Quaternary Science Reviews 25 (2006) 1152–1167 Paleoclimate history of Gala´pagos surface waters over the last 135,000 yr David W. Lea a,Ã , Dorothy K. Pak a , Christina L. Belanger a , Howard J. Spero b , Mike A. Hall c , Nicholas J. Shackleton c,{ a Department of Earth Science and Marine Science Institute, University of California, Santa Barbara, CA 93106-9630, USA b Department of Geology, University of California, Davis, CA 95616, USA c Department of Earth Sciences, Godwin Laboratory, Pembroke St., University of Cambridge, Cambridge CB2 3A, UK Received 3 August 2005; accepted 14 November 2005 Abstract Records of planktonic and benthic foraminiferal d 18 O and planktonic Mg/Ca from core TR163-22, just northwest of the Gala´pagos Islands, reveal a detailed (250–450 year resolution) climate history of the region over the last 135 thousand years (kyr). Sea surface temperatures (SSTs), reconstructed from G. ruber Mg/Ca, averaged 24.370.4 1C during the Holocene, 22.670.6 1C during marine isotope stage (MIS) 2, 3 and 4, and 26.070.9 1C during MIS 5e. Changes in SST lead changes in both planktonic and benthic d 18 O by an average 3 kyr, suggesting that SST changes in this region predated continental ice volume changes. Changes in SST display clear millennial scale variability, especially in marine isotope stage 3, with behavior somewhat similar to Antarctic proxy air temperature and South Pacific SST records. Removal of the temperature component from the planktonic d 18 O record demonstrates that glacial- interglacial d 18 O-water changes at this site were 1.070.2%, similar to estimates for mean ocean shifts, implying that salinity changes due to regional hydrological variation between the Last Glacial Maximum and Holocene in the Gala´ pagos region were minimal. Comparison between the TR163-22 SST record and an SST record from core TR163-19 North of the Equatorial Front reveals a largely similar broad- scale climate history, suggesting that changes in the Gala´pagos region were caused by large scale forcing rather than by local or regional dynamical changes. Changes in atmospheric greenhouse forcing are the most plausible explanation for the observed large-scale climate changes in the eastern equatorial Pacific. r 2006 Elsevier Ltd. All rights reserved. 1. Introduction Establishing the late Pleistocene temperature and salinity history of key tropical oceanic regions is fundamental to establishing the climate impact of the tropics on both millennial and orbital time scales (Bard et al., 1997; Cane and Clement, 1999; Kienast et al., 2001; Koutavas et al., 2002; Lea et al., 2000, 2003; Rosenthal et al., 2003; Schmidt et al., 2004; Stott et al., 2002, 2004; Visser et al., 2003). The eastern equatorial Pacific (EEP) plays a central role in the oceanic tropics. The EEP is a tropical region greatly dominated by vertical and horizontal advection of cold waters, which leads to steep horizontal and vertical temperature gradients. Because of the link to El Nin˜ o/ southern Oscillation (ENSO) phenomenon, the EEP is the tropical oceanic region that experiences the greatest inter- annual variability. It is also the major oceanic source region for carbon dioxide (Takahashi et al., 2002). For all these reasons, past changes in the EEP are expected to be a key diagnostic for the role of the tropics in global climate change. The Gala´pagos Island region is in the center of the EEP cold tongue and experiences the full range of annual and interannual variability unique to this region (Palacios, 2004). The archipelago lies at the intersection of the Cocos and Carnegie Ridges and is surrounded by a variety of bathymetric regimes hosting carbonate-rich marine sedi- ments. Sediments from the shallow tectonic ridges and volcanic platforms can be used to reconstruct aspects of ARTICLE IN PRESS 0277-3791/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2005.11.010 Ã Corresponding author. Tel.: +1 805 893 8665; fax: +1 805 893 7182. E-mail address: lea@geol.ucsb.edu (D.W. Lea). { Deceased 24 January 2006