Nitrous oxide in the surface layer of the tropical North Atlantic Ocean along a west to east transect

Nitrous oxide (N 2 O) was measured during the first German SOLAS (Surface Ocean – Lower Atmosphere Study) cruise in the tropical North Atlantic Ocean on board R/V Meteor during October/November 2002. About 900 atmospheric and dissolved N 2 O measurements were performed with a semi‐continuous GC‐ECD system equipped with a seawater‐gas equilibrator. Surface waters along the main transect at 10°N showed no distinct longitudinal gradient. Instead, N 2 O saturations were highly variable ranging from 97% to 118% (in the Guinea Dome Area, 11°N, 24°W). When approaching the continental shelf of West Africa, N 2 O surface saturations went up to 113%. N 2 O saturations in the region of the equatorial upwelling (at 0–1.5°N, 23.5–26°W) were correlated with decreasing sea surface temperatures and showed saturations up to 109%. The overall mean N 2 O saturation was 104 ± 4% indicating that the tropical North Atlantic Ocean is a net source of atmospheric N 2 O.