Say we evacuate Panama and lob a couple hundred nukes to blast away the land between the Atlantic and Pacific. What would the effects be? Would one flow into the other? How would the currents change? Do we have any geological records from the last time they were separated to get some idea? Alternatively, if we took all the soil and hauled it over to make a land bridge between Africa and Europe, how long would it take the Mediterranean to dry?
I recall that Cecil did a small column on that a long time ago; here.
Thanks. Would the Pacific flow into the Atlantic indefinitely, or would there be some balance in the future? Also, in terms of the species mingling, are there any good specific hypothetical examples?
I’m not sure the Mediterranean Sea would dry. There are numerous large rivers bringing in water (including the Nile). Even if the inflow isn’t sufficient to keep the water level stable (or even raise, I don’t know if currently the Mediterranean flows out in the Atlantic or the other way around), it wouldn’t dry completely in any case.
At one point there was a land bridge between Africa and Europe and the Mediterranean did really go dry, so why wouldn’t it happen again?
I’m sure that the price of gas would go up,but other than that,It shouldn’t create any problems what so ever!
A man, a plan, a con. TNT! No canal! Panama 
From what I’ve read, the flow is from the Atlantic into the Mediterranean.
The Med is saltier than the Atlantic, so that makes sense.
It actually flows both ways - surface water in, deep water out but the net flow is from the Atlantic to the Med. Surface evaporation actually takes out more water than flows in from the various rivers - the Med is actually saltier than the Atlantic - and it is kept topped up by the flow from the Atlantic.
So the Mediterranean basin would be mostly dry, with some fairly large briney lakes where the major rivers enter it.
I once read a SF story that used this idea (except they had an earthquake destroying Central America instead of nuclear explosions). In the story, the gap diverted the Gulf Stream. The absence of that warm water caused temperatures in Western Europe to significantly drop.
Golf clap…
Clearly South America would float away.
Whaddya mean, “golf clap”? That was brilliant! Hearty cheer!
I am afraid I do not have a cite for this,* but I am pretty sure that I have read that the original formation of the Central American land bridge (which I believe was largely due to volcanic activity, and so relatively fast by geological standards) had a really major effect on the Earth’s climate. IIRC it played a large part in precipitating the current series of ice ages (i.e. the pleistocene glaciation, which is still currently in progress, although we, and the whole of recorded human history, are actually in an interglacial period within the the Pleistocene ice age).
That being so, I think it is pretty certain that a sudden removal of the land bridge would also have a huge effect on climate, probably precipitating a new geological era, with mass extinctions and new dominant life forms evolving.
*Actually the Wiki page on the pleistocene/quarternary glaciation does mention it briefly.
The Altlantic, Pacific, and Indian Oceans already connect, in the southern hemisphere. Why would the Med dry up?
Tha Med is drying up because we took all the debris from the isthmus of Panama and filled in the Straits of Gibralter with it. It’s in the OP.
:smack: Sorry. I obviously read through the OP too quickly.
This is a pretty well known theory, and is widely accepted. At one time there was a wide water gap between North and South America, with full circulation of water between the Atlantic and Pacific. The continents gradually began drifting closer to one another, starting about 20 million years ago. The final closure of the Isthmus of Panama was about 3-4 million years ago. Once the flow of water between the oceans ceased, the Gulf Stream strengthened and the current pattern of thermohaline circulation, or oceanic conveyor belt. This is believed to have helped trigger glaciation cycles in the northern hemisphere. Removal of the Central American isthmus would unquestionably have very significant effects on global climate.
(However, this idea is not universally accepted. I saw a seminar just last week in which a researcher proposed that the Ice Ages were actually triggered when New Guinea and Australia drifted north far enought to restrict oceanic circulation through Indonesia, changing sea-surface conditions across the Pacific.)