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Atmospheric CO2 & Temperature – what is normal?
Presented byPresented by Julie Brigham-Grette andJulie Brigham-Grette and
Beth CaissieBeth Caissie
Season Change in the Biosphere
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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.