One million years of glaciation and denudation history in west Greenland

Astrid Strunk,David L Egholm,Mads Faurschou Knudsen,Nicolaj K Larsen,Bo H Jacobsen,Laura B Levy,John D Jansen

doi:10.1038/ncomms14199

Abstract

The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Here we quantify exposure and denudation histories in west Greenland by applying a novel Markov-Chain Monte Carlo modelling approach to all available paired cosmogenic 10Be-26Al bedrock data from Greenland. We find that long-term denudation rates in west Greenland range from >50 m Myr−1 in low-lying areas to ∼2 m Myr−1 at high elevations, hereby quantifying systematic variations in denudation rate among different glacial landforms caused by variations in ice thickness across the landscape. We furthermore show that the present day ice-free areas only were ice covered ca. 45% of the past 1 million years, and even less at high-elevation sites, implying that the Greenland Ice Sheet for much of the time was of similar size or even smaller than today.

Highlights

The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation
When the secondary neutrons and muons penetrate an exposed rock surface, nuclear reactions produce in situ terrestrial cosmogenic nuclides (TCNs), of which common nuclides used for dating purposes are 10Be and 26Al
We show that the denudation rate decreases with increasing elevation, from 450 m Myr À 1 in low-lying areas to 1–5 m Myr À 1 at highelevation summit flats (4850 m a.s.l.)

Summary

Introduction

The influence of major Quaternary climatic changes on growth and decay of the Greenland Ice Sheet, and associated erosional impact on the landscapes, is virtually unknown beyond the last deglaciation. Paired 10Be-26Al bedrock data from high-elevation sites in west Greenland and the Baffin Bay area indicate long and complex exposure histories with significant periods of burial, suggesting preservation under weakly erosive, cold-based ice over several glacial cycles[18,19].

Results

Conclusion