Past Temperatures Directly from the Greenland Ice Sheet

TLDR

A Monte Carlo inverse method was applied to temperature profiles from the GRIP and Dye 3 boreholes to reconstruct past temperatures. The reconstructions provide a 50,000‑year record at GRIP and a 7,000‑year record at Dye 3, resolving major climate events with amplitudes from –23 K to +2.5 K and showing that Dye 3 exhibits 1.5× larger variability, while the GRIP inversion yields a terrestrial heat flow density of 51.3 mW m⁻².

Abstract

A Monte Carlo inverse method has been used on the temperature profiles measured down through the Greenland Ice Core Project (GRIP) borehole, at the summit of the Greenland Ice Sheet, and the Dye 3 borehole 865 kilometers farther south. The result is a 50, 000-year-long temperature history at GRIP and a 7000-year history at Dye 3. The Last Glacial Maximum, the Climatic Optimum, the Medieval Warmth, the Little Ice Age, and a warm period at 1930 A.D. are resolved from the GRIP reconstruction with the amplitudes -23 kelvin, +2.5 kelvin, +1 kelvin, -1 kelvin, and +0.5 kelvin, respectively. The Dye 3 temperature is similar to the GRIP history but has an amplitude 1.5 times larger, indicating higher climatic variability there. The calculated terrestrial heat flow density from the GRIP inversion is 51.3 milliwatts per square meter.