Presentation on theme: "Atmospheric CO 2 & Temperature – what is normal? Presented by Julie Brigham-Grette and Julie Brigham-Grette and Beth Caissie Beth Caissie."— Presentation transcript:
Atmospheric CO 2 & Temperature – what is normal? Presented by Julie Brigham-Grette and Julie Brigham-Grette and Beth Caissie Beth Caissie
Season Change in the Biosphere
Season changes cause zigzags in CO 2 in Atm. Esp. driven by Northern Hemisphere. In Spring - photosynthesis drops CO 2, in Fall, decomposition causes increase in CO 2
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 surface temperature and accumulation rate Camp Century, Greenland: ~68 m below ice sheet surface Vostok, Antarctica: ~100 m below ice sheet surface 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/cm 3 –Add wind -- varies 0.1 to 0.4 g/cm 3 Firn -- transitional g/cm 3 g/cm 3 -- all air passages sealed off –Increase in density to due to compression of ice bubbles Glacial ice -- g/cm 3
EPICA, 2004, Nature; This figure was produced by Leland McInnes for WikipediaLeland McInnes
Oxygen (8 protons) 16 O 17 O 18 O 99.8% 0.04% 0.2% Hydrogen (1 proton) 1 H 2 H ( Deuterium ) 3 H ( tritium ) 99.98% 0.016% (bombs) So, can make 9 isotopic combinations of H 2 O, e.g., 18 ( 1 H 2 16 O) to 22 ( 2 H 2 18 O) light water heavy water In paleoclimate studies… 1 H 1 H 16 O to 1 H 2 18 O
General Equation: 18 O = 18 O/ 16 O sample - 18 O/ 16 O standard x O/ 16 O standard Expressed in per mille ( 0 / 00) Negative values = lower ratios = isotopically lighter (less 18 O than 16 O) Positive values = higher ratios = isotopically heavier (more 18 O than 16 O)
Ice Sheet ocean O isotopic depletion In Sea In Ice Glacials = enriched 18 O depleted 18 O Interglacials = depleted 18 O enriched 18 O Evaporation of more 16 O
Ice Sheet ocean D isotopic depletion depends 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) = (δD + 440) / 6 See also
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.