A first chronology for the East Greenland Ice-core Project (EGRIP) over the Holocene and last glacial termination

This paper provides the first chronology for the deep ice core from the East Greenland Ice-core Project (EGRIP) over the Holocene and the late last glacial period. We rely mainly on volcanic events and common peak patterns recorded by dielectric profiling (DEP) and electrical conductivity measurement (ECM) for the synchronization between the EGRIP, North Greenland Eemian Ice Drilling (NEEM) and North Greenland Ice Core Project (NGRIP) ice cores in Greenland. We transfer the annual-layer-counted Greenland Ice Core Chronology 2005 (GICC05) from the NGRIP core to the EGRIP ice core by means of 381 match points, typically spaced less than 50 years apart. The NEEM ice core has previously been dated in a similar way and is only included to support the match-point identification. We name our EGRIP timescale GICC05-EGRIP-1. Over the uppermost 1383.84 m, we establish a depth-Age relationship dating back to 14 967 years b2k (years before the year 2000 CE). Tephra horizons provide an independent validation of our match points. In addition, we compare the ratio of the annual layer thickness between ice cores in between the match points to assess our results in view of the different iceflow patterns and accumulation regimes of the different periods and geographical regions. For the next years, this initial timescale will be the basis for climatic reconstructions from EGRIP high-resolution proxy data sets, e.g. stable water isotopes, chemical impurity or dust records. © 2020 BioMed Central Ltd.. All rights reserved.This research has been supported by the A. P. Møller Foundation, University of Copenhagen; US National Science Foundation, Office of Polar Programs; Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research; National Institute of Polar Research and Arctic Challenge for Sustainability, Japan; University of Bergen and Bergen Research Foundation; Swiss National Science Foundation (SNFS); French Polar Institute Paul-Emile Victor, Institute for Geosciences and Environmental research; Chinese Academy of Sciences and Beijing Normal University; Carlsberg Foundation (project ChronoClimate); Spanish Ministry of Science, Innovation, the Spanish Government through the María de Maeztu excellence accreditation 2018–2022 (ref. MDM-2017-0714); Basque Government (BERC 2018–2021 programme); and the Oeschger Center for Climate Change Research. Acknowledgements. We thank Frédéric Parrenin and two anonymous reviewers for fruitful comments that improved the paper a lot. We thank all people involved in logistics, drilling and ice-core processing in the field. EGRIP is directed and organized by the Centre for Ice and Climate at the Niels Bohr Institute, University of Copenhagen. It is supported by funding agencies and institutions in Denmark (A. P. Møller Foundation, University of Copenhagen), USA (US National Science Foundation, Office of Polar Programs), Germany (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research), Japan (National Institute of Polar Research and Arctic Challenge for Sustainability), Norway (University of Bergen and Bergen Research Foundation), Switzerland (Swiss National Science Foundation), France (French Polar Institute Paul-Emile Victor, Institute for Geosciences and Environmental research) and China (Chinese Academy of Sciences and Beijing Normal University). Sune Olander Rasmussen and Giulia Sinnl gratefully acknowledge the Carlsberg Foundation for supporting the project ChronoClimate. Sergio Henrique Faria acknowledges support for the iMechPro project (RTI2018-100696-B-I00) from the Spanish Ministry of Science, Innovation, the Spanish Government through the María de Maeztu excellence accreditation 2018– 2022 (ref. MDM-2017-0714) and the Basque Government through the BERC 2018–2021 programme. Tobias Erhardt acknowledges the long-term support of ice-core research by the Swiss National Science Foundation (SNFS) and the Oeschger Center for Climate Change Research