North Atlantic Dansgaard-Oeschger Cycle Salinity Reconstructions ----------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program ----------------------------------------------------------------------- NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!! NAME OF DATA SET: North Atlantic Dansgaard-Oeschger Cycle Salinity Reconstructions LAST UPDATE: 10/2006 (Original receipt by WDC Paleo) CONTRIBUTORS: Matthew W. Schmidt, Maryline J. Vautravers, Howard J. Spero IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2006-094 SUGGESTED DATA CITATION: Schmidt, M.W., et al. 2006. North Atlantic Dansgaard-Oeschger Cycle Salinity Reconstructions. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2006-094. NOAA/NCDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Schmidt, M.W., M.J. Vautravers, and H.J. Spero. 2006. Rapid subtropical North Atlantic salinity oscillations across Dansgaard–Oeschger cycles. Nature, Vol. 443, No. 7111, pp.561-564, doi:10.1038/nature05121, 5 Oct 2006. ABSTRACT: Geochemical and sedimentological evidence suggest that the rapid climate warming oscillations of the last ice age, the Dansgaard-Oeschger cycles, were coupled to fluctuations in North Atlantic meridional overturning circulation through its regulation of poleward heat flux. The balance between cold meltwater from the north and warm, salty subtropical gyre waters from the south influenced the strength and location of North Atlantic overturning circulation during this period of highly variable climate. Here we investigate how rapid reorganizations of the ocean- atmosphere system across these cycles are linked to salinity changes in the subtropical North Atlantic gyre. We combine Mg/Ca palaeothermometry and oxygen isotope ratiomeasurements on planktonic foraminifera across four Dansgaard-Oeschger cycles (spanning 45.9-59.2 kyr ago) to generate a seawater salinity proxy record from a subtropical gyre deep-sea sediment core. We show that North Atlantic gyre surface salinities oscillated rapidly between saltier stadial conditions and fresher interstadials, covarying with inferred shifts in the Tropical Atlantic hydrologic cycle and North Atlantic overturning circulation. These salinity oscillations suggest a reduction in precipitation into the North Atlantic and/or reduced export of deep salty thermohaline waters during stadials. We hypothesize that increased stadial salinities preconditioned the North Atlantic Ocean for a rapid return to deep overturning circulation and high-latitude warming by contributing to increased North Atlantic surface-water density on interstadial transitions. GEOGRAPHIC REGION: North Atlantic PERIOD OF RECORD: 59-45 KYrBP FUNDING SOURCES: JOI-ODP Schlanger Ocean Drilling Fellowships to M.W.S. and a US National Science Foundation grant to H.J.S. DESCRIPTION: Reconstructed surface salinities across four Dansgaard–Oeschger cycles at Ocean Drilling Program (ODP) site 1060, located on the Blake Outer Ridge near the modern position of the northward flowing Gulf Stream. ODP1060: 30 46'N, 74 28'W, 3480 meters depth Seawater d18O covaries linearly with surface salinity, making it one of the most direct proxies for estimating salinity in the modern ocean. Because foraminiferal calcite (d18OC) is controlled by temperature and d18OSW, d18OSW can be computed if temperature is determined independently. Using combined Mg/Ca palaeothermometry and d18O analyses of shells from the surface-dwelling foraminifera Globigerinoides ruber (white variety), we produce a continuous millennial-scale record (4 cm sampling, 75–250-year resolution) of gyre d18OSW variability. DATA: ODP1060 G. ruber stable isotopes and Mg/Ca data, plus calculated Mg/Ca SST and d18O-sw. Core Section Interval (cm) Depth Age(kyr) G.ruber G.ruber Mg/Ca Mg/Ca d18O-sw Begin End d13C d18O mmol/mol SST ODP 1060A 2H-5 10 12 1704 45.88 -0.48 -0.59 3.086 25.4 1.53 ODP 1060A 2H-5 14 16 1708 46.08 -0.44 -0.72 3.356 26.3 1.58 ODP 1060A 2H-5 18 20 1712 46.28 -0.45 -0.77 3.405 26.5 1.57 ODP 1060A 2H-5 22 24 1716 46.47 -0.58 -0.90 3.447 26.6 1.47 ODP 1060A 2H-5 26 28 1720 46.67 -0.05 -0.77 3.433 26.6 1.59 ODP 1060A 2H-5 30 32 1724 46.87 0.33 -0.78 4.106 28.6 1.99 ODP 1060A 2H-5 34 36 1728 47.06 0.42 -0.71 3.853 27.9 1.92 ODP 1060A 2H-5 38 40 1732 47.26 -0.13 -0.40 3.606 27.1 2.07 ODP 1060A 2H-5 42 44 1736 47.34 0.60 -0.09 3.349 26.3 2.21 ODP 1060A 2H-5 46 48 1740 47.41 0.10 -0.02 3.111 25.5 2.12 ODP 1060A 2H-5 50 52 1744 47.48 0.07 -0.06 3.157 25.6 2.11 ODP 1060A 2H-5 54 56 1748 47.56 0.12 -0.07 3.341 26.3 2.22 ODP 1060A 2H-5 58 60 1752 47.63 -0.22 -0.13 3.393 26.4 2.20 ODP 1060A 2H-5 62 64 1756 47.71 0.03 -0.06 3.504 26.8 2.35 ODP 1060A 2H-5 66 68 1760 47.78 0.11 -0.02 3.339 26.3 2.28 ODP 1060A 2H-5 70 72 1764 47.85 -0.09 -0.11 3.301 26.1 2.15 ODP 1060A 2H-5 74 76 1768 47.93 -0.48 -0.05 ODP 1060A 2H-5 78 80 1772 48.00 -0.60 -0.05 3.511 26.8 2.36 ODP 1060A 2H-5 82 84 1776 48.08 -0.02 -0.06 3.285 26.1 2.20 ODP 1060A 2H-5 86 88 1780 48.15 0.12 0.00 3.163 25.7 2.17 ODP 1060A 2H-5 90 92 1784 48.22 0.32 0.12 3.086 25.4 2.23 ODP 1060A 2H-5 94 96 1788 48.30 0.00 0.09 3.225 25.9 2.31 ODP 1060A 2H-5 98 100 1792 48.37 -0.38 0.05 3.099 25.4 2.18 ODP 1060A 2H-5 102 104 1796 48.45 -0.24 0.13 3.139 25.6 2.28 ODP 1060A 2H-5 106 108 1800 48.52 -0.81 -0.29 3.802 27.7 2.30 ODP 1060A 2H-5 110 112 1804 48.59 -0.04 -0.13 3.120 25.5 2.01 ODP 1060A 2H-5 114 116 1808 48.67 0.04 0.12 3.461 26.7 2.50 ODP 1060A 2H-5 118 120 1812 48.74 -0.13 0.02 3.159 25.7 2.18 ODP 1060A 2H-5 122 124 1816 48.82 -0.19 0.07 3.475 26.7 2.46 ODP 1060A 2H-5 126 128 1820 48.89 0.22 0.31 3.039 25.2 2.38 ODP 1060A 2H-5 134 136 1828 49.04 0.10 0.03 3.467 26.7 2.42 ODP 1060A 2H-5 142 144 1836 49.19 1.13 0.17 3.125 25.5 2.31 ODP 1060A 2H-6 2 4 1846 49.37 0.08 0.19 3.575 27.0 2.64 ODP 1060A 2H 6W 6 8 1850 49.45 0.14 0.21 3.212 25.8 2.42 ODP 1060A 2H 6W 10 12 1854 49.52 0.57 -0.18 3.463 26.7 2.20 ODP 1060A 2H 6W 14 16 1858 49.69 0.00 -0.15 3.116 25.5 1.98 ODP 1060A 2H 6W 18 20 1862 49.76 0.55 -0.05 2.736 24.1 1.78 ODP 1060A 2H 6W 22 24 1866 49.84 0.46 0.16 2.576 23.4 1.86 ODP 1060A 2H 6W 26 28 1870 50.09 0.43 0.05 2.556 23.3 1.73 ODP 1060A 2H 6W 30 32 1874 50.34 0.33 -0.17 2.627 23.6 1.57 ODP 1060A 2H 6W 34 36 1878 50.59 0.38 -0.01 2.727 24.0 1.81 ODP 1060A 2H 6W 38 40 1882 50.84 0.01 0.00 3.067 25.3 2.10 ODP 1060A 2H 6W 42 44 1886 51.09 -0.01 -0.20 3.174 25.7 1.98 ODP 1060A 2H 6W 46 48 1890 51.34 -0.40 -0.48 3.336 26.3 1.81 ODP 1060A 2H 6W 50 52 1894 51.59 0.06 -0.30 3.090 25.4 1.82 ODP 1060A 2H 6W 54 56 1898 51.84 0.23 -0.33 3.296 26.1 1.93 ODP 1060A 2H 6W 58 60 1902 52.09 -0.25 -0.55 3.040 25.2 1.53 ODP 1060A 2H 6W 62 64 1906 52.34 -0.04 -0.71 3.321 26.2 1.57 ODP 1060A 2H 6W 66 68 1910 52.58 0.16 -0.52 3.422 26.5 1.83 ODP 1060A 2H 6W 70 72 1914 52.83 -0.38 -0.74 3.123 25.5 1.40 ODP 1060A 2H 6W 74 76 1918 53.08 -0.14 -0.58 3.318 26.2 1.70 ODP 1060A 2H 6W 78 80 1922 53.33 -0.70 -0.55 3.203 25.8 1.65 ODP 1060A 2H 6W 82 84 1926 53.58 -0.62 -0.49 3.173 25.7 1.69 ODP 1060A 2H 6W 86 88 1930 53.83 -0.55 -0.78 3.288 26.1 1.48 ODP 1060B 3H 1W 34 36 1932 53.96 -0.49 -0.43 3.397 26.5 1.90 ODP 1060B 3H 1W 38 40 1936 54.21 -0.47 -0.55 3.353 26.3 1.76 ODP 1060B 3H 1W 42 44 1940 54.46 0.38 -0.61 3.246 26.0 1.62 ODP 1060B 3H 1W 46 48 1944 54.71 -0.17 -0.43 3.204 25.8 1.77 ODP 1060B 3H 1W 50 52 1948 54.96 0.14 -0.52 3.144 25.6 1.63 ODP 1060B 3H 1W 54 56 1952 55.12 -0.65 -0.60 3.089 25.4 1.51 ODP 1060B 3H 1W 58 60 1956 55.21 -0.28 -0.13 3.159 25.7 2.03 ODP 1060B 3H 1W 62 64 1960 55.30 -0.35 -0.15 3.028 25.2 1.92 ODP 1060B 3H 1W 66 68 1964 55.39 0.07 -0.12 3.257 26.0 2.12 ODP 1060B 3H 1W 70 72 1968 55.48 0.22 0.08 2.926 24.8 2.07 ODP 1060B 3H 1W 74 76 1972 55.57 0.31 0.31 3.070 25.3 2.41 ODP 1060B 3H 1W 78 80 1976 55.66 0.37 0.38 3.285 26.1 2.63 ODP 1060B 3H 1W 82 84 1980 55.75 -0.08 0.09 3.307 26.2 2.36 ODP 1060B 3H 1W 86 88 1984 55.84 -0.44 -0.42 3.306 26.2 1.85 ODP 1060B 3H 1W 90 92 1988 55.93 0.01 -0.39 3.268 26.0 1.86 ODP 1060B 3H 1W 94 96 1992 56.02 0.11 0.13 2.612 23.5 1.86 ODP 1060B 3H 1W 98 100 1996 56.11 -0.09 0.20 3.028 25.2 2.27 ODP 1060B 3H 1W 102 104 2000 56.20 0.31 -0.08 3.093 25.4 2.04 ODP 1060B 3H 1W 106 108 2004 56.29 0.58 0.04 3.029 25.2 2.11 ODP 1060B 3H 1W 110 112 2008 56.38 0.07 0.13 3.075 25.4 2.24 ODP 1060B 3H 1W 114 116 2012 56.47 0.47 0.18 2.604 23.5 1.90 ODP 1060B 3H 1W 118 120 2016 56.56 0.25 0.40 3.240 25.9 2.63 ODP 1060B 3H 1W 122 124 2020 56.65 0.03 0.11 2.982 25.0 2.14 ODP 1060B 3H 1W 126 128 2024 56.74 0.02 0.10 2.778 24.2 1.97 ODP 1060B 3H 1W 130 132 2028 56.83 0.55 0.04 3.084 25.4 2.15 ODP 1060B 3H 1W 134 136 2032 56.92 0.34 0.36 3.187 25.8 2.55 ODP 1060B 3H 1W 138 140 2036 57.01 0.02 -0.14 3.551 27.0 2.30 ODP 1060B 3H 1W 142 144 2040 57.10 0.30 0.28 2.598 23.5 1.99 ODP 1060B 3H 1W 146 148 2044 57.18 -0.14 0.21 2.875 24.6 2.15 ODP 1060B 3H 2W 2 4 2050 57.49 -0.26 -0.24 2.911 24.7 1.74 ODP 1060B 3H 2W 6 8 2054 57.66 -0.50 -0.21 3.088 25.4 1.91 ODP 1060B 3H 2W 10 12 2058 57.83 -0.23 -0.16 3.021 25.2 1.91 ODP 1060B 3H 2W 14 16 2062 58.00 -0.89 -0.56 2.939 24.9 1.44 ODP 1060B 3H 2W 18 20 2066 58.18 -0.14 -0.45 3.383 26.4 1.87 ODP 1060B 3H 2W 22 24 2070 58.35 0.10 -0.36 3.314 26.2 1.91 ODP 1060B 3H 2W 26 28 2074 58.52 0.28 -0.29 3.601 27.1 2.18 ODP 1060B 3H 2W 30 32 2078 58.69 0.07 -0.13 3.040 25.2 1.95 ODP 1060B 3H 2W 34 36 2082 58.87 0.05 -0.22 3.173 25.7 1.95 ODP 1060B 3H 2W 38 40 2086 59.04 -0.33 -0.40 3.140 25.6 1.75 ODP 1060B 3H 2W 42 44 2090 59.21 0.21 0.07 3.307 26.2 2.34