Combined coccolith, foraminiferal, and biomarker reconstruction of paleoceanographic conditions over the past 120 kyr in the northern North Atlantic (59°N, 23°W)

Alkenone Paleotemperature Determinations

“…Thomsen et al (1998) determined U k 0 37 values in shallow sediment traps consistent with production in (cold) SST but showed that deeper traps and surface sediments had U k 0 37 indices 5-10 C too warm for the locations. The presence of pre-Quaternary coccoliths in floral assemblages unequivocally indicates that some portion of the flux comes from the erosion of older slope and shelf sediments Heussner, 1999, 2001;Weaver et al, 1999). A number of other sediment trap studies have found higher coccolith fluxes at depth than in shallow traps, indicating a lateral source of material (Antia et al, 2001;Sprengel et al, 2000Sprengel et al, , 2002.…”

Hyperstratification following glacial overturning events in the northern Arabian Sea

“…More likely, hyperstratification may develop under only a narrow range of boundary conditions. Reduced regional warming, caused by overall increased glacial conditions at those times [Cutler et al, 2003;Mix et al, 2001;Weaver et al, 1999], may have prevented development of the shallow density gradient needed for P. zoharyi to bloom. Conditions comparable to those following Heinrich events 6, 5, and 4 again prevailed for the transition from the Younger Dryas to the Holocene climatic optimum (Figure 3).…”

A strong temperature effect on U/Ca in planktonic foraminiferal carbonates

“…8b) (Weaver et al, 1999). Because Mg/Ca SST suggest that this site has remained relatively cold (<$13°C) during the past 40 kyr, the U/Ca-SST calibration obtained using G. bulloides from cold environments (north of 50°N) is used.…”

“…Therefore, possible preferential dissolution during laboratory cleaning could not explain the lowered Mg/Ca (Yu et al, 2007a). The dis- (Petit et al, 1999) and seawater ½CO 3 2À reconstructed from foraminiferal weight (Barker and Elderfield, 2002), compared with seawater ½CO 3 2À values calculated from U/Ca by ½CO 3 2À ¼ lnðU=Ca=14:5Þ= À 0:0025 (Russell et al, 2004) with the pre-exponential constant being adjusted to 14.5 to match the pre-industrial value; (b) temperatures reconstructed from Mg/Ca by Mg/Ca SST = ln(Mg/Ca/0.75)/0.09 and U/Ca by U/Ca SST = ln(U/Ca/4.69)/0.067 together with faunal (SIMAX) and alkenone ½U k 37 SSTs from a nearby BOFS 16K (Weaver et al, 1999). The shaded bar represents MIS 2.…”