HR: 1340h
AN: B13B-1187    [Abstracts]
TI: Interannual Variability and Trends of Atmospheric Radiocarbon (14CO2) Over the Tropical Western Pacific
AU: * Terao, Y
EM: yterao@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AU: Kitagawa, H
EM: hiroyuki.kitagawa@nagoya-u.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Nagoya, 464- 8601, Japan
AU: Mukai, H
EM: lnmukaih@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AU: Nojiri, Y
EM: nojiri@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AU: Uchida, M
EM: uchidama@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AU: Shibata, Y
EM: yshibata@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AU: Aramaki, T
EM: ara@nies.go.jp
AF: National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, 305-8506, Japan
AB: Radiocarbon concentration in the surface atmospheric carbon dioxide (¹⁴CO₂) on the Japan-Australia transect has been measured since 1994 [Kitagawa et al., 2004]. We investigate the interannual variability and trends of atmospheric ¹⁴CO₂ for northern tropics (latitudes from 20N to 30N) and southern tropics (10S-20S). Time series analysis using a digital filtering and harmonic regression curve fitting [Nakazawa et al., 1997] elucidates two-year cycles of ¹⁴CO₂ and little seasonal cycles for both hemispheres. The decrease trend of ¹⁴CO₂ since nuclear bomb tests, mainly due to uptakes by the ocean, has been leveled off around 2000. These characteristics of ¹⁴CO₂ over the tropical Pacific are quite different from those over the Europe [Levin et al., 2004], in which the strong seasonal cycle and continuous decrease trends of ¹⁴CO₂ are observed. To explain the ¹⁴CO₂ time series in tropics, we are developing a model, in terms of impulse response functions of biosphere [Thompson and Randerson, 1999] and atmospheric transport. Preliminary results on the ¹⁴CO₂-based estimation of carbon exchange between biosphere-atmosphere in tropics will be shown.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0365 Troposphere: composition and chemistry
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting