Effect of the pliocene closure of the Panamanian Gateway on Caribbean and east Pacific sea surface temperatures and salinities by applying combined Mg/Ca and d18O measurements (5.6 - 2.2 Ma)
The divergence of the SST and SSS records between Caribbean Sites 999 and 1000, and east Pacific Site 1241 monitors the progressive closure of the Panamanian Gateway. The divergence of Caribbean-Pacific SSS is first recognized at Site 1000 (at 5.6 Ma) and ~1.4 million years later at Site 999 (at 4.2 Ma). This evolution reflects the decreasing inflow of relatively fresh Pacific water masses (Site 1241) into the Caribbean that led to the gradual establishment of the modern Pacific-Caribbean SSS-contrast. With the onset of Northern Hemisphere Glaciation at 2.7 Ma, sea level changes started to influence the throughflow through the Panamanian Gateway. Sea level lowstands with 50-80 m during Marine Isotope Stages (MIS) 96, 98, and 100 caused the glacial closure of the Panamanian Gateway. SSTMg/Ca in the east Pacific (Site 1241) followed the global cooling signal, while SSTMg/Ca in the Caribbean (Site 999) increased during glacials due to the cessation of the inflow of colder east Pacific watermasses.
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