Numerical Simulation And Analysis Of Global Carbon Cycle

Global carbon cycle processes are very important to global climate change study, and global carbon cycle and climate coupled model called earth system model is the direction of climate model development. In this study, the global ocean carbon cycle and land carbon cycle processes are simulated first, then a carbon cycle and climate coupled model is built.The three dynamical global ocean carbon cycle model is built based on the global ocean circulation model POP and the ocean biogeochemical model OCMIP-2. The ocean physical processes and biogeochemical processes are well simulated after camparing the model results with the observation data. Then the ocean carbon cycle of the pre-industrial, industrial history period and the 21st century, is simulated under different atmospheric CO₂ concentration forcing. The model results tells that the ocean absorbs the atmospheric CO₂ in the middle latitude of the south hemisphere and the middle and high latitude in north hemisphere, while the ocean release CO₂ to the atmosphere in the equatorial area and the Antarctic Circumpolar Current area. The oceanic CO₂ sink is rising duing the historical time, but in the 21st century, the oceanic sink reaches a peak then decrese even though the atmospheric CO₂ concentration rising all the time. The noth Atlantic absorbs the most anthropogenic carbon during the historical and future time. In 2100, the anthropogenic carbon will be transported through the entire Atlantic by the north Atlantic deep water , while it will be transferred to 50°S by the Antarctic bottom water. The pH of sea water decrease 0.1 during the history time and will go on decrease in the 21st century. Under the RCP8.5 emiss scenario, the sea water pH wil be 7.73, and decreases 0.43, while the H+ concentration will be 2.7 times of pre-industrial level.The land carbon cycle processes are simulated for the pre-industrial and history time by the land surface model CLM3.5 of NCAR, using the carbon cycle model CASA'. The model results of leaf area index (LAI, gross pimary production (GPP) and the net primary production (NPP) are quite same to the MODIS observation data. NPPand land-atmospheric CO₂ net exchange called NEP are arising at almost area of the world, especially the low latitude area, following the increase of the atmospheric CO₂ concentration. There is significant interannual variation of NPP and NEP. While the atmospheric temperature increases and precipitation decreases anomaly, the land sink of atmospheric CO₂ is decrease anomaly.Based on the asimulation of ocean and land carbon cycle processes, the ocean carbon model OCMIP-2 and land carbon model CASA'are introduced to the climate model FIO-ESM, then a global carbon cycle and climate coupled model is built. The pre-industial control run is carried out using the new global carbon cycle model. The model simulated atmospheric CO₂ concentration is 284.3±0.37ppm which is the same as the observation. The atmospheric CO₂ concentration is higher in south hemisphere than north hemisphere, and it decreases with height in the equatorial area and the south hemisphere, while it increases in the north of 30°N. The land-atmospheric CO₂ exchange plays an importand role in the change of the bottom atmospheric CO₂ concentrtion. The ocean carbon cycle processes and be well simulated by this global carbon cycle model, while some simulated results of the land carbon cycle processes (eg. GPP) is smaller the observation.