Seasonal and interannual variability of oceanic carbon cycling in the western and central tropical-subtropical pacific: A physical-biogeochemical modeling study |
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| Authors: | Masahiko Fujii Fei Chai Lei Shi Hisayuki Y Inoue Masao Ishii |
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| Institution: | 1.Graduate School of Environmental Science,Hokkaido University,Sapporo, Hokkaido,Japan;2.Sustainability Governance Project, Center for Sustainability Science,Hokkaido University,Sapporo, Hokkaido,Japan;3.School of Marine Sciences,University of Maine,Orono,USA;4.Meteorological Research Institute,Nagamine, Tsukuba, Ibaraki,Japan |
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| Abstract: | The oceanic carbon cycle in the tropical-subtropical Pacific is strongly affected by various physical processes with different
temporal and spatial scales, yet the mechanisms that regulate air-sea CO2 flux are not fully understood due to the paucity of both measurement and modeling. Using a 3-D physical-biogeochemical model,
we simulate the partial pressure of CO2 in surface water (pCO2sea) and air-sea CO2 flux in the tropical and subtropical regions from 1990 to 2004. The model reproduces well the observed spatial differences
in physical and biogeochemical processes, such as: (1) relatively higher sea surface temperature (SST), and lower dissolved
inorganic carbon (DIC) and pCO2sea in the western than in the central tropical-subtropical Pacific, and (2) predominantly seasonal and interannual variations
in the subtropical and tropical Pacific, respectively. Our model results suggest a non-negligible contribution of the wind
variability to that of the air-sea CO2 flux in the central tropical Pacific, but the modeled contribution of 7% is much less than that from a previous modeling
study (30%; McKinley et al., 2004). While DIC increases in the entire region SST increases in the subtropical and western tropical Pacific but decreases
in the central tropical Pacific from 1990 to 2004. As a result, the interannual pCO2sea variability is different in different regions. The pCO2sea temporal variation is found to be primarily controlled by SST and DIC, although the role of salinity and total alkalinity,
both of which also control pCO2sea, need to be elucidated by long-term observations and eddy-permitting models for better estimation of the interannual variability
of air-sea CO2 flux. |
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