Accumulation Rates during 1311–2011 CE in North-Central Greenland Derived from Air-Borne Radar Data

Nanna B Karlsson,Frank Wilhelms,Johannes Freitag,John D Paden,Lisbeth T Nielsen,Anna Winter,Cameron Lewis,Olaf Eisen,Sepp Kipfstuhl,Dorthe Dahl-Jensen

doi:10.3389/feart.2016.00097

Abstract

Radar–detected internal layering contains information on past accumulation rates and patterns. In this study, we assume that the radar layers are isochrones, and use the layer stratigraphy in combination with ice-core measurements and numerical methods to retrieve accumulation information for the northern part of central Greenland. Measurements of the dielectric properties of an ice core from the NEEM (North Greenland Eemian Ice Drilling) site, allow for correlation of the radar layers with volcanic horizons to obtain an accurate age of the layers. We obtain accumulation patterns averaged over 100 a for the period 1311–2011. Our results show a clear trend of high accumulation rates west of the ice divide and low accumulation rates east of the ice divide. At the NEEM site the accumulation pattern is persistent during our study period and only small temporal variations occur in the accumulation rate. However, from approximately 200 km south of the NEEM drill site, the accumulation rate shows temporal variations based on our centennial averages. We attribute this variation to shifts in the location of the high–low accumulation boundary that usually is aligned with the ice divide, but appears to have moved across the divide in the past.

Highlights

Knowledge of past accumulation is essential for studying the evolution of ice sheets and their response to climate change
Numerous studies have confirmed that this topographic barrier results in high accumulation rates on the west coast, decreasing rates as the elevation rises toward the interior, and very low accumulation rates east of the ice divide (e.g., Bales et al, 2001; Ettema et al, 2009; Burgess et al, 2010; Box et al, 2013)
Our modeled accumulation rates agree with spatially distributed model results from regional climate models

Summary

Introduction

Knowledge of past accumulation is essential for studying the evolution of ice sheets and their response to climate change. The location of the ice divide influences the SMB, especially in central northern Greenland, since it marks the highest points in the interior of the ice sheet (see Figure 1, inset). For this region, Ohmura and Reeh (1991) showed that the ice divide acts as a topographic barrier for water vapor transported from the west coast. Numerous studies have confirmed that this topographic barrier results in high accumulation rates on the west coast, decreasing rates as the elevation rises toward the interior, and very low accumulation rates east of the ice divide (e.g., Bales et al, 2001; Ettema et al, 2009; Burgess et al, 2010; Box et al, 2013). Another example of elevation-controlled SMB is the ice rises in coastal East Antarctica (Lenaerts et al, 2014), they are of a substantially smaller spatial scale (a few tens of kilometers)

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Discussion

Conclusion