli

Stephens

Commane

et al. 2023

Global Biogeochemical Cycles

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“…Regional data deficiencies make isolation of the potential drivers very difficult (Mathis et al 2010;Gregg et al 2014;Roden et al 2016;Bushinksy et al 2017;Hammond et al 2017;Rosso et al 2017;Frey et al 2018;Bai et al 2019). Satellite, aircraft and float observations of some key variables (such as plankton density, sea ice algal productivity, oxygen and carbon dioxide fluxes) are as yet very sparse in high latitudes (Liang et al 2017;Gray et al 2018;Bushinsky et al 2017Bushinsky et al , 2019Pinkerton & Hayward 2021;Stephens et al 2021) and remote sensing may not quantify under-ice productivity (Tremblay et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Sea ice and oxygen

Hambler

2022

Preprint

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1) Atmospheric oxygen cycles on a seasonal basis, as does carbon dioxide. 2) Photosynthesis is likely contributing to these cycles, but the dominant spatial regions are unknown and the contribution of marine plankton has been assumed to be small. 3) Since the cyclic rate of change of carbon dioxide is very highly correlated with that of sea ice, I predict the cyclic rate of change of oxygen will also be, at least at high latitudes. 4) I test and confirm the prediction that seasonal sea ice and oxygen rates are highly coherent at high latitudes, with peak oxygen emission in months of peak rates of sea ice loss within each Hemisphere. 5) No stronger similarity has yet been found between seasonal changes in oxygen and terrestrial productivity (NDVI), but much more detailed comparison is required. 6) These results are consistent with a hypothesised major influence of Arctic plankton in the seasonality of 'global' oxygen levels. 7) Air temperature near the Poles is very closely synchronized with the seasonal rate of change of oxygen at high latitudes. 8) Determining causality requires far more observations and experimentation. 9) These results provide further evidence that polar phenomena have been neglected in studies of the oxygen and carbon cycles and are consistent with a proposed major role of high latitudes in these cycles.

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“…from Stull (2012). T (K) is the temperature of air; w (kg of water vapor per kg of air mass) is the water vapor mixing ratio; R d (287.04 J kg −1 K −1 ) is the gas constant for air; C pd (1005.7 J kg −1 K −1 ) is the specific heat of dry air at constant pressure; P 0 (1013.25 mbar) is the reference pressure at the surface, and L v (T ) is the latent heat of evaporation at temperature T .…”

Section: Equivalent Potential Temperature (θ E ) and Dry Air Mass (M) Of The Atmospheric Fieldsmentioning

confidence: 99%

A mass-weighted isentropic coordinate for mapping chemical tracers and computing atmospheric inventories

et al. 2021

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Abstract. We introduce a transformed isentropic coordinate Mθe, defined as the dry air mass under a given equivalent potential temperature surface (θe) within a hemisphere. Like θe, the coordinate Mθe follows the synoptic distortions of the atmosphere but, unlike θe, has a nearly fixed relationship with latitude and altitude over the seasonal cycle. Calculation of Mθe is straightforward from meteorological fields. Using observations from the recent HIAPER Pole-to-Pole Observations (HIPPO) and Atmospheric Tomography Mission (ATom) airborne campaigns, we map the CO2 seasonal cycle as a function of pressure and Mθe, where Mθe is thereby effectively used as an alternative to latitude. We show that the CO2 seasonal cycles are more constant as a function of pressure using Mθe as the horizontal coordinate compared to latitude. Furthermore, short-term variability in CO2 relative to the mean seasonal cycle is also smaller when the data are organized by Mθe and pressure than when organized by latitude and pressure. We also present a method using Mθe to compute mass-weighted averages of CO2 on a hemispheric scale. Using this method with the same airborne data and applying corrections for limited coverage, we resolve the average CO2 seasonal cycle in the Northern Hemisphere (mass-weighted tropospheric climatological average for 2009–2018), yielding an amplitude of 7.8 ± 0.14 ppm and a downward zero-crossing on Julian day 173 ± 6.1 (i.e., late June). Mθe may be similarly useful for mapping the distribution and computing inventories of any long-lived chemical tracer.

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Airborne measurements of oxygen concentration from the surface to the lower stratosphere and pole to pole

Cited by 7 publications

References 31 publications

Evaluating Northern Hemisphere Growing Season Net Carbon Flux in Climate Models Using Aircraft Observations

Evaluating Northern Hemisphere Growing Season Net Carbon Flux in Climate Models Using Aircraft Observations

Sea ice and oxygen

A mass-weighted isentropic coordinate for mapping chemical tracers and computing atmospheric inventories

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