Relationship Between Climate Sensitivity And Ocean Heat Uptake

Climate sensitivity is an important measure of the relationship between the change of global temperature and the change of greenhouse gas concentration.However,there are large uncertainties in the simulation of transient climate response(TCR,or climate sensitivity).This paper discussed the uncertainty about effect of ocean heat uptake on global warming.By utilizing the experiments of 1%/year increase of CO2(lpctCO2)simulated by multi-models in CMIP5,assesses and analyses the relationship between climate sensitivity and ocean heat uptake are performed.The results illustrates as follow:The climate sensitivity values are range between 1.39 K and 2.34 K in multi-models simulation,while the FGOALS-s2 model is the highest,and the GGIS-E2-R model is the smallest.With the change of global mean surface temperature,the relationship between warming of the ocean temperature and the ocean heat uptake also becomes increasingly clear.The results have shown that the larger(smaller)heat uptake in the upper ocean(0-700m)always corresponded to the larger(smaller)TCR,and the simulated upper ocean heat uptake significantly affected the climate sensitivity.Meanwhile,the strength of North Atlantic Meridional Overturning Circulation(AMOC)simulated by multi-models in CMIP5 was weakened under the lpctCO2 experiment,and it also showed obvious interannual and interdecadal variability.Further analyses showed that characteristic that the stronger strength of the initial AMOC,the deeper depth of AMOC,and the greater AMOC variability under the lpctCO2 experiment.As for interconnection among the climate sensitivity,ocean heat uptake,and AMOC,the research found that the stronger(weaker)strength of the initial AMOC and the deeper(shallower)of depth are associated with the smaller(larger)ocean heat uptake in the upper ocean and the TCR is smaller(larger).Therefore,the anomalous AMOC influence ocean heat uptake and climate sensitivity.Due to the existence of mesoscale eddies in the Southern Ocean,we designed a sensitivity experiment with different thicknesses of diffusion coefficient.It is found that,with a larger the thickness diffusion coefficient and stronger mesoscale eddies,the ocean heat uptake in the Southern Ocean is stronger,so is the climate sensitivity.