Paleo sea surface salinities in the low‐latitude Atlantic: The δ18O record of Globigerinoides ruber (white)

Abstract

On the basis of the comparison of δ18O values of Globigerinoides ruber (white) (δ18OG. ruber) from modern sediments and measured sea surface temperatures (SST) and salinity (SSS), δ18OG. ruber values most clearly record summer SST and SSS of the uppermost 50 m of water in the low‐latitude Atlantic. A new transfer equation is presented for estimating local summer paleo SSS at 0–50 m depth using δ18OG. ruber, paleo SST, and the global δ18O ice effect of sea water, with the standard error reaching ±0.72 ‐ ±0.77‰ SSS. The equation was applied to a 35 kyr long δ18OG. ruber record and paleo SST estimates based on planktonic foraminiferal assemblages to reconstruct the paleo SSS changes along the east Atlantic margin off the northwest Sahara. The resulting local SSS show a general increase by 0.3–1.4‰ during the last glacial maximum (LGM) and large parts of glacial Termination I, suggesting a general increase in the upwelling of the highly saline North Atlantic Central Water and/or a reduced lateral advection of less saline Canary Current water. Two short salinity lows (up to 0.35‰ less than today) during and after the LGM are coeval with the Heinrich meltwater events 1 and 2 in the North Atlantic, indicating the breakdown of coastal upwelling and meltwater advection from the north. Both events are followed by an extreme SSS maximum (38.15‰) along with the restoration of the salinity conveyor belt. At 9.0–5.5 ka the salinity minimum (up to 0.65‰ less than today) reflects the continental runoff linked to the phase of strong North Saharan humidity during the early Holocene climatic optimum.