Supplementary Figure 1. New downcore data from this study. Triangles represent the depth of radiocarbon dates. Error bars represent 2 standard error

Transcription

1 Supplementary Figure 1. New downcore data from this study. Triangles represent the depth of radiocarbon dates. Error bars represent 2 standard error of measurement (s.e.m.). 1

2 Supplementary Figure 2. Particle effects on the sedimentary 231 Pa/ 230 Th ratio. The 231 Pa/ 230 Th ratio in all available cores compared to opal fluxes (a) carbonate fluxes (b) and detrital fluxes (c) 5,9-11. Each point represents a single sample from a single core. The Coretop series represents three new coretop data points presented here (see Supplementary Data 2 for core names and locations). Cores RC16-66 and RC account for most of the positive correlation in (c) (see Results). 2

3 Supplementary Figure 3. Particle effects on the sedimentary 231 Pa/ 230 Th ratio in the depth survey. The 231 Pa/ 230 Th ratio in sediments from 21 of the 25 cores included in the depth surveys (Figures 2, 3 of the main text) compared to opal fluxes (a) and total 230 Th normalized fluxes (21cores; b). Each point represents the average 231 Pa/ 230 Th ratio (flux) from one core for the indicated time period. 3

4 Supplementary Figure 4. All available 231 Pa/ 230 Th data. Data are plotted against water depth and distinguished by depositional setting for the Holocene (a), HS1 (b) and the LGM (c). Error bars represent 95% confidence intervals around the mean of data from each core for each time period. Sites on the margin and in the two opal belts might be expected to experience greater particle scavenging. 4

5 Supplementary Figure 5. The difference between HS1 and LGM 231 Pa/ 230 Th compared to the HS1-LGM difference in opal flux. Data come from all cores in the 25-core depth survey with available opal flux data (n=20). As time moves forward from the LGM to HS1 the 231 Pa/ 230 Th ratio generally increases, with little discernable pattern of change in opal fluxes. 5

6 Supplementary Figure 6. The mean 231 Pa/ 230 Th ratio in sediments and alternate weightings of the data. The arithmetic mean 231 Pa/ 230 Th ratio in sediments from the Holocene (0-10 kyr BP) 2,5,6; this study,7,10-17,19-21,23-31,33, HS1 ( kyr BP) 2,7,10-14,15; this study,17,19 and the LGM (18-25 kyr BP) 2,3,5,6; this study,7,10-20 compared to the mean from Yu et al. 6 and different weighted averages of the data. Error bars indicate 95% confidence intervals. Descriptions of each weighting can be found in the Methods section in the main text. 6

7 Supplementary Table 1. A comparison of 231 Pa/ 230 Th data from equatorial Atlantic cores with data from all cores. The data are compared with respect to the mean and median of all cores. Holocene HS1 LGM All Eq. Atl. All Eq. Atl. All Eq. Atl. Mean Median Supplementary References 1 Chase, Z., Anderson, R. F., Fleisher, M. Q. & Kubik, P. W. The influence of particle composition and particle flux on scavenging of Th, Pa and Be in the ocean. Earth and Planetary Science Letters 204, (2002). 2 Bradtmiller, L. I., Anderson, R. F., Fleisher, M. Q. & Burckle, L. H. Opal burial in the equatorial Atlantic Ocean over the last 30kyr: implications for glacial-interglacial changes in the ocean silicon cycle. Paleoceanography 22, PA4216. doi: /2007pa (2007). 3 Lippold, J. Does sedimentary 231Pa/230Th from the Bermuda Rise monitor past Atlantic Meridional Overturning Circulation? Geophys. Res. Lett. 36, L12601 (2009). 4 Bradtmiller, L. I., Anderson, R. F., Fleisher, M. Q. & Burckle, L. H. Diatom productivity in the equatorial Pacific Ocean from the last glacial period to the present: A test of the silicic acid leakage hypothesis. Paleoceanography 21, PA4201, doi: /2006pa (2006). 5 Lippold, J. et al. Strength and geometry of the glacial Atlantic Meridional Overturning Circulation. Nature Geoscience 5, , doi: /ngeo1608 (2012). 6 Yu, E. F., Francois, R. & Bacon, M. P. Similar rates of modern and last-glacial ocean thermohaline circulation inferred from radiochemical data. Nature 379, (1996). 7 Gherardi, J. et al. Glacial-interglacial circulation changes inferred from 231Pa/230Th sedimentary record in the North Atlantic region. Paleoceanography 24, PA2204, doi: /2008pa (2009). 8 Hemming, S. R. et al. Provenance change coupled with increased clay flux during deglacial times in the western equatorial Atlantic. Palaeogeography Palaeoclimatology Palaeoecology 142, , doi: /s (98) (1998). 9 Bradtmiller, L., Anderson, R., Fleisher, M. & Burckle, L. Opal burial in the equatorial Atlantic Ocean over the last 30[thinsp]kyr: Implications for glacial-interglacial changes in the ocean silicon cycle. Paleoceanography 22, PA4216 (2007). 10 Christl, M. 231Pa/230Th: A proxy for upwelling off the coast of West Africa. Nucl. Instrum. Methods Phys. Res. B 268, (2009). 11 Meckler, A. N. et al. Deglacial pulses of deep-ocean silicate into the subtropical North Atlantic Ocean. Nature 495, 495-+, doi: /nature12006 (2013). 7

8 12 Gherardi, J. M. et al. Evidence from the Northeastern Atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation. Earth and Planetary Science Letters 240, (2005). 13 Hall, I. R. et al. Accelerated drawdown of meridional overturning in the late-glacial Atlantic triggered by transient pre-h event freshwater perturbation. Geophysical Research Letters 33, L16616, doi: /2006gl (2006). 14 McManus, J., Francois, R., Gherardi, J., Keigwin, L. & Brown-Leger, S. Collapse and rapid resumption of Atlantic meridional circulation linked to deglacial climate change. Nature 428, (2004). 15 Negre, C. et al. Reversed flow of Atlantic deep water during the Last Glacial Maximum. Nature 468, 84-87, doi: /nature09508 (2010). 16 Lippold, J., Gherardi, J. & Luo, Y. Testing the 231Pa/230Th paleocirculation proxy- A data versus 2D model comparison. Geophys. Res. Lett. 38, L20603 (2011). 17 Lippold, J. et al. Boundary scavenging at the East Atlantic margin does not negate use of Pa-231/Th-230 to trace Atlantic overturning. Earth and Planetary Science Letters 333, , doi:doi /J.Epsl (2012). 18 Bacon, M. P. Glacial to interglacial changes in carbonate and clay sedimentation in the Atlantic Ocean estimated from Th-230 measurements. Isotope Geoscience 2, (1984). 19 Roberts, N. L., McManus, J., Piotrowski, A. M. & McCave, I. N. Advection and scavenging controls of Pa/Th in the northern NE Atlantic. Paleoceanography 29, , doi: /2014pa (2014). 20 Pichat, S. et al. Lower export production during glacial periods in the equatorial Pacific derived from (Pa-231/Th-230)(xs,0) measurements in deep-sea sediments. Paleoceanography 19, PA4023, doi:doi: /2003PA (2004). 21 Anderson, R. F. et al. Anomalous boundary scavenging in the Middle Atlantic Bightevidence from Th-230, Pa-231, Be-10 and Pb-210. Deep-Sea Research Part II-Topical Studies in Oceanography 41, (1994). 22 Bacon, M. P. & Anderson, R. F. Distribution of thorium isotopes between dissolved and particulate forms in the deep sea. Journal of Geophysical Research 87, (1982). 23 DeMaster, D. J. The Marine Budgets of Silica and 32Si, Ph.D. Thesis, Yale Univ., (1979). 24 Ku, T. L. Uranium series disequilibrium in deep sea sediments, Ph.D. Thesis, Columbia Univ., (1966). 25 Ku, T. L., Boersma, A. & Bischoff, J. L. Age studies of mid-atlantic ridge sediments near 42 degrees N and 20 degrees N. Deep-Sea Research 19, 233 (1972). 26 Legeleux, F., Reyss, J. L. & Schmidt, S. Particle Mixing Rates in Sediments of the Northeast Tropical Atlantic-Evidence from Pb-210(xs), Cs-137, Th-228(xs) and Th- 234(xs) Downcore Distributions. Earth and Planetary Science Letters 128, (1994). 27 Mangini, A. & Diester-Haass, L. in Coastal Upwelling: Its Sediment Record (eds E. Suess & J. Thiede) (NATO Conference Series, Plenum Press, 1982). 28 Scholten, J. C., van der Loeff, M. M. R. & Michel, A. Distribution of Th-230 and Pa-231 in the water column in relation to the ventilation of the deep Arctic basins. Deep Sea Research Part II: Topical Studies in Oceanography 42, (1995). 8

9 29 Walter, H. J., vanderloeff, M. M. R. & Hoeltzen, H. Enhanced scavenging of Pa-231 relative to Th-230 in the south Atlantic south of the Polar front: Implications for the use of the Pa-231/Th-230 ratio as a paleoproductivity proxy. Earth And Planetary Science Letters 149, (1997). 30 Asmus, T. et al. Variations of biogenic particle flux in the southern Atlantic section of the Subantarctic Zone during the late Quaternary: Evidence from sedimentary Pa-231(ex) and Th-230(ex). Marine Geology 159, (1999). 31 Kumar, N. et al. Increased biological productivity and export production in the glacial Southern Ocean. Nature 378, (1995). 32 Marchal, O., Francois, R., Stocker, T. F. & Joos, F. Ocean thermohaline circulation and sedimentary Pa-231/Th-230 ratio. Paleoceanography 15, (2000). 33 Bacon, M. P. & Rosholt, J. N. Accumulation Rates of Th-230, Pa-231, and Some Transition-Metals on the Bermuda Rise. Geochimica Et Cosmochimica Acta 46, (1982). 9