(Table 1) Results of alkenone analyses of ODP Hole 165-1002C

We determined alkenone concentrations (µg/g dry sediment) and unsaturation indices (Uk'37) on 280 samples from Ocean Drilling Program Hole 1002C over the last full glacial cycle (marine oxygen isotope Stages [MIS] 1-6). Alkenone concentrations vary dramatically in relation to glacial-interglacial cycles, with high concentrations typical of interglacial stages, high sea level, inferred high surface productivity, and bottom-water anoxia. Our reconstruction of low productivity during the last glacial maximum is consistent with previous reports of a sharp decline in the foraminiferal species Neogloboquadrina dutertrei, an upwelling index. Alkenone paleotemperatures show little cooling at both the last glacial maximum and MIS 6. Variations of as much as 4°C occurred during the earlier part of MIS 3 and MIS 4 as well as the latter part of MIS 5. The absence of cooling during glacial maxima determined from alkenone paleothermometry is consistent with faunal reconstructions for the western Caribbean but requires that much of the oxygen isotopic record of the planktonic foraminifer Globigerinoides ruber be influenced by salinity variations rather than temperature.

(Table S1) Age determination of ODP Site 165-1002

A series of 14C measurements in Ocean Drilling Program cores from the tropical Cariaco Basin, which have been correlated to the annual-layer counted chronology for the Greenland Ice Sheet Project 2 (GISP2) ice core, provides a high-resolution calibration of the radiocarbon time scale back to 50,000 years before the present. Independent radiometric dating of events correlated to GISP2 suggests that the calibration is accurate. Reconstructed 14C activities varied substantially during the last glacial period, including sharp peaks synchronous with the Laschamp and Mono Lake geomagnetic field intensity minimal and cosmogenic nuclide peaks in ice cores and marine sediments. Simulations with a geochemical box model suggest that much of the variability can be explained by geomagnetically modulated changes in 14C production rate together with plausible changes in deep-ocean ventilation and the global carbon cycle during glaciation.