Environmental Engineering Reference
In-Depth Information
Table 19.2 (
cont.
)
Maximum
p
CO
2
(ppm)
Maximum
sea surface
T
(
C)
Minimum surface
saturation state of
calcite (
13
C
source
δ
Minimum
pH
(
‰
)
Ω
calcite
)
-
60
5186
23.4
3.69
7.33
Ω
calcite, init
¼
2.5
-
9
72 945
34.4
0.46
6.23
-
12
31 598
30.6
0.74
6.54
-
15
19 163
28.5
0.98
6.72
-
20
111 876
26.5
1.25
6.89
-
25
8966
25.5
1.45
6.99
-
40
5893
23.9
1.77
7.14
-
60
4645
23.0
1.97
7.22
amount of C added during peak C addition is
~
330 000 Gt C for scenario 1, and
13
becomes smaller as both
δ
C
source
and
Ω
calcite,init
decreases (
Table 19.2
). The
13
minimum
Ω
calcite
value during the peak C addition is a function of
δ
C
source
and
the initial
calcite
is elevated compared to the initial
value at 20 kyr after the onset of the extinction, mostly clearly seen for a smaller
Ω
Ω
calcite
(
Figure 19.2d-f).
-
Ω
calcite, init
. This is an expected response to an increased delivery of alkalinity from
the higher weathering rate due to warming.
We select scenario 12 (
13
Ω
¼
δ
¼ -
‰
) for a more compre-
hensive analysis of the overall environmental response to C addition (
Figure 19.3
).
With reference to
Figure 19.2
, we note that the response of the other scenarios
follows the trends shown in
Figure 19.3
with increased or diminished amplitude.
We present the time-series results relative to the onset of the extinction, which is
de
5 and
C
source
25
calcite
ned as the time where the C isotopes initiate the sharp decline at bed 24e (age
252.3 Ma) according to Shen
et al
.(
2011
). The peak
flux of C addition is
~
3Gt
Cyr
-
1
, appearing at
9 kyr after the onset of the extinction, and is followed by a
substantial C burial event (
Figure 19.3a
). The total amount of C added peaks at
~
~
30 000 Gt C, and stabilizes at about 17 000 Gt C by the end of the simulation
(
Figure 19.3b
). The peak
p
CO
2
level reaches 11 000 ppm, and stabilizes at about
5000 ppm at 60 kyr after the onset of the extinction event (into the earliest Triassic)
(
Figure 19.3c
). The globally averaged sea-surface temperature follows the shape of
p
CO
2
, peaks at a little more than 26
C(
5
C), and stabilizes at about 23
C
into the Early Triassic (
Figure 19.3d
). Both globally averaged
Δ
T
¼
Ω
calcite
and pH drop
to their minimum value (
Ω
¼
2.5 and pH
min
¼
7.06) during the peak
calcite, min
C addition. However,
calcite
returns to its pre-extinction level by the end of the
simulation, whereas the pH remains low (
Figures 19.3e
,
f
).
We also group the speci
Ω
cal
values and plot the maximum
response of the six environmental parameters relative to the
ed three initial
Ω
13
δ
C
source
(
Figure 19.4
).
