Central American Seaway

The closure of the Central American Seaway had tremendous effects on oceanic circulation and the biogeography of the adjacent seas, isolating many species and triggering speciation and diversification of tropical and sub-tropical marine fauna.

[1] The inflow of nutrient-rich water of deep Pacific origin into the Caribbean was blocked and so local species had to adapt to an environment of lower productivity.

A closed seaway would have led to a very different North Atlantic Ocean circulation, but it impacted the surrounding atmospheric temperatures, which in turn affected the glacial cycle.

The emergence of the isthmus caused a reflection of the westward-flowing North Equatorial Current northward and enhanced the northward-flowing Gulf Stream.

[12] The closure of the seaway led to an increased poleward salt and heat transport, which strengthened the North Atlantic thermohaline circulation 2.95–2.82 million years ago.

The Central American Seaway separated North America from South America
The Great American Interchange , a faunal exchange that occurred after formation of the Isthmus of Panama bridged North and South America. Examples of migrant species in both Americas are shown.