Captain Research to the Rescue!

This paper (warning: PDF) estimates $115 billion in costs to protect Japan's ports and coastal areas from a one-metre rise in the sea level. So presumably, yes, ports would be severely adversely affected. In Green Mars, Kim Stanley Robinson wrote about a scenario in which the sea level rose three metres in a matter of months, sparked by the collapse of the WAIS. Like I said, I don't think we need to think necessarily of catastrophic collapse of the Ice Shelf for it to still be a global disaster. 2/3 of global trade moves by ship. If every transoceanic port were to become flooded and useless, we'd be seriously fucked. Pardon my french. It's hard to think of a scenario in which we could deal with any sea level rise above 2m, no matter how slowly it occurred.

But don't forget - only Communists and homosexuals support the Kyoto Accords!