Dating firn cores by vertical strain measurements

ROBERT L. HAWLEY, EDWIN D. WADDINGTON, DAVID L. MORSE,
NELIA W. DUNBAR, GREGORY A. ZIELINSKI

$^1$Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195, USA
$^2$Currently at Institute of Geophysics, University of Texas, Austin TX 78759
$^3$New Mexico Institute of Mining and Technology, Socorro, NM 87801
$^4$Institute for Quaternary and Climate Studies, University of Maine, Orono, ME 04469-5790

ABSTRACT. We have developed a system for measuring a vertical strain rate profile in the firn on polar ice sheets using a readily available video camera to detect metal bands inserted in an air-filled hole. We used this system in 1995 and 1996 at Taylor Dome, Antarctica. We use density measurements combined with our strain rates to infer vertical velocities. From our velocities we calculate a steady state depth-age scale for the firn at Taylor Dome. The age of a visible ash layer from 79.1 meters is 675 $\pm$ 25 years; this ash can be correlated with ash found at 97.2 meters in a recent ice core at Siple Dome, West Antarctica.