Sensitivity of CFCs and Anthropogenic CO2 Uptake in a North Pacific GCM to Mixing Parameterization and Surface Forcing |
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| Authors: | Akio Ishida Kisaburo Nakata Shigeaki Aoki Hiroshi Kutsukake Michio J Kishi Masahisa Kubota |
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| Institution: | (1) Kansai Environmental Engineering Center Co., Ltd., 1-3-5 Aduchi-cho, Chuo-ku, Osaka 541-0052, Japan;(2) School of Marine Science and Technology, Tokai University, Shimizu 424-8610, Japan;(3) Environmental Assessment Department, National Institute for Resources and Environment, Tsukuba 305-8569, Japan;(4) Institute of Environmental Information, Metocean Environment Inc., Yokohama 224-0025, Japan;(5) Graduate School of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan |
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| Abstract: | Distributions and characteristics of water mass and chlorofluorocarbons (CFCs) in the North Pacific are investigated by using
a General Circulation Model (GCM). The anthropogenic CO2 uptake by the ocean is estimated with velocity fields derived from the GCM experiments. The sensitivity of the uptake to
different diffusion parameterizations and different surface forcing used in the GCM is investigated by conducting the three
GCM experiments; the diffusive processes are parameterized by horizontal and vertical eddy diffusion which is used in many
previous models (RUN1), parameterized by isopycnal diffusion (RUN2), and isopycnal diffusion and perpetual winter forcing
for surface temperature and salinity (RUN3). Realistic features for water masses and CFCs can be simulated by the isopycnal
diffusion models. The horizontal and vertical diffusion model fails to simulate the salinity minimum and realistic penetration
of CFCs into the ocean. The depth of the salinity minimum layer is better simulated under the winter forcing. The results
suggest that both isopycnal parameterization and winter forcing are crucial for the model water masses and CFCs simulations.
The oceanic uptake of anthropogenic CO2 in RUN3 is about 19.8 GtC in 1990, which is larger by about 10% than that in RUN1 with horizontal and vertical diffusive
parameterization. RUN3 well simulates the realistic water mass structure of the intermediate layer considered as a candidate
of oceanic sink for anthropogenic CO2. The results suggest that the previous models with horizontal and vertical diffusive parameterization may give the oceanic
uptake of anthropogenic CO2 underestimated.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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| Keywords: | General Circulation Model water mass chlorofluorocarbons anthropogenic CO2 the North Pacific |
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