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| Titel |
Projections of oceanic N2O emissions in the 21st century using the IPSL Earth system model |
| VerfasserIn |
J. Martinez-Rey, L. Bopp, M. Gehlen, A. Tagliabue, N. Gruber |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 13 ; Nr. 12, no. 13 (2015-07-13), S.4133-4148 |
| Datensatznummer |
250118018
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| Publikation (Nr.) |
 copernicus.org/bg-12-4133-2015.pdf |
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| Zusammenfassung |
| The ocean is a substantial source of nitrous oxide (N2O) to the
atmosphere, but little is known about how this flux might change in the future.
Here, we investigate the potential evolution of marine N2O emissions in
the 21st century in response to anthropogenic climate change using the
global ocean biogeochemical model NEMO-PISCES. Assuming nitrification as the
dominant N2O formation pathway, we implemented two different
parameterizations of N2O production which differ primarily under low-oxygen (O2) conditions. When forced with output from a climate model
simulation run under the business-as-usual high-CO2 concentration
scenario (RCP8.5), our simulations suggest a decrease of 4 to 12 % in
N2O emissions from 2005 to 2100, i.e., a reduction from 4.03/3.71 to
3.54/3.56 TgN yr−1 depending on the parameterization. The emissions
decrease strongly in the western basins of the Pacific and Atlantic oceans,
while they tend to increase above the oxygen minimum zones (OMZs), i.e., in
the eastern tropical Pacific and in the northern Indian Ocean. The reduction
in N2O emissions is caused on the one hand by weakened nitrification as
a consequence of reduced primary and export production, and on the other
hand by stronger vertical stratification, which reduces the transport of
N2O from the ocean interior to the ocean surface. The higher emissions
over the OMZ are linked to an expansion of these zones under global warming,
which leads to increased N2O production, associated primarily with
denitrification. While there are many uncertainties in the relative
contribution and changes in the N2O production pathways, the increasing
storage seems unequivocal and determines largely the decrease in N2O
emissions in the future. From the perspective of a global climate system,
the averaged feedback strength associated with the projected decrease in
oceanic N2O emissions amounts to around −0.009 W m−2 K−1,
which is comparable to the potential increase from terrestrial N2O
sources. However, the assessment for a potential balance between the terrestrial
and marine feedbacks calls for an improved representation of N2O
production terms in fully coupled next-generation Earth system models. |
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