You weren't paying attention in 6th grade science class. It's called "sublimation". Sun shining on ice can convert from solid ice to water vapor. A little wind carries it off so the small vapor pressure keeps converting from solid to vapor. It is common to observe snow/ice with local melting due to dark soil or plants collecting sunlight even when the ambient temperature is well below freezing.
Still, the premise that global warming is the consequence of human activity is BS. There are no humans on other planets in our solar systen, yet they are warming as well. There is a common astro-physical phenomenon driving the change. It isn't human activity.
Wouldn't the wind carrying the water vapor tend to refreeze and drop it as snow? Especially over a cold surface?