Changes in planktic foraminiferal faunas, temperature and salinity in the Gulf Stream during the last 30,000 years: influence of meltwater via the Mississippi River

Variations in the distribution of planktic foraminiferal faunas, temperature and salinity in the surface water of the Gulf Stream during the last 30,000 years have been reconstructed based on a sediment core from the Blake Ridge, subtropical western Atlantic Ocean. Temperatures and salinities were calculated using planktic foraminiferal transfer functions and previously published oxygen isotope values. Productivity was estimated using the >106 μm size fraction of planktic foraminifera. The reconstructed values show that temperature variations have been small during the investigated period with a total range of only 3 °C. The highest temperatures, about 1.5 °C above the present temperature in the area, occurred during the late Glacial, Heinrich event 1 and the mid Holocene time periods. The lowest temperatures, about 1.5 °C below the present temperatures, occurred during the Bølling interstadial. The early Holocene period was relatively cool. The low temperatures during the Bølling interstadial and during the early Holocene are in contrast to the northeastern Atlantic, where the Bølling interstadial was the warmest period of the deglaciation, and the early Holocene the warmest during the Holocene. We attribute the lower temperatures during the Bølling and early Holocene periods to colder meltwater from the Laurentide Ice Sheet flowing into the Gulf of Mexico through the Mississippi River system and carried to the Blake Ridge via the Gulf Stream.

► The SST of the Gulf Stream has varied less than 3 °C during the last 30,000 years.
► During the deglaciation Mississippi meltwater reached the core site off NE Florida.
► Meltwater continued to cool the surface water during the early Holocene.
► The SST off Florida varied in anti-phase with the SST of the NE Atlantic Ocean.