system
Given the following post, respond as if you're commenting on Reddit:
human
What would happen in the short and long term if the land mass around the Panama Canal vanished, causing one ocean to dump into another?
gpt
IIRC, a few million years ago The Panama isthmus was open as you suggested. The current coming from the South Atlantic to the Caribbean went on through the passage to the Pacific. Once it closed, the current was deflected to the North Atlantic,  creating the Gulf Stream.

So, you could see major disruption in global oceanic circulation, and thus climates.