Abstract We measured the nitrogen isotopic composition of surface seawater and aerosol ammonium in the Weddell Sea region of the Southern Ocean to investigate the natural atmospheric cycle of marine ammonia emissions and aerosol ammonium formation in a region not overwhelmed by anthropogenic emissions. Seawater ammonium δ15N covered a narrow range (−6.9 to 2.4‰), in contrast to aerosol ammonium δ15N (−24.6 to 23.5‰). Aerosol values clustered in two distinct groups, one with low δ15N (−14.6 ± 7.1‰) and one with high δ15N (18.8 ± 6.7‰). The low δ15N aerosols are best explained by the surface ocean as the only source. By contrast, the higher δ15N aerosols are likely due to seabird emissions. This work demonstrates the potential of nitrogen isotopes to constrain the contribution of the ocean to natural ammonia emissions and to improve our understanding of aerosol ammonium formation away from anthropogenic sources.
Last updated: April 11, 2026 04:23 PM
CO₂
432.5ppm
+2.5
/ year
CH₄
1945.85ppb
+8.44
/ year
Temp
+1.48°C
Peak +1.73°C
Population
8.1B
+67M
/ year