Clathrates
<My Clathrate links
Yes, clathrates are more stable than normal ice in the presence of appropriate gases, probably at all pressures.
OTOH, they form slower than normal ice so may be selected out if the H2O ice of the martian polecaps froze in a series of short but rapid bursts.
On the Gripping hand, if interbedded layers of CO2 ice and H2O ice are stacked for a million years or so, there should be a solid-state stransformation to clathrate.