  For accretion rates Mdot~0.1 Msun/s to a few solar mass black hole the inner
part of the disk is expected to make a transition from advection dominance to
neutrino cooling. This transition is characterized by sharp changes of the disk
properties. I argue here that during this transition, a modest increase of the
accretion rate leads to powerful enhancement of the Poynting luminosity of the
GRB flow and decrease of its baryon loading. These changes of the
characteristics of the GRB flow translate into changing gamma-ray spectra from
the photosphere of the flow. The photospheric interpretation of the GRB
emission explains the observed narrowing of GRB pulses with increasing photon
energy and the luminosity-spectral peak relation within and among bursts.
