the compost-bomb instability and the petmumn mathematics of climate seminar november 12, 2013 1 the...
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The Compost-Bomb Instability and the PETM
Jonathan Hahn
UMN Mathematics of Climate Seminar
November 12, 2013
1
The Paleocene-Eocene Thermal Maximum
2
The Paleocene-Eocene Thermal Maximum
3
Carbon Mass Balance
Mfinal ⇥ �13Cfinal = Minitial ⇥ �13Cinitial +Madded ⇥ �13Cadded
Mfinal = Minitial +Madded
CIE = �13Cfinal - �13Cinitial
Madded = -CIE ⇥ Minitial�13
Cfinal-�13
Cadded
�13Csample = (Rsample/Rstandard - 1)
Rsample = C13/C12
4
�13C of Carbon Sources
Source
Methane clathrates:
Wildfires:
Drying of inland seas:
Thermogenic methane:
Permafrost and peat:
�13C
-6%
-2.2%
-2.2%
-3%
-3%
5
Estimating the CIE
6
Mass of Carbon Added to the Atmosphere
7
Source of carbon unclear
Zeebe et. al.:
Panchuck et. al. and Pagani et. al.:
Wright & Schaller:
Most geologists:
must have been methane
definitely not methane
probably a comet
unlikely to be a comet
8
CIE time frame
This data suggests the onset happens in about 20,000 years
9
CIE time frame
Wright and Schaller say:
13 years
10
Peat and Permafrost
DeConto et. al. use GCM with orbital forcing
11
Compost-Bomb Instability
Luke & Cox:
The compost bomb: thermal instability in peatland soils
dC
dt= ⇧- Cr(T )
✏dT
dt= Cr(T )-
�
A(T - Ta)
CTTa
r(T ) = r0
e↵T
Vertically integrated soil carbon content (kg/m2)Soil temperatureAtmospheric TemperatureSoil respiration rate
12
Compost-Bomb Instability
dC
dt= ⇧- Cr(T )
✏dT
dt= Cr(T )-
�
A(T - Ta)
r(T ) = r0
e↵T
r0
= 0.01(yr-1); ↵ = ln(2.5)/10Pi = 1.055(kgm-2yr-1)� = 5.049 ⇤ 106 (Jyr-1m-2
degC-1)
A = 3.9 ⇤ 107(Jkg-1)µ = 2.5 ⇤ 106(Jm-2 degC-1)✏ = µ/A = .064
microbial respiration parameterslitter fall from plantssoil-to-air heat transfer coe�cientspecific heat from microbial respirationsoil heat capacity
13
Compost-Bomb Instability
Equilibrium analysis
0 = dCdt = ⇧- C eqr(T eq)
0 = dTdt = C eqr(T eq)- �
A(Teq - Ta)
C eq = ⇧/r(T eq)T eq = AC eqr(T eq)/�+ Ta
C eq = ⇧/r(T eq)T eq = A⇧/�+ Ta
14
Compost-Bomb Instability
Equilibrium analysis
0 = dCdt = ⇧- C eqr(T eq)
0 = dTdt = C eqr(T eq)- �
A(Teq - Ta)
C eq = ⇧/r(T eq)T eq = AC eqr(T eq)/�+ Ta
C eq = ⇧/r(T eq)T eq = A⇧/�+ Ta
14
Compost-Bomb Instability
Equilibrium analysis
0 = dCdt = ⇧- C eqr(T eq)
0 = dTdt = C eqr(T eq)- �
A(Teq - Ta)
C eq = ⇧/r(T eq)T eq = AC eqr(T eq)/�+ Ta
C eq = ⇧/r(T eq)T eq = A⇧/�+ Ta
14
Compost-Bomb Instability
15
Compost-Bomb Instability
J =
0
@- �
A✏ + C↵r(T)✏
r(T)✏
-C↵r(T ) -r(T )
1
A
det(J - I�) = �2 + �
✓�
A✏-
C↵r(T )
✏+ r(T )
◆+
�
A✏r(T )
Instability condition:�
A✏-
C eq↵r(T eq)
✏+ r(T eq) < 0
�
A✏-
⇧↵
✏+ r(T eq) < 0
Stable!
16
Compost-Bomb Instability
J =
0
@- �
A✏ + C↵r(T)✏
r(T)✏
-C↵r(T ) -r(T )
1
A
det(J - I�) = �2 + �
✓�
A✏-
C↵r(T )
✏+ r(T )
◆+
�
A✏r(T )
Instability condition:�
A✏-
C eq↵r(T eq)
✏+ r(T eq) < 0
�
A✏-
⇧↵
✏+ r(T eq) < 0
Stable!
16
Compost-Bomb Instability
J =
0
@- �
A✏ + C↵r(T)✏
r(T)✏
-C↵r(T ) -r(T )
1
A
det(J - I�) = �2 + �
✓�
A✏-
C↵r(T )
✏+ r(T )
◆+
�
A✏r(T )
Instability condition:�
A✏-
C eq↵r(T eq)
✏+ r(T eq) < 0
�
A✏-
⇧↵
✏+ r(T eq) < 0
Stable!
16
Compost-Bomb Instability
However, Luke & Cox claim there is instability if the decrease insoil carbon cannot keep up with the increase in soil temperature.
Assume C = C0
is constant (dCdt << dTdt ).
Then according to the previous condition, the system is unstable if:
�
A✏-
C0
↵r(T eq)
✏+ r(T eq) < 0
T eq > (1/↵) ln
✓-�/(r
0
A✏)
1- C0
↵/✏
◆
17
Compost-Bomb Instability
Equilibrium for T are given by: T eq - AC0
r(T eq)/� = Ta
18
Canard Trajectories
Wieczorek et. al. examine the same system but including:
dTa
dt= v
In this system, a “canard explosion” occurs for v > vcritical .
Canards: trajectories which transition from small amplitude limitcycles to large ones with a small perturbation in a parameter.
19
Canard Trajectories
20
Canard Trajectories
21
Canard Trajectories
22
Canard Trajectories
23
Canard Trajectories
24
Canard Trajectories
25
Canard Trajectories
26
Canard Trajectories
27
Canard Trajectories
28
Canard Trajectories
29
Canard Trajectories
30
Canard Trajectories
31
Rate-induced tipping
32
Credits
McInerny & Wing: “The Paleocene-Eocene Thermal
Maximum: A Perturbation of Carbon Cycle, Climate, and
Biosphere with Implications for the Future”
Luke, C. M, & Cox, P.M.: “Soil carbon and climate change:
from the Jenkinson e↵ect to the compost-bomb instability”
Wieczorek et. al.: “Excitability in ramped systems: the
compost-bomb instability”
33
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