An observed negative trend in West Antarctic accumulation rates from 1975 to 2010: Evidence from new observed and simulated records

Abstract

[1] Observations of snow accumulation rates from five new firn cores show a negative trend that is statistically significant over the past several decades across the central West Antarctic ice sheet (WAIS). A negative temporal trend in accumulation rates is unexpected in light of rising surface temperatures as well as model simulations predicting higher accumulation rates for the region. Both the magnitude of the mean accumulation rates and the range of interannual variability observed in the new records compare favorably to older records collected from a broad area of the WAIS, suggesting that the new data may serve as a regional proxy for recent temporal trends in West Antarctic accumulation rates. The observed negative trend in accumulation is likely the result of a shift in low-pressure systems over the Amundsen Sea region, dominated by changes in the austral fall season. Regional-scale climate models and reanalysis data do not capture the negative trend in accumulation rate observed in these firn cores. Nevertheless the models and reanalyses agree well in both accumulation-rate means and interannual variability, with no single model or dataset standing out as significantly more skilled at capturing the observed magnitude of and trend in accumulation rates in this region of the WAIS.

Constraining the recent mass balance of Pine Island and Thwaites glaciers, West Antarctica, with airborne observations of snow accumulation

“…While the recent period is relatively high, radar-derived annual accumulation shows no significant trend over Thwaites Glacier between 1980. While recent work by Burgener et al (2013) found a negative trend in several shallow cores straddling the divide between the Ross Sea and Amundsen Sea drainages, the three cores presented in this work indicate that accumulation rates within the Pine Island-Thwaites drainage system do not exhibit a recent trend, consistent with the snow radar record from Medley et al (2013).…”

Simultaneous solution for mass trends on the West Antarctic Ice Sheet

“…4b). There is, however, some agreement with new in situ data from ice cores (Medley et al, 2013;Burgener et al, 2013). It should be remarked that in the ASE, where we also observe an ice loss maximum, the statistical framework might have difficulty in partitioning SMB and ice dynamics.…”

Variable relationship between accumulation and temperature in West Antarctica for the past 31,000 years

“…While the WDC results support a coherent response of temperature and accumulation at multi-millennial timescales, the timescale of interest for future sea level is centennial. Modern observations have shown that despite rapid warming in central West Antarctica over the past~60 years [Steig et al, 2009;Bromwich et al, 2013], there has been no discernible increase in accumulation [Medley et al, 2013;Burgener et al, 2013]. In Dronning Maud Land in East Antarctica, a similar disconnect has been observed; large positive accumulation anomalies in 2009 and 2011 are associated with only muted temperature increases [Lenaerts et al, 2013].…”

“…Modern observations of accumulation and temperature in Antarctica have not shown a consistent relationship because of large interannual variability in both parameters [e.g., Monaghan et al, 2006;Lenaerts et al, 2013] and because of limitations in the available reanalysis data [Nicolas and Bromwich, 2011b;Bromwich et al, 2011]. In central West Antarctica, which has experienced pronounced recent warming [Steig et al, 2009;Orsi et al, 2012;Bromwich et al, 2013], there has been no discernible increase in accumulation [Medley et al, 2013;Burgener et al, 2013].…”