Physical properties of internal layers in Greenland ice sheet: measurements and modelling data analysis

• Main Authors: Mojtabavi, Seyedhamidreza, Wilhelms, Frank, Rasmussen, S. O., Eisen, Olaf, Franke, Steven, Jansen, Daniela, Cook, Eliza, Davies, Siwan, Sinnl, Giulia, Skov Jensen, Mathias, Steinhage, Daniel, Kipfstuhl, Sepp, Dahl-Jensen, D.
• Format: Conference Object
• Language: unknown
• Published: 2020
• Subjects: Greenland; Arctic; East Greenland; East Greenland Ice-core Project; Greenland ice core; Greenland Ice core Project; ice core; Ice Sheet; NGRIP
• Online Access: https://epic.awi.de/id/eprint/50836/; https://www.jcar.org/isar-6/program/; https://hdl.handle.net/10013/epic.57f1601b-f2cc-4ed3-a031-be83c243a3fc

The aim of our study is to analyse physical properties of internal layers of deep ice cores in Greenland (NGRIP and NEEM) and a new ice core record from the East GReenland Ice-core Project (EGRIP) on the North East Greenland Ice Stream (NEGIS). For this purpose, in the first part of this study, we have established the initial chronology for the EGRIP ice core over the Holocene and the late last glacial period. We rely on conductivity patterns and volcanic events determined by means of dielectric profiling (DEP), electrical conductivity measurements (ECM) and tephra records for the synchronization between the EGRIP, NEEM and NGRIP ice cores in Greenland. We have transferred the annual-layer-counted Greenland ice Core Chronology 2005 (GICC05) timescale from the NGRIP core to the EGRIP ice core by means of 373 match points. The second part of this study compares numerically modelled radargrams and the airborne radar measurements (radio-echo sounding) to understand the recorded physical properties of internal layers towards reflection mechanisms. Synthetic modelling of electromagnetic wave propagation has been applied to the EGRIP, NEEM and NGRIP2 ice cores based on the conductivity and permittivity, as measured at 250 kHz by DEP. For the comparison between synthetic and observed data, we have used radio-echo sounding data from AWI’s multichannel ultra-wideband radar around the EGRIP drill site, that were recorded during the 2018 field season, and the CReSIS data from the University of Kansas around the NEEM and NGRIP2 drill sites. The timescales (depth-age relation from first part of our study) have been transferred to the synthetic and observed radargrams by means of sensitivity studies. We have found that conductivity only explains a fraction of the radar signals in Greenland ice sheet and the orientated fabric is widespread and influences the radar data.