Environmental Engineering Reference
In-Depth Information
2012
). Carbon dioxide release is poorly constrained in all cases, but depends on
country-rock lithology and the composition of the mantle melt source. Siberian
magmas transited a series of particularly volatile-rich sedimentary rocks, including
evaporites, carbonates and hydrocarbon-bearing layers (Kontorovich
et al
.,
1997
;
Meyerhoff,
1980
). This geologic setting may have contributed to the overall CO
2
and methane
flux, and is a necessary precondition for the production of CH
3
Cl and
other organohalogens (Svensen
et al
.,
2009
).
To simulate the effects of both CO
2
updraw and pulsed release of sulfur and
other relatively short-lived gases as estimated by Black
et al
.(
2012
), we employ a
comprehensive global model of climate and chemistry (Black
et al
.,
2014
; Kiehl
and Shields,
2005
; Lamarque
et al
.,
2012
). In the next section, we describe the set-
up, physical processes, chemistry and assumptions implicit in this model.
20.4 Model and simulation descriptions
The Community Earth System Model is a comprehensive global climate model
that includes ocean, land, sea-ice and atmosphere components. It is capable of
simulating fully interactive atmospheric chemistry with the CAM-Chem module
(Lamarque
et al
.,
2012
). The chemistry scheme includes reactions between 134
Here we present results from two types of simulations: one con
gured to capture
climate change, and one con
gured to capture atmospheric chemistry. The
rst
con
guration is that of Kiehl and Shields (
2005
) who ran equilibrium simulations
at 3.75
by 3.75
resolution, with online ocean circulation coupled to a land model,
a sea-ice model, and an atmosphere with 26 vertical levels. Atmospheric chemistry
is not simulated in this set-up, but the radiative effects of CO
2
and other green-
house gases are allowed to percolate completely through the Earth system until a
new equilibrium state is reached.
We use ocean sea-surface temperatures from an updated Community Climate
System Model 4 version of the Kiehl and Shields (
2005
) equilibrium simulations
as a boundary condition for the second con
guration, in which we simulate
atmospheric chemistry at 1.9
by 2.5
horizontal resolution in the atmosphere.
The primary targets of these atmospheric chemistry simulations are rainfall pH and
ozone chemistry.
For both con
gurations, we employ the model of palaeotopography from Kiehl
and Shields (
2005
) as shown in
Figure 20.1
.De
ning a realistic palaeobathymetry
for the pre-Mesozoic is particularly challenging, and likely constitutes one of the
major uncertainties for the simulation of ocean circulation. Another set of major
uncertainties involves the composition of the Permian
-
Triassic atmosphere and the
magnitude of magmatic and thermogenic
fluxes. In all simulations, we hold CO
2
