# Saharan dust fluxes over the last 22 ka in the Bahamas and central tropical Atlantic #----------------------------------------------------------------------- # World Data Center for Paleoclimatology, Boulder # and # NOAA Paleoclimatology Program #----------------------------------------------------------------------- # NOTE: Please cite original publication, online resource and date accessed when using this data. # If there is no publication information, please cite Investigator, title, online resource and date accessed. # # Description/Documentation lines begin with # # Data lines have no # # # Online_Resource: https://www.ncdc.noaa.gov/paleo/study/20775 # Online_Resource: http://www1.ncdc.noaa.gov/pub/data/paleo/paleocean/by_contributor/williams2016/williams2016-vm20-234.txt # # Archive: Paleoceanography # # Parameter_Keywords: radiogenic isotope, geochemistry #--------------------------------------- # Contribution_Date # Date: 2016-11-17 #--------------------------------------- # Title # Study_Name: Saharan dust fluxes over the last 22 ka in the Bahamas and central tropical Atlantic #--------------------------------------- # Investigators # Investigators: Williams, Ross H.; McGee, David; Kinsley, Christopher W.; Ridley, David A.; Hu, Shineng; Fedorov, Alexey; Tal, Irit; Murray, Richard W.; deMenocal, Peter B. #--------------------------------------- # Description and Notes # Description: Dust fluxes spanning the last 22 ka determined by Th-normalization in cores in the Bahamas and central tropical Atlantic # Provided Keywords: Saharan dust; Bahamas; North Atlantic; Th-normalization; Last Glacial Maximum; African Humid Period; Holocene #--------------------------------------- # Publication # Authors: R.H. Williams, D. McGee, D.A. Ridley, C.W. Kinsley, S. Hu, A. Fedorov, I. Tal, R. Murray, and P.B. deMenocal # Published_Date_or_Year: 2016 # Published_Title: Glacial to Holocene changes in trans-Atlantic Saharan dust transport and dust-climate feedbacks # Journal_Name: Science Advances # Volume: 2 # Edition: # Issue: # Pages: # Report Number: # DOI: 10.1126/sciadv.1600445 # Online_Resource: # Full_Citation: # Abstract: Saharan mineral dust exported over the tropical North Atlantic is thought to have significant impacts on regional climate and ecosystems, but limited data exists documenting past changes in long-range dust transport. This data gap limits investigations of the role of Saharan dust in past climate change, in particular during the early Holocene, when climate models consistently underestimate the intensification of the West African monsoon documented by paleorecords. Here we present reconstructions of African dust deposition in sediments from the Bahamas and the tropical North Atlantic spanning the last 23,000 years. Both sites show early Holocene dust fluxes 40-50% lower than recent values and maximum dust fluxes during the deglaciation, demonstrating strong agreement with records from the northwest African margin. These quantitative estimates of trans-Atlantic dust transport offer important constraints on past changes in dust-related radiative and biogeochemical impacts. Using idealized climate model experiments to investigate the response to reductions in Saharan dust's radiative forcing over the tropical North Atlantic, we find that small (0.15 °C) dust-related increases in regional sea surface temperatures are sufficient to cause significant northward shifts in the Atlantic Intertropical Convergence Zone, increased precipitation in the western Sahel and Sahara, and reductions in easterly and northeasterly winds over dust source regions. Our results suggest that the amplifying feedback of dust on sea surface temperatures and regional climate may be significant, and that accurate simulation of dust's radiative effects is likely essential to improving model representations of past and future precipitation variations in North Africa. #--------------------------------------- # Funding_Agency # Funding_Agency_Name: NSF # Grant: OCE-1030784, OCE-09277247 #--------------------------------------- # Funding_Agency # Funding_Agency_Name: NASA # Grant: NN14AP38G #--------------------------------------- # Site Information # Site_Name: VM20-234 # Location: Central Atlantic Ocean # Country: # Northernmost_Latitude: 5.33 # Southernmost_Latitude: 5.33 # Easternmost_Longitude: -33.03 # Westernmost_Longitude: -33.03 # Elevation: #--------------------------------------- # Data_Collection # Collection_Name: VM20-234 Williams2016 # First_Year: 21112 # Last_Year: 967 # Time_Unit: cal yr BP # Core_Length: # Notes: #--------------------------------------- # Chronology_Information # Chronology: # Radiocarbon data for core VM20-234 # depth Depth of sample (cm) # mat.dated Material Dated # 14C.raw conventional radiocarbon age, years before 1950AD # 14C.raw_err radiocarbon age, standard error # calib.14C Calibrated age # calib.14C_2sig_lo Calibrated age, 2-sigma lower confidence bound # calib.14C_2sig_up Calibrated age, 2-sigma upper confidence bound # calib_method Calibration method # rejected Rejected sample (yes/no) # notes Notes # # depth mat.dated 14C.raw 14C.raw_err calib.14C calib.14C_2sig_lo calib.14C_2sig_up calib_method rejected notes # 1.5 G. ruber 5055 35 5401 5515 5302 Marine13 YES NaN # 13.5 G. ruber 5395 30 5771 5871 5672 Marine13 NaN NaN # 31.25 G. ruber + G. sacc. 10870 30 12421 12568 12216 Marine13 NaN NaN # 41.5 G. ruber 11940 35 13388 13490 13290 Marine13 NaN NaN # 45 G. sacc. 13050 50 15450 15652 15264 Marine13 NaN Two 14C ages at this depth combined # 45 G. ruber 13600 50 NaN NaN NaN Marine13 NaN NaN # 58.5 G. ruber 16640 60 19600 19841 19407 Marine13 NaN NaN # 66 G. ruber + G. sacc. 23490 90 27397 27596 27182 Marine13 YES NaN # 95 G. sacc. 23100 90 27806 27963 27652 Marine13 NaN Two 14C ages at this depth combined # 95 G. ruber 24900 90 NaN NaN NaN Marine13 NaN NaN # #--------------------------------------- # Variables # Data variables follow that are preceded by "##" in columns one and two. # Variables list, one per line, shortname-tab-longname components (9 components: what, material, error, units, seasonality, archive, detail, method, C or N for Character or Numeric data) ## core core ID,,,unitless,,,,,C ## depth_cm Depth,,,cm,,,,,N ## age Age,,,calendar ka BP,,,,,N ## water_depth_m Depth of water column,,,m,,,,,N ## 232Th 232Th activity,detrital ,,dpm/g,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## 232Th_error 232Th activity,detrital ,one standard deviation margin of error,dpm/g,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## 230Th 230Th activity,detrital ,,dpm/g,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## 230Th_error 230Th activity,detrital ,one standard deviation margin of error,dpm/g,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## 238U 238U activity,detrital ,,dpm/g,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## 238U_error 238U activity,detrital ,one standard deviation margin of error,dpm/g,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## 230Th_norm 230Th normalized sediment flux,detrital ,,g/cm^2/ka,,Paleoceanography,assumes detrital U/Th activity ratio of 0.6 ± 0.1,instrument: inductively coupled plasma mass spectrometer,N ## 230Th_norm_error 231st normalized sediment flux,detrital ,one standard deviation margin of error,g/cm^2/ka,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## 232Th_conc 232Th concentration,detrital ,,µg/g,,Paleoceanography,,instrument: inductively coupled plasma mass spectrometer,N ## detrital_flux Dust flux,,,g/cm2/kyr,,Paleoceanography,assumes 232Th concentration of 13.7 ± 1.0 µg/g in dust,,N ## detrital_flux_error Dust flux,,one standard deviation margin of error,g/cm2/kyr,,Paleoceanography,,,N #------------------------ # Data # Data lines follow (have no #) # Data line format - tab-delimited text, variable short name as header # Missing Value: NA core depth_cm age water_depth_m 232Th 232Th_error 230Th 230Th_error 238U 238U_error 230Th_norm 230Th_norm_error 232Th_conc detrital_flux detrital_flux_error VM20-234 1.5 0.97 3133 0.833 0.008 7.551 0.076 0.393 0.004 1.18 0.019 3.412 0.294 0.013 VM20-234 5 2.33 3133 1.194 0.012 11.151 0.112 0.54 0.005 0.787 0.012 4.891 0.281 0.009 VM20-234 6.5 2.91 3133 1.179 0.012 11.661 0.117 0.524 0.005 0.746 0.011 4.828 0.263 0.008 VM20-234 8.5 3.68 3133 1.147 0.011 12.484 0.125 0.511 0.005 0.688 0.01 4.698 0.236 0.008 VM20-234 10.5 4.46 3133 1.074 0.011 12.769 0.128 0.513 0.005 0.664 0.009 4.398 0.213 0.007 VM20-234 12.5 5.24 3133 0.923 0.009 13.223 0.132 0.429 0.004 0.631 0.008 3.78 0.174 0.007 VM20-234 14.5 6.03 3133 0.856 0.009 12.859 0.129 0.484 0.005 0.643 0.008 3.505 0.165 0.007 VM20-234 17.5 7.17 3133 0.744 0.007 13.055 0.131 0.383 0.004 0.623 0.007 3.049 0.139 0.006 VM20-234 19.5 7.95 3133 0.771 0.008 12.55 0.126 0.372 0.004 0.645 0.007 3.158 0.149 0.007 VM20-234 20.5 8.34 3133 0.717 0.007 12.292 0.123 0.351 0.004 0.655 0.007 2.936 0.14 0.007 VM20-234 22.5 9.12 3133 0.867 0.009 11.584 0.116 0.386 0.004 0.697 0.008 3.55 0.181 0.007 VM20-234 24.5 9.90 3133 1.027 0.01 11.031 0.11 0.426 0.004 0.735 0.01 4.207 0.226 0.008 VM20-234 27.5 11.07 3133 0.827 0.008 7.165 0.072 0.341 0.003 1.135 0.017 3.389 0.281 0.012 VM20-234 29.5 11.83 3133 0.772 0.008 7.099 0.071 0.314 0.003 1.132 0.016 3.162 0.261 0.012 VM20-234 31.5 12.37 3133 0.887 0.009 6.496 0.065 0.376 0.004 1.253 0.021 3.635 0.332 0.014 VM20-234 33 12.53 3133 1.271 0.013 9.381 0.094 0.586 0.006 0.866 0.014 5.208 0.329 0.01 VM20-234 33.5 12.58 3133 1.029 0.01 6.866 0.069 0.433 0.004 1.193 0.021 4.216 0.367 0.014 VM20-234 35.5 12.79 3133 1.1 0.011 6.52 0.065 0.459 0.005 1.269 0.025 4.507 0.417 0.015 VM20-234 36.5 12.90 3133 1.38 0.014 8.525 0.085 0.703 0.007 0.967 0.018 5.652 0.399 0.012 VM20-234 37.5 13.01 3133 1.416 0.014 8.51 0.085 0.66 0.007 0.97 0.019 5.8 0.411 0.013 VM20-234 38.5 13.12 3133 1.487 0.015 8.408 0.084 0.707 0.007 0.987 0.02 6.09 0.439 0.013 VM20-234 39.5 13.22 3133 1.467 0.015 8.005 0.08 0.747 0.007 1.041 0.022 6.008 0.457 0.014 VM20-234 40.5 13.32 3133 1.482 0.015 8.055 0.081 0.923 0.009 1.038 0.022 6.071 0.46 0.014 VM20-234 41.5 13.44 3133 1.126 0.011 6.283 0.063 0.475 0.005 1.318 0.027 4.613 0.444 0.016 VM20-234 42.5 13.89 3133 1.209 0.012 6.406 0.064 0.512 0.005 1.295 0.028 4.953 0.468 0.016 VM20-234 43.5 14.60 3133 1.189 0.012 6.034 0.06 0.513 0.005 1.373 0.03 4.871 0.488 0.017 VM20-234 44.5 15.20 3133 1.234 0.012 6.295 0.063 0.535 0.005 1.308 0.029 5.055 0.483 0.017 VM20-234 45.5 15.54 3133 1.295 0.013 6.294 0.063 0.56 0.006 1.312 0.03 5.304 0.508 0.017 VM20-234 46.5 15.81 3133 1.476 0.015 6.736 0.067 0.655 0.007 1.234 0.03 6.046 0.545 0.018 VM20-234 47.5 16.13 3133 1.396 0.014 6.381 0.064 0.617 0.006 1.298 0.031 5.72 0.542 0.018 VM20-234 48.5 16.45 3133 1.455 0.015 6.543 0.065 0.641 0.006 1.265 0.031 5.961 0.551 0.018 VM20-234 49.5 16.78 3133 1.9 0.019 8.315 0.083 0.967 0.01 0.999 0.025 7.782 0.568 0.017 VM20-234 51.5 17.44 3133 2.001 0.02 8.397 0.084 1.071 0.011 0.991 0.026 8.196 0.593 0.018 VM20-234 53.5 18.09 3133 1.516 0.015 5.799 0.058 0.698 0.007 1.444 0.041 6.21 0.654 0.023 VM20-234 55.5 18.75 3133 1.502 0.015 5.854 0.059 0.65 0.006 1.415 0.039 6.154 0.635 0.023 VM20-234 57.5 19.37 3133 1.505 0.015 6.285 0.063 0.67 0.007 1.296 0.033 6.165 0.583 0.02 VM20-234 59 19.67 3133 1.545 0.015 6.176 0.062 0.695 0.007 1.325 0.035 6.329 0.612 0.021 VM20-234 60 19.86 3133 1.338 0.013 5.332 0.053 1.022 0.01 1.559 0.042 5.481 0.624 0.023 VM20-234 61.5 20.20 3133 1.952 0.02 8.06 0.081 0.92 0.009 1.006 0.026 7.997 0.587 0.018 VM20-234 62.5 20.42 3133 1.902 0.019 7.971 0.08 0.913 0.009 1.013 0.026 7.79 0.576 0.018 VM20-234 65.5 21.11 3133 1.967 0.02 7.846 0.078 0.905 0.009 1.029 0.027 8.057 0.605 0.019