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Modeled Microbial Dynamics Explain the Apparent Temperature Sensitivity of Wetland Methane Emissions
Author(s) -
Chadburn Sarah E.,
Aalto Tuula,
Aurela Mika,
Baldocchi Dennis,
Biasi Christina,
Boike Julia,
Burke Eleanor J.,
ComynPlatt Edward,
Dolman A. Johannes,
DuranRojas Carolina,
Fan Yuanchao,
Friborg Thomas,
Gao Yao,
Gedney Nicola,
Göckede Mathias,
Hayman Garry D.,
Holl David,
Hugelius Gustaf,
Kutzbach Lars,
Lee Hanna,
Lohila Annalea,
Parmentier FransJan W.,
Sachs Torsten,
Shurpali Narasinha J.,
Westermann Sebastian
Publication year - 2020
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2020gb006678
Subject(s) - methane , environmental science , wetland , greenhouse gas , atmospheric sciences , latitude , climate change , atmospheric methane , global warming , methane emissions , seasonality , climatology , ecology , biology , geodesy , geology , geography
Methane emissions from natural wetlands tend to increase with temperature and therefore may lead to a positive feedback under future climate change. However, their temperature response includes confounding factors and appears to differ on different time scales. Observed methane emissions depend strongly on temperature on a seasonal basis, but if the annual mean emissions are compared between sites, there is only a small temperature effect. We hypothesize that microbial dynamics are a major driver of the seasonal cycle and that they can explain this apparent discrepancy. We introduce a relatively simple model of methanogenic growth and dormancy into a wetland methane scheme that is used in an Earth system model. We show that this addition is sufficient to reproduce the observed seasonal dynamics of methane emissions in fully saturated wetland sites, at the same time as reproducing the annual mean emissions. We find that a more complex scheme used in recent Earth system models does not add predictive power. The sites used span a range of climatic conditions, with the majority in high latitudes. The difference in apparent temperature sensitivity seasonally versus spatially cannot be recreated by the non‐microbial schemes tested. We therefore conclude that microbial dynamics are a strong candidate to be driving the seasonal cycle of wetland methane emissions. We quantify longer‐term temperature sensitivity using this scheme and show that it gives approximately a 12% increase in emissions per degree of warming globally. This is in addition to any hydrological changes, which could also impact future methane emissions.