# Northwest Atlantic Sediment Data Across the Marine Isotope Stage 5a/4 Boundary #----------------------------------------------------------------------- # World Data Center for Paleoclimatology, Boulder # and # NOAA Paleoclimatology Program #----------------------------------------------------------------------- # NOTE: Please cite original publication, online resource and date accessed when using these data, # If there is no publication information, please cite investigator, title, online resource and date accessed. # # # Online_Resource: http://hurricane.ncdc.noaa.gov/pls/paleox/f?p=519:1:::::P1_STUDY_ID:16556 # # Online_Resource: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2013/thornalley2013-odp1057.txt # # Archive: Paleoceanography # #-------------------- # Contribution_Date # Date: 2014-06-05 #-------------------- # Title # Study_Name: Northwest Atlantic Sediment Data Across the Marine Isotope Stage 5a/4 Boundary #-------------------- # Investigators # Investigators: Thornalley, D.J.R.; Barker, S.; Becker, J.; Hall, I.R.; Knorr, G. #-------------------- # Description_and_Notes # # #-------------------- # Publication # Authors: Thornalley, D.J.R., S. Barker, J. Becker, I.R. Hall, and G. Knorr # Published_Date_or_Year: 2013 # Published_Title: Abrupt changes in deep Atlantic circulation during the transition to full glacial conditions # Journal_Name: Paleoceanography # Volume: 28 # Issue: # Pages: 253-262 # DOI: 10.1002/palo.20025 # Abstract: Six Ocean Drilling Program (ODP) sites, in the Northwest Atlantic have been used to investigate kinematic and chemical changes in the "Western Boundary Undercurrent" (WBUC) during the development of full glacial conditions across the Marine Isotope Stage 5a/4 boundary (~70,000?years ago). Sortable silt mean grain size inline image measurements are employed to examine changes in near bottom flow speeds, together with carbon isotopes measured in benthic foraminifera and % planktic foraminiferal fragmentation as proxies for changes in water-mass chemistry. A depth transect of cores, spanning 1.8–4.6?km depth, allows changes in both the strength and depth of the WBUC to be constrained across millennial scale events. inline image measurements reveal that the flow speed structure of the WBUC during warm intervals (“interstadials”) was comparable to modern (Holocene) conditions. However, significant differences are observed during cold intervals, with higher relative flow speeds inferred for the shallow component of the WBUC (~2?km depth) during all cold “stadial” intervals (including Heinrich Stadial 6), and a substantial weakening of the deep component (~3-4 km) during full glacial conditions. Our results therefore reveal that the onset of full glacial conditions was associated with a regime shift to a shallower mode of circulation (involving Glacial North Atlantic Intermediate Water) that was quantitatively distinct from preceding cold stadial events. Furthermore, our chemical proxy data show that the physical response of the WBUC during the last glacial inception was probably coupled to basin-wide changes in the water-mass composition of the deep Northwest Atlantic. # #--------------------- # Funding_Agency # Funding_Agency_Name: Natural Environment Research Council # Grant: NE/F002734/1, NE/I006370/1 and NE/G004021/1 #--------------------- # Site_Information # Site_Name: ODP1057 # Location: North Atlantic Ocean # Country: # Northernmost_Latitude: 32.033333 # Southernmost_Latitude: 32.033333 # Easternmost_Longitude: -76.05 # Westernmost_Longitude: -76.05 # Elevation: -2584 #------------------ # Data_Collection # Collection_Name: ODP1057 Sortable Silt T13 # Earliest_Year: 85300 # Most_Recent_Year: 59250 # Time_Unit: calyr BP # Core_Length: # Notes: Age model construction for the cores based on tuning of planktic d18O and % carbonate [Giosan et al., 2001] records to abrupt changes in NGRIP d18O [NGRIP members, 2004]. #------------------ # Chronology: # Age model construction for the cores based on tuning of planktic d18O and % carbonate [Giosan et al., 2001] records to abrupt changes in NGRIP d18O [NGRIP members, 2004]. # #------------------ # Variables # # Data line variables format: one variable per line, shortname- 9 components: what, material, error, units, seasonality, archive, detail, method, C or N for Character or Numeric data) # Data line format: tab-delimited text, variable short name as header ## age_calkaBP age,,,calendar kyr before 1950AD,,,,,N ## SS sortable silt mean grain size,,,µm,,paleoceanography,,,N ## SS-norm sortable silt mean grain size,,,µm,,paleoceanography,normalized to site long-term mean,,N #----------------- # Data: # Missing Value: age_calkaBP SS SS-norm 59.250 16.4 -0.87 59.500 NaN NaN 59.766 18.2 0.52 60.031 17.4 -0.10 60.297 18.4 0.68 60.562 NaN NaN 60.828 19.2 1.30 61.093 17.6 0.06 61.359 16.8 -0.56 61.624 NaN NaN 61.890 16.9 -0.49 62.155 18 0.37 62.421 18.5 0.76 62.686 NaN NaN 62.952 16.1 -1.11 63.217 17.1 -0.33 63.483 17 -0.41 63.748 NaN NaN 64.014 16.5 -0.80 64.279 NaN NaN 64.545 16.5 -0.80 64.810 16.55 -0.76 65.076 16.73 -0.62 65.341 NaN NaN 65.341 17.35 -0.14 65.607 17.55 0.02 65.872 18.72 0.93 66.138 17.38 -0.11 66.403 NaN NaN 66.403 16.27 -0.98 66.669 16.90 -0.49 66.934 17.46 -0.05 67.200 17.42 -0.08 67.775 NaN NaN 67.775 16.53 -0.77 68.350 17.01 -0.40 68.925 18.18 0.51 69.500 18.19 0.52 69.967 NaN NaN 69.967 16.83 -0.54 70.433 16.08 -1.12 70.900 15.64 -1.46 71.120 16.12 -1.09 71.340 NaN NaN 71.340 18.94 1.10 71.560 15.80 -1.34 71.780 16.28 -0.97 72.000 22.63 3.96 72.567 NaN NaN 72.567 19.88 1.83 73.133 20.90 2.62 73.700 16.28 -0.97 74.367 16.10 -1.11 75.033 NaN NaN 75.033 18.83 1.01 75.700 19.34 1.41 76.700 NaN NaN 76.700 19.52 1.55 77.700 17.18 -0.27 78.700 16.07 -1.13 79.600 17.21 -0.25 80.500 NaN NaN 80.500 17.62 0.07 81.125 16.49 -0.80 81.750 15.99 -1.19 82.375 16.91 -0.48 83.000 NaN NaN 83.000 16.67 -0.66 83.767 17.82 0.23 84.533 19.67 1.66 85.300 20.66 2.43