Long-term projections of climate and marine carbon cycle using a comprehensive coarse-resolution earth system model
Arne Winguth, Univ. of Texas, Arlington
A complex earth system model including atmosphere, ocean, ice sheets, marine carbon cycle and terrestrial vegetation was used to study the long-term response (100-2000 yrs) of the climate to anthropogenic carbon emissions. Global mean surface temperature increases between 1 and 5 K depending on the emission scenario under the assumption that the emission will exponentially decline after the end of this century. For high emission scenarios, the breakdown with no recovery of the thermohaline circulation in the North Atlantic is predominantly controlled by an increase in atmospheric moisture transport. For the next 100 years, uptake of anthropogenic carbon by land and ocean is predicted to be about equal. Thereafter, the large carbon storage capacity of the ocean dominates with 60-70% for the high emission SRES A2 scenario the total land and ocean biosphere uptake of anthropogenic carbon. The total carbon uptake is substantially reduced to 19% for the SRES emission scenarios and up to 28% for the stabilization scenarios if climate change is considered in the simulations.
An adjoint carbon cycle model has been developed in order to assess important factors that regulates the air-sea CO2 gas exchange. The single contributing terms for the total change in pCO2, including the temperature effect and non-temperature effects (DIC, ALK, S), are analyzed. Adjoint simulation reveals that the temperature and non-temperature effects are mostly balanced in the equatorial regions, whereas in the Southern Ocean more non-linear processes control the pCO2.
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