Paleoclimate history of Galapagos surface waters over the last 135,000 yr

Records of planktonic and benthic foraminiferal delta O-18 and planktonic Mg/Ca from core TR163-22, just northwest of the Galapagos 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 24.3+0.4 degrees C during the Holocene, 22.6+0.6 degrees C during marine isotope stage (MIS) 2, 3 and 4, and 26.0 +/- 0.9 degrees C during MIS 5e. Changes in SST lead changes in both planktonic and benthic delta O-18 by an average similar to 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 delta O-18 record demonstrates that glacial-interglacial delta O-18-water changes at this site were 1.0 +/- 0.2 parts per thousand, 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 Galapagos 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 Galapagos 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. (c) 2006 Elsevier Ltd. All rights reserved.