  The phase diagram of H2O is extremely complex, in particular, it is believed
that a second critical point exists deep below the supercooled water (SCW)
region where two liquids of different densities coexist. The problem however,
is that SCW freezes at temperatures just above this hypothesized liquid-liquid
critical point (LLCP) so direct experimental verification of its existence has
yet to be realized. Here, we report two anomalies in the complex dielectric
constant during warming in the form of a peak anomaly near Tp=203 K and a sharp
minimum near Tm=212 K from ice samples prepared from SCW under hydrostatic
pressures up to 760 MPa. The same features were observed about 4 K higher in
heavy ice. Tp is believed to be associated to the nucleation process of
metastable cubic ice Ic and Tm the transitioning of ice Ic to either ices Ih or
II depending on pressure. Given that Tp and Tm are nearly isothermal and
present up to at least 620 MPa and ending as a critical point near 33-50 MPa,
it is deduced that two types of SCW with different density concentrations
exists which affects the surface energy of ice Ic nuclei in the "no man's land"
region of the phase diagram. Our results are consistent with the LLCP theory
and suggest that a metastable critical point exists in the region of 33-50 MPa
and Tc > 212 K.
