Regional Antarctic snow accumulation over the past 1000 years

Elizabeth R Thomas,Elisabeth Schlosser,Elisabeth Schlosser,Jason Roberts,Jason Roberts,Jason Roberts,Brooke Medley,Paul Vallelonga,Nancy Bertler,Nancy Bertler,Massimo Frezzotti,Barbara Stenni,Barbara Stenni,Elisabeth Isaksson,Jan Lenaerts,Tyler J Fudge,Mark Curran,J Melchior Van Wessem,Daniel A Dixon,Michiel R Van Den Broeke,Alexey A Ekaykin,Alexey A Ekaykin

doi:10.5194/cp-13-1491-2017

Abstract

Abstract. Here we present Antarctic snow accumulation variability at the regional scale over the past 1000 years. A total of 79 ice core snow accumulation records were gathered and assigned to seven geographical regions, separating the high-accumulation coastal zones below 2000 m of elevation from the dry central Antarctic Plateau. The regional composites of annual snow accumulation were evaluated against modelled surface mass balance (SMB) from RACMO2.3p2 and precipitation from ERA-Interim reanalysis. With the exception of the Weddell Sea coast, the low-elevation composites capture the regional precipitation and SMB variability as defined by the models. The central Antarctic sites lack coherency and either do not represent regional precipitation or indicate the model inability to capture relevant precipitation processes in the cold, dry central plateau. Our results show that SMB for the total Antarctic Ice Sheet (including ice shelves) has increased at a rate of 7 ± 0.13 Gt decade−1 since 1800 AD, representing a net reduction in sea level of ∼ 0.02 mm decade−1 since 1800 and ∼ 0.04 mm decade−1 since 1900 AD. The largest contribution is from the Antarctic Peninsula (∼ 75 %) where the annual average SMB during the most recent decade (2001–2010) is 123 ± 44 Gt yr−1 higher than the annual average during the first decade of the 19th century. Only four ice core records cover the full 1000 years, and they suggest a decrease in snow accumulation during this period. However, our study emphasizes the importance of low-elevation coastal zones, which have been under-represented in previous investigations of temporal snow accumulation.

Highlights

The Antarctic Ice Sheet (AIS) is the largest reservoir of fresh water on the planet and has the potential to raise global sea level by about 58.3 m if melted completely (IPCC, 2013)
Before we investigate the temporal changes in the records we first establish how representative each composite is of regional Surface mass balance (SMB) by testing annual average snow accumulation against annual average (January to December) SMB from RACMO2.3p2 (Fig. 2) and precipitation from ERA-Interim (Fig. 3; direct SMB is not available from the reanalysis product)
Eighty ice core snow accumulation records were quality checked and separated into seven geographical regions to reduce the bias towards over-represented regions and separate the highaccumulation coastal zones from the low-accumulation highelevation sites

Summary

Introduction

The Antarctic Ice Sheet (AIS) is the largest reservoir of fresh water on the planet and has the potential to raise global sea level by about 58.3 m if melted completely (IPCC, 2013). (3) Surface mass balance (SMB) and solid ice discharge can be individually estimated and subtracted (Rignot et al, 2011). (2) Ice sheet mass changes can be directly measured using the Gravity Recovery and Climate Experiment (GRACE) satellite system. These three techniques have significantly advanced our understanding of contemporary AIS mass balance, with growing evidence of increased mass loss over recent decades (Velicogna and Wahr, 2006; Allison et al, 2009; Chen et al, 2009; Rignot et al, 2011; Shepherd et al, 2012). The uncertainties in these assessments may be as high as 75 % (Shepherd et al, 2012), and another study even suggested a positive trend over the same period (Zwally et al, 2015)

Objectives

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Results

Conclusion