Transcript IV. Intersection: what we know, would like to know, will never know, and what can we contribute to the debate. III.

IV. Intersection: what we know, would like to know, will
never know, and what can we contribute to the debate.
III. Atmospheric & Ocean Biogeochemistry: Second
element of climate and environmental science
Atmospheric and ocean composition, past and
present
Human impact, global change
II. Atmospheric & Ocean Physics: First element of
climate and environmental science
Atmospheric structure (T, P in "4-D")
Winds, Weather, General Circulation, Climate
I. Physical Principles: The foundation & the tools
Newton's laws: forces, pressure, motion
Energy: Temperature, radiant energy
BioGEOCHEMICAL CYCLES
THE EARTH: ASSEMBLAGE OF ATOMS OF THE 92 NATURAL ELEMENTS
•
Most abundant elements: oxygen (in solid earth!), iron (core),
silicon (mantle), hydrogen (oceans), nitrogen, carbon, sulfur…
•
The elemental composition of the Earth has remained essentially
unchanged over its 4.5 Gyr history
– Extraterrestrial inputs (e.g., from meteorites, cometary
material) have been relatively unimportant
– Escape to space has been restricted by gravity
•
Biogeochemical cycling of these elements between the different
reservoirs of the Earth system determines the composition of the
Earth’s atmosphere and oceans, and the evolution of life
BIOGEOCHEMICAL CYCLING OF ELEMENTS:
examples of major processes
Physical exchange, redox chemistry, biochemistry are involved
Surface
reservoirs
HISTORY OF EARTH’S ATMOSPHERE
N2
CO2
H2O
O2
oceans CO2
form
dissolves
Outgassing
4.5 Gy
B.P
Life forms
in oceans
4 Gy
B.P.
O2 reaches
current levels;
life invades
continents
Onset of
photosynthesis
3.5 Gy
B.P.
0.4 Gy
B.P.
present
Source: EARLY EARTH Oxygen for heavy-metal fans: Lyons TW,
Reinhard CT
COMPARING THE ATMOSPHERES
OF EARTH, VENUS, AND MARS
Venus
Earth
Mars
Radius (km)
6100
6400
3400
Surface pressure (atm)
Mass (1024 kg)
91
4.87
1
5.98
0.007
0.64
CO2 (mol/mol)
0.96
3x10-4
0.95
N2 (mol/mol)
3.4x10-2
0.78
2.7x10-2
O2 (mol/mol)
6.9x10-5
0.21
1.3x10-3
3x10-3
1x10-2
3x10-4
H2O (atm, mol/mol)
H2O (total, bars)
0.3
400
2 x 10-6
Atmospheric
Composition
(average)
1 ppm= 1x10-6
red = increased by
human activity
¶
Gas
Mole fraction
Nitrogen (N2)
0.78
Oxygen (O2)
0.21
Water (H2O)
0.04 to < 5x10-3; 4x10-6 -strat
Argon (Ar)
0.0093
Carbon Dioxide (CO2)
385 370x10-6 (date: 2009 2000)
Neon (Ne)
18.2x10-6
Ozone (O3) ¶
0.02x10-6 to 10x10 –6
Helium (He)
5.2x10-6
Methane (CH4)
1.7x10-6
Krypton (Kr)
1.1x10-6
Hydrogen (H2)
0.55x10-6
Nitrous Oxide (N2O)
0.32x10-6
Carbon Monoxide (CO)
0.03x10-6 to 0.3x10-6
Chlorofluorocarbons
3.0x10-9
Carbonyl Sulfide (COS)
0.1x10-9
Ozone has increased in the troposphere, but decreased in the stratosphere.
NOAA Greenhouse Gas records
How is the composition of Earth's
atmosphere controlled by geochemical
and biological processes ?
FAST OXYGEN CYCLE: ATMOSPHERE-BIOSPHERE
• Source of O2: photosynthesis
nCO2 + nH2O -> (CH2O)n + nO2
• Sink: respiration/decay
(CH2O)n + nO2 -> nCO2 + nH2O
O2 lifetime: 5000 years
CO2
Photosynthesis
less respiration
O2
orgC
litter
orgC
decay
…however, abundance of organic carbon in
biosphere/soil/ocean reservoirs is too small to control
atmospheric O2 levels
SLOW OXYGEN CYCLE: ATMOSPHERE-LITHOSPHERE
O2 lifetime: 3 million years
O2: 1.2x106 Pg O
O2
OCEAN
Photosynthesis
decay
CO2
Fe2O3runoff weathering
H2SO4
FeS2 orgC
CONTINENT
orgC
Uplift
burial
CO2
orgC: 1x107 Pg C
FeS2: 5x106 Pg S
microbes
SEDIMENTS
CO2
O2
orgC
FeS2
Compression
subduction
Antarctic Ice Core Data
CO2 varies over geologic time, within the range 190 – 280 ppm for the last
420,000 years. The variations correlate with climate: cold  low CO2 . Is
CO2 driving climate or vice versa?
The heavier temperature lines 160,000 BP to present reflect more data points, not necessarily greater variability.
Source: Climate and Atmospheric History of the past 420,000 years from the Vostok Ice Core, Antarctica, by Petit
J.R., Jouzel J., Raynaud D., Barkov N.I., Barnola J.M., Basile I., Bender M., Chappellaz J., Davis J. Delaygue G.,
Delmotte M. Kotlyakov V.M., Legrand M., Lipenkov V.M., Lorius C., Pépin L., Ritz C., Saltzman E., Stievenard M.,
Nature, 3 June 1999.
Notice:
• atmospheric increase is ~50% of fossil fuel emissions
• significant interannual variability
Arrows indicate
El Nino events
GLOBAL PREINDUSTRIAL CARBON CYCLE
Inventories in
Pg C
Flows in
Pg C a-1
The carbon cycle can be viewed as a set of
"reservoirs" or compartments, each
characterizing a form of C (e.g. trees; rocks
containing calcium carbonate [limestone]).
The cycle of C globally is then represented
as a set of transfer rates between
compartments.
The total amount of carbon in the
atmosphere + ocean + rocks that exchange
with the atmosphere/ocean is fixed by very
long-term geophysical processes.
Human intervention may be regarded as
manipulation of the rates of transfer
between important reservoirs.
68
PgC/yr
Carbon Cycle on Land
•Photosynthesis:
CO2 + H2O + light => "H2CO" + O2
•Respiration:
"H2CO" + O2 => CO2 + H2O + energy
Very little organic matter is stored, on average.
Carbon Cycle in the ocean
•Dissolution/evasion
CO2(g) + H2O + CO3(aq) =  2 HCO3¯
Global CO2 cycle
Global CO2 budget (PgC yr-1 )
Sources
Sinks
1980 – 1990
1990 –2000
Fossil Fuel+ cement
5.3
6.5
Deforestation
1-2
.5-1
Total
6.3 - 7.3
Atmospheric
accumulation
Ocean uptake
7-7.5
3.2
3.2
2.1
1.5-2
"Missing Sink"
1-2
1.8-2.8
Total
6.3 - 7.3
7-7.5
2.1 Pg C = 1 ppm atmospheric CO2 [source: Cias et al., Science 269, 1098, (1995)]
EVIDENCE FOR LAND UPTAKE
OF CO2 FROM TRENDS IN O2,
1990-2000
Composition of Sea Water
Charge balance in the ocean:
[HCO3-] + 2[CO32-] = [Na+] + [K+] + 2[Mg2+] + 2[Ca2+] - [Cl-] – 2[SO42-] – [Br-]
The alkalinity [Alk] ≈ [HCO3-] + 2[CO32-] = 2.3x10-3M
"alkalinity" defines Σ' Zi [i] : response of H+ and OH- to addition of CO2
Alkalinity
•
[alk] = i Z+[i+] - i Z-[i-] = [HCO3-] + 2 [CO3=]
•
[alk] is a re-arrangement of the charge balance equation. It cannot
change when adding or removing an uncharged species like CO2.
•
[alk] = 2 x 10-3 M -- only 1 in 1000 of total ions!
ATMOSPHERE
OCEAN
CO2(g)
KH = 3x10-2 M atm-1
CO2.H2O
K1 = 9x10-7 M CO2.H2O
K2 = 7x10-10 M
UPTAKE OF CO2 BY THE OCEANS
HCO3-
HCO3- + H+
CO32- + H+
CO2.H2O
HCO3-
CO32-
Equilibrium calculation
for [Alk] = 2.3x10-3 M
Charge balance in the ocean:
[HCO3-] + 2[CO32-] = [Na+] + [K+] + 2[Mg2+] +
2[Ca2+] - [Cl-] – 2[SO42-] – [Br-]
2.1
2.0
1.9
[CO2.H2O]+[HCO3-]
+[CO32-], 10-3M
1.8
1.6
1.4
4
3
LIMIT ON OCEAN UPTAKE OF CO2:
CONSERVATION OF ALKALINITY
[HCO3-],
10-3M
[CO32-],
10-4 M
The alkalinity [Alk] ≈ [HCO3-] + 2[CO32-] =
2.3x10-3M is the excess base relative to the
CO2-H2O system
It is conserved upon addition of CO2
uptake of CO2 is limited by the existing
supply of CO32-:
CO2(g) + CO32 + H2O
2HCO3-
2
Increasing Alk requires dissolution of
sediments:
8.6
8.4
8.2
100
Ocean pH
CaCO3
200 300 400 500
pCO2 , ppm
Ca2+ + CO32-
…which takes place over a time scale
of thousands of years
EQUILIBRIUM PARTITIONING OF CO2
BETWEEN ATMOSPHERE AND GLOBAL OCEAN
Equilibrium for present-day ocean:
NCO 2 ( g )
F

NCO 2 ( g )  NCO 2 (aq)
1
1
Voc PK H 
K1
K1K 2 
1


N a  [H  ] [H  ]2 
 0.03
 only 3% of total inorganic carbon is currently in the atmosphere
But CO2(g) k  [H+] k  F k
… positive feedback to increasing CO2
Pose problem differently: how does a CO2 addition dN partition between
the atmosphere and ocean at equilibrium?
f 

dNCO 2 ( g )
1

 0.28
dNCO 2 ( g )  dNCO 2 (aq) 1  Voc PK H K1 K 2
+ 2
N a   H 
28% of added CO2 remains in atmosphere!
 (buffer factor) Sundquist et al. 1979
FURTHER LIMITATION OF CO2 UPTAKE:
SLOW OCEAN TURNOVER (~ 200 years)
Inventories in 1015 m3 water
Flows in 1015 m3 yr-1
Uptake by oceanic mixed layer only (VOC= 3.6x1016 m3)
would give f = 0.94 (94% of added CO2 remains in atmosphere)
Observed uptake of fossil fuel CO2 by the oceans
compare to ~300 moles CO3=
6500
8200 in 2007!
1990
1980
1970
1960
1950
Year
7800 in 2005!
Global Fuel Use
3800
History of consumption of
fossil fuels.
Emissions have increased
by more than 2X since 1970.
There rise in the last 5 years
has been really dramatic.
But there has not been a
corresponding rise in the
annual increment of CO2. In
1970 ~75% of the emitted
CO2 stayed in the
atmosphere, but only ~40%
in 2000.
2007
1.5
US
0
109 metric tons of C / yr
1.
.5
fossil fuel use
(source: CDIAC –Trends –updated)
The US is the
largest consumer of
fossil fuels. Per
capita use is very
high, ~5 tons C per
person per year.
This rate has not
changed much in 50
years.
Metric tons C per person
US per capita fossil fuel use
US and World Per Capita
Fossil Fuel Use since
1950
Why don't we see a big
upswing due to the
emergence of economies
in China and India ?
China is projected to
exceed US emissions
in 2009.
NET UPTAKE OF CO2 BY TERRESTRIAL BIOSPHERE
(1.4 Pg C yr-1 in the 1990s; IPCC [2001])
is a small residual of large atm-bio exchange
•
Gross primary production (GPP):
GPP = CO2 uptake by photosynthesis = 120 PgC yr-1
•
Net primary production (NPP):
NPP = GPP – “autotrophic” respiration by green plants = 60 PgC yr-1
•
Net ecosystem production (NEP):
NEP = NPP – “heterotrophic” respiration by decomposers = 10 PgC yr-1
•
Net biome production (NBP)
NBP = NEP – fires/erosion/harvesting = 1.4 PgC yr-1
CO2 + H2O  "H2CO" + O2
Photosynthesis and Respiration
Atmospheric CO2 observations show that the net uptake is at northern
midlatitudes but cannot resolve American vs. Eurasian contributions
CYCLING OF CARBON WITH TERRESTRIAL BIOSPHERE
Inventories in PgC
Flows in PgC yr-1
Relatively small reservoirs  Short time scales  net uptake from
reforestation is transitory...unless resources are managed to preserve
organic matter
Carbon-Climate Futures
Coupled simulations of climate and the carbon cycle
Carbon Flux: Land to Air
10
8
6
4
2
0
-2
-4
-6
-8
-10
1850
Cox et al (2000)
Friedlingstein et al (2001)
PgC/yr
PgC/yr
Carbon
Flux: Ocean to Air
Global Mean
Temperature
1900
1950
2000
2050
2100
10
8
6
4
2
0
-2
-4
-6
-8
-10
1850
1900
1950
2000
2050
2100
Atmospheric CO2
~ 2º K
in 2100
ppm
1000
900
800
700
600
500
400
300
200
1850
1900
1900
1950
2000
2050
2100
1950
2000
2050
2100
Vegetation matters!
Different
models
project dramatically
different futures
using different ecosystem models.
PROJECTIONS OF FUTURE CO2 CONCENTRATIONS
[IPCC, 2001]
PROJECTED FUTURE TRENDS IN CO2 UPTAKE
BY OCEANS AND TERRESTRIAL BIOSPHERE
IPCC [2001]
C4MIP:
coupled
climatebiosphere model
comparison
(used in IPCC
2007)
US and World Per
Capita Fossil Fuel
Use since 1950
Japan and Europe…
HIPPO completed the 1st of 5 global surveys in
January, 2009
Net Exchange (mol CO2/m2/s)
2001
R
0
A
-
-20
-
-10
NEE
GEE
-
-30
B
3471
3471.5
3472
3472.5
3473
Time (days)
1992
0
- GEE
emission
C
1996 1998 2000
YR
-5
R
uptake
Harvard Forest
NEE
NEE MgC/ha/yr
-4
-3
-2
-1
R, (-1)*GEE MgC/ha/yr
10
12
14
16
18
A. Eleven years of hourly data for Net Ecosystem Exchange. B. Two days of hourly data. C. 13
years of respiration (R), GEE, and D. 13 years of NEENEE annual sums.
2004
D
1992
1996 1998 2000
2004
Harvard Forest, Petersham, MA. A "typical" New England forest…an artifact!
0.5
0.0
102
-5
93-798 99 00 01 02 03 04
1996 1998 2000
2004
1994
1996
1998
2000
2002
2004
1992
R
uptake
- GEE
emission
1996 1998 2000
YR
“LUE”1200-1500
GEE 1200-1500
-28
-26
-24
-22
R, (-1)*GEE MgC/ha/yr
10
12
14
16
18
1992
1.0
1.5
Live Biomass
AGWI MgC/ha/yr
NEE
AGWB MgC/ha
106
110
Harvard Forest
NEE MgC/ha/yr
-4
-3
-2
-1
0
Long-term changes at Harvard Forest
2004
More Efficient
1992
1996 1998 2000
Year
2004
100
MA
40
60
80
NH
20
% of land area in forests
A legacy: land use change in New England
Year
Fitzjarrald et al., 2001
1700
1800
1900
2000
120oak
NEE = -1.28 - 0.146 x (yr-1990); R2 = 0.337
0
other spp
-2
-3
-4
-5
-1 x GEE
GEE = 11.1 + 0.363 x (yr-1990);
16
Mg-C ha-1yr-1
Aboveground woody biomass (MgCha-1)
NEE (Mg-Cha-1yr-1)
-1
R2
= 0.732
Resp
R = 9.82 + 0.217 x (yr-1990); R2 = 0.626
14
100
80
60
40
20
12
0
10
1992
1994
1996
1998
2000
2002
2004
93 94 95 96 97 98 99 00 01 02 03 04 05
Year
Year
Rates for growth and for carbon uptake are accelerating in this 80year-old New England Forest…why is that? Will that continue? How
big do North American trees grow?
Non-CO2 Greenhouse Gases
• CH4 – dominated by fossil
emissions over USA and much of
Canada
• N2O – mostly agricultural
emissions
• CO – a mix of combustion and
hydrocarbon sources
Atmospheric Methane (CH4)
SOURCES OF ATMOSPHERIC METHANE
WETLANDS
180
BIOMASS
BURNING ANIMALS
90
20
LANDFILLS
50
GLOBAL METHANE
SOURCES (Tg CH4 yr-1)
TERMITES
25
RICE
85
GAS
60
COAL
40
Atmospheric CH4: Past Trends, Future Predictions
Variations of CH4 Concentration (ppbv)
Over the Past 1000 years
[Etheridge et al., 1998]
IPCC [2001] Projections of Future
CH4 Emissions (Tg CH4) to 2050
Scenarios
900
1600
1400
800
1200
700
1000
800
1000
A1B
A1T
A1F1
A2
B1
B2
IS92a
600
1500
Year
2000
2000
2020
Year
2040
COBRA-2003§ flight region and footprints
§a
CCE ( LBA !) project
1600 1700 1800 1900 2000
CH4
0
50
100 150 200 250 300
Flask number
June 16, 2003
36.72N,96.94W 609 m AGL
WRF
LPDM Model: STILT
Emissions: EDGAR-2000
Met fields: WRF (AER, 35
km, LPDM outputs, Grell-2)
WRF/STILT/EDGAR
model vs data, with
gray and green.
Errors used in fitting
are + 38 ppbv for the
model, and + 23 ppbv
for the measurements
Slope = 0.9
slope = ±0.1
EDGAR—2000
confirmed ±10%
for CH4 !
This result pertains
to urban-industrial
sources, which
dominate the flight
region
Nitrogen:
Nitrogen is a major component of the atmosphere, but an essential nutrient in short
supply to living organisms. Why is "fixed" nitrogen in short supply? Why does it stay
in the atmosphere at all?
OXIDATION STATES OF NITROGEN
N has 5 electrons in valence shell 9 oxidation states from –3 to +5
Increasing oxidation number (oxidation reactions)
-3
0
+1
+2
+3
+4
+5
NH3
Ammonia
NH4+
Ammonium
R1N(R2)R3
Organic N
N2
N2O
Nitrous
oxide
NO
Nitric oxide
HONO
Nitrous acid
NO2Nitrite
NO2
Nitrogen
dioxide
HNO3
Nitric acid
NO3Nitrate
free radical
free radical
Decreasing oxidation number (reduction reactions)
THE NITROGEN CYCLE: MAJOR PROCESSES
ATMOSPHERE
N2
combustion
lightning
free radical
NO
oxidation
HNO3
biofixation
orgN
BIOSPHERE
burial
denitrification
deposition
decay
assimilation
NH3/NH4+
nitrification
NO3weathering
LITHOSPHERE
"fixed" or "odd" N is less stable globally=> N2
Dissolved O2 mole/kg
The cycle of organic/inorganic C, solubility of O2 in seawater, and
onset of denitrification, limit the amount of nitrate in the deep ocean
Dissolved NO3
mole/kg
-
(C106H124O36) (NH3)16 (H3PO4) + 150 O2 => 106 CO2 + 16 HNO3 +
H3PO4 + 78 H2O + energy
Oceanic Nitrogen Processes
-3
-2
-1
0
1
2
3
5
N2
N2O
Org N
NO
?
NH2OH ?
NH4+
ox state
-3
N2H4
-2
NO2-
NO3-
2 3
5
N2
-1
0
1
“There are lies, there are big lies, and then there are…box models.”
Box models are usually considered linear models. Nature isn’t linear.

 It matters how you choose to divide up the problem into boxes.
Box 1
k=1; M1=1, M2=10; Co = .01 (M1o)
C1=Co/M1+2{M2 exp(-k(M1+2/(M1M2)t) +M1 }
C2=CoM1 /M1+2{1 - exp(-k(M1+2/(M1M2)t ) }
Only Box 1
*
* Box 1 of 2
*
*
*
*
*
*
*
*
**
**
**
***
****
****** ****
Only Box 2
** ****************************************************************
Box 2 of 2
0.0
0.002
C1 or C2
0.004
0.006
Box 2
Box 2
only
*
*
0.008
k
k
0.010
•
0
2
4
6
time
8
10
BOX MODEL OF THE NITROGEN CYCLE
Inventories in Tg N
Flows in Tg N yr-1
N2O: LOW-YIELD PRODUCT OF BACTERIAL
NITRIFICATION AND DENITRIFICATION
Important as
• source of NOx radicals in stratosphere
• greenhouse gas

+
+
NH4 +3/2O2  NO2 + H2O + 2 H

NO3 + Org-C  N2 + …
N2O
IPCC
[2001]
N2O versus depth in the Greenland Ice sheet.
Constraints on N2O budget changes since pre-industrial time from new firn air
and ice core isotope measurements
S. Bernard, T. R¨ockmann, J. Kaiser, J.-M. Barnola, H. Fischer, T. Blunier, and J.
Chappellaz, Atmos. Chem. Phys., 6, 493–503, 2006
320
N2O (ppb)
mean annual increase 0.74 ppb/yr
300
305
310
315
N2O in the atmosphere
1980
1985
1990
time
1995
2000
2005
PRESENT-DAY GLOBAL BUDGET
OF ATMOSPHERIC N2O
SOURCES (Tg N yr-1)
Natural
18 (7 – 37)
10 (5 – 16)
Ocean
3 (1 - 5)
Tropical soils
4 (3 – 6)
Temperate soils
2 (1 – 4)
Anthropogenic
8 (2 – 21)
Agricultural soils
4 (1 – 15)
Livestock
2 (1 – 3)
Industrial
1 (1 – 2)
SINK (Tg N yr-1)
Photolysis and oxidation in
stratosphere
12 (9 – 16)
ACCUMULATION (Tg N yr-1)
4 (3 – 5)
IPCC
[2001]
Although a closed budget can be constructed, uncertainties in sources are l
BOX MODEL OF THE N2O CYCLE
1.53 103 N2O
6
Inventories in Tg N
Flows in Tg N yr-1
8
3
N2O Observed vs Model (EDGAR—2000 )
Model STILT/ N2O (ppbv)
COBRA-2003
Observed N2O (ppbv)
US sources of N2O are ~2.5x
higher than EDGAR Kort et al., 2008