Methane mole fraction and δ13C above and below the trade wind inversion at Ascension Island in air sampled by aerial robotics

R. Brownlow; D. Lowry; R. M. Thomas; R. E. Fisher; J. L. France; M. Cain; T. S. Richardson; C. Greatwood; J. Freer; J. A. Pyle; A. R. MacKenzie; E. G. Nisbet

doi:10.1002/2016GL071155

Methane mole fraction and δ¹³C above and below the trade wind inversion at Ascension Island in air sampled by aerial robotics

R. Brownlow^*, D. Lowry, R. M. Thomas, R. E. Fisher, J. L. France, M. Cain, T. S. Richardson, C. Greatwood, J. Freer, J. A. Pyle, A. R. MacKenzie, E. G. Nisbet

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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Abstract

Ascension Island is a remote South Atlantic equatorial site, ideal for monitoring tropical background CH₄. In September 2014 and July 2015, octocopters were used to collect air samples in Tedlar bags from different heights above and below the well-defined Trade Wind Inversion (TWI), sampling a maximum altitude of 2700 m above mean sea level. Sampling captured both remote air in the marine boundary layer below the TWI and also air masses above the TWI that had been lofted by convective systems in the African tropics. Air above the TWI was characterized by higher CH₄, but no distinct shift in δ¹³C was observed compared to the air below. Back trajectories indicate that lofted CH₄ emissions from Southern Hemisphere Africa have bulk δ¹³C_CH4 signatures similar to background, suggesting mixed emissions from wetlands, agriculture, and biomass burning. The campaigns illustrate the usefulness of unmanned aerial system sampling and Ascension's value for atmospheric measurement in an understudied region.

Original language	English
Pages (from-to)	11,893-11,902
Journal	Geophysical Research Letters
Volume	43
Issue number	22
Early online date	5 Nov 2016
DOIs	https://doi.org/10.1002/2016GL071155
Publication status	Published - 28 Nov 2016

Keywords

Ascension Island
global carbon cycle
greenhouse gas
methane
stable carbon isotope
UAS

ASJC Scopus subject areas

Geophysics
General Earth and Planetary Sciences

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

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10.1002/2016GL071155Licence: Creative Commons: Attribution (CC BY)

Brownlow_et_al-2016-Geophysical_Research_LettersFinal published version, 1.38 MBLicence: Creative Commons: Attribution (CC BY)

http://onlinelibrary.wiley.com/doi/10.1002/2016GL071155/epdfLicence: Creative Commons: Attribution (CC BY)

Investigation of the Southern Methane Anomaly: causes, implications, and relevance to past global events
MacKenzie, R. (Principal Investigator)
Natural Environment Research Council
1/03/13 → 29/02/16
Project: Research Councils

Cite this

Brownlow, R., Lowry, D., Thomas, R. M., Fisher, R. E., France, J. L., Cain, M., Richardson, T. S., Greatwood, C., Freer, J., Pyle, J. A., MacKenzie, A. R., & Nisbet, E. G. (2016). Methane mole fraction and δ¹³C above and below the trade wind inversion at Ascension Island in air sampled by aerial robotics. Geophysical Research Letters, 43(22), 11,893-11,902. https://doi.org/10.1002/2016GL071155

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abstract = "Ascension Island is a remote South Atlantic equatorial site, ideal for monitoring tropical background CH4. In September 2014 and July 2015, octocopters were used to collect air samples in Tedlar bags from different heights above and below the well-defined Trade Wind Inversion (TWI), sampling a maximum altitude of 2700 m above mean sea level. Sampling captured both remote air in the marine boundary layer below the TWI and also air masses above the TWI that had been lofted by convective systems in the African tropics. Air above the TWI was characterized by higher CH4, but no distinct shift in δ13C was observed compared to the air below. Back trajectories indicate that lofted CH4 emissions from Southern Hemisphere Africa have bulk δ13CCH4 signatures similar to background, suggesting mixed emissions from wetlands, agriculture, and biomass burning. The campaigns illustrate the usefulness of unmanned aerial system sampling and Ascension's value for atmospheric measurement in an understudied region.",

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author = "R. Brownlow and D. Lowry and Thomas, {R. M.} and Fisher, {R. E.} and France, {J. L.} and M. Cain and Richardson, {T. S.} and C. Greatwood and J. Freer and Pyle, {J. A.} and MacKenzie, {A. R.} and Nisbet, {E. G.}",

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Brownlow, R, Lowry, D, Thomas, RM, Fisher, RE, France, JL, Cain, M, Richardson, TS, Greatwood, C, Freer, J, Pyle, JA, MacKenzie, AR & Nisbet, EG 2016, 'Methane mole fraction and δ¹³C above and below the trade wind inversion at Ascension Island in air sampled by aerial robotics', Geophysical Research Letters, vol. 43, no. 22, pp. 11,893-11,902. https://doi.org/10.1002/2016GL071155

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AU - Greatwood, C.

AU - Freer, J.

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AU - MacKenzie, A. R.

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