Methane in the atmosphere: measurements, lifetime, estimation
Bloom, A., Palmer, P., Fraser, A., Reay, D., Frankenberg, C., 2010. Large-scale controls
of methanogenesis inferred from methane and gravity spaceborne data. Science,
327, pp. 322-325.
Used GRACE satellite to estimate water-table height and temperature to estimate
wetland methanogenisis and plugged into GEOSchem. Compared with SCIAMACHY
satellite methane measurements. Found higher sensitivity to temperature in mid-
latitudes, higher sensitivity to water-table in tropics. Found less emission (50%) than
others (70%).
Cicerone, R., Oremland, R., 1988. Biogeochemical aspects of atmospheric methane.
Global Biogeochemical cycles, v.2, n.4, pp. 299-327.
Older article, describes basic atmospheric chemistry of methane clearly, has
less effective descriptions of methanogenisis and methane oxidation.
Lelieveld, J., Crutzen, P., Dentener, F., 1998. Changing concentration, lifetime and
climate forcing of atmospheric methane. Tellus, 50B, 128-150.
Chemical transport model estimates global atmospheric distribution of methane, non-
prognostic sources. The description of atmospheric methane breakdown is more
complete (reflects ten more years of knowledge), but is less detailed than Cicerone.
Werner, C., Davis, K., Bakwin, P., Yi, C., Hurst, D., Lock, L., 2003. Regional-scale
measurements of CH4 exchange from a tall tower over a mixed temperate/boreal
lowland and wetland forest. Global Change Biology, 9, 1,251-1,261.
Measurement of methane gradient at the WLEF tower from 1997-1999. Maximum in
June-August of 24±14.4 mg m-2 day-1. Methane phenology limited by both temperature
and snow melt. Read it for more details.
Wuebbles, D., Hayhoe, K., 2002. Atmospheric methane and global change. Earth
Science Reviews, 57, 177-210.
Nice review article describing history of CH4 concentration and emission, estimates of
its sources and sinks, lots of references.
Methanogenisis & methane oxidation
Bridgham, S., Pastor, J., Dewey, B., Welzin, J., Updegraff, K., 2008. Rapid carbon
response of peatlands to climate change. Ecology, 89(11), pp. 3,041-3,048.
Water table and temperature experiments on peat monoliths, focusing of soil carbon.
Bridgham, S., Megonigal, P., Keller, J., Bliss, N., Trettin, C., 2006. The carbon balance
of North American wetlands. Wetlands, v. 26, n. 4, pp. 889-916.
Review of many studies in North America. Found a carbon sink of 49 Tg C yr-1 with an
uncertainty greater than 100% and a methane release of 9 Tg yr-1, again with more
than 100% uncertainty.
von Fischer, J., Hedin, L., 2007. Controls on soil methane fluxes: tests of biophysical
mechanisms using stable isotope tracers. Global Biogeochemical Cycles, v. 21.
Isotopic and GS analysis of methane flux in Hawaii and New York. 60% WFPS
produced methane, strong water-table response. Carbon mineralization was not an
important factor in flux. Production was more important that consumption in
estimating emissions. Only 0.04% of carbon mineralization through methanogenisis
needed for positive methane flux. See 2002 paper by the same authors.
Whalen, S., 2005. Biogeochemistry of methane exchange between natural wetlands
and the atmosphere. Environmental Engineering Science, v. 22, n. 1, pp. 73-94.
A review of biogenic methanogenisis and methane oxidation as well as the physical
process affecting methane emission from wetlands. Has Q10 from different types of
wetlands and references the studies these came from.
Whiting, G., Chanton, J., 2001. Greenhouse carbon balance of wetlands: methane
emission versus carbon sequestration. Tellus, 53B, 521-528.
Chamber experiment in Florida, Virginia and Alberta, comparing CH4 emission and
CO2 sequestration and the greenhouse warming potential compensation points.
Florida and Virginia are emitting enough methane to compensate for the CO2, and
contribute to warming.
Wetland methane models
Potter, C., 1997. An ecosystem simulation model for methane production and
emission from wetlands. Global Biogeochemical Cycles, v. 11, n. 4, pp. 495-506.
Methane model built into CASA, CH4 production based on soil temperature, water
table depth, and CO2 production. Transport terms are also addressed. Water table
depth was specified. Temperature seems to have been included twice, 1st in the CH4
production term explicitly and again in that it controls the production of CO2. The
model does not match site data well.
Walter, B., Heimann, M., Shannon, R., White, J., 1996. A process-based model to
derive methane emissions from natural wetlands. Geophysical Research Letters, v.
23, n. 25, pp. 3,731-3,734.
Model based on temperature, water table height, porosity, carbon avalabililty, forced
with observations and compared to observations from Shannon & White, 1994. The
model includes three transport mechanisms: molecular diffusion, ebullition, plant-
mediated transport. Methanotrophy is included. Appears to matched observations
well, but I don’t know much about them, an ombrotrophic peat bog in Michigan.
Walter, B., Heimann, M., 2000. A process-based, climate-sensitive model to derive
methane emissions from natural wetlands: Application to five wetland sites,
sensitivity to model parameters, and climate. Global Biogeochemical Cycles, v. 14, n.
3, pp. 745-765.
Refinement of model presented in 1996, with a much more extensive description.
Tested against five sites Michigan, Minnesota, Finland, Alaska, and Panama. Seemed
to simulate methane well despite not simulating water table well.
Walter, B., Heimann, M., Matthews, E., 2001. Modeling modern methane emissions
from natural wetlands 1. Model description and results. Journal of Geophysical
Research, v. 106, n. D24, pp. 34,189-34,206.
The model is best described in the 2000 paper. This time it was coupled to Matthews’
global wetland database. The hydrologic model may have been refined or is just
elaborated on in this paper.
Walter, B., Heimann, M., Matthews, E., 2001. Modeling modern methane emissions
from natural wetlands 2. Interannual variations 1982-1993. Journal of Geophysical
Research, v. 106, n. D24, pp. 34,207-34,219.
Haven’t read it yet, the figures are illegible.
Whitting, G., Chanton, J., 1993. Primary production control of methane emission
from wetlands. Nature, v. 364, pp. 794-795.
Measurments of CO2 and CH4 flux in a variety of different wetlands indicate that
simple assuming that the methane flux is 3% of the NEP might be the best
approximation. Also has some references to studies estimating Q10 values.
Hydrological modeling: TOPMODEL, wetland extent
Bevin, K., Kirkby, M., 1979. A physically based, variable contributing area model of
basin hydrology. Hydrological Sciences—Bulletin, v. 254, n. 1, pp. 43-69.
One of the original TOPMODEL papers. Section 4 carefully outlines the calculation of
saturated area and its use for calculating surface runoff (which is non-linear and
requires short timesteps). Most important is eq. (8), relying on eq. (7).
Ambroise, B., Beven, K., Freer, J., 1996. Toward a generalization of the TOPMODEL
concepts: Topographic indices of hydrological similarity. Water Resources
Research, v. 32, n. 7, pp. 2135-2145.
The original TOPMODEL formulation of the topographic index relies on the
assumption of exponential decrease in trasmissivity with increasing saturation. This
paper constructs analogous indices with the assumption of parabolic and linear
decreases in trasmissivity. This paper is also a nice review of TOPMODEL, math.
Ambroise, B., Beven, K., Freer, J., 1996. Application of a generalized TOPMODEL to
the small Ringelbach catchment, Vosges, France. Water Resources Research, v. 32, n.
7, pp. 2147-2159.
Uses the alternative TOPMODEL formulations presented in the accompanying paper at
a particular site and compares them. 36-ha, elevations from 100-748m, mean slope
28˚, pastureland. Four years, 18 min. steps. Results are hard to judge as the figures
didn’t come out right in the scan, one would have to find the physical paper.
Bevin, K., 1997. TOPMODEL: A Critique. Hydrological Processes, v. 11, pp. 1069-
1085.
A review of implementations of TOPMODEL and some discussion of the observed
variability in its parameters at different sites. Goes over the various assumptions that
are made in the model and the assumptions that are commonly made in order to use it:
also makes some suggestions as to how these assumptions might be explicitly modeled.
Curie, F., Gaillard, S., Ducharne, A., Bendjoudi, H., 2007. Geomorphological methods
to characterize wetlands at the scale of the Seine watershed. Science of the Total
Environment, v. 375, pp. 59-68.
Estimates wetland extent using 100m resolution and topographic index times the
average rainfall. Estimates are perhaps high, but their isn’t much to test against, they
note, somewhat strangely I think, that this is a measure of potential wetlands and that
human activities may reduce their extent.
Ducharne, A., 2009. Reducing scale dependence in TOPMODEL using a
dimensionless topographic index. Hydrological Earth Systems Science, v. 13, pp.
2399-2412.
Instead of using area to calculate topographic index, she uses the pixel length of the
raster data set. This gives a new index yi=xi-lnC; where xi is the original topographic
index and C is the pixel length or the downhill contour length. This makes the
topographic index, the log of a unit-less quantity, which is good. Hope I can get a hold
of this code.
Gedney, N., Cox, P., 2003. The sensitivity of global climate model simulations to the
representation of soil moisture heterogeneity. Journal of Hydrometeorology, v. 4, pp.
1265-1275.
A 12m thick layer was added below a 4m thick land surface model. Only in the 12m
layer was TOPMODEL used. 1x1 km resolution was used, they argue that topography
is self-similar. They used the model to estimate wetland area, establishing a maximum
oversaturation at which water was no longer thought to be stagnant, a different
method was used in area with significant frozen soil moisture fractions. Runoff rates
when coupled to a GCM with various atmospheric CO2 concentrations are compared.
Merot, Ph., Squividant, H., Aurousseau, P., Hefting, M., Burt, T., Maitre, V., Kruk, M.,
Butturini, A., Thenail, C., Viaud, V., 2003. Testing a climato-topographic index for
predicting wetlands distribution along an European climate gradient. Ecological
Modeling, v. 163, pp. 51-71.
Uses topographic index multiplied by effective precipitation at a number of different
sites. This allows you to use a single critical value to describe likelihood of saturation
in areas with different precipitation rates. Uses downhill slope rather than local slope.
The critical value is reported as effective rainfall (R-PET) times drainage area,
140000m3; I don’t understand this, and the reference is to an internal note in French.
Notes the hole-filling problem for ombrotrophic mires. Says that 20m resolution is just
enough to predict mires, 20x20 to 40x40 meters.
Rodhe, A., Seibert, J., 1999. Wetland occurrence in relation to topography: a test of
topographic indices as moisture indicators. Agricultural and Forest Meteorology, v.
99, pp. 325-340.
Used topographic index in several ways to predict mires in two Swedish sites, both at
50m resolution. This was too course for one site and predicted only ~12% of mires, the
other predicted ~40%. I like the formulation of TOPMODEL in this paper, but I have
doubts about their control.
Quinn, P., Beven, K., Lamb, R., 1995. The ln(a/tan) index: How to calculate it and
how to use it within the TOPMODEL framework. Hydrological Processes, v. 9, pp.
161-182.
Topographic index calculated from sizes ranging between 1 am 50m; 100m is too
large. Different grid sizes are valid predictors of flow, for prediction of finer scale
features, finer resolution is needed. The paper stresses the importance of the choice of
the number of channel grid cells and describing different routing methods and their
impacts.
Mapping wetlands
Aselmann, I., Crutzen, P., 1989. Global distribution of natural freshwater wetlands
and rice paddies, their net primary productivity, seasonality and possible methane
emissions. Journal of Atmospheric Chemistry, 8, 307-358.
Maps assembled from other maps.
Matthews, E., Fung, I., 1987. Methane emissions from natural wetlands: Global
distribution, area and environmental characteristics of sources. Global
Biogeochemical Cycles, 1, 61-68.
Better maps than Aselmann & Crutzen.
Frey, K., Smith, L., 2007. How well do we know the northern land cover? Comparison
of four global vetation and wetland products with a new ground-truth database for
West Siberia. Global Biogeochemical Cycles, v. 21.
Ground-truthing the MODIS and AVHRR and the GLWD and another wetland map. All
products underestimated the extent of wetlands and got many other things wrong,
particularly needleleaf forest being mistaken for other things.
Jung, M., Henkel, K., Herold, M., Churkina, G., 2006. Exploiting synergies of global
land cover products for carbon cycle modeling. Remote Sensing of Environment,
101, 534-553.
Comparison of different land-surface products MODIS, AVHRR, & GLC200. Highlights
differences and produces a synthesis that has maximal similarity between the three.