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Missing role of inland water on global carbon cycle by developing advanced process-based model

Tadanobu Nakayama1, Shamil Maksyutov1
1 Center for Global Environmental Research, National Institute for Environmental Studies (NIES)

O 2.13 in Environmental controls on fluxes and processes in ecosystems

17.07.2014, 16:10-16:30, H18

Recent research has suggested that inland water might act as a gigantic transport pathway for water/substances and play some role in continental biogeochemical cycle although its overall contribution has remained because of limited available data (Battin et al. 2009). The author has developed process-based National Integrated Catchment-based Eco-hydrology (NICE) model (Nakayama, 2008a-b, 2010, 2011a-b, 2012a-c, 2013; Nakayama and Fujita, 2010; Nakayama and Hashimoto, 2011; Nakayama and Shankman, 2013a-b; Nakayama and Watanabe, 2004, 2006, 2008a-b; Nakayama et al., 2006, 2007, 2010, 2012). This model incorporates surface-groundwater interactions, includes up- and down-scaling processes between local, regional and global scales, and can simulate iteratively nonlinear feedback between hydrologic, geomorphic, and ecological processes. In this study, NICE was extended to evaluate global hydrologic cycle by using various global datasets. Because the original NICE incorporates three-dimensional groundwater sub-model and expands from previous one-/two-dimensional and steady state, so-called equilibrium, this advanced model can simulate lateral transport of groundwater more pronounced at steeper-slope regions or riparian/floodplain with frequent surface water-groundwater interaction. The river discharge and groundwater level simulated by NICE agreed reasonably with those in previous research (Fan et al., 2013) and extended to clarify further eco-hydrological process in global scale though 1.0 ° grid resolution was coarser than that in the previous one at 30 arc-second grid. In particular, this improvement indicated lateral subsurface flow also has important role on hydrologic and biogeochemical cycles even in continental scale (Nakayama, 2011b; Nakayama and Shankman, 2013b). This extends traditional 'dynamic equilibrium' with atmospheric forcing (Maxwell and Kollet, 2008), and helps to improve the accuracy of methane emission estimation from wetland where the groundwater is a dominant factor for this emission. NICE was further developed to incorporate biogeochemical cycle including reaction between inorganic and organic carbons (DOC, POC, DIC, pCO2, etc.) in biosphere, so-called, terrestrial and aquatic ecosystems including surface water and groundwater, accompanied by the hydrologic cycle. In particular, CO2 evasion from inland water in global scale (total flux was estimated as about 1.0 PgC/yr), was relatively in good agreement in that estimated by empirical relation using previous pCO2 data (Aufdenkampe et al., 2011; Global River Chemistry Database, 2013). This result also shows NICE could simulate missing role of carbon cycle in inland water beyond empirical regression model in those previous researches. This advanced simulation system would play important role in identification of full greenhouse gas balance of the biosphere, and bridging gap between top-down and bottom-up approaches of carbon cycle estimation (Cole et al. 2007; Frei et al. 2012).



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last modified 2014-03-25