It's yet another safety that is going to disappear.
Lighter surfaces (snow, ice, clouds) typically reflect more light and heat. Darker surfaces (water, ground, asphalt) absorb light and emit thermal radiation, which is then trapped within the atmosphere by greenhouse gasses.
The atmosphere is differentially transparent to visible-light frequencies (high transparency) and infra-red radiation (low-transparency). That's the essence of what causes greenhouse warming, and we're adding more of the gasses (CO2, methane, and others) which are more effective at trapping heat.
Changes to surface characteristics (such as glacial melting) and atmospheric conditions (cloud formation, with dependencies on whether these are high-altitude or low), as a result of greenhouse-gas induced warming, provide feedback cycles which amplify or dampen effects. Many of the known feedbacks accelerate warming.
That's in addition to other feedbacks such as warming arctic-region permafrost, releasing both trapped CO2 and methane and triggering decomposition which generates more of these, or the "clathrate gun hypothesis", in which frozen and dissolved methane hydrates, themselves exceedingly powerful greenhouse gasses, are released at a rapid and accelerating rate. Among potential scenarios is a runaway greenhouse gas effect where global climates warm far beyond human or biological tolerance, either regionally or globally.
> 1.74% of total water on earth
Of course the ocean itself is warming up, so I guess we're screwed either way. ¯\_(ツ)_/¯