Diagnosis of Relative Variations in Atmospheric Greenhouse Gas Contents and Temperature from Vostok Antarctic Ice-Core Paleoreconstructions

摘要

The evolution of radiation-active atmospheric components and climatic characteristics derived from Vostok Antarctic ice-core data is analyzed over 420000 years with a time resolution of 500 years.These data include the temperature variations DELTA T (determined from the deuterium content delta D_i in the ice core) and the contents of carbon dioxide q(CO_2) and methane q(CH_4) in the atmosphere.Cross correlation analysis shows that,on the whole,the variations in q(CO_2) and q(CH_4) are lagged with respect to the delta_i and temperature variations on time scales from millennia to several hundred thousand years.The characteristic time lag DELTAt of the variations in q(CO_2) and q(CH_4) relative to the variations in DELTAT over the entire analyzed period is about 1000 and 500 years,respectively.At the same time,in individual 100 000-yr intervals,the value of DELTA t reaches 1500 years for q(CO_2) and 1000 years for q(CH_4).For the earliest 100000-yr interval,the temperature variations lag behind the variations in the atmospheric greenhouse gas contents.Cross-spectral analysis suggests that the variations in the carbon dioxide and methane contents are generally lagged relative to the temperature variations at periods of approximately 20 000 years or longer except for periods of about 20 000 years for methane.The cross wavelet analysis of the data derived from the Vostok Antarctic ice core over the last 420 000 years reveals that the variations in q(CO_2) and q(CH_4) lag behind the temperature variations,including the modes characteristic of variations in the Earth's orbital parameters (Milankovitch cycles),while opposite phase lags are observed in individual time intervals and frequency ranges.The coevolution of DELTA T and q(CH_4) is less conclusive than that of DELTA T and q(CO_2).Over the last 100000-yr period,the fundamental 100000-yr mode of the deuterium content and temperature does not lead that of the greenhouse gas contents.An opposite effect is observed,with the temperature variations lagged more pronouncedly relative to the methane-content variations than to the carbon dioxide content variations.For the 100 000-yr mode,the variations in q(CH_4) lead those in q(CO_2) during the last period.