HR: 14:10h
AN: A13H-02    [Abstracts]
TI: Recent Trends in Atmospheric 14CO2
AU: * Turnbull, J C
EM: jocelyn.turnbull@lsce.ipsl.fr
AF: LSCE, CEA-CNRS Unité Mixte de Recherche CEA/Saclay, Orme des Merisiers Bâtiment 701 - Point Courrier 129, Gif-sur-Yvette Cedex, 91190, France
AU: Rayner, P
EM: peter.rayner@lsce.ipsl.fr
AF: LSCE, CEA-CNRS Unité Mixte de Recherche CEA/Saclay, Orme des Merisiers Bâtiment 701 - Point Courrier 129, Gif-sur-Yvette Cedex, 91190, France
AU: Bousquet, P
EM: philippe.bousquet@lsce.ipsl.fr
AF: LSCE, CEA-CNRS Unité Mixte de Recherche CEA/Saclay, Orme des Merisiers Bâtiment 701 - Point Courrier 129, Gif-sur-Yvette Cedex, 91190, France
AU: Cozic, A
EM: anne.cozic@lsce.ipsl.fr
AF: LSCE, CEA-CNRS Unité Mixte de Recherche CEA/Saclay, Orme des Merisiers Bâtiment 701 - Point Courrier 129, Gif-sur-Yvette Cedex, 91190, France
AU: Miller, J B
EM: john.b.miller@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305-3337, United States
AU: Miller, J B
EM: john.b.miller@noaa.gov
AF: University of Colorado at Boulder, 1560 30th St, Boulder, CO 80309-0450, United States
AU: Lehman, S J
EM: scott.lehman@colorado.edu
AF: University of Colorado at Boulder, 1560 30th St, Boulder, CO 80309-0450, United States
AU: Peters, W
EM: wouter.peters@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305-3337, United States
AU: Peters, W
EM: wouter.peters@noaa.gov
AF: University of Colorado at Boulder, 1560 30th St, Boulder, CO 80309-0450, United States
AU: Tans, P P
EM: pieter.tans@noaa.gov
AF: NOAA/ESRL, 325 Broadway, Boulder, CO 80305-3337, United States
AU: Ciais, P
EM: philippe.ciais@lsce.ipsl.fr
AF: LSCE, CEA-CNRS Unité Mixte de Recherche CEA/Saclay, Orme des Merisiers Bâtiment 701 - Point Courrier 129, Gif-sur-Yvette Cedex, 91190, France
AB: The radiocarbon content of atmospheric CO₂ (¹⁴CO₂) varies due to a number of factors. After the near-doubling of the ¹⁴CO₂ loading in the early 1960s (due to atmospheric nuclear weapons testing), many studies examined the fate of this 'bomb ¹⁴C' to understand exchange processes of CO₂ with the surface reservoirs. Today, however, the atmosphere and surface reservoirs are close to equilibrium with respect to bomb ¹⁴C, and instead, changes in ¹⁴CO₂ more strongly reflect the response to the addition of ¹⁴C-free fossil fuel CO₂ to the atmosphere. We use an atmospheric transport model to simulate recent atmospheric ¹⁴CO₂, and compare this to observations at several sites over the Northern Hemisphere continents. We show that, in the Northern Hemisphere, ¹⁴CO₂ variability is dominated by the effect of fossil fuel CO₂ emissions. The model simulates the time trends quite well, including both the overall secular trend and the seasonal cycle. A seasonal cycle in ¹⁴CO₂ is observed at the high altitude sites of Niwot Ridge, Colorado, and Jungfraujoch, Switzerland, but the magnitude varies from year to year. Our modeling studies demonstrate that this inter-annual variability can be explained by differences in atmospheric transport. This is in contrast to CO₂ concentration seasonal cycles, which are dominated by seasonal changes in CO₂ source strengths.
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
DE: 0428 Carbon cycling (4806)
DE: 0454 Isotopic composition and chemistry (1041, 4870)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting