Let’s imagine I take a giant magic bulldozer, and shove all land from central Mexico to southern Peru into the ocean.
Now water from the central Atlantic Equatorial Currents runs straight through into the Pacific rather than being deflected by land in the Americas.
What impact will that have on Earth’s climate?
I’d imagine that hurricanes are strengthened because they can run now from the Cape Verde Islands straight all the way to Hong Kong - possibly more precipitation in general for southeast Asia and Indonesia. What else might happen regarding the patterns of precipitation and heat?
Hurricanes would be the least of it. It is speculated, although not firmly established, that the final rise of the Isthmus of Panama breaking the last connection between the Atlantic and Pacific was a major factor in initiating the Ice Ages in the Northern Hemisphere. This was because it created the Thermohaline Circulation in the Oceans, aka “The Global Conveyor Belt,” by allowing salinity differences to develop between the two oceans.
At the very least, we can say such a major change in climate throughout the world. It would be difficult to predict the details of change in any one locality, however.
I get it. I’m also interested in wild supposition and ideas about changes with even the merest thread of fact to support them, so accuracy of the prediction is less important than plausibility.
The Trade Winds will still blow the equatorial Atlantic surface waters to the west and the Westerlies will still blow the North Atlantic water east … the mid-Atlantic gyre will remain … obviously some of the waters will pass through this gap between the Americas so this would reduce the rotational velocity of the gyre … however this would also reduce the heat transfer between the equator and poles via ocean water … this would have to be replaced by stronger winds which in turn increase the velocity of the gyre …
As Colibri noted, Central America plugging the gap between the Americas is speculated to have caused our current Ice Age about 30 million years ago … if true then the world will warm up and melt all the permanent ice that currently exists (except at the highest mountain tops) … so call it a 15º to 20ºC increase in average temperatures and tropical conditions pole to pole …
The average day would be shorter as well … all this mass you’ve bulldozed into the ocean will now be closer to the Earth’s center of gravity and with a healthy dose of conservation of angular momentum (c.f. a figure skate’s spin) the Earth would have to spin faster on its axis …
The insects would thrive in this environment and begin to develop technology including nuclear weapons … they like radiation and would be quick to irradiate all the land masses eliminating all their competition … starting with Nebraska …
I recently read an old sf short story on this exact scenario. I forgot the title. Suffice it to say that the world teamed up to refill the gap to restore the climate before too many people froze or starved to death. I think Europe froze. Pacific waters flowed East through the gap.
Nitpick: 3 million years ago. The Isthmus of Panama started to be created as a series of islands maybe 20 million years ago, but wasn’t filled in until about 3 million years ago and the Ice Ages started some time after that.
Now I had to go and find the story. Shifting Seas 400 mile gap from Panama through Nicaragua via the magical world and actions of science fiction.
From 1937:
They fear our corn base bio-espionage capabilities. You ever eat a serving of tasty corn and then see intact, undigested kernels in your excrement? Please don’t tell me that you think that’s an accident. We have data recovery agents in ever water treatment facility that services every city of a million or more people in the world. We find just one kernel and we know every thought you had between consumption and elimination.
3 million years ago is when the land bridge was completed and allowed animal life to migrate between the continents … the beginning of this process is far older and began as the Caribbean plate “hung up” forcing the Pacific plate to subduct under … the resulting volcanic arc is what we know as Central America today …
However, the article reports that modeling these events shows that only 50 feet ocean depth is all that’s needed for the free flow of surface currents between the oceans … so a little longer than 3 million years but no where even close to the 30 million years I claimed …
The OP will have to dig down with his magic bulldozer this 50 feet and keep working as more material comes up … sounds expensive if he’s paying union scale …
It also occurs to me that if a drastic alteration of climate is the goal, he might be better piling the Rocky Mountains into a heap … something that would rise up into the Stratosphere … this would cause the westerly flow to go around such a monolith and prevent to some degree the warm moist Gulf air from flowing up from the south, which may give the Midwest a distinct dry season during summers … this has the advantage of not needing maintenance, once done we’ll be fine and can sit back and watch the economic disaster unfold …
I personally know the geologists who made the claim. Note that the article is from 2012. It says that the proponent of a 3 million year closure was planning to write a rebuttal. That was published in 2016, and pretty thoroughly refutes the idea of a closure 10-12 million years ago.