Role of Panama uplift on oceanic freshwater balance

Comparison between planktic foraminiferal oxygen isotope records from the C aribbean Sea (Ocean Drilling Program [ODP] Site 999) and the equatorial eas t Pacific (ODP Site 851) suggests an increase in Caribbean surface-water sa linity between 4.7 and 4.2 Ma. The modern Atlantic-Pacific salinity contras t of about 1 parts per thousand became fully established at 4.2 Ma as refle cted by a 0.5 parts per thousand planktic foraminifera O-18 enrichment in t he Caribbean Sea. This is interpreted as the result of restricted surface-w ater exchange between the tropical Atlantic and Pacific in response to the shoaling of the Central American seaway. As a consequence, the Atlantic and Pacific surface-ocean circulation regime changed, as did the freshwater ba lance between the major ocean basins. Simultaneous shifts in benthic carbon isotope records in the Caribbean Sea suggest an intensification in North A tlantic thermohaline circulation. These results indicate that the Panamania n isthmus formation caused several new ocean-atmosphere feedback mechanisms that have affected climate since the early Pliocene.