  The surface of conservative coupled sandpiles in the self-organized
cooperative critical state is found to exhibit intermittency in both time and
space. The spatiotemporal intermittent structure is also found to be a
multifractal. The probability density of sand grain heights on the surface is
an asymptotic power law but with an exponential cut-off. The power spectra of
the time series of sand grain heights show a diversity of low-frequency
components over different sites on the surface and also over different ensemble
samples. This means that the long-term prediction according to the nearby
observations and the history experiences is very difficult in the world of
coupled sandpiles. Unlike the low-frequency spectra, the high-frequency spectra
seem to obey a universal $f^{-2}$ law.
