Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 3 4 2006 10.5194/bg-3-607-2006 http://www.biogeosciences.net/3/607/2006/ http://www.biogeosciences.net/3/607/2006/bg-3-607-2006.html http://www.biogeosciences.net/3/607/2006/bg-3-607-2006.pdf 607 619 2006-12-01 Nitrous oxide in the North Atlantic Ocean S. Walter s.walter@phys.uu.nl H. W. Bange U. Breitenbach D. W. R. Wallace Forschungsbereich Marine Biogeochemie, IFM-GEOMAR, Leibniz-Institut für Meereswissenschaften, Kiel, Germany now at: Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, the Netherlands In order to get a comprehensive picture of the distribution of nitrous oxide (N₂O) in the North Atlantic Ocean, measurements of dissolved nitrous oxide were made during three cruises in the tropical, subtropical and cold-temperate North Atlantic Ocean in October/November 2002, March/April 2004, and May 2002, respectively. To account for the history of atmospheric N₂O, we suggest a new depth-dependent calculation of excess N₂O (ΔN₂O). N₂O depth profiles showed supersaturation throughout the water column with a distinct increasing trend from the cold-temperate to the tropical region. Lowest nitrous oxide concentrations, near equilibrium and with an average of 11.0±1.7 nmol L^−1, were found in the cold-temperate North Atlantic where the profiles showed no clear maxima. Highest values up to 37.3 nmol L^−1 occurred in the tropical North Atlantic with clear maxima at approximately 400 m. A positive correlation of nitrous oxide with nitrate, as well as excess nitrous oxide with the apparent oxygen utilization (AOU), was only observed in the subtropical and tropical regions. 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