Snowboarding isn't going extinct in 20 years, you'll just have to drive further north
The one thing I'm interested in though is what melted icecaps will do to the current oceanic-atmospheric currents. Oceanic salinity plays interesting roles in weather patterns, and injecting that much freshwater into the system is going to change something.
The Day After Tomorrow movie is very loosely based off of scientific hypothesis of the above scenario.^
PowderHound and TreeNinja