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AGU: Global Biogeochemical Cycles

 

Keywords

  • ammonia
  • air-sea exchange
  • temperature

Index Terms

  • Atmospheric Composition and Structure: Air/sea constituent fluxes
  • Biogeosciences: Biogeochemical cycles, processes, and modeling
  • Biogeosciences: Nitrogen cycling

Abstract

GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 22, GB1019, 15 PP., 2008
doi:10.1029/2007GB003039

Field observations of the ocean-atmosphere exchange of ammonia: Fundamental importance of temperature as revealed by a comparison of high and low latitudes

Martin T. Johnson

School of Environmental Sciences, University of East Anglia, Norwich, UK

Peter S. Liss

School of Environmental Sciences, University of East Anglia, Norwich, UK

Thomas G. Bell

School of Environmental Sciences, University of East Anglia, Norwich, UK

Timothy J. Lesworth

School of Environmental Sciences, University of East Anglia, Norwich, UK

Alex R. Baker

School of Environmental Sciences, University of East Anglia, Norwich, UK

Andrew J. Hind

School of Environmental Sciences, University of East Anglia, Norwich, UK

Timothy D. Jickells

School of Environmental Sciences, University of East Anglia, Norwich, UK

Karabi F. Biswas

New York State Department of Health, Albany, New York, USA

E. Malcolm S. Woodward

Plymouth Marine Laboratory, Plymouth, UK

Stuart W. Gibb

Environmental Research Institute, UHI Millennium Institute, Thurso, UK

Simultaneous measurements of NH3 in the atmosphere and NH4 + in the ocean are presented from fieldwork spanning 10 years and 110 degrees of latitude, including the first such simultaneous measurements in the remote marine environment at >55°N. At high latitudes, fluxes were almost exclusively from air to sea, in contradiction with previous lower-latitude studies, which have suggested that the open oceans are predominantly sources of ammonia to the atmosphere. Sensitivity analysis demonstrates that the direction and magnitude of the ocean-atmosphere NH3 exchange is highly dependent on water temperature. This temperature effect is sufficiently strong to outweigh the effects of variability in concentrations in seawater and atmosphere in many parts of the (open) ocean. This is highlighted in data from the Atlantic oligotrophic gyres, where fluxes were found to be predominantly out of the ocean despite extremely low dissolved ammonium concentrations in surface waters.

Received 22 June 2007; accepted 10 October 2007; published 16 February 2008.

Citation: Johnson, M. T., P. S. Liss, T. G. Bell, T. J. Lesworth, A. R. Baker, A. J. Hind, T. D. Jickells, K. F. Biswas, E. M. S. Woodward, and S. W. Gibb (2008), Field observations of the ocean-atmosphere exchange of ammonia: Fundamental importance of temperature as revealed by a comparison of high and low latitudes, Global Biogeochem. Cycles, 22, GB1019, doi:10.1029/2007GB003039.

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