Fremont Glacier 1991 Core Age Model ----------------------------------------------------------------------- NOAA Paleoclimatology Program and World Data Center for Paleoclimatology, Boulder ----------------------------------------------------------------------- NOTE: PLEASE CITE CONTRIBUTORS WHEN USING THIS DATA!!!!! NAME OF DATA SET: Fremont Glacier 1991 Core Age Model LAST UPDATE: 11/2004 (Original Receipt by WDC Paleo) CONTRIBUTOR: Paul Schuster, USGS IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2004-079 SUGGESTED DATA CITATION: Schuster, P.F., et al., 2004, Fremont Glacier 1991 Core Age Model, IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series # 2004-079. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA. ORIGINAL REFERENCE: Schuster, P.F., D.E. White, D.L., Naftz, and L.D. Cecil. 2000. Chronological refinement of an ice core record at upper Fremont Glacier in south central North America. Journal of Geophysical Research, Vol. 105, p. 4657-4666. ABSTRACT: The potential to use ice cores from alpine glaciers in the midlatitudes to reconstruct paleoclimatic records has not been widely recognized. Although excellent paleoclimatic records exist for the polar regions, paleoclimatic ice core records are not common from midlatitude locations. An ice core removed from the Upper Fremont Glacier in Wyoming provides evidence for abrupt climate change during the mid-1800s. Volcanic events (Krakatau and Tambora) identified from electrical conductivity measurements (ECM) and isotopic and chemical data from the Upper Fremont Glacier were reexamined to confirm and refine previous chronological estimates of the ice core. At a depth of 152 m the refined age-depth profile shows good agreement (1736 +/- 10 A.D.) with the 14C age date (1729 +/- 95 A.D.). The d18O profile of the Upper Fremont Glacier (UFG) ice core indicates a change in climate known as the Little Ice Age (LIA). However, the sampling interval for d18O is sufficiently large (20 cm) such that it is difficult to pinpoint the LIA termination on the basis of d18O data alone. Other research has shown that changes in the d18O variance are generally coincident with changes in ECM variance. The ECM data set contains over 125,000 data points at a resolution of 1 data point per millimeter of ice core. A 999-point running average of the ECM data set and results from f tests indicates that the variance of the ECM data decreases significantly at about 108 m. At this depth, the age-depth profile predicts an age of 1845 A.D. Results indicate the termination of the LIA was abrupt with a major climatic shift to warmer temperatures around 1845 A.D. and continuing to present day. Prediction limits (error bars) calculated for the profile ages are +/- 10 years (90% confidence level). Thus a conservative estimate for the time taken to complete the LIA climatic shift to present-day climate is about 10 years, suggesting the LIA termination in alpine regions of central North America may have occurred on a relatively short (decadal) timescale. GEOGRAPHIC REGION: Wyoming, USA PERIOD OF RECORD: 1717-1991 AD. DESCRIPTION: Fremont ice core (1991): age-depth relation Age in years = 0.00739 (D^2) + 0.55589(D) DATA: Fremont ice core (1991): age-depth relation depth Years Age AD meters before 1991 0 0.00 1991 12 7.73 1983 15 10.00 1981 22 15.80 1975 22.5 16.25 1975 26 19.44 1972 29 22.33 1969 30 23.32 1968 32 25.35 1966 38 31.79 1959 41 35.21 1956 42 36.37 1955 52 48.88 1942 54 51.55 1939 65 67.34 1924 67 70.40 1921 71 76.70 1914 74 81.58 1909 75 83.24 1908 76 84.91 1906 78 88.30 1903 83 97.02 1894 84 98.81 1892 88 106.12 1885 90 109.86 1881 98 125.41 1866 100 129.45 1862 101 131.49 1860 113 157.13 1834 114 159.36 1832 118 168.44 1823 122 177.75 1813 123 180.12 1811 126 187.31 1804 127 189.73 1801 130 197.09 1794 131 199.58 1791 132 202.08 1789 138 217.38 1774 144 233.21 1758 152 255.15 1736 158.7 274.25 1717