EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

A revised Greenland ice-core chronology for the last 3800 years: the GICC21

Giulia Sinnl1, Mai Winstrup2, Tobias Erhardt3, Eliza Cook1, Camilla Jensen4, Anders Svensson1, Bo Vinther1, Raimund Muscheler5, and Sune Rasmussen1
Giulia Sinnl et al.
  • 1Physics of Ice Climate and Earth, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
  • 2DTU Space, National Space Institute, Technical University of Denmark, Kongens Lyngby, Denmark
  • 3Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
  • 4Climate and Environmental Physics, Physics Institute and Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
  • 5Quaternary Sciences, Department of Geology, Lund University, Lund, Sweden

Ice-core timescales are vital for our understanding of the past climate; hence they should be updated whenever significant amounts of new data become available. Here, the Greenland ice-core chronology GICC05 was revised for the last 3835 years by synchronizing six deep ice-cores and three shallow ice-cores from the central Greenland ice sheet. A new method was applied by combining automated counting of annual layers on multiple parallel proxies and manual fine-tuning. A layer-counting bias was found in all ice cores because of site-specific signal disturbances, therefore the manual comparison of all ice cores was deemed necessary to increase timescale accuracy. After examining sources of error and their correlation lengths, the uncertainty rate was quantified to be one year per century.

The new timescale, called GICC21, is younger than GICC05 by about 13 years at 3835 years ago. The most recent 800 years are largely unaffected by the revision. Between 800 and 2000 years ago, the offset between timescales increases steadily, with the steepest offset occurring between 800 and 1100 years ago. Moreover, offset-oscillations of about 5 years around the average are observed between 2500 and 3800 years ago. The non-linear offset behavior is attributed to previous mismatches of volcanic eruptions, to the much more extensive data set available to this study, and to the finer resolution of the new ice-core ammonium matching. By analysis of the common variations of cosmogenic radionuclides, the new ice-core timescale is found to be in alignment with the IntCal20 curve.

How to cite: Sinnl, G., Winstrup, M., Erhardt, T., Cook, E., Jensen, C., Svensson, A., Vinther, B., Muscheler, R., and Rasmussen, S.: A revised Greenland ice-core chronology for the last 3800 years: the GICC21, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-289,, 2023.

Supplementary materials

Supplementary material file