When the freezing level is 15,000', higher than Mount Rainier, what impact does that have on Mount Rainier?
First, recall that the freezing level refers to the 'free air' altitude at which the temperature will be freezing. It may actually be warmer 'on the mountain'. That's because rocks, etc absorb solar heating, raising the temperature immediately adjacent to the mountain. Certainly above freezing temperatures will result in melting snow or ice. That's typical each summer. But if the total 'melt' exceeds the addition of snow/ice over the entire year, the glaciers will shrink.