Atmospheric CO2 & Temperature – what is normal?

Presented byPresented by Julie Brigham-Grette andJulie Brigham-Grette and

Beth CaissieBeth Caissie

Season Change in the Biosphere

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Season changes cause zigzags in CO2 in Atm. Esp. driven by Northern Hemisphere. In Spring - photosynthesis drops CO2, in Fall, decomposition causes increase in CO2

Atmospheric Carbon Dioxide measured at Mauna Loa, Hawaii

300

320

340

360

380

400

1958 1963 1968 1973 1978 1983 1988 1993 1998 2003 2008

Year

CO

2 (p

pm

v)

Annual CO2 cycle

1 2 3 4 5 6 7 8 9 10 11 12

Month

CO

2 (

pp

mv)

What causes this change in annual Carbon dioxide?

Monitoring of CO2 and other Greenhouse gases recorded around the world

All get very similar measurements

Why?

Firn-ice transition• Depth of transition depends on surfacetemperature and accumulation rate• Camp Century, Greenland: ~68 m below icesheet surface• Vostok, Antarctica: ~100 m below ice sheetsurface

Low precipt and cold = long time to make ice

High precipt and warm =short time to make ice

Summit Station, Greenland photo by Michael Morrison, GISP2 SMO, University of New Hampshire; NOAA Paleoslide SetCore: Eric Cravens, Assistant Curator, U.S. National Ice Core Laboratory;

Matt Nolan, UAF

Fossil air!

Trapped in the ice;

records past atmosphere

Raynaud, 1992

Gases within bubbles = palaeo atmospheric air

Glaciers maintained by Snowfall

• Snow -- density (g/cm3

– Add wind -- varies 0.1 to 0.4 g/cm3

• Firn -- transitional 0.4 - 0.83 g/cm3

– @0.83 g/cm3 -- all air passages sealed off

– Increase in density to 0.914 due to compression of ice bubbles

• Glacial ice -- g/cm3

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EPICA, 2004, Nature; This figure was produced by Leland McInnes for Wikipedia

Oxygen (8 protons)

16O 17O 18O

99.8% 0.04% 0.2%

Hydrogen (1 proton)

1H 2H (Deuterium) 3H (tritium)

99.98% 0.016% (bombs)

So, can make 9 isotopic combinations of H2O,e.g., 18 (1H2

16O) to 22 (2H218O)

“light water” “heavy water”

In paleoclimate studies…1H1H16O to 1H218O

General Equation:

18O = 18O/16O sample - 18O/16O standard x 1000 18O/16O standard

Expressed in per mille (0/00)

Negative values = lower ratios = isotopically lighter(less 18O than 16O)

Positive values = higher ratios = isotopically heavier(more 18O than 16O)

Ice Sheet

ocean 0

-10

-20-30

-40-50∂ 18O isotopic depletion

In Sea In Ice

Glacials = enriched 18O depleted 18O

Interglacials = depleted 18O enriched 18O

Evaporation of more 16 O

Ice Sheet

ocean

∂D isotopic depletiondepends on temp of source area,Distance and processes during precipitation

Isotopic ratios are used to model temperature, at Vostok; empirically this is roughly:

Temperature (deg-C) = -55.5 + (δD + 440) / 6http://eesc.columbia.edu/courses/ees/climate/labs/vostok/

See also http://www.globalchange.umich.edu/gctext/Inquiries/Inquiries_by_Unit/Unit_8a.htm

Classroom options:

Plot by hand on graph paper

Plot on computer using Excel

Instructions for Excel provided

Analysis:

Defining amplitude, frequency, periodicity

Defining Normal?

Understanding the relationship between Greenhouse gases and temperature.