Millennial climate variability: GCM-simulation and Greenland ice cores

The low frequency variability of the near surface temperature in a climate simulation is compared with Greenland ice core delta O-18 time series during the holocene. The simulation is performed with the coupled CSIRO atmosphere-ocean model under present-day conditions. The variability, analyzed by the detrended fluctuation analysis, reveals power-law scaling of the power-spectrum for frequency f, S( f) similar to f(-beta), and long term memory (LTM) given by beta > 0. The near surface temperature shows intense LTM in the North Atlantic south of Greenland, weak LTM in parts of the Antarctic ocean and the tropical Atlantic, and no LTM in the Pacific ocean. The power-law exponent beta approximate to 0.5 near Greenland agrees with ice core temperature proxies up to time scales of 1000 years. The LTM of the surface temperature is explained by the high low frequency variability of the zonally averaged stream-function in the Atlantic with maxima in the Arctic ocean.