Sajama Ice Core Data: Readme file --------------------------------------------------------------------- World Data Center for Paleoclimatology, Boulder and NOAA Paleoclimatology Program --------------------------------------------------------------------- NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!! NAME OF DATA SET: Sajama Ice Core Data LAST UPDATE: 1/2001 (Original receipt by WDC Paleo) CONTRIBUTOR: Lonnie G. Thompson, Byrd Polar Research Center of The Ohio State University IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2001-009 SUGGESTED DATA CITATION: Thompson, L.G., 2001, Sajama Ice Core Data, IGBP PAGES/World Data Center A for Paleoclimatology Data Contribution Series #2001-009. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Thompson, L.G., M.E.Davis, E.M.Thompson, T.A.Sowers, K.A.Henderson, V.S.Zagorodnov, P.N.Lin, V.N. Mikhalenko, R.K.Campen, J.F.Bolzan, J.Cole-Dai and B.Francou. 1998. A 25,000 year tropical climate history from Bolivian ice cores. Science, 282(5295), 1858-1864. Thompson et al., Science, v. 282, 1998, p. 1858-1864 GEOGRAPHIC REGION: South America, Bolivian Altiplano PERIOD OF RECORD: 25 KYrBP-Present LIST OF FILES: Readme_Sajama.txt (this file), ASCII text data files: s1-dates.txt Core 1 dating scheme sc12-5m.txt 5m/3m/.5m averages d18oatm.txt Sowers' d18Oatm data sc1-100a.txt All Core 1 100-yr averages sc1-acc.txt Accumulation reconstruction DESCRIPTION: General Information about the Sajama Ice Cores Site Description and Analysis In June-July 1997, two ice cores to bedrock were recovered from the summit of the extinct Sajama volcano, Bolivia (18øS, 69øW, elevation 6540 m) and were subsequently transported back in a frozen state to the cold room facility at the Byrd Polar Research Center (BPRC). Core 1 (SjC1, 132.4 m) was sectioned in the BPRC laboratory into 5063 samples decreasing in thickness from ~15 cm at the top to ~1-2 cm at the base. Core 2 (SjC2, 132.8 m), drilled just 3m from the SjC1 site, was sampled more coarsely, only 803 samples collected from its length. Borehole temperatures ranged from -11.3 to -9.5øC and indicate that the glacier remains frozen to the bed. Each ice sample from SjC1 and SjC2 were prepared in a Class 100 clean room environment, and analyzed for major anion concentrations (Cl-, NO3-, and SO42-) on a Dionex DX-500 ion chromatograph, d18O on a Finnigan Mat mass spectrometer (Craig, Geochim. Cosmochim. Acta, v. 12, 1957, p. 133-149), and for particulate concentration and size distribution using a Coulter TA-II particle counter (Thompson, OSU IPS Report 46, 1973). For display purposes, variable averaging on the core depth scale was utilized to show the major large-scale events in the record without the confusion of the large annual variations superimposed upon the upper portion. Hence, for SjC1, 5-m integrated averages were calculated for between the surface and 75 meters depth and then 3-m averages were generated between 75 and 105 meters, and finally 50-cm averages were generated between 105 m and the bottom. The identical scheme was used for SjC2, and all of these data are included in sc12-5m.txt in this data archive, and the graph can be seen in Thompson et al., Science, v. 282, 1998, p. 1858-1864 (Fig. 3). This figure is included in this archive as fig3.jpg. Development of the time/depth relationship As for the Huascarán, Peru ice cores, the upper section of the Sajama cores contain an annually-resolved portion that can be accurately layer-counted. For developing the full-core age-depth scale, 100 years of accumulation was fixed according to the annual layer-counting. Measurements of tritium in SjC1 detected a strong peak at ~25.2 m depth, and confirmed the counting of 33 layers at 1964 A.D. The strength of the annual oscillations in nitrate, dust, and d18O are shown in Fig. 2 (Thompson et al, 1998) for the relevant period. This figure is archived here as fig2.jpg. The Sajama ice cores contain intact insects, insect fragments, and polylepis bark with a sufficient mass for 14C dating. An abundance of plant material at 130.8 min SjC1 was split into two samples and independently dated by two AMS facilities (20,400 and 21,200 14C yrs. BP). Additional stratigraphic information for the lower portion of the Sajama cores was obtained by measuring the 18O/16O ratio of paleoatmospheric O2 (d18Oatm) trapped in the bubbles. 31 samples between 56 and 130 m depth were measured and compared to results for the GISP 2 ice core (Sowers and Bender, Science, v. 269, 1995, p. 210). Anomalous results were generally coincident with elevated dAr/N2 values, that indicate some post-depositional alteration. The d18Oatm results are depicted in fig4.jpg in this archive, the data included in d18oatm.txt. In each, the regions of anomalous gases are indicated. Additionally, a single ash horizon was identified in SjC1 that yielded one more absolute date. The identification of Huaynaputina 1600 A.D. ash in SjC1 at 64.85 m, was further confirmed by the nearby 14C date of 354 yrs. BP (1596 A.D.) at 67.0 m. ICP- OES analysis of the major elements from the dust layer in SjC1 corresponded very well with the simultaneous analysis of the ash collected from the Huaynaputina eruption from the Cerro Trapiche archeological site (Thompson et al., 1998). A summary of all age information determined from SjC1 is tabulated in s1- dates.txt. From seven important age markers (tabulated in s1-dates.txt), including the layer counts, tritium measurements, d18Oatm measurements, and Huaynatputina, a single exponential-polynomial expression was determined for age control over the uppermost 9.7 kyr BP. For glacial stage ice, the AnalySeries 1.0a program (D. Palliard et al., EOS, v. 77, 1996, p. 379) was used to transfer the depth-based Sajama geochemical records to the GISP 2-based time scale. Constant layer-thicknesses were assumed between the 14 d18Oice matching points, given in s1-dates.txt file in this archive. Constant layers were also assumed between the earliest GISP 2 matchpoint and the final 14C-dated layer, just above the bed. An average of the two corrected dates (24,485 yrs. BP) was used as an absolute time marker for this depth (130.8 m). Using the AnalySeries New Sampling feature, 100-year averages of all major ice core parameters were generated, archived here in the file sc1-100a.txt. Fig. 6 in Thompson et al., 1998 shows all of these data for the entire 25,000 year length of record, and is archived here as fig6.jpg. The d18O profile is further compared to five other important glacial-stage ice core records in Fig. 7, archived as fig7.jpg. A subset of the 100-yr. averages in Fig. 6 was shown in the PAGES volume of Quat. Sci. Rev. (v. 19, 2000, p. 29) for 20 kyr BP, to compare with a similar figure for Huascarán. This is archived here as pages14.jpg. Accumulation reconstruction Establishing dated horizons in SjC1 enables us to estimate an accumulation history. The observed depth-age profile suggests that annual layers thin much more rapidly in the upper part of the ice cap than predicted by simple laminar flow or by numerical modeling of ice divide deformation. The observed thinning is similar to that seen in ice caps at Dunde (Thompson et al., Science, v. 246, 1989, p. 474) and Guliya (Thompson et al., Science, v. 276, 1997, p. 1821). In the absence of the appropriate data (the vertical strain rate), we assume that the vertical velocity profile is similar to that inferred from the Dunde and Guliya ice cores. If changes in ice thickness are ignored, the average accumulation rate a(ij) between the dated depth horizons zi and zj (where i, and j, are any two dated horizons) is given by: Aij = {1/dt(ij)} * (Integral from zi to zj) (1 - z/H)^-p dz where H is the ice thickness, z is the ice-equivalent depth, p is a constant, and dt(ij) is the number of years between zi and zj. Reconstructed accumulation values (in terms of standard deviation, since absolutes are difficult to estimate) from these relationships are tabulated in sc1-acc.txt and are shown in fig6.jpg. s1-dates: Sajama Core 1 (1997) 3rd order exp Core Initial Age Model Age Coeff. for 3rd order Depth, z kyr BP '50 kyr BP '50 exponential age model Tritium 25.20 -0.014 -0.014 (kyr BP '97) Layer Counts 41.50 0.053 0.050 b[0] = -2.4116 Huaynaputina 64.80 0.350 0.360 b[1] = 0.0452 C-14* 78.30 0.970 0.997 b[2] = -3.85E-04 C-14 92.10 3.390 3.292 b[3] = 2.616E-06 d18Oatm 101.20 9.100 8.359 Model Age = 10^(b[0]+b[1]z+b[2]z^2+b[3]z^3)-.047 valid to: 102.56 9.726 From here down, dates are treated as "absolute," with linear interpolation used in between d18Oatm 103.80 10.300 GISP II d18Oice matchpoints 1 105.45 11.575 2 106.95 11.925 3 108.45 12.575 4 109.05 12.775 5 109.85 13.125 6 111.05 14.075 7 113.05 14.725 8 114.15 15.125 9 114.55 15.475 10 115.65 16.025 11 116.45 16.525 12 117.85 17.025 13 118.75 17.975 14 123.25 21.625 C-14* 130.80 24.487 Bottom 132.35 25.075 * used average of two dates Sajama 1997 Ice Core, Bolivia Top Age Total Part. kyr BP'50 d18O >0.63 um Cl- NO3- SO4-- -0.05 -17.06 1.606 0.116 0.227 0.818 0.05 -17.80 2.275 0.140 0.213 0.656 0.15 -17.52 1.937 0.148 0.229 0.706 0.25 -17.22 5.760 0.339 0.267 1.140 0.35 -17.00 3.656 0.635 0.231 2.092 0.45 -16.39 2.584 0.450 0.271 1.944 0.55 -15.94 5.562 0.454 0.320 1.902 0.65 -16.19 2.739 0.140 0.262 0.811 0.75 -15.61 3.562 0.108 0.271 0.509 0.85 -16.82 2.888 0.202 0.256 0.787 0.95 -15.42 11.356 0.406 0.263 1.619 1.05 -16.54 4.209 0.346 0.242 1.317 1.15 -16.43 1.455 0.138 0.201 0.461 1.25 -17.90 1.942 0.248 0.245 1.030 1.35 -16.49 2.302 0.217 0.273 1.077 1.45 -16.77 2.622 0.306 0.260 1.520 1.55 -14.23 2.707 1.217 0.651 5.530 1.65 -15.86 3.268 0.375 0.211 1.295 1.75 -16.00 3.004 0.592 0.323 3.439 1.85 -15.34 3.025 0.714 0.340 3.493 1.95 -16.53 1.053 0.262 0.279 1.456 2.05 -16.63 1.249 0.181 0.252 0.626 2.15 -16.82 1.682 0.165 0.254 0.683 2.25 -17.44 1.188 0.309 0.243 1.472 2.35 -14.24 40.578 0.869 0.349 6.773 2.45 -16.44 8.324 1.934 0.495 5.492 2.55 -16.36 2.836 0.386 0.294 1.425 2.65 -17.51 8.185 0.220 0.280 0.623 2.75 -15.71 1.970 0.322 0.337 1.485 2.85 -16.87 2.114 0.729 0.376 3.875 2.95 -16.67 2.907 1.230 0.500 6.620 3.05 -15.65 3.549 0.999 0.464 4.709 3.15 -16.31 2.289 0.432 0.341 2.026 3.25 -15.86 3.964 0.523 0.334 2.641 3.35 -14.32 10.738 2.268 0.573 14.918 3.45 -16.18 3.413 0.713 0.360 6.477 3.55 -15.72 1.905 0.351 0.376 2.480 3.65 -17.04 1.846 0.530 0.299 1.377 3.75 -16.11 6.640 0.217 0.277 0.760 3.85 -16.14 2.196 0.513 0.241 2.064 3.95 -17.10 27.314 0.943 0.465 5.835 4.05 -16.47 3.100 0.199 0.369 1.034 4.15 -16.87 1.204 0.130 0.262 0.678 4.25 -16.71 7.206 0.417 0.357 1.043 4.35 -16.12 2.433 0.209 0.282 0.725 4.45 -16.48 7.137 0.185 0.336 0.695 4.55 -15.48 32.505 0.761 0.486 2.700 4.65 -16.05 9.418 0.578 0.405 3.595 4.75 -16.13 2.058 0.172 0.324 1.048 4.85 -15.85 3.467 0.172 0.313 0.934 4.95 -16.81 3.352 0.446 0.356 2.755 5.05 -14.90 1.678 0.580 1.358 3.581 5.15 -14.01 1.149 0.516 0.377 1.509 5.25 -16.42 1.496 0.145 0.289 0.766 5.35 -17.07 1.926 0.140 0.250 0.462 5.45 -16.71 27.345 0.240 0.295 0.874 5.55 -17.06 40.879 0.259 0.160 0.972 5.65 -17.05 5.340 0.327 0.352 1.165 5.75 -16.86 0.931 0.122 0.275 0.670 5.85 -16.85 1.532 0.117 0.272 0.548 5.95 -16.26 1.263 0.177 0.322 0.951 6.05 -15.89 1.327 0.255 0.398 1.757 6.15 -16.40 1.546 0.146 0.322 0.871 6.25 -16.49 1.772 0.368 0.298 1.507 6.35 -16.91 1.013 0.518 0.535 2.728 6.45 -17.41 1.163 0.132 0.262 0.650 6.55 -16.23 2.031 0.073 0.311 0.670 6.65 -16.24 3.657 0.096 0.353 1.369 6.75 -15.66 2.942 0.142 0.399 1.634 6.85 -17.08 11.453 0.228 0.290 1.891 6.95 -16.65 0.768 0.190 0.374 1.400 7.05 -17.05 2.166 0.083 0.329 0.771 7.15 -16.40 1.455 0.075 0.277 0.514 7.25 -16.81 1.968 0.156 0.332 0.942 7.35 -17.42 5.165 0.180 0.290 0.972 7.45 -15.90 5.446 0.311 0.491 2.040 7.55 -16.76 1.189 0.195 0.433 1.386 7.65 -15.87 1.775 0.130 0.326 0.752 7.75 -16.18 2.131 0.183 0.377 1.094 7.85 -16.78 2.803 0.384 0.487 2.843 7.95 -16.93 0.702 0.114 0.301 0.703 8.05 -16.40 3.156 0.342 0.412 2.000 8.15 -17.12 2.740 0.250 0.419 1.565 8.25 -16.70 2.673 0.120 0.352 0.708 8.35 -16.44 2.479 0.165 0.342 0.879 8.45 -17.15 1.358 0.159 0.323 0.905 8.55 -16.57 3.818 0.239 0.397 2.040 8.65 -16.37 2.077 0.199 0.304 1.173 8.75 -16.58 3.498 0.365 0.508 2.483 8.85 -17.24 1.765 0.225 0.384 1.410 8.95 -17.51 1.584 0.115 0.304 0.987 9.05 -17.12 1.659 0.098 0.293 0.620 9.15 -16.90 2.015 0.090 0.280 0.457 9.25 -16.61 2.021 0.112 0.288 0.598 9.35 -17.11 2.772 0.124 0.312 0.717 9.45 -17.05 1.672 0.080 0.269 0.489 9.55 -16.47 2.537 0.130 0.312 0.776 9.65 -17.04 1.785 0.094 0.293 0.597 9.75 -16.55 1.905 0.110 0.307 0.561 9.85 -17.00 2.878 0.093 0.278 0.938 9.95 -17.00 2.349 0.080 0.270 0.446 10.05 -17.05 2.175 0.068 0.264 0.402 10.15 -16.49 2.777 0.084 0.293 0.504 10.25 -16.65 2.102 0.097 0.281 0.594 10.35 -17.08 1.730 0.101 0.263 0.564 10.45 -16.87 1.451 0.101 0.242 0.447 10.55 -16.81 1.133 0.034 0.241 0.279 10.65 -17.31 0.966 0.033 0.246 0.290 10.75 -17.30 1.414 0.042 0.252 0.342 10.85 -17.15 1.283 0.046 0.261 0.338 10.95 -17.45 0.756 0.057 0.244 0.375 11.05 -17.59 2.107 0.169 0.228 0.544 11.15 -17.62 1.037 0.047 0.236 0.392 11.25 -17.95 0.835 0.041 0.215 0.360 11.35 -17.72 1.195 0.039 0.205 0.246 11.45 -17.08 1.585 0.047 0.244 0.322 11.55 -18.36 0.831 0.045 0.204 0.230 11.65 -20.71 1.376 0.054 0.143 0.245 11.75 -21.77 0.903 0.094 0.128 0.287 11.85 -21.50 2.694 0.114 0.145 0.325 11.95 -21.22 2.226 0.091 0.168 0.331 12.05 -20.86 2.551 0.120 0.156 0.279 12.15 -20.25 2.716 0.082 0.190 0.236 12.25 -20.53 2.722 0.072 0.199 0.228 12.35 -21.34 2.434 0.070 0.212 0.328 12.45 -21.73 2.023 0.095 0.169 0.204 12.55 -21.67 1.900 0.070 0.119 0.227 12.65 -21.00 2.483 0.080 0.152 0.241 12.75 -20.64 2.733 0.077 0.185 0.259 12.85 -19.30 3.715 0.063 0.188 0.322 12.95 -19.97 2.487 0.044 0.161 0.258 13.05 -21.99 1.338 0.047 0.125 0.189 13.15 -22.23 1.137 0.049 0.125 0.181 13.25 -21.40 1.918 0.048 0.137 0.179 13.35 -21.24 2.146 0.049 0.142 0.189 13.45 -20.48 2.385 0.055 0.129 0.189 13.55 -19.49 4.047 0.149 0.214 0.436 13.65 -18.51 4.282 0.218 0.237 0.628 13.75 -18.77 3.630 0.154 0.211 0.473 13.85 -20.13 3.814 0.082 0.140 0.365 13.95 -20.47 2.807 0.089 0.156 0.247 14.05 -20.23 2.698 0.070 0.140 0.233 14.15 -15.91 4.814 0.496 0.545 1.301 14.25 -14.32 6.387 0.379 0.615 1.212 14.35 -15.30 6.411 0.316 0.501 0.965 14.45 -15.93 7.295 0.417 0.488 1.400 14.55 -18.16 5.136 0.176 0.263 0.732 14.65 -20.13 0.778 0.047 0.150 0.317 14.75 -20.98 1.011 0.069 0.151 0.209 14.85 -21.09 4.974 0.435 0.307 1.518 14.95 -20.78 3.538 0.233 0.147 0.479 15.05 -19.07 5.822 0.555 0.302 1.722 15.15 -20.14 1.897 0.207 0.158 0.384 15.25 -20.58 1.070 0.090 0.147 0.207 15.35 -18.76 3.889 0.273 0.307 0.884 15.45 -19.74 2.845 0.149 0.178 0.419 15.55 -21.32 1.270 0.061 0.137 0.181 15.65 -21.97 0.997 0.054 0.125 0.140 15.75 -22.34 1.158 0.049 0.120 0.140 15.85 -22.86 1.231 0.044 0.116 0.147 15.95 -21.88 2.091 0.059 0.125 0.237 16.05 -22.14 4.170 0.059 0.139 0.271 16.15 -21.90 0.934 0.054 0.124 0.148 16.25 -21.87 0.587 0.044 0.119 0.204 16.35 -22.13 0.663 0.043 0.117 0.156 16.45 -22.60 0.698 0.049 0.111 0.160 16.55 -21.84 0.897 0.053 0.120 0.136 16.65 -21.79 0.725 0.063 0.126 0.192 16.75 -22.04 0.556 0.056 0.117 0.152 16.85 -22.17 0.517 0.061 0.117 0.197 16.95 -22.52 0.563 0.058 0.119 0.177 17.05 -22.56 0.478 0.055 0.114 0.135 17.15 -22.36 0.585 0.053 0.120 0.159 17.25 -22.28 0.680 0.047 0.115 0.134 17.35 -22.01 0.804 0.057 0.131 0.177 17.45 -22.10 0.487 0.050 0.127 0.182 17.55 -22.38 0.371 0.050 0.117 0.138 17.65 -22.33 0.457 0.052 0.115 0.179 17.75 -21.92 0.803 0.068 0.149 0.265 17.85 -21.60 0.533 0.055 0.127 0.199 17.95 -21.64 0.904 0.060 0.149 0.204 18.05 -22.15 0.461 0.049 0.122 0.176 18.15 -22.80 0.787 0.072 0.150 0.218 18.25 -22.70 0.511 0.053 0.120 0.157 18.35 -22.82 0.406 0.063 0.138 0.188 18.45 -22.78 0.470 0.060 0.153 0.172 18.55 -22.74 0.630 0.062 0.142 0.226 18.65 -22.80 0.519 0.055 0.132 0.176 18.75 -22.82 0.381 0.075 0.123 0.175 18.85 -22.49 0.316 0.108 0.149 0.329 18.95 -22.02 0.231 0.080 0.157 0.262 19.05 -21.72 0.242 0.122 0.146 0.374 19.15 -21.72 0.268 0.230 0.119 0.386 19.25 -21.73 0.336 0.303 0.106 0.301 19.35 -21.82 0.315 0.307 0.103 0.290 19.45 -21.99 0.261 0.319 0.100 0.315 19.55 -22.14 0.299 0.343 0.103 0.343 19.65 -22.18 0.230 0.346 0.104 0.384 19.75 -22.40 0.215 0.345 0.108 0.412 19.85 -22.61 0.291 0.372 0.110 0.327 19.95 -22.44 0.414 0.400 0.125 0.474 20.05 -22.19 0.263 0.388 0.124 0.470 20.15 -22.04 0.283 0.414 0.116 0.384 20.25 -21.84 0.277 0.443 0.114 0.416 20.35 -21.61 0.167 0.495 0.104 0.382 20.45 -21.52 0.235 0.582 0.100 0.438 20.55 -21.53 0.290 0.619 0.094 0.453 20.65 -21.68 0.237 0.668 0.097 0.519 20.75 -21.80 0.214 0.737 0.109 0.704 20.85 -21.88 0.252 0.790 0.094 0.609 20.95 -21.91 0.277 0.851 0.095 0.592 21.05 -22.02 0.344 0.916 0.087 0.549 21.15 -22.22 0.263 0.941 0.076 0.483 21.25 -22.29 0.198 0.939 0.061 0.442 21.35 -22.37 0.220 1.021 0.070 0.600 21.45 -22.29 0.178 1.129 0.086 0.849 21.55 -22.35 0.159 1.095 0.064 0.759 21.65 -22.40 2.337 1.258 0.083 5.091 21.75 -22.32 0.166 0.638 0.047 0.360 21.85 -22.21 0.190 0.314 0.098 0.296 21.95 -22.15 0.235 0.110 0.180 0.255 22.05 -22.13 0.283 0.082 0.176 0.217 22.15 -22.13 0.427 0.074 0.162 0.584 22.25 -22.03 0.461 0.090 0.139 0.236 22.35 -21.86 0.358 0.126 0.163 1.117 22.45 -21.69 0.469 0.094 0.134 0.288 22.55 -21.61 0.480 0.093 0.135 0.318 22.65 -21.52 0.489 0.096 0.133 0.236 22.75 -21.44 0.642 0.107 0.143 0.319 22.85 -21.41 0.552 0.111 0.141 0.285 22.95 -21.30 0.588 0.105 0.136 0.254 23.05 -21.28 0.676 0.105 0.139 0.258 23.15 -21.11 1.044 0.114 0.149 0.231 23.25 -21.08 0.721 0.124 0.161 0.349 23.35 -20.89 0.787 0.120 0.151 0.252 23.45 -20.78 0.788 0.117 0.152 0.307 23.55 -20.71 0.727 0.122 0.156 0.428 23.65 -20.72 0.585 0.117 0.159 0.340 23.75 -20.66 0.698 0.099 0.144 0.159 23.85 -20.57 0.530 0.103 0.147 0.176 23.95 -20.62 0.523 0.105 0.154 0.174 24.05 -20.61 0.708 0.119 0.170 0.271 24.15 -20.57 0.783 0.119 0.172 0.286 24.25 -20.61 0.846 0.120 0.171 0.291 24.35 -20.65 0.801 0.126 0.184 0.290 24.45 -20.69 0.567 0.129 0.192 0.202 24.55 -20.66 0.598 0.113 0.156 0.188 24.65 -20.74 0.354 0.111 0.142 0.169 24.75 -20.71 0.365 0.128 0.131 0.244 24.85 -20.84 0.595 0.112 0.126 0.232 24.95 -20.66 0.616 0.112 0.114 0.349 25.05