Climate Impact of Late Quaternary Equatorial Pacific Sea Surface Temperature Variations

Abstract

Magnesium/calcium data from planktonic foraminifera in equatorial Pacific sediment cores demonstrate that tropical Pacific sea surface temperatures (SSTs) were 2.8 degrees +/- 0.7 degrees C colder than the present at the last glacial maximum. Glacial-interglacial temperature differences as great as 5 degrees C are observed over the last 450 thousand years. Changes in SST coincide with changes in Antarctic air temperature and precede changes in continental ice volume by about 3 thousand years, suggesting that tropical cooling played a major role in driving ice-age climate. Comparison of SST estimates from eastern and western sites indicates that the equatorial Pacific zonal SST gradient was similar or somewhat larger during glacial episodes. Extraction of a salinity proxy from the magnesium/calcium and oxygen isotope data indicates that transport of water vapor into the western Pacific was enhanced during glacial episodes.

Planktonic foraminiferal Mg/Ca as a proxy for past oceanic temperatures: a methodological overview and data compilation for the Last Glacial Maximum

“…Erez and Honjo, 1981;Deuser and Ross, 1989;Anand et al, 2003). This issue does not seem to be critical for surface and mixed layer species such as G. sacculifer and G. ruber (w) as demonstrated by the close agreement between the calibrations for G. ruber (w) reported by Lea et al (2000) using SST and Anand et al (2003) using isotopically derived calcification temperatures (Table 1). However, the distinction becomes more important when dealing with deeper dwelling species.…”

“…There have been various methods suggested for accounting for Mg/Ca variations due to dissolution. Lea et al (2000) show that Mg/Ca ratios in G. ruber (w) from core-top samples across the Ontong Java Plateau (OJP) decrease by about 12% per kilometre increase in water depth. They use this finding to suggest a potential uncertainty in their glacial paleotemperature reconstructions of about +0.5 1C taking into account published records of carbonate preservation from that region (Farrell and Prell, 1989;Le and Shackleton, 1992).…”

“…More recently Mg/Ca thermometry has been greatly refined and applied almost routinely to paleoceanographic questions concerning temperature variability through time (e.g. Nu¨rnberg et al, 1996;Hastings et al, 1998;Lea et al, 1999Lea et al, , 2000Lea et al, , 2002Mashiotta et al, 1999;Elderfield and Ganssen, 2000;Rosenthal et al, 2000;Koutavas et al, 2002;Stott et al, 2002;Pahnke et al, 2003;Rosenthal et al, 2003;Visser et al, 2003). Mg/ Ca ratios of other calcifying organisms have also been shown to be sensitive to changes in temperature.…”

The role of North Brazil Current transport in the paleoclimate of the Brazilian Nordeste margin and paleoceanography of the western tropical Atlantic during the late Quaternary

“…per practical salinity unit (psu), considerably lower than found in some previous studies (e.g., Arbuszewski et al, 2010 Lea et al (2000) using the temperature and δ 18 O relation derived for Orbulina universa (Bemis et al, 1998) of T=14.9-4.8(δ 18 Oc -δ 18 Osw), which was shown to be applicable to G.…”

Phenyl- and cyclopentylimino derivatization for double bond location in unsaturated C37-C40 alkenones by GC-MS

“…Cultures of these species showed that the proportion of di-and triunsaturated alkenones changed linearly with water temperature [5,6]. This finding and the ubiquity of C 37 -C 39 alkenones in recent and past marine sediments has led to the widespread use of the C 37 homologs for the estimation of sea surface temperatures in climate change studies [7][8][9][10]. This method has become, at present, a reference standard for the measurement of paleotemperatures in paleo-oceanography.…”