The North Atlantic Ocean as a source of atmospheric N,O

In 1969, 1970, and 1971 N,O measurements of sea water were carried out during 3 cruises in the open North Atlantic ocean. Water samples were taken from the sea's surface and from depths down to 3 000 m at several stations. Surface water concen-trations in the tropical-subtropical latitudes averaged 0.5 pg N,O per liter sea water. For the range from 38.5 " N to 48.5 " N, an average of 0.4 pg N,O per liter sea water was found. In the area of the Iceland-Faroe ridge, the surface water concentrations averaged 0.4 pg N,O per liter'sea water when water temperatures were 10°C, and 0.5,ug N,O per liter sea water when water temperatures were 5°C. The vertical N,O concentration profiles often show two maxima: a smaller one between 100 and 200 m and a large one between 400 and 1000 m with N,O concentrations up to 0.8 pg per liter sea water. With the exception of a few samples, the measurements indicated that the North Atlantic sea water is supersaturated with N,O. Supersaturation values up to more than 100 % were found in the upper layers of the sea water from the tropical-subtropical latitudes up to 48.5 " N. Further north the N,O supersaturation of the sea water decreases. For the upper sea water layers down to 1 000 m the following average values were obtained from vertical profiles: in tropical latitudes about 66 % super-saturation, in subtropical latitudes about 47 %, in the range from 38.5 ' N to 48.5 " N about 42 %, and in the area of the Iceland-Faroe ridge about 12-20 yo supersaturation. One may conclude that the North Atlantic ocean acts as a net source of atmospheric N,O. It is probable that the other oceans have the same ability