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

Seyedhamidreza Mojtabavi,Vasileios Gkinis,Helle Astrid Kjær,Mathias Skov Jensen,Eliza Cook,Giulia Sinnl,Siwan M Davies,Kerim H Nisancioglu,Nanna B Karlsson,Frank Wilhelms,Sune Olander Rasmussen,Iben Koldtoft,Sepp Kipfstuhl,Tobias Erhardt,Bo M Vinther,Dorthe Dahl-Jensen,Anders Svensson,Gwydion Jones,Sérgio H Faria ,Sarah M P Berben

doi:10.5194/cp-16-2359-2020

Abstract

Abstract. 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 ice-flow 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.

Highlights

The dating of an ice core establishes the depth–age relationship to derive a chronology of past climatic conditions from the measured proxy parameters
The main objective of this work is to facilitate analysis of the data from the core by transferring the Greenland Ice Core Chronology 2005 (GICC05) timescale – which has already been transferred from the North Greenland Ice Core Project (NGRIP) to the Greenland Ice Core Project (GRIP), Greenland Ice Sheet Project 2 (GISP2) and North Greenland Eemian Ice Drilling (NEEM) deep ice cores (Seierstad et al, 2014; Rasmussen et al, 2013) – to East Greenland Ice-core Project (EGRIP) by aligning features in the dielectric profiling (DEP) and electrical conductivity measurement (ECM) data sets of the EGRIP, NGRIP and NEEM ice cores
We have established the initial chronology for the EGRIP deep ice core in Greenland which encompasses the Holocene and late glacial periods

Summary

Introduction

The dating of an ice core establishes the depth–age relationship to derive a chronology of past climatic conditions from the measured proxy parameters. The proxy parameters reflect past atmospheric conditions and biogeochemical events along the core. Concerning the ice sheet as a whole, the depth–age relation is needed to map the ice sheet’s internal architecture to interpret and understand the climatic evolution and the behaviour of ice streams (MacGregor et al, 2015). This is a particular focus of the East Greenland Icecore Project (EGRIP). A main objective of the EGRIP project is to study the dynamics of the ice flow in the NEGIS ice stream by analysing the ice core’s rheology and its relation to the deformation of the ice

Objectives

Results

Conclusion