Assume that all the ice in the major ice sheets melted. Maybe it's a couple centuries or a couple millenia from now. How would human civilization adjust? What would be the climatic effects?
The cause isn't necessarily important. It could be "sudden global warming" (courtesy of Stephen Hawking) or an ice melting asteroid impact or volcanism. My theoretical postulate is that a minor global warming further destabilizes the West Antarctic Ice Shelf leading to it's failure. This causes further isostatic effects that increase (catastrophic) volcanism along the Trans-Antarctic Mountains that start melting and shifting the East Antarctic ice. This rise in sea level with a minor Global warming effect eventually bouys and melts Greenland too. I'm not sure how probable this scenario is or how long it might take, but I think the mechanics are possible.
Seal level rise estimates range from 60m to 80m (200ft to 260). Rapid post-glacial rebound (7.5cm/3inches per year are not uncommon) would eventually lift parts of Greenland and Antarctica back above the waves, but for several centuries parts of those areas would probably remain archipelagos (most of West Antarctica is below Mean Sea Level now and much of Greenland's sub-glacial interior is near MSL at the present time). Given a couple centuries for the glaciated areas to rebound a bit, solar-driven thermal expansion of the oceans, local sinking of newly inundated continents from sea water along the shore, continental gravity effects along the shore, erosion along the shore, and estimate errors of current glacial volume and ice density I think it is not improbable to postulate a total sea level rise of 92 meters (300ft). After all, that corresponds nicely with my map's topography interval.
Here's a cool mod for Google Maps that allows you to select sea level rise from 1-14m.
Here's an interesting set of maps of eastern North America at several intervals, and Europe and the world at 100m. The 100m map is a little higher (27ft higher) than what I am postulating.
- On the bright side:
The northwest passage would be open and would allow quicker shipping between eastern Asia and western Europe.
The increase in shallow sea area might mean better fishing banks.
The enlarged gulf of Mexico might send storms farther west and north bringing rain to drier plains and mountainous desert regions of North America, increasing agricultural production.
The warmed tundra may become agriculturally productive.
The alterations of climate to Antarctica may make non-contamination concerns of the "pristine" continent a non-issue and allow for the possible mining of coal and oil known to exist in the region.
Lots of jobs building dikes for cities that can be saved.
Lots of jobs builting cities at sea that will rise with the waters as they flood.
New canals between the Atlantic and Pacific might be built with shorter distances.
What else can y'all think of?
- On the down side:
Lots of places get flooded.
Hurricanes reach can farther with warm gulf water farther north, causing storm surges that reach into Illinois.
Arable land is flooded reducing agricultural productivity.
What else bad could happen?
- Places that get flooded:
The US loses all of FL, LA and DE (maybe some small islands). Major sections of RI, MA, RI, MD, NJ, VA, NC ,SC, GA, and AL up to the piedmont regions get flooded. NY loses long island, most of NYC and the Hudson River Valley connects the Saint Lawrence Seaway with the Atlantic making New England and New Brunswick one large island. Sections of MS along both east and west borders flood turning central MS into a peninsula. Half of AR is lost. The gulf extends into TX a hundred miles or so and a new Mississippi Gulf replaces the Lower Mississippi Valley nearly making Saint Louis a port city (Cairo, Illinois becomes a delta city for the Miss while Cairo, Egypt on the Nile partially disappears).
In the western US, CA and Mexico lose the Imperial Valley and Baja CA is isolated from the rest of Mexico. The sea extends halfway up the Colorado river towards the Hoover Dam. California's Central Valley floods (unless a big dike is built across the narrow Carquinez Strait . The pacific northwest's river valleys are inundated at Seattle/Tacoma in WA and the Columbia Willamette valley floods making Eugene, OR a port city.
I'm not as sure what happens in the north, but low areas of Alaska in the far north and west along the Bering Sea probably flood. Hudson Bay's shoreline increases a hundred miles in places. The sea floods the Saint Lawrence Seaway and turns Lake Ontario into a salt water sea unless damed at the strait. The other great lakes remain above sea level. Ships sail down the center of what used to be Greenland's interior.
In South America, Brazil finds the Amazon is a new inland sea and the Platte is also a new gulf. Parts of Columbia, Venezuela are flooded into the interior as Surinam and the Guianas shrink by half.
Much of Ireland and southern England are flooded. London is gone. Large areas of France are under water. The low countries are gone including half of Germany, a quarter of Poland and all of Denmark. Latvia, Estonia, and Lithuania are mostly flooded including a large portion of Russia along the baltic. Northern Italy is flooded and Seville, Spain, becomes a bay. Israel's interior floods from the outside with a strait near Haifa, making the Jordan River valley, the Dead Sea and the Sea of Gallilee one sea. The Black Sea rises and may even flood far up the Danube creating several seas inside Romania and Hungary. The Black Sea may also flood into the Capsian turning it into a salt water sea that is double its current size, flooding up the Volga and into the Russian interior. The Persian Gulf extends further north over mesopotamia in Iraq. A large part of north central Siberia is inundated from the Arctic Ocean.
Sections of North Africa slide under the waves forming a small sea in Tunisia and Algeria. Parts of Libya and Eqypt become seas. The low areas of Mauritania and Senegal are flooded.
North East China is flooded as are parts of Manchuria. Coastal areas of South East Asia are flooded in Cambodia, Thailand, Burma and Bangladesh. The Indian subcontinent becomes the Indian Peninsula as the Ganges and Indus Valleys both flood. A large portion of Pakistan is under water.
Australia appears to get an inland sea opening to the ocean in the south, along with an enlargement of the Gulf of Carpenteria in the north. Lots of various islands in the oceans either shrink or disappear entirely.