Remember this water ice or clathrate is within 4" of the surface is near the equator.
Near equatorial temperatures can exceed 80 degrees Fahrenheit maximum.
Notice also this ice or clathrate disappears and reappears seasonally.
But what's also surprising is that one of the increases occurs during late Summer in the north, when daytime temperatures can exceed the freezing point. So this water is being deposited in these areas and persists even though during daytime the temperatures will be above the melting point.
I'm arguing that at low altitude locations this water will melt to liquid water this close to the surface.
Bob Clark