1600

1400

1200

1000

800

Atm. CH

4

(ppbV)

20001950190018501800Calender Years (AD)

360

340

320

300

280

Atm. CO

2

(ppmV)

5

4

3

2

1

x103

310

300

290

280

270

Atm. N

2

O (ppbV)

1

2

3

4

5

World Population (billions)

Atmospheric CH4

Atmospheric CO2

World Population

The Anthropogenic Impact

First Direct Measurements

AtmosphericN2O

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Before 1950, atm. CO2 values come from ice cores.

Scholander made first measurements of gases in icebergs in Baffin Bay in 1950’s.

The National Ice Core Laboratory in Denver, Colorado

Depth

Bubble Close-Off Region

Free Atmosphere

Glacier Surface

0

115

123

120

100

80

60

40

20

0

Depth (mbs)

1.00.80.60.40.20.0CO2 Diffusivity (m2/day)

0.700.600.500.400.300.200.100.00Open Porosity

S. Pole Firn Properties from Density Measurements

Issues:1) Ice age - gas age2) Trapped gases are ave.3) Gravity and thermal frac.

Depth

Bubble Close-Off Region

Free Atmosphere

Glacier Surface

0

115

123

Convection

Zone

Static-AirColumn

Non-diffusive

Zone

Depth

N (‰)15

0.0

Barometric Equation: Pz = Po(e(mgz/RT))

δ15N=

15N14N

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟ sample

15N14N

⎛

⎝

⎜ ⎜ ⎜

⎞

⎠

⎟ ⎟ ⎟ atmN2

-1

⎡

⎣

⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢ ⎢

⎤

⎦

⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥

103

0.35

0.50

0.35

0.50

0.80

0.83

Bubble close-off region

To Waste

Density (g/cc)

Depth

Rubber Bladder

Firn AirSampling Device

To Inflate bladderTo Flasks

Bender Baffle

120

100

80

60

40

20

0

Depth (mbs)

0.700.600.500.400.300.200.10

15N

15 (‰)N

South Pole Gravitational Signal

Using 15N to assess the depth of bubble close-off in the past

• Bubble close off is primarily a function of temperature (colder temps -> deeper close off depths).

• Gravitational fractionation is also a function of temp.Pz = Po(e(mgz/RT))

• Age difference between bubbles and surrounding ice is proportional to accumulation rate which is also tied to surface temperature

-41

-40

-39

-38

-37

-36

-35

18

Oice

(‰ )SMOW

12.011.811.611.411.211.0 ( ) Age ka BP

0.60

0.55

0.50

0.45

0.40

0.35

15

N

(‰ )air750

700

650

600

550

500

450

CH4

( )ppb

Younger DyrasPreboreal Period

δ18Oice

δ15N (ΔSurface Temp.)

CH4

(Severinghaus et al., Nature vol 391, '98)(Severinghaus et al., Nature vol 391, '98)

T=10.4±2oC

280

260

240

220

200

CO2

(ppm)

100806040200 Gas Age (kry BP)

Vostok

Taylor Dome

Byrd

Dry Extraction technique onlyNumerous labs using different techniquesNumerous Antarctic ice cores drilled differently

300

250

200

150

CO2

(ppm)

100806040200 Gas Age (kry BP)

Vostok

Taylor Dome

Byrd

GISP II (Greenland)

280

240

200

CO2 (ppm)

8007006005004003002001000Gas Age (kyr BP)

800

700

600

500

400

CH4 (ppb)

-440

-420

-400

-380Temp. Proxy

EPICA Ice Core Results

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IPCC 2007 Synthesis report

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Sources of CO2 to atmosphere

Weathering reactions

H2SO4 + CaCO3 → CaSO4 + H2CO3

Fossil Fuel Burning

CH4 + 2 O2 → CO2 + 2 H2O Respiration

C6H12O6 → 2 CO2 + 2 C2H5OH

Volcanoes emit CO2 from subducted oceanic sediment

Sinks of Atmospheric CO2

• Increase Corg reservoir

• Increase CaCO3 reservoir (coral reefs)

• Store CO2 in deep ocean

• Sequestration