Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations

Paulot, F, Jacob, DJ, Johnson, MT, Bell, TG, Baker, AR, Keene, WC, Lima, ID, Doney, SC and Stock, CA 2015 Global oceanic emission of ammonia: Constraints from seawater and atmospheric observations. Global Biogeochemical Cycles, 29 (8). 1165-1178.

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Current global inventories of ammonia emissions identify the ocean as the largest natural source. This source depends on seawater pH, temperature, and the concentration of total seawater ammonia (NHx(sw)), which reflects a balance between remineralization of organic matter, uptake by plankton, and nitrification. Here we compare [NHx(sw)] from two global ocean biogeochemical models (BEC and COBALT) against extensive ocean observations. Simulated [NHx(sw)] are generally biased high. Improved simulation can be achieved in COBALT by increasing the plankton affinity for NHx within observed ranges. The resulting global ocean emissions is 2.5 TgN a−1, much lower than current literature values (7–23 TgN a−1), including the widely used Global Emissions InitiAtive (GEIA) inventory (8 TgN a−1). Such a weak ocean source implies that continental sources contribute more than half of atmospheric NHx over most of the ocean in the Northern Hemisphere. Ammonia emitted from oceanic sources is insufficient to neutralize sulfate aerosol acidity, consistent with observations. There is evidence over the Equatorial Pacific for a missing source of atmospheric ammonia that could be due to photolysis of marine organic nitrogen at the ocean surface or in the atmosphere. Accommodating this possible missing source yields a global ocean emission of ammonia in the range 2–5 TgN a−1, comparable in magnitude to other natural sources from open fires and soils.

Item Type: Publication - Article
Subjects: Atmospheric Sciences
Ecology and Environment
Marine Sciences
Divisions: Plymouth Marine Laboratory > Science Areas > Cycling in the Sunlit Ocean (expired)
Depositing User: Dr Thomas George Bell
Date made live: 28 Jan 2016 11:12
Last Modified: 23 Dec 2019 14:44

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