Influence of Liquid Inclusions to Explosive Instability of Ice

The influence of the nuclei of the liquid phase arising during mechanical deformations of polycrystalline ice at temperatures below -40 ... -45 C on its explosive instability is considered. The nucleus of the liquid phase appear in ice when part of the hydrogen bonds are broken when high pressure is applied to ice crystals. The resulting clusters can have characteristics close to those of bulk metastable water. It is known that such water in the region of negative temperatures has anomalous thermodynamic characteristics. In particular, at a temperature of -60 C and a pressure of 100 MPa, there is a second critical point of water for the liquid-liquid transition. It was found that the transition occurs between the two types of water LDL (low density water) and HDL (high density water), with the Widom line coming out into the one-component region of the water phase diagram. This line is the locus of increased fluctuations in entropy and density. Near atmospheric pressure, the temperature on the Widom line is -45 C. If the pressure inside the ice and its temperature turn out to be close to the line of coexistence of LDL and HDL, then liquid inhomogeneities can become a source of mechanical instability of the medium due to the growth of fluctuations in the energy of molecules and destruction of the ice structure. Such conditions can occur at temperatures below -45 C and pressures above 100 MPa.

Explosive instability due to flow over a rippled bottom

In this paper, we study Bragg resonance, i.e., the triad interaction between surface and/or interfacial waves with a bottom ripple, in the presence of background velocity. We show that when one of the constituent waves of the triad has negative energy, the amplitudes of all the waves grow exponentially. This is very different from classic Bragg resonance in which one wave decays to cause the growth of the other. The instabilities we observe are “explosive” and are different from normal mode shear instabilities since our velocity profiles are linearly stable. Our work may explain the existence of large-amplitude internal waves over periodic bottom ripples in the presence of tidal flow observed in oceans and estuaries.

Explosive instability due to flow over a rippled bottom

In this paper, we study Bragg resonance, i.e. the triad interaction between surface and/or interfacial waves with bottom ripple, in the presence of background velocity. We show that when one of the constituent waves of the triad has negative energy, the amplitudes of all the waves grow exponentially. This is very different from classic Bragg resonance in which one wave decays to cause the growth of the other. The instabilities we observe are explosive and are different from normal mode shear instabilities since our velocity profiles are linearly stable. Our work may explain the existence of large amplitude internal waves over periodic bottom ripples in the presence of tidal flow observed in oceans and estuaries.