Abstract:
Variations in the strength of North Atlantic Ocean thermohaline circulation
have been linked to rapid climate changes during the last glacial cycle
through oscillations in North Atlantic Deep Water formation and northward
oceanic heat flux. The strength of the thermohaline circulations depends
on the supply of warm, salty water to the North Atlantic, which, after
losing heat to the atmosphere,
... produces the dense water masses that sink
to great depths and circulate back south. Here we analyse two Caribbean
Sea sediment cores, combining Mg/Ca palaeothermometry with measurements
of oxygen isotopes in foraminiferal calcite in order to reconstruct tropical
Atlantic surface salinity during the last glacial cycle. We find that
the Caribbean salinity oscillated between saltier conditions during the
cold oxygen isotope stages 2, 4 and 6, and lower salinities during the
warm stages 3 and 5, covarying with the strength of North Atlantic Deep
Water formation. At the initiation of the Bolling/Allerod warm interval,
Caribbean surface salinity decreased abruptly, suggesting that the advection
of salty tropical waters into the North Atlantic amplified thermohaline
circulation and contributed to high-latitude warming. 
