EOS 260 Part II Flashcards
(510 cards)
1
Q
steady state
A
dx/dt = 0
no change in position with time
stable or unstable
2
Q
unstable steady state
A
unstable to a small perturbation- like on top of a hill
starting close to steady state system will diverge away
d2x/dt2>0
3
Q
non-steady behaviour
A
transient
4
Q
stable steady state
A
starting close to steady state system will converge to it
stable to a small perturbation
d2x/dt2<0
5
Q
studying steady states
A
helps us understand the system
6
Q
two stable steady states
A
must be separated by an unstable steady state
7
Q
bistable system
A
chair, thermohaline circulation, geomagnetic reversals
can be resting in two states, states need not be symmetric with respect to stored energy
defining characteristic of bistability- 2 stable states (minima) are separated by a peak (maximum)
8
Q
forcing
A
input to or control parameter affecting the system
will affect the state of the system
not affected itself by the state of the system
9
Q
examples of forcing
A
solar forcing- sunlight earth receives
putting consecutively steeper ramps under a chair- force it to tip over
10
Q
feedback
A
how the system will respond to a small perturbation or to a change in forcing
2 kinds
11
Q
stabilizing feedback
A
negative feedback
diminishes effect of a perturbation, makes change smaller
pushes system back to stable steady state
12
Q
Couplings
A
positive- change in A gives a change of same sign in B
shown by an arrow
negative- change in A gives a change of opposite sign in B
shown by line with dot
13
Q
feedback loops
A
+1 to positive feeback
-1 to negative feedback
combined effect by multiplying them
14
Q
most important gas absorbing insolation in atmosphere
A
H20 vapour
15
Q
flux density units
A
W/m^2 = J / m^2 s
16
Q
incoming solar radiation
A
341 W/m^2
17
Q
destabilizing feedback
A
positive feedback
enhances the effect of a perturbation, makes change larger
pushes system on to next stable steady state after passing unstable steady state
18
Q
outgoing longwave radiation
A
239 W/m^2
19
Q
reflected solar radiation
A
102 W/m^2
20
Q
total planetary albedo
A
outgoing/incoming
102/341 =~ 0.28 ~ 0.3
21
Q
insolation absorbed by surface
A
161 W/m^2
22
Q
average sunlight over whole earth
A
S/4 ~ 341 W/m^2
23
Q
S
A
solar constant
S ~ 1368 W/m^2
relatively constant
24
Q
where does insolation go
A
absorbed by atmosphere
absorbed by surface
reflected by surface
reflected by clouds/atmosphere
25
net energy absorbed by earth
0.9 W/m^2
| absorbing ~1 W/m^2 more than it is emitting
26
where does surface radiation go
```
thermals
evapotranspiration
emitted by atmosphere
back radiation- emitted back to surface
out of atmosphere- through atm. window
```
27
rate of temperature change
proportional to energy imbalance ∆F
inversely proport. to system mass x specific heat capacity
dT/dt = ∆F/mc
∆F x area (of earth)
28
sunlight in the atmosphere
reflected/deflected by clouds, atmospheric molecules
29
atmospheric molecules
why the sky is blue
30
area of earth
1.5x10^14 m^2
31
why did our dt calculation for 2k in the ocean underestimate the time it would take
we found 730yrs
| our model assumes ocean mixing, which takes ~1000yrs
32
what can be seen from calculating dt of certain temperature change in the atmosphere vs. the ocean
ocean takes much longer to heat
| global warming is dependent on the ocean
33
how many seconds in a year
60x60x24x365.25 = 31557600s
34
2 layers of the atmosphere
troposphere
| stratosphere
35
troposphere
lower layer, T profile set by large scale convection, T decreasing with altitude
36
stratosphere
upper layer, minimal motion, T set by radiative absorption and emission (O3), increases with altitude
37
between troposphere and stratosphere
tropopause
38
before ozone was formed
stratosphere would be constant T with altitude
39
black body
absorbs all electromagnetic radiation- appears black
| emits radiation dependent on wavelength and temperature
40
Planck function
describes radiative emission of a black body
41
Stefan-Boltzmann law
integration of the Planck function
F_BB = σ T^4
F is flux, σ is constant, T is in Kelvin
42
mean earth surface T and F
```
T = 289 K
F_BB = 396 W/m^2
```
43
Wein's displacement law
describes peak emission
as T of BB increases, emission peak moves to shorter λ
λ_max = b / T
λ_max is mx emission (µm), b is 2898µm K
44
some example λ_max
earth - 10µm (IR)
sun - ~500nm (visible)
largely different spectral regions
45
visible radiation absorption
not absorbed strongly by atmosphere
| most radiation absorbed is at the surface
46
thermal radiation absorption
absorbed strongly by atmosphere
47
epsilon
emissivity band of thermal radiation absorption
48
Earth energy balance
sunlight absorbed
| thermal radiation emitted
49
sunlight absorbed
earth absorbs energy from sun as a circle, some reflected back to space by clouds/atmos/surface
suns energy doesn't reach all points of earth at one time
50
absorbing area
π r_e^2
51
emitting area
4πr_e^2
52
thermal radiation emitted
earth emits thermal energy from a spherical surface
| emitting at all points on earths surface
53
effective temperature of emission
T_eff
| if earth had no atmosphere/greenhouse effect
54
effective temperature equation
S/4 (1-alpha) = σ T_eff^4
S is solar constant = 1368 W/m^2
alpha is albed = 0.3
55
attenuation
is the gradual loss in intensity of any kind of flux through a medium
56
attenuation of radiation in atmosphere
Reflectivity (R), Absorptivity (A), Transmissivity (T)
R + A + T = 1
reflectivity is also called albedo
57
solar radiation in the atmosphere, attenuation assumptions
R = A = 0
T = 1
'all insolation goes to E's surface'
58
thermal radiation in the atmosphere, attenuation assumptions
R = 0
A ~ 0.75
T ~ 0.25
all IR is absorbed and transmitted, no albedo of IR
59
Kirchoff's Law
A_λ = ε_λ
absorptivity = emissivity
only valid where the λ is the same on both sides
60
grey body
F_grey = ε σ T^4
| some fraction of the planck function, a function of every λ
61
Radiative equilibrium equations
surface
S/4 (1 -alpha) + ε σ Ta^4 = σ Ts^4
atmosphere
ε σ Ts^4 = 2 ε σ Ta^4
62
rearranging equilibrium equations gives you
Ts^4 = 2Ta^4 surface T is always bigger
63
a greenhouse gas is
a gas that absorbs thermal radiation
64
2 most important greenhouse gases
CO2, H20
65
strength of the greenhouse effect felt by a gas
depends on logarithm of abundance
| recall that an increase in 1 is an increased factor of 10 with logarithm
66
radiative forcing
change in net flux at tropopause (down minus up)
67
surface temperature changes is proportional to
radiative forcing
68
Earths surface T without greenhouse effect
~255K
69
greenhouse effect requires
absorption and re-radiation of thermal energy in atmosphere by greenhouse gases
that atmosphere is colder than surface
70
strongest radiative forcing change
if you add CH4 you'll see a stronger effect than CO2 because the base value is so low, log properties, larger change
71
Climate feedbacks
Planck (temperature) feedback (-)
Water vapour feedback (+)
Ice-Albedo feedback (+)
72
Planck feedback
solar forcing--> Temp--->outgoing thermal rad----.temp
| increase T = more energy emitted = cools down
73
water vapour feedback
amplifies T change
solar F-->T--->Atmos. H2O vapour--->greenhouse effect---. outgoing thermal radiation
could lead to runaway greenhouse if Planck feedback stopped working
74
saturation vapour pressure
e_s is proportional to exp T
equilibrium between liquid and gas
increase water vapour = increase T
e_s is pH2O
75
greenhouse forcing depend on
change of logarithm of gas abundance
76
strength of water vapour forcing depends
linearly on temperature change
77
Ice-albedo feedback
solar F-->solar radiation absorbed--->T---.albedo---.solar radiation absorbed
cold--snow---higher albedo---colder
where there is snow we can see a lower temperature
78
albedo examples
```
fresh snow 70-90
sea ice 50-75
desert 25-40
Forest/Grass 10-25
Ocean <10 -70 depending on incident ray
```
79
quick changing feedback
ice-albedo
| there is snow, or there isnt
80
tau
thermal optical depth
strength of greenhouse effect
tau = tau_CO2 + tau_H2O
81
steady state energy balance on daisy world (no atmosphere)
σ T^4 = (1 - alpha)F_s
| global albedo is a weighted sum of bare ground, black, white
82
solar flux on daisyworld
`increases linearly with time
83
daisyworld albedos
bareground: alpha_bare = 0.5
black: alpha_b = 0.25
white: alpha_w = 0.75
84
daisies are mesophile
growth rate beat depends on local T
| max at 22.5ºC, no growth above 40ºC or below 5ºC
85
daisy growth
(A)(x)(beta)
x = p - A_w - A_b
p is proportion of planet surface that is fertile
A_w is area covered by white daisies
86
daisy death
gamma A
87
daisyworld model
```
dA_w/dt = A_w ( x beta - gamma)
dA_b/dt = A_b ( x beta - gamma)
```
88
statement of Gaia hypothesis
Organisms and their material environment evolve as a single coupled system, from which emerges the sustained self regulation of climate and chemistry and habitable state for whatever is the current biota
89
what does Gaia hypothesis mean
life has controlling influence on physical/chemical climate
life changes atmosphere, maintains habitability through time
theory led to Earth System science
90
why earth is special
temperature and pressure allow all three phases of water
91
triple point of phase diagram
all 3 phases exist in equilibrium
| pressure on y axis, temperature on x
92
cryosphere
the frozen water part of the Earth system
93
southern hemisphere snow
snowy year round, not a lot of year round change
94
northern hemisphere snow
highly variable, huge variation w/ season, ice albedo changes are a function of the NH
95
antarctic sea ice cycle
not a lot of variation due to Antarctic circumpolar current
96
arctic sea ice minimum
september
97
forming a glacier requires
accumulation of multi-yr ice on land
| precipitation (snow) in winter and failure of this to melt fully in summer
98
consequence of temperature change with altitude in regards to snow/ice
mountains receive most precipitation
snowmelt least likely at high altitude, and on poleward facing slopes
mountain glaciers form first
99
glacier
valleys, follow topography
100
ice field
big glacier, still constricted by topography but 'drapes' topography, flow direction directed by topography
101
ice sheet
unrestricted by topography, covers it and goes where it wants
102
ice shelf
floats at edge of ice sheet/glacier
103
net ice build up
accumulation
104
net ice loss
ablation
105
above glacier equilibrium line
snow > melt
| accumulation zone
106
below glacier equilibrium line
melt > snow
| ablation zone
107
mountain glaciers in the absence of melt
can grow to form ice sheets
108
ice sheet-altitude feedback
growth of ice sheet--raises altitude of ice surface-- surface temperature is colder-- melt inhibited
positive feedback
109
ice sheet flow
from centre of ice dome (high pt.) outward
110
thicker ice sheet
more likely to slide at base
111
movement of ice as a function of base T
base > 0º, melt, wet base, glacier can slide, flow quickly, lubricated by melt-water percolated to bottom
base < 0º, bed frozen, glaciers flow more slowly, movement requires deformation
112
warming ice sheet
speed up flow--loss of altitude--warmer T--more melt
| positive feedback
113
glacial records
glacial valleys, moraines, striations, tillites, loess
114
ice rafted debris
piece breaks off of iceberg--flows away-- starts melting-- drops sediment-- can deform bottom sediment
115
glacial loess
When glaciers grind rocks to a fine powder, loess can form. Streams carry the powder to the end of the glacier. This sediment becomes loess
116
large ice cap instability
if ice reaches mid latitudes positive feedback will lead to global glaciation
from O-D energy balance model with ice-albedo feedback
117
small ice cap instability
if ice decreases too much it will all melt, no glaciation
| ice sheets don't get smaller, they collapse
118
north american ice sheets
lost: Laurentide, Cordillian, Scandanavian
remain: greenland
119
Phanerozoic/Proterozoic glaciations
```
Oligocene-Present (poles)
Devonian, Cretaceous, Permian
Ordovician- Siluria
Cryogenian (Neoproterozoic)
Siderian (paleoproterozoic)
```
120
faint young sun paradox
with lower S glaciation would be deep (with todays atmospheric composition)
yet geological evidence shows less glaciation earlier in history
stronger greenhouse?
121
isotope
same number of protons, different number of neutrons, same atomic number, different mass, same chemical properties, different physical properties
122
oxygen isotopes
16O - 99.76%
17O - 0.04%
18O - 0.2%
16,18 most commonly used for palaeoclimate
123
hydrogen isotopes
1H - 99.984%
| 2H - 0.016%
124
2H
deuterium 'D'
125
isotopologues
different forms of the same molecules, varying by isotopic composition
molecules with different isotopes, multiple heavy isotopes in one molecule, rare
ex. H2O with 0,1,2, deuterium
126
most common water isotopologues
(1H)2(16O)
(1H)2(18O)
(1H)(2H)(16O) - HDO
in order of commonality
127
isotopic ratio
R = rare X / common X
| ex. D: R = D/H = 0.016/99.984 = 0.00016
128
problem with isotope ratio
variations are very small numbers
129
delta notation ratio
δX = 1000 ((Rsample-Rstandard)/Rstandard)
| units are 'permil' parts per thousand
130
δD =
1000 [ ( (D/H)sample - (D/H)smow ) / (D/H)smow ]
131
SMOW
standard mean ocean water
| standard for H and O for ice sheets
132
isotopic mass balance
m_tot = m_1 + m_2
| m_tot δ_tot = m_1 δ_1 + m_2 δ_2
133
δ18Osmow =
0%o
134
negative delta isotope values
depleted in 18O
preferentially left behind
the more negative, the colder
135
saturation vapour pressure
describes amount of water vapour in equilibrium with liquid water
136
saturation vapour pressure of isotopologues
lower for heavier isotop., light isotopes evaporate preferentially
e_s((1H)2(16O)) is 1% lower than e_s((1H)2(18O))
e_s(HDO) is 10% lower than e_s((1H)2(16O)
137
water vapour isotopes compared to ocean water
water vapour is isotopically light
δ18O_wv < δ18O_ocean
δD_wv < δD_ocean
138
precipitation is isotopically heavy relative to water vapour
δ18O_wv < δ18O_precip
| δD_wv < δD_precip
139
as temperature decreases from the source region of moisture
increasingly higher fractions of the atmospheric water vapour have precipitated out
remaining water becomes increasingly isotopically light and further precipitation will be lighter
140
isotopic concentration of precipitate a function of
temperature at which precipitation occurs
141
precipitation is isotopically lighter
further from the source
| at higher altitudes
142
why ice cores are drilled at the summit of an ice cap
reduces distortion due to ice flow
143
stratigraphy of ice core with depth
~54m down- hard to see layers, use conductivity based on dust
~1800m down- clear layers can be seen
~3000m down- lots of sediment, layers may be lost
ability to resolve layers decreases with depth
144
ways to date stratigraphic layers
δ18O variation with seasonal cycle due to T variation
microparticle/glaciergeochemistry seasonal cycles
electrical conductivity- seasonal variations of contaminant load
reference horizons- radioactives, volcanic ash
145
trade off between time resolution of ice core and length of record
higher snow accumulation rate = better time resolution
faster accumulation = faster flow, shorter time record
longer record, lower resolution ex.greenland
146
why layers are thinner down ice core
pressure
147
why might δD be better than δ18O in ice
mass differences
H 1/2 (half of mass)
O 16/18
148
δD versus age graph
less (-), warmer T's, interglacials
| glacials last longer than interglacials
149
packed snow
firn
150
bubble formation in glacier
pressure of firn compresses packed snow into ice ~50m
100's of years at warm, high accumulation
1000's of yrs at cold, interior, low accumulation
151
age of air in ice
younger than ice itself (because they take so long to close)
| and they close at different times
152
pacemaker of ice-ages
insolation changes (which affect ice volumes)
153
isotopes of ice sheets
accumulation of ice sheet removes light isotopes
| ocean water become isotopically heavy
154
foraminifera
CaCO3 tests, must determine benthic vs. planktic
155
how forams represent ice volume
18O concentrated in CaCO3 relative to water (more with colder water), bust be planktonic (benthic waters don't show much T variation)
156
marine δ18O graph
y-axis is opposite- heavy = high ice volume = cold
157
Pleistocen glaciation
regular glacial-interglacial cycles
before 700ka periodicity = 40ka
after 700ka periodicity = 100ka
158
change in glacial-interglacial periodicity
mid-Pleistocene climate transition
159
why are glacial studies better from antarctic
right on the pole-harder to melt ice sheet, more information contained in that
arctic ice is away from the pole, higher insolation
160
Croll-Milankovitch theory
Eccentricity
Axial tilt
Precession
161
eccentricity
how elliptical earths orbit it
162
eccentricity periodicity
100,000yrs
163
what eccentricity does
changes distribution of solar energy throughout year
164
perihelion
closest to sun (right now in NH Jan)
| earth moving faster at this point of orbit to cover same amount of area
165
axial tilt
obliquity, the degree to which the axis is tilted changes
166
axial tilt periodicity
41,000yrs
167
axial tilt implications
changes strength of season
168
aphelion
earth farthest from sun
169
if obliquity were 0
no seasons
170
precession
wobble, change in where N/S axis points
171
precession periodicity
23,000 yrs
172
precession implications
relative strength and length of seasons
173
Croll-Milankovitch theory explains timing of glaciations
NH summer insolation is critical in determining ice volume, summer insolation determines whether glaciers survive ice-albedo feedback, most land mass- largest changes in ice extent
174
organic carbon dominantly fixed by
oxygenic photosynthesis
CO2 + H2O + hv ---- CH2O + O2
inorganic matter reduced to organic matter
175
aerobic respiration
CH2O + O2 --- CO2 + H2O
176
photosynthesis + aerobic respiration
closed cycle
177
decomposition of organic carbon in oxygen low environment
fermentation followed by methanogenesis
| net: 2CH2O --- CO2 + CH4
178
inorganic carbon
HCO3 -
CO3 2-
H2CO3
179
counter reaction to fermentation/methanogenesis
CH4 + 2O2 -- CO2 + 2H2O
| again, closed system
180
carbon reservoir cycling
biological reservoirs cycle quick
| geochemical reservoirs cycle slow
181
atmospheric CO2 reservoir
760
photosynthesis takes 60 out
60 goes back in, fast cycling
182
residence time
tau = steady state reservoir size / flux
| ex. 760 / 60 = ~13 yrs
183
basic structure of the ocean
2 layers: Mixed layer, deep ocean
184
mixed layer
~100m, geochemical equilibrium with atmosphere, well mixed by wind
185
ocean gradients
thermocline
chemocline
light penetration
186
thermocline
sudden small T decrease then, decreases gradually with depth down to ~100m where it reaches the minimum and stays ~constant
187
chemocline
ex. nutrient availability, abrupt decrease with depth
188
light penetration gradient
gradual decrease, area light penetrates = photic zone
189
Henry's law
```
assuming air-sea surface gas exchange in equilibrium
[x] = k_H px
[x] dissolved molar concentration (M)
k_H henrys law constant (M/atm)
px partial pressure (atm)
```
190
1atm =
101325 pa
191
gases are more soluble in
cold water
192
DIC reservoirs, smallest to biggest
H2CO3
CO2
CO3 2-
HCO3 -
193
carbonate chemistry
collective chemistry of DIC species
194
conserved oceanic carbon quantities
DIC
| Alkalinity
195
DIC =
[CO2] + [H2CO3] + [HCO3 -] + [CO3 2-]
196
Alkalinity
expresses charge balance, net + charge from conservative ions balanced by net - charge of weak acids
197
circumneutral conditions in ocean
pH > 4
198
pH =
- log [H+]
199
conservative ions
ions that don't do much chemistry at ciarcumneutral conditions in ocean, salts, net +
[Na+] - [Cl-] + 2[Mg 2+] + 2[Ca 2+] > 0
200
Alkalinity, Alk =
[HCO3 -] + 2[CO3 2-] - [H+]
201
DIC reactions
CO2 + H20 -------- H2CO3
H2CO3 -------- H+ + HCO3 -
HCO3 - -------- H+ + CO3 2-
202
increasing pCO2
increases [CO2] -- increases [H2CO3] --- increases [H+] and [HCO3-] --- increases [HCO3-] ---- decreases [CO3 2-]
increased hydrogen ions, decreases pH, ocean acidification
203
why do we subract [Cl-] in conservative ion equation
because we are adding up the positive charges
204
pCO2 in DIC vs. Alkalinity graph
below ~where we are now (~0) - not possible
| increasing in DIC = increased pCO2 (up to ~6µatm)
205
CO3 ^2- in DIC vs. Alkalinity graph
proportion of CO3 that is DIC
now ~0.2, slightly above 'possible range'
increases in a very narrow band with increasing alkalinity up to 1
narrow band beyond the 1 that is 1 - (~0.2)
majority of the graph space is 0
206
HCO3 ^- in DIC vs Alkalinity graph
proportion of DIC that is HCO3 ^-
currently pretty close to 1
thin strip going down to zero below where we are now, most of graph space is above where we are now and decreases gradiently to 0
207
CO2 in DIC vs. alkalinity graph
proportion of DIC that is CO2
currently 0
increases gradiently above present value, most of graph space is 1
208
pH in DIC vs. alkalinity graph
currently 7-9
7+ is all in a very narrow band, around where we are now
above present day values graph space is 5-3
209
where we are now in terms of DIC and alkalinity
DIC ~ Alkalinity ~ 10^3
210
If DIC were >> alkalinity
pCO2 - high (6µatm)
pH - low (3)
~all Carbon is in CO2
211
if alkalinity >> DIC
can't be
| this is the 'impossible' part of the graph
212
if alkalinity and DIC both maxed
pCO2 medium (~3-4)
pH - ~8
most Carbon in HCO3 ^1
note that this is very similar to current conditions- staying along line of same slope
213
why - [H+] in Alk equation
adding up the negative ions
| ** H+ is generally negligible anyway
214
max alkalinity
all carbon in carbonate
Alk = [HCO3] + 2[CO3] - [H+]
the 2 coefficient is key, how to maximize equation
215
if Alkalinity = DIC
all carbon in HCO3
216
alkalinity high relative to DIC
carbon mostly in carbonate
| very little carbon in CO2
217
decrease in alkalinity : DIC
transition to CO2 dominance
218
weathering rocks
adds to DIC and alkalinity
219
adding CO2 from atmosphere
only increases DIC
220
alkalinity units
we have been saying M (concentrations), but its actually supposed to be measured in equivelants/L
221
solid calcium carbonate precipitation from ocean
Ca^2+ + CO3^2- ------- CaCO3(s)
222
solubility product
k_sp = [Ca^2+]_sat . [CO3^2-]_sat
products over reactants, only reactant is solid {1}
note that this equation is derived from the reverse equation of CaCO3 precipitation
223
saturation product
Ω = [Ca^2+].[CO3^2-] / k_sp
224
Ω < 1
subsaturated
| CaCO3 dissolves
225
Thermodynamic Theory
Ω < 1 subsaturated
Ω = 1 saturated
Ω > 1 supersaturated
Ω > 3 biological precipitation
226
Ω > 1
supersaturated
| CaCO3 precipitates
227
Ω > 30
authigenic precipitation (abiotic)
228
CaCO3 polymorphs
calcite
| aragonite
229
aragonite properties
k_sp: 6.5x10^-7 mol^2/kg^2
| Ω: 4
230
calcite properties
k_sp: 4.3x10^-7
| Ω: 6
231
more soluble CaCO3 polymorph
aragonite- lower Ω, get to saturation point at lower concentration
232
decrease in ocean [CO3 ^2-]
decrease in saturation product (Ω)
| problem for calcifying organisms
233
k_sp,cal/arag =
( [Ca2+].[CO3^2-] )_sat,cal
234
Ω_cal/arag =
[Ca2+][CO3^2-] / k_sp,cal/arag
235
variations in k_sp dominated by
depth (pressure)
236
as pressure increases k_sp
increases (solubility increases)
237
solubility increase with depth
2X / 4km depth
238
biologically precipitated CaCO3
sinks when organisms die-- sedimented or dissolved in deep
239
CCD
carbonate compensation depth
rain rate of CaCO3 = CaCO3 dissolution
no sediment below
240
preservation of CaCO3 in sediment
~20-30%
241
depth that Ω = 1
saturation horizon, Lysocline
| CaCO3 starts to dissolve
242
lysocline graph
Ω relatively high in surface
decreasing to saturation horizon
stays at 1 with increasing depth until reaches CCD then decreases further to 0
243
change in [CO3^2-] dominate
over changes in [Ca2+]
244
surface [CO3^2-] =~
250µmol/kg
245
Atlantic depth characteristics
deep ocean [CO3^2-] - 113µmol/kg
| saturation horizon - 4.5km
246
Indian ocean depth characteristics
deep ocean [CO3^2-] - 83µmol/kg
| saturation horizon - 3km
247
North Pacific ocean depth characteristics
deep ocean [CO3^2-] - 70µmol/kg
| saturation horizon - <1km (not much CaCO3 sediment)
248
more deep ocean [CO3^2-]
deeper saturation horizon
| Ω = Ca x CO3 / ksp --- increase CO3 = increase Ω
249
deepest saturation horizon of the 3 oceans
Atlantic
250
changes in surface when CaCO3 precipitates
alkalinity decreases by 2 units
| DIC decreases by 1 unit
251
changes in deep ocean when CaCO3 dissolves
Alkalinity increases by 2 units
| DIC increases by 1 unit
252
carbonate pump
moves CaCO3 from surface to depth
253
why ocean carbon reservoir is so large
more C is stored in deep ocean than there would be if ocean was in equilibrium with atmosphere
254
Walker 1983
carbonate sedimentation throughout earths history constrains oceans chemistry and atmospheric composition
255
DIC is fixed to organic carbon by
photosynthesis in surface ocean
256
photosynthesis
CO2 + H2O == CH2O + O2
257
total organic carbon
GPP
258
GPP
gross primary productivity
259
total organic carbon after respiration by producers
NPP
260
NPP
net primary productivity
261
carbon sinking out of photic zone due to organism death
export production
262
in deep ocean most sinking carbon is
respired
263
carbon in deep ocean that is buried in sediment
burial flux
264
burial flux percentage of carbon in deep ocean
0.1%
265
organic carbon buried in sediment
massive deposits
266
massive deposits
black shale
| up to 10% organic carbon
267
how much organic carbon is needed to turn sediment black
only a few %
268
pockets of organic carbon
diffuse deposits, kerogen
269
organic carbon fluxes
GPP - 100GtC/yr
NPP - 50 GtC/yr
export production - 10 GtC/yr
Burial flux - 0.1 GtC/yr
270
organic carbon that makes it out of surface ocean into deep ocean
~10%
271
carbon isotope ratios
12C - 0.9893
13C - 0.0107
14C - 10^ -17
272
stable carbon isotopes
12C
| 13C
273
molecules with different isotopic compositions
isotopologue
| ex. 13CO2
274
δ (‰) =
[ R_sample / R_standard - 1 ] x10^3
275
R_sample or R_standard =
heavy isotope / light isotope
| ie. 13C/12C
276
carbon standard
Pee Dee Belemnite (PeeDee formation)
277
R [13C/12C] PDB
0.011237
| δ 13C= 0‰
278
R [13C/12C] CO2_atmospheric
0.01114486
| lower than ocean
279
( - ) isotope values
depleted
280
permil
no units
| ≠ ppt (mass/volume)
281
δ 13C _CO2, atmospheric
-8.2‰
282
δ 13C_organic
~ -25‰
| -20 - -40‰
283
δ 13C_carbonates
~ 0‰
284
δ 13C_HCO3-
~ 0‰
285
δ 13C_volcano
-5‰
286
δ 13C_fossil fuel
very low
| graph of δ13C vs time is a decreasing trend, almost exact opposite of CO2 accumulations
287
fractionate
vibrational movements/energy differs btw. isotopes
light isotope bonds are weaker relative to heavy
light isotopes are easier to evaporate relative to heavy
288
vibrational movement graph
```
# of atoms vs. velocity
normal distribution, most atoms in mean area, some in tails
tails of distribution are longer in light isotopes
```
289
fractionation steps in plants
diffusion
| carboxylation
290
Diffusion
ε = 4.4‰
lighter molecule enters cell preferentially
cell depleted in 13C
291
carboxylation
ε = (-15) - (-30)‰
energetically expensive process
easier to break bond in light isotopes
292
ε
difference in δ values between 2 species
293
after 2 steps of fractionation
cell becomes ~ -25‰
| but this depends on whether we are talking about land or ocean plants
294
why does overall plant cell depletion depend on land/ocean
source of original carbon that is taken into cell in step 1
air: -8.2‰
HCO3- : 0‰
295
surface carbon cycle
F_in = F_org + F_carb = F_out
296
F_in
volcanoes
| -5‰
297
F_org
ΔB
| -25‰
298
F_carb
δ 13HCO^3-
| 0‰
299
ΔB
biologic fractionation
300
f_org =
F_org / F_in
= δin - δcarb / δorg - δcarb
= ( -5 - 0 ) / ( -25 - 0 ‰ ) = 1/5 = 0.2
301
which F is stable through earths history
Fin
302
% of carbon buried as organic carbon
20%- preserves oxygenated state of atmosphere
303
increase in δ 13C_carb
more f_org
| higher productivity
304
increase in f_org
burying alot of light carbon so δ13C increases because f_carb decreases, have to maintain isotopic balance
305
represent ordinary continental silicate rocks as
CaSiO3
306
ordinary continental silicate rocks
granite, basalt
307
carbonic acid in rain
2[CO2 + H2O --- H2CO3]
308
continental rocks weathered by carbonic acid in rain
CaSiO3 + 2H2CO3 --- Ca^2+ + 2HCO^3- + SiO2 + H2O
309
consequence of weathering continental rocks
draws down 2CO2 from atmosphere, transfers Ca,2HCO3 to ocean
310
continental rock weathering drawing down CO2
2CO2 removed from atmosphere = 2 units of DIC
311
continental rock weathering transferred ions
add 2 units of DIC
| add 2 units of Alk
312
net changes from weathering of continental rock
ocean gain:
0 units DIC
2 units Alk
atmos. CO2 cancelled out by ocean CO2 (Henrys Law)
313
why can we call the atmospheric CO2 ~ ocean CO2, and cancel out gains and losses?
because they equilibrate so rapidly
314
continental rock weathering shifts carbon
from CO2 -- CO3 ^ 2-
315
shifting carbon from CO2 to CO3 ^2- results in
increase in CaCO3 saturation
| higher CaCO3 deposition
316
weathering continental rock, shifting carbon equations
Ca^2+ + 2HCO3- --- Ca^2+ + CO3^2- + H2O + CO2
| Ca^2+ + CO3^2- ----CaCO3
317
overall, weathering of continental silicate rocks
CO2 + CaSiO3 --- SiO2 + CaCO3
318
weathering of silicate rocks is
a CO2 sink
319
silicate weathering followed by carbonate deposition causes a
drawdown of CO2
320
weathering rates depend on
temperature
[H2CO3]_rain
supply of H2CO3
321
temperature for weathering is a function of
pCO2
322
[H2CO3] of rain (for weathering) is a function of
pCO2
323
supply of H2CO3 for weathering is a function of
rainfall rate, which is a function of T
324
** weathering rates directly depend on
pCO2
| Temperature
325
silicate weathering cycle feedback
negative feedback on T over geologic time
volcanic/meta. CO2 flux--> atmos.CO2--> surface T-->silicate weathering + carbonate deposition--. atmos CO2
also a line from atmos.CO2-->silicate weathering
326
reverse of weathering
carbonate metamorphism
| CaCO3 + SiO2 --> CaSiO3 + CO2
327
in silicate weathering feedback what are the arrows from surface T to silicate weathering/carbonate deposition
reaction rate
| rainfall rate
328
in silicate weathering feedback what is arrow from atmospheric CO2-->silicate weathering/carbonate deposition
[H2CO3]_rain
329
carbonate metamorphism depends on
amount of CaCO3 rock
tectonism (uplift)
volcanism
330
carbonate metamorphism does not depend on
pCO2
T_surf
no feedback
331
silicate weathering feedback is also called
WHAK feedback
332
WHAK
Walker, Hayes, and Kasting, 1981
333
silicate weathering timescales
```
τ = AO carbon / silicate weathering
τ = 40,000 PgC / 0.03PgC/yr
τ = 4/3 x 10^6 yr
```
334
based on timescales silicate weathering is important for
10^5 yr scales
| 1 000 000
335
other factors affecting weathering rates
```
rock type
changes in uplift rate
biotic enhancement of weathering
biotic control
amount of shelf seas
location of CaCO3 deposits
spreading/volcanism rates
```
336
biological pump schematic
surface: DIC --via NPP----C_org---via Respiration---DIC
C_org-- Out of surface ocean
deep ocean: from C_org in surface--- EP--burial flux (down)
EP--- DIC--- back up to surface ocean via upwelling
Burial flux---- C_org buried (down into sed.)
Burial flux---- back up to DIC (respiration)
337
biological pump changes in surface ocean
CO2 + H2O -- CH2O + O2
C_org fixed removes
1 Unit DIC
0 Unit Alk
338
biological pump changes in deep ocean
adds
1 Unit DIC
0 Unit Alk
339
biological pump compared to carbonate pump
like: more DIC moved to deep ocean
unlike: increases DIC relative to Alk (no change in Alk)
340
biological pump moving DIC but not Alk
acidifies deep ocean
enhance CaCO3 dissolution
raises CCD
341
CaCO3 dissolution is especially enhanced (by biological pump)
in top of sediment column (~few cm's)
342
organic carbon and oxygen
are intrinsically linked
| added and removed by a closed biological cycle
343
oxygen variability in different ocean layers
surface- source
deep- sink
sediment- sink
344
surface oxygen source
oxygenic photosynthesis
345
deep ocean oxygen sink
aerobic respiration
346
ocean sediment oxygen sink
aerobic respiration (only if O2 available)
347
spatial variability of oxygen forms
gradients
348
low O2 supple or high C_org flux
anoxia (all O2 used)
349
anoxia leads to
enhance C_org burial- anaerobic respiration is less effective
350
anoxia example
saanich inlet- deep sill limits cycling of water, oxic layer overlays anoxic layer, bottom sediment is dark C_org
351
*** major long term O2 source
burial of organic carbon
352
burial or organic carbon
CO2 + H20 -- CH2O + O2
CH2O buried- form rock
O2 left over--- atmosphere
353
O2 in C_org burial
accumulates as by-product
354
** long term oxygen sink
oxidative weathering or organic sedimentary rock
355
carbon fluxes that affect oxygen
GPP 100GtC/yr-- 99.9% respired (big flux)
| Burial 0.1GtC/yr-- allows accumulation (small flux, big change over geologic time)
356
what happens to sediment
deposited in ocean crust
| deposited/accreted on continent
357
carbon deposited on ocean crust
deposited on ocean crust--- sea floor spreading, ocean crust to trench--- subduct--- carbon into mantle
trench-~- scrape off sediment-- part of continents
subduct-~- devolatilize slab--- c to atmos. as CO2/CO via arc volcano
358
carbon deposited on continents
deposited/accreted on continent--- tectonic uplift--- weathering--- carbon to atmos/ocean system
uplift-~- metamorphism-- carbon to atmos./ocean system
359
weathering of silicate rocks is a
CO2 sink
360
CO2 drawdown
silicate weathering followed by carbonate deposition
361
weathering rate depends on
temperature
[H2CO3]
supply of H2CO3
362
temperature is a function of
pCO2
363
[H2CO3]_rain is a function of
pCO2
364
supply of H2CO3 is a function of
rainfall rate... function of temperature
365
weathering rate directly depends on
pCO2 and temperature
366
geology and climate
are inherently linked over geologic time
| silicate weathering cycle is (-) feedback on T over geologic time
367
reverse of weathering
carbonate metamorphism
368
carbonate metamorphism
CaCO3 + SiO2 --- CaSiO3 + CO2
369
carbonate metamorphism depends on
amount of CaCO3 rock
tectonism (uplift)
volcanism
370
carbonate metamorphism does not depend on
pCO2
| T_surf
371
silicate weathering feedback
volcanic/metamorphic CO2 flux--> atmos. CO2--> surface T--> silicate weathering followed by carbonate deposition--. atmos. CO2
also.. atmos CO2--> silicate weathering
372
in silicate weathering feedback what is the surface T ---> silicate weathering
1. reaction rate
| 2. rainfall rate
373
in silicate weathering feedback what is the atmospheric CO2 ---> silicate weathering
[H2CO3]_rain
374
silicate weathering feedback is called
WHAK feedback
375
WHAK feedback
Walker, Hayes, and Kasting, 1981
376
residence time
tau = AO carbon / silicate weathering = 40,000 PgC / 0.03 PgC/yr = 4/3 x10^6 yr
377
other factors affecting weathering rate
rock type
changes in uplift rate
biotic enhancement of weathering
378
how rock types affect weathering
Basalt weathers easily- unstable mineral structure at surface P,T
granite doesnt
379
how changes in uplift rate affect weathering rate
supply of weatherable rock
380
how biotic enhancement affects weathering rate
plants acidifying soils
381
factors affection carbonate precipitation
biotic control
| amount of shelf seas
382
biotic control of carbonate precipitation
Ω: 3 vs. Ω: 30
| biogenic precipitation or authigenic
383
factors affecting CO2 flux
location of CaCO3 deposits
| spreading/volcanisms rates
384
cenozoic basics
65ma
good, detailed records
rise of mammals
385
major events at bottom of cenozoic
K-T extinction (dinosaurs)
386
boundaries in geologic time are usually set by
biostratigraphy
387
earth 65ma
Europe fragmented
India in Indian ocean
Australia very south
388
earth 50ma
atlantic opens more
| India moves north
389
earth 35ma
collisions between India/Asia begin
| Australia moves north
390
earth 20ma
drake passage opens
India 'in place'
lower sea level
Europe closing up
391
drake passage
area between SA and antartica
392
earth now
Panama shut
| very clear circumpolar seaway
393
Eocene
last hothouse climate
| start to get antarctic glaciation near end
394
deconvolve ice volume
subtracting ice volumes to get T changes
| relating deep ocean T to surface ocean T
395
deep ocean temperature tells
mostly about polar temperatures
| really cold bottom waters formed underneath ice shelf
396
determining past climate from stomata
bigger stomata = lower CO2 levels
397
warm epochs
paleocene
eocene
high levels CO2
398
cool epochs
oligocene
miocene
pliocene
CO2 drop from Eocene - Oligocene
399
~20ma cooling from
india ramming into asia-- himalayans-- monsoons and weathering
400
strontium isotopes
87Sr / 86Sr
401
87Sr
daughter product of rubidium, accumulates in continental rocks
402
increase in 87Sr
increased weathering of continental rocks
403
Tunguska treefall
Siberia, radial downfall of trees 40-50km, trees in middle didn't fall
404
why didn't trees in middle of impact zone fall down
blast wave goes straight down under 'bomb', doesn't push trees over
on edges wave pushes trees outwards
405
why was there a blast wave
exploding rock increases T and PV, area surrounding rock is intensified in pressure, Heating causes rapid expansion; the air explodes outwards as blast wave
406
ideal gas law
pV = nRT
407
The velocity of a meteorite
from summing the escape velocity and some fraction of the Earth's orbital velocity in quadrature
408
velocity of meteorite, v =
√ v^2 + ( 1/a . v_orbit )^2
409
v escape =
√ 2GM / r
| M into page
410
v orbit =
√ GM / d
| M out of page
411
typical a
2
412
typical impact velocity
19 km/s
413
specific energy of a meteor
e_k = 1/2 . v^2
414
impacts compared to explosives
typical impact is 41X the specific energy of an explosive
impact = 1.7x10^8 J kg
TNT = 4.2x10^6 L kg
415
simple crater
one impact zone with fracturing, breccia, impact melt, and impact ejecta on sides of crater
416
complex crater
central peak uplift in middle
| also fracturing, breccia, impact melt, impact ejecta on sides, sides are rougher
417
why 1/a in velocity equation
what fraction of orbit speed is taken into account
| ex. if rock is going to earth along earths orbit, orbit speed is negligible
418
arizona crater
best preservation
419
craters usually not well preserved
plate tectonics
vegetation
hydrologic cycle/weathering
420
central peak
rebound from impact
421
crater rim
excavated material
422
knowing amount of material excavated in crater
allows estimate of energy of impact and mass of bolide
423
Yucatan Peninsula, Mexico
Chicxulub crater (hit ground)
424
using craters for dating
amount of craters vs. how often craters occur
425
within 10 sec of impact
vaporization of impact material
| local/regional blast damage
426
within 1 min of impact
fires set by fireball
427
within 10min of impact
ejecta, burial
| earthquake, landslides, tsunami
428
within 1 hour of impact
ejecta enter atmosphere
429
hours-year of impact
```
worldwide wildfires, smoke
total darkness
impact winter/ global cooling
ozone destruction by NOx
acid rain
geochemistry changes, nothing can grow
```
430
years-millenia after impact
higher CO2- global warming
acid rain, warming-- faster weathering
mass extinctions
431
impact winter
massive amounts of dust in atmosphere, absorb all incoming sunlight
432
NEOs
nearth-earth objects
433
Power law
population of NEOs used to estimate frequencies of collision sizes
434
power law graph
cumulative probability of impact/ yr (higher probability at top) vs. impact energy
decreasing graph
other y axis: average interval between impacts (yrs, decreasing up)
435
what breaks down ozone
water- water doesn't really make it to stratosphere because troposphere cools with altitude
436
extinctions are usually from
consequences of impact, not impact itself
437
large impact basin on moon
Orientale, Imbrium
438
early bombardment era
more frequent, bigger impacts
| lots of stray bodies floating around in early solar system
439
late heavy bombardment
as evidenced by impact melts in lunar rocks dating 3.8-3.9Ga
| may have been 0-4 ocean vaporizing impacts on earth
440
power law today vs. hadean
todays line is lower, power of 10 lower intercept
441
energy of impact required to vaporize ocean
10^34 - 10^36
442
energy of KT impact
~10^31
443
energy of imbrium impact
~10^33
444
vaporizing the ocean
vaporize water and rock-- release greenhouse gases and steam = steam atmosphere-- LWR can't escape
in time, everything rains out and reforms ocean
445
time for ocean evaporation
few months
446
time for formation of clouds and total drying of surface
1000 years
447
time for cloud tops to cool, rain, and reform ocean
2000 years
448
Tunguska event features
peewee, R >40m, local effects, romantic sunsets
449
K-T impact summary
large, R >10km, half os species extinct, T changes, fires, darkness, chemical changes
450
Moon forming event summary
super colossal, R >2000km, melt planet, drive off volatiles, wipe out life on planet
451
the late veneer
delivery of volatiles to earth due to impacts
| ocean came from comets
452
mass flux of meteorite material to earth
10-100tons per day (mainly micrometeorites)
| may add condensation nuclei
453
cretaceous time
145-55mya
454
cretaceous paleogeography
opening and closing of tethys sea
| ~105mya NA, SA, and Africa start to become familiar looking
455
superchron
A superchron is a polarity interval lasting at least 10 million years. There are two well-established superchrons, the Cretaceous Normal and the Kiaman
456
transgression
sea level rise
457
regression
sea level drop
458
sea level 150-65mya
apparently theres a transgression?
459
why did the magnetic field not switch directions for much of the cretaceous
geomagnetic dynamo- sucking heat across core/mantel boundary, hard to reverse poles
460
how often do geomagnetic reversals typically occur
in the last 20ma every 200,000- 300,000yr, although it has been more than twice that long since the last reversal
In the last 10 million years, there have been, on average, 4 or 5 reversals per million years
461
superplume
occurs when a large mantle upwelling is convected to the Earth's surface
should not be confused with a hot-spot- a superplume forms at the mantle-core boundary while a hot-spot occurs at the mantle-crust layer
create cataclysmic events, affect whole world when explode
462
geodynamo and core mantle heat flux
continental scale superplume
| huge areas of marine volcanism
463
super plume needs a
superchron (Big Black Bar)
464
why was there a transgression
young hot crust- buoyant and elevated = more mantle upwelling = lower continent
lower continent + displaced H2O = sea level rise = transgression
465
LIP
large igneous province
466
large igneous province
extremely large accumulation of igneous rocks, including liquid rock (intrusive) or volcanic rock formations (extrusive)
hot magma extrudes from inside Earth and flows out, source of LIPs is mantle plumes or plate tectonics
467
cretaceous LIPs
~10 at the pacific MOR.. when atlantic was ~newly formed
468
cretaceous events
superplume + dynamo
Big Black Bar
fast spreading rate + transgression
extensive, massive chalk deposits
469
equator to pole range no
equator: 27ºC
pole: -21ºC
470
equator to pole difference cretaceous
equator: 42ºC
Pole: 18ºC
471
cretaceous CO2
~2000ppmv
| higher volcanism = higher CO2
472
polar amplification
any change in net radiation balance = larger T change near poles than the planetary average
poles increase faster than equator
473
Strontium isotopes
84Sr: 0.56%
86Sr: 9.86%
87Sr: 7.00%
88Sr: 82.58%
474
heat transport
movement of energy from equator to poles
475
cretaceous heat transport
must have been higher since poles were warmer
| mostly due to ocean transport
476
primordial isotope
nuclides found on the Earth that have existed in their current form since before Earth was formed
ex. all 4 Sr isotopes
477
radiogenic Sr isotope
87Rb---- 87Sr
| t1/2 = 4.88x10^10yr
478
Sr will substitute for
Ca
479
Rb is
lithophile
| incompatible in mantle, found dominantly in continents
480
changes in 87Sr/86Sr
increasing: weathering of continents
decreasing: more basalt creation
87Sr decay on cont., 86Sr seafloor
481
if 87Sr/86Sr decreasing
more basalt creation = more mantle flux = rise in sea level
482
sea level rise in geologic history 90-100ma
associated with increase in 87Sr/86Sr- not what would be expected
coastal weathering from inland seas, increased mid latitude precipitation
483
cretaceous chalk deposits
high Alk by increased continental weathering (silicate weathering)
484
why increased continental weathering in cretaceous
superplume pushes up sea level- increase silicate weathering- higher CaCO3 deposit- anoxic bottom waters leave thick organic layers
485
anoxic events from
rise in temperature
| loss of O2 through thermohaline circulation due to respiration
486
anoxic events cause
thick organic rich layers
487
respiration
CH2O + O2 -- CO2 + H2O
488
carbon burial efficiency =
burial flux / depositional flux
using O2 buries C
high burial efficiency = low O2
489
OAE
ocean anoxic events
| geologically short, <1Myr
490
contributors of OAE
```
warm ocean, low O2 solubility
high C burial efficiency
high P supply from weathering/flooding
nutrient trapping in enclosed basins
Enhanced P regeneration under anoxic bottom waters
```
491
Redfield ratio
C:N:P = 106:16:1
492
sources of C,N,P
C,N have atmos. cycles, more available
| P only source is cont. weathering
493
why does increased P contribute to anoxia
it is generally the limiting resource ( + feedback)
494
P burial efficiency
lower when anoxic
495
EECO
early eocene climate optimum
496
climate optimum
broad scale warm climates
| high CO2
497
after EECO
oligocene glaciation---sea level drop-- MMCO
498
basalt weathering
2-10X faster than granite- less stable minerals at surface conditions
499
most important if basalt is
in equatorial/ITC region-- hot and wet-- lots of weathering
500
ITC location
moves throughout year
501
Deccan traps
basalt traps in India, 120Ma in SH, 65-30Ma migrate through ITC- major weathering
502
movement of Deccan traps through ITC represents
Drift-weathering hypothesis
503
why are Ethiopia traps less of a CO2 draw down
right on ITC but E side of continent-- drier climate
504
peak in basaltic + mixed blocks
~40-60Ma, also peak in all land mass, and granitic + sedimentary crust
consistent with EECO peek
hypothesis only considers CO2 sink (increased weathering)
505
processes in interpreting paleoclimate
isotope records
look at graphs
build models
plate tectonics
506
residence time =
steady state reservoir size / flux
507
drift hypothesis
weatherable rocks drifting through high weathering zone
508
sign of an OAE
a lot of chalk (Dover)
509
weird think about OAE feedback
burying Corg is usually a nutrient loss (would be a - feedback) but in an AE, nutrients are easier to 'strip out'--- + feeback
510
when we talk about OAE's we mean what part
whole ocean except top ~100m's
