Twentieth century increase in snowfall in coastal West Antarctica

E R Thomas,R R Tuckwell,E C Ludlow,R A Warren,J S Hosking

doi:10.1002/2015gl065750

Abstract

AbstractThe Amundsen Sea sector of the West Antarctic ice sheet has been losing mass in recent decades; however, long records of snow accumulation are needed to place the recent changes in context. Here we present 300 year records of snow accumulation from two ice cores drilled in Ellsworth Land, West Antarctica. The records show a dramatic increase in snow accumulation during the twentieth century, linked to a deepening of the Amundsen Sea Low (ASL), tropical sea surface temperatures, and large‐scale atmospheric circulation. The observed increase in snow accumulation and interannual variability during the late twentieth century is unprecedented in the context of the past 300 years and evidence that the recent deepening of the ASL is part of a longer trend.

Highlights

Extensive thinning of fast flowing glaciers [Pritchard et al, 2009] has made the Amundsen coast region one of the largest Antarctic contributors to sea level rise [Shepherd et al, 2012]
At Ferrigno and 31% higher at Bryan coast than the baseline values determined from 1712 to 1899. This twentieth century increase is consistent with the Gomez ice core record from the southwestern Antarctic Peninsula (Figure 1a) which revealed a doubling of snow accumulation since 1854 with an increasing trend that began in the ~1930s and accelerated in the mid-1970s [Thomas et al, 2008]
Looking at the individual records, the increase at Ferrigno is less pronounced with 8 of the last 30 years exceeding 2σ above baseline average compared to 13 of the last 30 years at Bryan Coast. This is in contrast to the insignificant trend observed at WAIS divide (WDC05Q) ice core (Figure 1a) [Banta et al, 2008], and the negative trends observed from the Satellite Era Accumulation Traverse (SEAT 2010) ice cores from central West Antarctica [Burgener et al, 2013], suggesting that the observed twentieth century increase is confined to the Antarctic Peninsula and Ellsworth Land, with the magnitude decreasing from east (Gomez) to west (Ferrigno). 3.1.1

Summary

Introduction

Extensive thinning of fast flowing glaciers [Pritchard et al, 2009] has made the Amundsen coast region one of the largest Antarctic contributors to sea level rise [Shepherd et al, 2012]. Calculating Antarctic mass balance and its potential contribution to sea level rise is dependent on a good understanding of spatial and temporal changes in Antarctic snow accumulation, the net result of precipitation, sublimation, snow drift, and melt. Snow accumulation is a difficult parameter to measure and is largely based on remote sensing and atmospheric modeling. Despite a reported insignificant change in total Antarctic snow accumulation since the 1950s (1957–2004) [Monaghan et al, 2006], regionally there are significant trends. In the Antarctic Peninsula models reveal an upward trend in regional precipitation since 1979 [Lenaerts et al, 2012; van den Broeke et al, 2006], an increase in elevation (1992–2003) [Davis et al, 2005], and an increase in ice core derived snow accumulation [Thomas et al, 2008]. In West Antarctica no trend in either measured or modeled snow accumulation is observed between 1980 and 2009 on Thwaites Glacier [Medley et al, 2013], while in central West Antarctica observed and simulated records show a negative trend in accumulation rates during this period [Burgener et al, 2013]

Methods

Results

Conclusion