# #----------------------------------------------------------------------- # 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:16559 # # Original_Source_URL: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/thornalley2013-cop/thornalley2013-cop-depth.txt # # Archive: Paleoceanography #-------------------- # Contribution_Date # Date: 2014-06-06 #-------------------- # Title # Study_Name: Iceland Basin Sortable Silt Data During the Holocene #-------------------- # Investigators # Investigators: Thornalley, D.J.R.; Blaschek, M.; Davies, F.J.; Praetorius, S.; Oppo, D.W.; McManus, J.F.; Hall, I.R.; Kleiven, H.; Renssen., H.; McCave, I.N. #-------------------- # Description_and_Notes # Description: # #-------------------- # Publication # Authors: Thornalley, D.J.R., Blaschek, M., Davies, F.J., Praetorius, S., Oppo, D.W., McManus, J.F., Hall, I.R., Kleiven, H., Renssen., H. and McCave, I.N. # Published_Date_or_Year: 2013 # Published_Title: Long-term variations in Iceland-Scotland overflow strength during the Holocene # Journal_Name: Climate of the Past # Volume: 9 # Issue: # Pages: 2073-2084 # DOI: 10.5194/cp-9-2073-2013 # Abstract: The overflow of deep water from the Nordic seas into the North Atlantic plays a critical role in global ocean circulation and climate. Approximately half of this overflow occurs via the Iceland–Scotland (I–S) overflow, yet the history of its strength throughout the Holocene (~ 0–11 700 yr ago, ka) is poorly constrained, with previous studies presenting apparently contradictory evidence regarding its long-term variability. Here, we provide a comprehensive reconstruction of I–S overflow strength throughout the Holocene using sediment grain size data from a depth transect of 13 cores from the Iceland Basin. Our data are consistent with the hypothesis that the main axis of the I–S overflow on the Iceland slope was shallower during the early Holocene, deepening to its present depth by ~ 7 ka. Our results also reveal weaker I–S overflow during the early and late Holocene, with maximum overflow strength occurring at ~ 7 ka, the time of a regional climate thermal maximum. Climate model simulations suggest a shoaling of deep convection in the Nordic seas during the early and late Holocene, consistent with our evidence for weaker I–S overflow during these intervals. Whereas the reduction in I–S overflow strength during the early Holocene likely resulted from melting remnant glacial ice sheets, the decline throughout the last 7000 yr was caused by an orbitally induced increase in the amount of Arctic sea ice entering the Nordic seas. Although the flux of Arctic sea ice to the Nordic seas is expected to decrease throughout the next century, model simulations predict that under high emissions scenarios, competing effects, such as warmer sea surface temperatures in the Nordic seas, will result in reduced deep convection, likely driving a weaker I–S overflow. # #--------------------- # Funding_Agency # Funding_Agency_Name: # Grant: #--------------------- # Site_Information # Site_Name: Iceland Basin # Location: North Atlantic Ocean # Country: # Northernmost_Latitude: 62.9755 # Southernmost_Latitude: 60.403333 # Easternmost_Longitude: -17.5895 # Westernmost_Longitude: -24.066667 # Elevation: #------------------ # Data_Collection # Collection_Name: Depth Group Sortable Silt T13-cop # Earliest_Year: 11200 # Most_Recent_Year: 350 # Time_Unit: cal yr BP # Core_Length: # Notes: Average sortable silt mean grain size (SS) for groups of cores organized by depth. Group 1 (1200-1375m): EW9302-30GGC, EW9302-29GGC, RAPiD-10-1P; # Group 2 (1375-1575m): EW9302-26GGC, EW9302-25GGC; Group 3 (1575-1750m): NEAP-4K, EW9302-24GGC, ODP984, EW9302-23GGC; # Group 4 (1750-2250m): EW9302-22GGC, EW9302-11GGC, ODP 983, EW9302-32GGC #------------------ # Chronology: # # #------------------ # 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.1200-1375 sortable silt mean grain size,,,µm,,paleoceanography,1200-1375m depth,,N ## SS.1200-1375_err sortable silt mean grain size,,2-sigma error,µm,,paleoceanography,1200-1375m depth,,N ## SS.1375-1575 sortable silt mean grain size,,,µm,,paleoceanography,1375-1575m depth,,N ## SS.1375-1575_err sortable silt mean grain size,,2-sigma error,µm,,paleoceanography,1375-1575m depth,,N ## SS.1575-1750 sortable silt mean grain size,,,µm,,paleoceanography,1575-1750m depth,,N ## SS.1575-1750_err sortable silt mean grain size,,2-sigma error,µm,,paleoceanography,1575-1750m depth,,N ## SS.1750-2250 sortable silt mean grain size,,,µm,,paleoceanography,1750-2250m depth,,N ## SS.1750-2250_err sortable silt mean grain size,,2-sigma error,µm,,paleoceanography,1750-2250m depth,,N #----------------- # Data: # Missing Value: NaN age_calkaBP SS.1200-1375 SS.1200-1375_err SS.1375-1575 SS.1375-1575_err SS.1575-1750 SS.1575-1750_err SS.1750-2250 SS.1750-2250_err 0.35 -0.61 0.36 -1.87 0.94 -0.13 0.22 -0.75 0.43 1.2 -0.03 0.53 -1.66 1.37 -0.11 0.30 -0.31 0.30 2.2 -0.53 0.35 -0.88 0.33 -0.37 0.32 -0.29 0.30 3.2 -0.09 0.93 -1.20 0.19 -0.31 0.30 0.13 0.46 4.2 -1.07 0.78 -0.58 0.24 0.19 0.47 0.33 0.32 5.2 -1.45 0.54 -0.86 0.31 0.12 0.20 0.64 0.32 6.2 -0.49 0.46 0.66 1.16 0.17 0.23 0.76 0.36 7.2 -0.37 0.35 0.48 0.14 0.66 0.56 0.73 0.51 8.2 -0.20 0.40 1.15 0.89 0.09 0.40 -0.43 0.37 9.2 0.19 1.27 0.26 1.02 0.01 0.26 -0.37 0.34 10.2 1.04 0.35 0.82 1.60 -0.06 0.59 -0.20 0.76 11.2 1.78 0.42 0.05 1.09 -0.48 0.91 -1.22 0.56