St. Lawrence Estuary Younger Dryas Geochemical Data ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: St. Lawrence Estuary Younger Dryas Geochemical Data LAST UPDATE: 5/2009 (Original receipt by WDC Paleo) CONTRIBUTOR: Anders E. Carlson, University of Wisconsin-Madison IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2009-049 WDC PALEO CONTRIBUTION SERIES CITATION: Carlson, A.E., et al. 2009. St. Lawrence Estuary Younger Dryas Geochemical Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2009-049. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Carlson, A.E., P.U. Clark, B.A. Haley, G.P. Klinkhammer, K. Simmons, E.J. Brook, and K.J. Meissner. 2007. Geochemical proxies of North American freshwater routing during the Younger Dryas cold event. Proceedings of the National Academy of Sciences, vol. 104, no. 16, pp. 6556-6561, April 17, 2007. doi: 10.1073/pnas.0611313104 ABSTRACT: The Younger Dryas cold interval represents a time when much of the Northern Hemisphere cooled from ~12.9 to 11.5 kiloyears B.P. The cause of this event, which has long been viewed as the canonical example of abrupt climate change, was initially attributed to the routing of freshwater to the St. Lawrence River with an attendant reduction in Atlantic meridional overturning circulation. However, this mechanism has recently been questioned because current proxies and dating techniques have been unable to confirm that eastward routing with an increase in freshwater flux occurred during the Younger Dryas. Here we use new geochemical proxies (DMg/Ca, U/Ca, and 87Sr/86Sr) measured in planktonic foraminifera at the mouth of the St. Lawrence estuary as tracers of freshwater sources to further evaluate this question. Our proxies, combined with planktonic d18Oseawater and d13C, confirm that routing of runoff from western Canada to the St. Lawrence River occurred at the start of the Younger Dryas, with an attendant increase in freshwater flux of 0.06 +/- 0.02 Sverdrup (1 Sverdrup = 106 m3 s-1). This base discharge increase is sufficient to have reduced Atlantic meridional overturning circulation and caused the Younger Dryas cold interval. In addition, our data indicate subsequent fluctuations in the freshwater flux to the St. Lawrence River of ~0.06–0.12 Sverdrup, thus explaining the variability in the overturning circulation and climate during the Younger Dryas. GEOGRAPHIC REGION: St. Lawrence Estuary, western North Atlantic PERIOD OF RECORD: Younger Dryas cold interval, ~12,900 - 11,500 YrBP FUNDING SOURCES: US National Science Foundation Paleoclimate Program (P.U.C.) and US National Science Foundation (G.P.K.). DESCRIPTION: Planktonic foraminifera geochemical data (U/Ca, Mg/Ca, and Sr isotopes) as tracers of St. Lawrence River freshwater source areas. Data are from two cores in the outer St. Lawrence estuary spanning the Younger Dryas interval. Globigerina bulloides and Neogloboquadrina pachyderma (s) data from core HU90031-047, and G. bulloides data from core HU90031-044. Core HU90031-047: 45°51.14'N, 57°37.56'W, 473m depth Core HU90031-044: 44°39.41'N, 55°37.13'W, 1381m depth DATA: 1. U/Ca, G. bulloides and N. pachyderma, cores HU90031-044 and HU90031-047 Column 1: Age, Calendar KYrBP Column 2: U/Ca ratio Age U/Ca 10.778 13.906 11.148 18.052 11.288 14.095 11.398 10.575 11.553 23.392 11.697 28.570 11.794 26.901 11.858 16.364 11.939 7.481 12.035 22.650 12.197 38.854 12.280 58.440 12.350 46.536 12.437 22.207 12.542 35.596 12.716 25.770 12.960 17.653 13.071 14.573 13.093 19.745 13.115 15.811 13.457 23.656 13.595 12.089 13.710 40.031 13.917 10.961 14.032 20.068 14.147 25.203 14.285 21.059 2. Mg/Ca, G. bulloides, core HU90031-044 Column 1: Age, Calendar KYrBP Column 2: D Mg/Ca (seawater), mmol/mol Column 3: D Mg/Ca ratio, G. bulloides, mmol/mol Age Mg/Ca-sw Mg/Ca 10.778 1.320 2.374 11.148 2.020 2.506 11.288 1.640 2.185 11.398 2.251 2.764 11.553 1.273 2.145 11.697 1.198 1.833 11.794 1.057 1.315 11.858 1.290 1.359 11.939 2.262 1.960 12.035 3.938 2.489 12.197 4.296 2.187 12.280 5.060 2.864 12.350 4.722 2.471 12.437 4.340 2.046 12.542 4.509 2.313 12.716 3.537 2.090 12.960 3.433 2.255 13.071 2.210 2.390 13.093 2.999 3.360 13.115 1.825 2.222 13.200 0.921 2.200 13.228 1.160 2.109 13.457 0.857 1.387 13.595 0.682 1.194 13.710 0.596 1.163 13.917 0.002 1.071 14.032 0.320 1.129 14.147 1.437 1.723 14.285 0.860 1.300 14.377 0.054 1.042 3. Stable Isotopes, core HU90031-044 Column 1: Age, Calendar KYrBP Column 2: SST_dyno Column 3: N. pachyderma d18O, per mil Column 4: N. pachyderma d18O (seawater), per mil Column 5: N. pachyderma d13C, per mil Age SST_dyno Npl_d18O Npl_d18Osw Npl_d13C 0.000 15.805 2.55 2.675 0.93 1.252 15.781 2.45 2.567 1 2.385 15.854 2.42 2.550 1.06 3.364 16.058 2.05 2.204 0.94 4.343 16.394 1.94 2.154 0.8 5.006 15.065 1.61 1.541 0.57 5.670 16.545 1.9 2.121 0.73 6.333 16.334 1.9 2.058 0.59 6.997 15.787 2.06 2.079 0.45 7.660 15.763 2.22 2.219 0.57 8.323 16.702 2.05 2.193 0.54 8.987 15.744 2.07 1.945 0.49 9.650 16.799 2.55 2.570 0.39 10.314 15.096 2.5 2.080 0.46 10.977 17.103 2.65 2.524 0.44 11.133 15.777 2.23 1.798 0.37 11.288 15.414 2.62 2.062 0.4 11.444 15.635 2.42 1.895 0.26 11.600 16.093 2.99 2.547 0.09 11.761 14.549 2.93 2.151 -0.04 11.923 12.797 3.17 2.012 0.24 12.084 6.914 2.81 0.412 0.05 12.245 6.000 2.81 0.208 0.01 12.419 5.740 2.7 0.029 -0.14 12.594 6.034 2.87 0.245 -0.14 12.768 10.426 2.77 1.045 -0.14 12.943 9.319 2.87 0.899 -0.07 13.082 14.933 2.75 1.936 -0.17 13.138 14.271 3.28 2.340 0.14 13.194 16.772 3.16 2.731 0.17 13.250 15.069 3.25 2.456 0.17 13.365 15.334 3.4 2.640 0.15 13.480 13.980 3.53 2.467 0.12 13.595 14.284 3.48 2.459 0.07 13.710 14.591 3.41 2.432 0.07 13.825 15.725 3.54 2.777 0.03 13.940 15.711 3.56 2.773 0.05 14.055 15.111 3.48 2.510 0.04 14.170 13.922 3.28 2.052 -0.05 14.285 14.281 3.51 2.346 -0.04 14.400 15.949 3.6 2.772 0.2 14.515 12.690 3.94 2.422 -0.03 4. Sr Isotopes, G. bulliodes, Core HU90031-044 (figure 2f) Column 1: Age, Calendar KYrBP Column 2: 87Sr/86Sr isotopic ratio Column 3: Sr error Age 87Sr/86Sr Sr error 10.778 0.70916 0.0000227 11.148 0.70917 0.000014 11.288 0.70918 0.0000073 11.398 0.70919 0.0000084 11.553 0.70919 0.000014 11.697 0.70920 0.0000208 11.939 0.70916 0.0000186 12.035 0.70917 0.000021 12.197 0.70918 0.0000057 12.280 0.70923 0.00000739 12.350 0.70923 0.00000771 12.437 0.70918 0.00000965 12.542 0.70917 0.00001 12.716 0.70917 0.000016 12.960 0.70919 0.0000222 13.071 0.70916 0.0000102 13.093 0.70918 0.0000092 13.200 0.70917 0.0000052 13.457 0.70916 0.0000158 13.710 0.70918 0.0000174 14.377 0.70918 0.000003 14.596 0.70917 0.000008 14.872 0.70918 0.000010