Tidal forces drive equatorial surface sea water westward, which forms the Gulf Stream when this strikes the solid barrier created by the Americas.
The Gulf Stream developed when the Panama Isthmus formed about 4 million years ago. Hot equatorial surface sea water flowed from the Atlantic to the Pacific before the Panama Isthmus formed. Humans diverged from chimpanzee and bonobo during the climate change triggered when equatorial current was cut off by Panama.
European climate was cooler and much more like Canada before the change. Equatorial climate was much warmer with more rainfall.