My proposal for migrations:
* Spain & Portugal: little movements, people flee from coastal regions. In Portugal: Lisbon and Porto will be abandoned; in Castille: Seville, Cadiz, Alicante and Santander; in Aragon: Barcelone, Valencia and Palma. As most of the population lives in Castille in the central plateaus they will be affected only by plagues and refugees.
* France: the northern coast disappears, Paris lost. People will flee to the Central Mountains and to the Pyrenees. Serious problems as central power disappears and thousands of refugees arrive.
* England&Ireland: most of their territory will disappear. The English could flee to the lands near Scotland, France or even Spain. The Irish could flee to Spain.
* Flanders&Germany: the Netherlands disappear, all the north of Germany disappear. Hundreds of thousands of refugees flooding France (Walloons), southern Germany (Flemish and Saxons) and Austria. Collapse of all organized states there.
* Italy: Venice disappears, Naples and Rome also disappear. Population would concentrate in the mountains. The Holy See would have to move (to somewhere else in Patrimonium Petrii, Avignon, Santiago?).
* Scandinavia: Denmark disappears, population would flee to Skane and Norway. Sweden would lose important populated areas, but they could move easily to the interior. Norway quite safe. Coastal populations moving to the interior.
* Austria and Hungary: Austria is quite untouched, lots of refugees from Germany, pestilences and the possibility of annexing what is left of Germany. Hungary would be saved from the Ottomans (with their own problems) but they would have a new interior see that would move lots of inhabitants.
* Ottomans: no further expansion in Europe. Estambul and most of their coastal towns are lost. Problems in northern Africa as Cirenaica is now an island and Mesopotamia is now part of the persian gulf.
* Poland, Russia and Baltic nations. Chaos. Most of populated areas are now under the sea. Muscovy would be hegemonic.
What do you think?