Interannual-decadal variability in the equatorial Pacific El Niño-Southern Oscillation (ENSO) induces climate changes at global scale, but its potential influence during past global climate change is not yet well constrained. New high-resolution eastern equatorial Pacific proxy records of thermocline conditions present new evidence of strong orbital control in ENSO-like variability over the last 275,000 years. Recurrent intervals of saltier thermocline waters are associated with the dominance of La Niña-like conditions during glacial terminations, coinciding with periods of low precession and high obliquity. The parallel dominance of d13C-depleted waters supports the advection of Antarctic origin waters toward the tropical thermocline. This "oceanic tunneling" is proposed to have reinforced orbitally induced changes in ENSO-like variability, composing a complex high- and low-latitude feedback during glacial terminations.

DEPTH, sediment/rock [m] is given in mcd. 14C ages measuerd on Neogloboquadrina dutertrei. Twelve raw radiocarbon ages younger than 20-ky were calibrated using Calib 5.0.1 software (S2) with the marine dataset MARINE04 that incorporates the global ocean reservoir effect (R ~ 400yr) (Hughen et al., 2004). An average local reservoir effect correction (deltaR) of 72+-35 yr was also incorporated in the calculations (http://calib.qub.ac.uk/marine/). The calibration of five radiocarbon ages between 22.1 14C ky and 34.7 14C ky was performed using the Fairbanks et al. (2005) marine calibration dataset. Beyond this age range we have applied two different approaches for the age scale construction based on visual tuning with Antarctic ice-core records on their orbital tuned age scale (Shackleton et al., 2000). The ages for the onset of the Terminations II and III were obtained in base to the findings of Spero et al. (2002), which demonstrated that the initiation of the N. dutertrei d13C minima in the EEP coincide with the initial rise in atmospheric CO2. Consistently, we have tied the onset of our N. dutertrei d13C minima to the CO2 increase in the Vostok high resolution CO2 record (Fischer et al., 1999) after conversion of CO2 ages to the orbital age scale (Shackleton et al., 2000). Further support to this approach is provided by the independently dated Termination I which confirms that the initiation of the N. dutertrei d13C minima in site 1240 was synchronous to the Vostok CO2 increase. Additional age controls have been obtained after graphical fitting between Site 1240 Mg/Ca derived SST and the Antactic Vostok dD records (Petit et al., 1997). An additional support to the resulting age model is provided by the resulting age of the so-called ash layer "L" (Ninkovich and Shackleton, 1975) which is clearly identified in Site 1240 at 25.71 meters composite depth (m.c.d.). The age of the ash layer "L" was previously estimated in 230,000+-10,000 yr (Ninkovich and Shackleton, 1975) whereas according to our age framework the age of the ash layer "L" would be 237,239 yr falling therefore well within the previous error range estimations and provides a further confirmation for the validity of our age scale construction approach.