Annual Greenland accumulation rates (2009–2012) from airborne snow radar

Lora S Koenig,Patrick M Alexander,Alvaro Ivanoff,Joesph R Mcconnell,Marco Tedesco,John D Paden,Joseph A Macgregor,Carl Leuschen,Indrani Das,Prasad Gogineni,Ben Panzer,Richard R Forster,Xavier Fettweis

doi:10.5194/tc-10-1739-2016

Abstract

Abstract. Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2–6.5 GHz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semiautomated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009–2012. The uncertainty in these radar-derived accumulation rates is on average 14 %. A comparison of the radar-derived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and long-term mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

Highlights

In the past 2 decades, climate warming over the Greenland Ice Sheet (GrIS) has accelerated its mass loss, nearly quadrupling from ∼ 55 Gt a−1 between 1993 and 1999 (Krabill et al, 2004) to ∼ 210 Gt a−1, equivalent to ∼ 0.6 mm a−1 of sea-level rise, between 2003 and 2008 (Shepherd et al 2012)
Two major accumulation-rate measurement campaigns have been undertaken across the GrIS: the first in the 1950s when the US Army collected pit data along long traverse routes (Benson, 1962) and the second in the 1990s when the Program on Arctic and Regional Climate Assessment (PARCA) collected an extensively distributed set of ice cores (e.g. Mosley-Thompson et al, 2001)
A semiautomated method was developed to process tens of thousands of kilometers of airborne snow radar data collected by Operation IceBridge (OIB) across the GrIS between 2009 and 2012

Summary

Introduction

In the past 2 decades, climate warming over the Greenland Ice Sheet (GrIS) has accelerated its mass loss, nearly quadrupling from ∼ 55 Gt a−1 between 1993 and 1999 (Krabill et al, 2004) to ∼ 210 Gt a−1, equivalent to ∼ 0.6 mm a−1 of sea-level rise, between 2003 and 2008 (Shepherd et al 2012). It switched from ice dynamics to surface mass balance (SMB) processes, which include accumulation and runoff (van den Broeke, 2009; Enderlin et al, 2014). This recent shift emphasizes the need to monitor SMB which, over most of the GrIS, is dominated by net accumulation. Radars detect the lateral persistence of isochronal layers within the firn When these layers are either (1) dated in conjunction with ice cores or (2) annually resolved from the surface, they can be used to determine along-track accumulation rates

Methods

Results

Discussion

Conclusion