Super ENSO and Global Climate Oscillations at Millennial Time Scales

Abstract

The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (delta18O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite delta18O record into components of temperature and local water delta18O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Niño-Southern Oscillation (ENSO). El Niño conditions correlate with stadials at high latitudes, whereas La Niña conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO2, N2O, and CH4 during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Niño.

A palynological and palaeoclimatological record from the southern Philippines since the Last Glacial Maximum

“…(1) Tropical mid-upper montane rainforest group: Phyllacladus, Podocarpus, Dacrydium, Figure 2 Comparison of the oxygen isotope record of core MD06-3075 and MD98-2181. Red crosses indicate AMS 14 C ages in the MD98-2181 core [11,14]; blue lines indicate control points used; shading approximates the LGM.…”

“…Rainfall averages between 300 and 400 mm/month during summer, and between 50 and 100 mm/month during winter [11]. The annual precipitation pattern is tied to the migration of the Intertropical Convergence Zone (ITCZ) over the site, the intensity of the East Asian monsoon and the ENSO system [11,12]. In these high temperature and rainfall conditions, the vegetation is enormously rich compared with that of temperate lands.…”

“…Precipitation is greatest in summer, with roughly 80% of the annual rainfall occurring between June and October. Rainfall averages between 300 and 400 mm/month during summer, and between 50 and 100 mm/month during winter [11]. The annual precipitation pattern is tied to the migration of the Intertropical Convergence Zone (ITCZ) over the site, the intensity of the East Asian monsoon and the ENSO system [11,12].…”

“…We compared detailed Planktonic Foraminifera δ 18 O records between core MD06-3075 and MD98-2181 (6.3°N, 125.83°E, controlled with reliable AMS 14 C dates [11,14]), gaining five control points: these were the transition between Marine Oxygen Isotopic Stage (MIS) 3 and 2, the LGM period, the Younger Dryas event and several points in the Holocene (Figure 2). Ages were linearly interpolated between control points.…”

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

“…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.…”