ePrints

Global reconstruction reduces the uncertainty of oceanic nitrous oxide emissions and reveals a vigorous seasonal cycle

Lookup NU author(s): Professor Sam Wilson

Downloads

Full text for this publication is not currently held within this repository. Alternative links are provided below where available.

Abstract

© 2020 National Academy of Sciences. All rights reserved.Assessment of the global budget of the greenhouse gas nitrous oxide (N2O) is limited by poor knowledge of the oceanic N2O flux to the atmosphere, of which the magnitude, spatial distribution, and temporal variability remain highly uncertain. Here, we reconstruct climatological N2O emissions from the ocean by training a supervised learning algorithm with over 158,000 N2O measurements from the surface ocean-the largest synthesis to date. The reconstruction captures observed latitudinal gradients and coastal hot spots of N2O flux and reveals a vigorous global seasonal cycle. We estimate an annual mean N2O flux of 4.2 ± 1.0 Tg N·y−1, 64% of which occurs in the tropics, and 20% in coastal upwelling systems that occupy less than 3% of the ocean area. This N2O flux ranges from a low of 3.3 ± 1.3 Tg N·y−1 in the boreal spring to a high of 5.5 ± 2.0 Tg N·y−1 in the boreal summer. Much of the seasonal variations in global N2O emissions can be traced to seasonal upwelling in the tropical ocean and winter mixing in the Southern Ocean. The dominant contribution to seasonality by productive, low-oxygen tropical upwelling systems (>75%) suggests a sensitivity of the global N2O flux to El Niño-Southern Oscillation and anthropogenic stratification of the low latitude ocean. This ocean flux estimate is consistent with the range adopted by the Intergovernmental Panel on Climate Change, but reduces its uncertainty by more than fivefold, enabling more precise determination of other terms in the atmospheric N2O budget.

Publication metadata

Author(s): Yang S, Chang BX, Warner MJ, Weber TS, Bourbonnais AM, Santoro AE, Kock A, Sonnerup RE, Bullister JL, Wilson ST, Bianchi D

Publication type: Article

Publication status: Published

Journal: Proceedings of the National Academy of Sciences of the United States of America

Year: 2020

Volume: 117

Issue: 22

Pages: 11954-11960

Print publication date: 02/06/2020

Online publication date: 18/05/2020

Acceptance date: 01/04/2020

ISSN (print): 0027-8424

ISSN (electronic): 1091-6490

Publisher: National Academy of Sciences

URL: https://doi.org/10.1073/pnas.1921914117

DOI: 10.1073/pnas.1921914117

PubMed id: 32424089

Altmetrics

Share