Air-sea CO2 exchange in the equatorial Pacific

Wade R. McGillis, James B. Edson, Christopher J. Zappa, Jonathan D. Ware, Sean P. McKenna, Eugene A. Terray, Jeffrey E. Hare, Christopher W. Fairall, William M Drennan, Mark Donelan, Michael D. DeGrandpre, Rik Wanninkhof, Richard A. Feely

Research output: Contribution to journalArticle

132 Citations (Scopus)

Abstract

GasEx-2001, a 15-day air-sea carbon dioxide (CO2) exchange study conducted in the equatorial Pacific, used a combination of ships, buoys, and drifters equipped with ocean and atmospheric sensors to assess variability and surface mechanisms controlling air-sea CO2 fluxes. Direct covariance and profile method air-sea CO2 fluxes were measured together with the surface ocean and marine boundary layer processes. The study took place in February 2001 near 125°W, 3°S in a region of high CO2. The diurnal variation in the air-sea CO2 difference was 2.5%, driven predominantly by temperature effects on surface solubility. The wind speed was 6.0 ± 1.3 m s-1, and the atmospheric boundary layer was unstable with conditions over the range -1 < z/L < 0. Diurnal heat fluxes generated daytime surface ocean stratification and subsequent large nighttime buoyancy fluxes. The average CO2 flux from the ocean to the atmosphere was determined to be 3.9 mol m-2 yr-1, with nighttime CO2 fluxes increasing by 40% over daytime values because of a strong nighttime increase in (vertical) convective velocities. The 15 days of air-sea flux measurements taken during GasEx-2001 demonstrate some of the systematic environmental trends of the eastern equatorial Pacific Ocean. The fact that other physical processes, in addition to wind, were observed to control the rate of CO2 transfer from the ocean to the atmosphere indicates that these processes need to be taken into account in local and global biogeochemical models. These local processes can vary on regional and global scales. The GasEx-2001 results show a weak wind dependence but a strong variability in processes governed by the diurnal heating cycle. This implies that any changes in the incident radiation, including atmospheric cloud dynamics, phytoplankton biomass, and surface ocean stratification may have significant feedbacks on the amount and variability of air-sea gas exchange. This is in sharp contrast with previous field studies of air-sea gas exchange, which showed that wind was the dominating forcing function. The results suggest that gas transfer parameterizations that rely solely on wind will be insufficient for regions with low to intermediate winds and strong insolation.

Original languageEnglish (US)
JournalJournal of Geophysical Research C: Oceans
Volume109
Issue number8
DOIs
StatePublished - Aug 15 2004

Fingerprint

Fluxes
air
Air
ocean surface
gas exchange
sea surface
oceans
Gases
ocean
daytime
stratification
boundary layer
Atmospheric radiation
buoys
Buoys
atmospheres
atmospheric boundary layer
Atmospheric boundary layer
insolation
Incident solar radiation

Keywords

  • Air-sea carbon dioxide fluxes
  • Direct covariance technique
  • Diurnal surface layer
  • Equatorial Pacific
  • Profile flux technique

ASJC Scopus subject areas

  • Oceanography
  • Astronomy and Astrophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Geophysics
  • Geochemistry and Petrology

Cite this

McGillis, W. R., Edson, J. B., Zappa, C. J., Ware, J. D., McKenna, S. P., Terray, E. A., ... Feely, R. A. (2004). Air-sea CO2 exchange in the equatorial Pacific. Journal of Geophysical Research C: Oceans, 109(8). https://doi.org/10.1029/2003JC002256

Air-sea CO2 exchange in the equatorial Pacific. / McGillis, Wade R.; Edson, James B.; Zappa, Christopher J.; Ware, Jonathan D.; McKenna, Sean P.; Terray, Eugene A.; Hare, Jeffrey E.; Fairall, Christopher W.; Drennan, William M; Donelan, Mark; DeGrandpre, Michael D.; Wanninkhof, Rik; Feely, Richard A.

In: Journal of Geophysical Research C: Oceans, Vol. 109, No. 8, 15.08.2004.

Research output: Contribution to journalArticle

McGillis, WR, Edson, JB, Zappa, CJ, Ware, JD, McKenna, SP, Terray, EA, Hare, JE, Fairall, CW, Drennan, WM, Donelan, M, DeGrandpre, MD, Wanninkhof, R & Feely, RA 2004, 'Air-sea CO2 exchange in the equatorial Pacific', Journal of Geophysical Research C: Oceans, vol. 109, no. 8. https://doi.org/10.1029/2003JC002256
McGillis WR, Edson JB, Zappa CJ, Ware JD, McKenna SP, Terray EA et al. Air-sea CO2 exchange in the equatorial Pacific. Journal of Geophysical Research C: Oceans. 2004 Aug 15;109(8). https://doi.org/10.1029/2003JC002256
McGillis, Wade R. ; Edson, James B. ; Zappa, Christopher J. ; Ware, Jonathan D. ; McKenna, Sean P. ; Terray, Eugene A. ; Hare, Jeffrey E. ; Fairall, Christopher W. ; Drennan, William M ; Donelan, Mark ; DeGrandpre, Michael D. ; Wanninkhof, Rik ; Feely, Richard A. / Air-sea CO2 exchange in the equatorial Pacific. In: Journal of Geophysical Research C: Oceans. 2004 ; Vol. 109, No. 8.
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