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Air–sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK

Air–sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK
Air–sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK
We present air–sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27 m above mean sea level, a.m.s.l.), each from a different period during 2014–2015. At sampling heights ≥ 18 m a.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable (≤±20 % in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20 ± 3; 38 ± 3; 29 ± 6 µmole m-2 d-1 at 15, 18, 27 m a.m.s.l.) than during falling tides (14 ± 2; 22 ± 2; 21 ± 5 µmole m-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 µmole m-2 d-1 over hourly timescales (4 µmole m-2d-1 over 24h).
5745-5761
Yang, Mingxi
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Bell, Thomas G.
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Hopkins, Frances E.
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Kitidis, Vassilis
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Cazenave, Pierre W.
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Nightingale, Philip D.
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Yelland, Margaret J.
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Prytherch, John
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Brooks, Ian M.
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Smyth, Timothy J.
d7850910-0bd6-43dc-acd4-ab5e7aae0f88
Yang, Mingxi
46902f09-514d-4461-91e6-85766fa50ad3
Bell, Thomas G.
e5eef569-e063-4f1a-832f-0230d5f6f961
Hopkins, Frances E.
d5999493-2a10-4284-8e1d-b0e1bf9aa579
Kitidis, Vassilis
dcefa34f-4596-4bbf-b7f8-6b3c422e2df8
Cazenave, Pierre W.
42e083e5-9fd3-42d4-b244-241c819e2e81
Nightingale, Philip D.
4557daaa-1923-4964-b38b-f45f90d1cc28
Yelland, Margaret J.
3b2e2a38-334f-430f-b110-253a0a835a07
Prytherch, John
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Brooks, Ian M.
24f4fdc5-e657-4def-a388-23cb6fe77dda
Smyth, Timothy J.
d7850910-0bd6-43dc-acd4-ab5e7aae0f88

Yang, Mingxi, Bell, Thomas G., Hopkins, Frances E., Kitidis, Vassilis, Cazenave, Pierre W., Nightingale, Philip D., Yelland, Margaret J., Prytherch, John, Brooks, Ian M. and Smyth, Timothy J. (2016) Air–sea fluxes of CO2 and CH4 from the Penlee Point Atmospheric Observatory on the south-west coast of the UK. Atmospheric Chemistry and Physics, 16 (9), 5745-5761. (doi:10.5194/acp-16-5745-2016).

Record type: Article

Abstract

We present air–sea fluxes of carbon dioxide (CO2), methane (CH4), momentum, and sensible heat measured by the eddy covariance method from the recently established Penlee Point Atmospheric Observatory (PPAO) on the south-west coast of the United Kingdom. Measurements from the south-westerly direction (open water sector) were made at three different sampling heights (approximately 15, 18, and 27 m above mean sea level, a.m.s.l.), each from a different period during 2014–2015. At sampling heights ≥ 18 m a.m.s.l., measured fluxes of momentum and sensible heat demonstrate reasonable (≤±20 % in the mean) agreement with transfer rates over the open ocean. This confirms the suitability of PPAO for air–sea exchange measurements in shelf regions. Covariance air–sea CO2 fluxes demonstrate high temporal variability. Air-to-sea transport of CO2 declined from spring to summer in both years, coinciding with the breakdown of the spring phytoplankton bloom. We report, to the best of our knowledge, the first successful eddy covariance measurements of CH4 emissions from a marine environment. Higher sea-to-air CH4 fluxes were observed during rising tides (20 ± 3; 38 ± 3; 29 ± 6 µmole m-2 d-1 at 15, 18, 27 m a.m.s.l.) than during falling tides (14 ± 2; 22 ± 2; 21 ± 5 µmole m-2 d-1), consistent with an elevated CH4 source from an estuarine outflow driven by local tidal circulation. These fluxes are a few times higher than the predicted CH4 emissions over the open ocean and are significantly lower than estimates from other aquatic CH4 hotspots (e.g. polar regions, freshwater). Finally, we found the detection limit of the air–sea CH4 flux by eddy covariance to be 20 µmole m-2 d-1 over hourly timescales (4 µmole m-2d-1 over 24h).

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Accepted/In Press date: 21 April 2016
e-pub ahead of print date: 11 May 2016
Published date: 11 May 2016
Organisations: Marine Physics and Ocean Climate

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Local EPrints ID: 397735
URI: http://eprints.soton.ac.uk/id/eprint/397735
PURE UUID: c4ebe7f9-a683-4102-8d53-f21e7fa0e3bb

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Date deposited: 04 Jul 2016 13:54
Last modified: 15 Mar 2024 01:22

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Contributors

Author: Mingxi Yang
Author: Thomas G. Bell
Author: Frances E. Hopkins
Author: Vassilis Kitidis
Author: Pierre W. Cazenave
Author: Philip D. Nightingale
Author: Margaret J. Yelland
Author: John Prytherch
Author: Ian M. Brooks
Author: Timothy J. Smyth

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