DOI: 10.25921/s6nb-9w96
title: NOAA/WDS Paleoclimatology - Eastern Equatorial Pacific 100Kyr Benthic d18O and SST Data

description: Amplifying both internally generated variability and remote climate signals from the Atlantic Ocean via coupled air-sea instabilities, the eastern tropical Pacific (ETP) is well situated to detect past climate changes and variations in Central American wind systems that dynamically link the Atlantic and the Pacific. Here we compare new and previously published alkenone-based sea surface temperature (SST) reconstructions from diverse environments within the ETP, i.e. the Eastern Pacific Warm Pool (EPWP), the equatorial and the northern Peruvian Upwelling regions over the past 100,000 years. Over this time period, a fairly constant meridional temperature gradient across the region is observed, indicating similar hydrographic conditions during glacial and interglacial periods. The data further reveal that millennial-scale cold events associated with massive iceberg surges in the North Atlantic (Heinrich events) generate cooling in the ETP from ~8°N to ~2°S. Data from Heinrich event 1 however indicate that the response changes sign south of 2'a1S. These millennial-scale alterations of the SST pattern across diverse environments of the ETP support previous climate modeling experiments that suggested an Atlantic-Pacific connection caused by the intensification of the Central American gap winds, enhanced upwelling and mixing north of the equator and supported by positive air-sea feedbacks in the eastern tropical Pacific.
description: The data set contains alkenone-based SST estimates, and benthic d18O from 3 cores from the eastern equatorial Pacific covering the late Quaternary.

 Methods: Cores ME0005A-24JC, ME0005A-27JC and ME0005A-43JC were analyzed for alkenone unsaturation at Dalhousie University following standard laboratory procedures detailed by Kienast et al. (2006). Sea-surface temperature estimates (UK'37 SST) were calculated from the ratio of the concentration of the di and triunsaturated alkenones, using the calibration of Prahl et al. (1988). The upper 500 cm of ME0005A-24JC were analyzed at WHOI following the same procedure and were previously published by Kienast et al. (2006). These data were shifted by +0.027 UK'37 units because of a laboratory offset determined from 10 replicate samples. Results from the last 25 kyr BP of core ME0005A-43JC were previously published in Dubois et al. (2009). Results of cores ME0005A-24JC and ME0005A-27JC were previously published in Dubois et al. (2011). 

 Stable oxygen isotope measurements of benthic foraminifera from cores ME0005A-24JC, ME0005A-27JC and ME0005A-43JC were performed at the Oregon State University College of Earth, Ocean, and Atmospheric Sciences (OSU/CEOAS) Stable Isotope Mass Spectrometer Facility using a Kiel III carbonate preparation device connected to a Thermo-Finnigan MAT-252 mass spectrometer. The data were corrected to the accepted PDB scale using an internal lab calcite standard (Wiley) and the international calcite standard NIST-8544 (NBS-19, d18O=-2.20). External precision (1 standard deviation) of the Wiley standard of similar weight to the foraminiferal samples was 'b1 0.05 per mil. Results of cores ME0005A-24JC were previously published  in Kienast et al. (2013). 

 ADDITIONAL REFERENCES: 
 Benway, H.M., Mix, A.C., Haley, B.A., Klinkhammer, G.P., 2006. Eastern Pacific Warm Pool paleosalinity and climate variability: 0-30 kyr. Paleoceanography 21, PA3008.

 Drexler, J.W., Rose, W.I.J., Sparks, R.S.J., Ledbetter, M.T., 1980. The Los Chocoyos Ash, Guatemala: a major stratigraphic marker in middle America and in three ocean basins. Quaternary Research 13, 327-345.

 Dubois, N., M. Kienast, C. Normandeau and T.D. Herbert. 2009. The east equatorial Pacific cold tongue during the last glacial maximum as seen from alkenone paleothermometry. Paleoceanography, v. 24, PA4207. 
 
 Dubois, N., M. Kienast, S. Kienast, C. Normandeau, S.E. Calvert, T.D. Herbert, and A. Mix. 2011. Millennial-scale variations in hydrography and biogeochemistry in the Eastern Equatorial Pacific over the last 100 kyr. Quaternary Science Reviews, Vol. 30, pp. 210-223. 

 Kienast, M., S.S. Kienast, S.E. Calvert, T.I. Eglinton, G. Mollenhauer, R. François and A. Mix. 2006. Eastern Pacific cooling and Atlantic overturning circulation during the last deglaciation. Nature, v. 443, 846Ð849, doi:10.1038/nature05222. 

 Kienast, S., Friederich, T., Dubois, N., Hill, P. S., Timmermann, A., Mix, A. C., Kienast, M., 2013. Near collapse of the meridional SST gradient in the eastern equatorial Pacific during Heinrich Stadial 1. Paleoceanography 28, 1-12.

 Kienast, S. S., M. Kienast, A. C. Mix, S. E. Calvert and R. Francois, 2007. Thorium-230 normalized particle flux and sediment focusing in the Panama Basin region during the last 30,000 years., Paleoceanography, 22, PA2213.

 Kusch, S., T. I. Eglinton, A. C. Mix and G. Mollenhauer, 2010. Timescales of lateral sediment transport in the Panama Basin as revealed by compound-specific radiocarbon ages of alkenones, Earth and Planetary Science Letters, 290, 340-350.

 Lisiecki, L. E. & Raymo, M. E., 2005. A Pliocene-Pleistocene stack of 57 globally distributed benthic d18O records. Paleoceanography 20, PA1003.

 Reimer, P. J., E. Bard, et al. (2013), IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0–50,000 Years cal BP, Radiocarbon, 55, 1869-1887.