THE DELTA-O-18 RECORD OF GLOBIGERINOIDES RUBER (WHITE)

On the basis of the comparison of delta(18)O values of Globigerinoides ruber (white) (delta(18)O(G.ruber)) from modern sediments and measured sea surface temperatures (SST) and salinity (SSS), delta(18)O(G.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 delta(18)O(G.ruber), paleo SST, and the global delta(18)O ice effect of sea water, with the standard error reaching +/-0.72 - +/-0.77 parts per thousand SSS. The equation was applied to a 35 kyr long delta(18)O(G.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 parts per thousand 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 parts per thousand 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 parts per thousand) along with the restoration of the salinity conveyor belt. At 9.0-5.5 ka the salinity minimum (up to 0.65 parts per thousand less than today) reflects the continental runoff linked to the phase of strong North Saharan humidity during the early Holocene climatic optimum.