(Table S1) Stable oxygen isotopic values and Mg/Ca ratios of Globigerinoides ruber w from sediment core AAS9_21

Variations in sea surface temperature (SST), d18O of sea water (?18Ow), and salinity were reconstructed for the past 68 ka using a sediment core (AAS9/21) from the eastern Arabian Sea (EAS) in order to understand the changes in evaporation and precipitation associated with the monsoon system. The Mg/Ca-derived SST record varies by ~4°C; it shows that marine isotope stage (MIS) 4 was warmer than MIS 3, that the Last Glacial Maximum was 4°C cooler than the present, and that there was a 2°C increase within the Holocene. MIS 4 records higher d18Ow and salinity values than MIS 2, suggesting variable flow of low-salinity Bay of Bengal flow into the EAS during glacial periods. The transition from MIS 4 to MIS 3 was marked with a conspicuous shift from higher to lower d18Ow values, which reflects a decrease in the evaporation-precipitation budget in the EAS, perhaps due to the strengthening of southwest monsoon. Monsoon reconstructions based on d18Ow reveal that monsoon-driven precipitation was higher during MIS 3 and MIS 1 and was lower during MIS 2 and MIS 4. This is consistent with earlier monsoon reconstructions based on upwelling indices from the western Arabian Sea. However, the amplitude of monsoon fluctuations derived through upwelling indices and d18Ow varies significantly, which may indicate spatial variability of monsoon rainfall.

XDX, Mg/Ca, and delta18O analyses of core top sediments

Mg/Ca and d18O data for four species of planktic foraminifera (G. ruber (white), G. sacculifer (without sac), N. dutertrei, and P. obliquiloculata) from core top sediments from the tropical Pacific, Atlantic, and western Indian Ocean. Deepwater calcite saturation values (Delta[CO3**2-]) at the sites range from 55 to -23 µmol/kg.

Palynological counts (dinoflagellate cysts) and foraminiferal geochemistry (d18O, d18C, Mg/Ca) of the Pliocene-Pleistocene transition in the North Atlantic

The position of the North Atlantic Current (NAC) during the intensification of Northern Hemisphere glaciation (iNHG) has been evaluated using dinoflagellate cyst assemblages and foraminiferal geochemistry from a ~260 kyr interval straddling the base of the Quaternary System from two sites: eastern North Atlantic Deep Sea Drilling Project Site 610 in the path of the present NAC and central North Atlantic Integrated Ocean Drilling Program Site U1313 in the subtropical gyre. Stable isotope and foraminiferal Mg/Ca analyses confirm cooling near the marine isotope stage (MIS) G7-G6 transition (2.74 Ma). However, a continued dominance of the dinoflagellate cyst Operculodinium centrocarpum sensu Wall and Dale (1966) indicates an active NAC in the eastern North Atlantic for a further 140 kyr. At MIS 104 (~2.60 Ma), a profound dinoflagellate cyst assemblage turnover indicates NAC shutdown in the eastern North Atlantic, implying elevated atmospheric pressure over the Arctic and a resulting shift in the westerlies that would have driven the NAC. These findings challenge recent suggestions that there was no significant southward shift of the NAC or the Arctic Front during iNHG, and reveal a fundamental climatic reorganization near the base of the Quaternary.

Sr/Ca and Cd/Ca ratios of benthic foraminifera in surface deep-sea sediments

Measurements of Sr/Ca of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera. New data for Cd/Ca support previous work in defining a contrast between waters shallower and deeper than ~2500 m. Measured element partition coefficients in foraminiferal calcium carbonate relative to sea water (D) have been described by means of a one-box model in which elements are extracted by Rayleigh distillation from a biomineralization reservoir that serves for calcification with a constant fractionation factor (alpha), such that D = (1 - f**alpha)/(l - f), where f is the proportion of Ca remaining after precipitation. A modification to the model recognises differences in element speciation. The model is consistent with differences between D[Sr], D[Ba], and D[Cd] in benthic but not planktonic foraminifera. Depth variations in D for Sr and Ba are consistent with the model, as are differences in depth variation of D[Cd] in calcitic and aragonitic benthic foraminifera. The shallower depth variations may reflect increasing calcification rates with increasing water depth to an optimum of about 2500 m. Observations of unusually lower DCd for some deep waters, not accompanied by similar [Sr], or D[Ba] may be because of dissolution or a calcification response to a lower carbonate saturation state.

Measurement results of d18O, Mg/Ca, and Ti/Ca of sediment cores GeoB10042-1 and GeoB10043-3

The advection of relatively fresh Java Sea water through the Sunda Strait is presently responsible for the low-salinity "tongue" in the eastern tropical Indian Ocean with salinities as low as 32 per mil. The evolution of the hydrologic conditions in the eastern tropical Indian Ocean since the last glacial period, when the Sunda shelf was exposed and any advection via the Sunda Strait was cutoff, and the degree to which these conditions were affected by the Sunda Strait opening are not known. Here we have analyzed two sediment cores (GeoB 10042-1 and GeoB 10043-3) collected from the eastern tropical Indian Ocean off the Sunda Strait that cover the past ~40,000?years. We investigate the magnitude of terrigenous supply, sea surface temperature (SST), and seawater d18O (d18Osw) changes related to the sea level-driven opening of the Sunda Strait. Our new spliced records off the Sunda Strait show that during the last glacial, average SST was cooler and d18Osw was higher than elsewhere in the eastern tropical Indian Ocean. Seawater d18O decreased ~0.5 per mil after the opening of the Sunda Strait at ~10 kyr B.P. accompanied by an SST increase of 1.7°C. We suggest that fresher sea surface conditions have persisted ever since due to a continuous transport of low-salinity Java Sea water into the eastern tropical Indian Ocean via the Sunda Strait that additionally increased marine productivity through the concomitant increase in terrigenous supply.

Mg/Ca and Sr/Ca in calcites and estimated distribution coefficients in marine sediments (Table 2)

Recrystallization processes in marine sediments can alter the extent to which biogenic calcite composition serves as a proxy of oceanic chemical and isotopic history. Models of calcite recrystallization developed to date have resulted in significant insights into these processes, but are not completely adequate to describe the conditions of recrystallization. Marine sediments frequently have concentration gradients in interstitial dissolved calcium, magnesium, and strontium which have probably evolved during sediment accumulation. Realistic, albeit simplified, models of the temporal evolution of interstitial water profiles of Ca, Mg, and Sr were used with several patterns of recrystallization rate variation to predict the composition of recrystallized inorganic calcite. Comparison of predictions with measured Mg/Ca and Sr/Ca ratios in severely altered calcite samples from several Deep Sea Drilling Project sites demonstrates that models incorporating temporal variation in interstitial water composition more successfully predict observed calcite compositions than do models which rely solely on present-day interstitial water chemistry. Temporal changes in interstitial composition are particularly important in interpreting Mg/Ca ratios in conjunction with Sr/Ca ratios. Estimates of Mg distribution coefficients from previous observations in marine sediments, much lower than those in laboratory studies of inorganic calcite, are confirmed by these results. Evaluation of the effects of diagenetic alteration of biogenic calcium carbonate sediment must be a site-specific process, taking into account accumulation history, present interstitial chemistry and its variation in the past, and sample depths and ages.