Let's say both of these glaciers let loose tomorrow. If I was at the beach on the Oregon or Washington coast, how long would it take before I noticed the three foot rise they are predicting? Days, weeks, years?
But that can't happen, these glaciers are mostly located on land, so for them to let loose requires that the entire mass of the glacier slide across the land and into the ocean. Even at four kilometers per year, you and I won't be alive to see the end of that process.
The numbers are for the ice sheet dropping into the ocean and melting completely. So, it would be quite a while before you got the last 10% of the sea level rise.
The first 90%, on the other hand, could get there fast. I guess this would cause waves that travel at speeds similar to those of seismic waves (hundreds of km/hour). So, within a day. Also, the initial ocean rise would be higher than what it would be once the water has calmed down.
Surprisingly, the rise is uneven and may lead to lower sea level depending on where you are. The mass of icecaps is so important that it attracts water around them by gravity, and it gets composed with the extreme centrifugal force. If the average rise is 5m, places like Vancouver could see a -0.5m movement while other places around the equator could see +6.5m.
