New paper finds an accelerating increase of snow accumulation on Greenland

A paper published today in The Journal of Climate reconstructs snow accumulation of the Greenland ice sheet from 1600-2009 and finds "a 12% or 86 Gigaton/yr increase in ice sheet accumulation rate from the end of the Little Ice Age in ~1840 to the last decade of the reconstruction. This 1840-1996 trend is 30% higher than that of 1600-2009, suggesting an accelerating accumulation rate."

Greenland ice sheet mass balance reconstruction. Part I: net snow accumulation (1600-2009)

Jason E. Box,^1,2 Noel Cressie,^3,4 David H. Bromwich,^1,2 Ji-Hoon Jung,^1,2 Michiel van den Broeke,⁵ J. H. van Angelen,⁵ Richard R. Forster,⁶ Clement Miège,⁶ Ellen Mosley-Thompson,^1,2 Bo Vinther,⁷ and Joseph R.McConnell⁸

¹ Byrd Polar Research Center, The Ohio State University, Columbus, Ohio, USA

² Department of Geography, The Ohio State University, Columbus, Ohio, USA

³ Department of Statistics, The Ohio State University, Columbus, Ohio, USA

⁴ National Institute for Applied Statistics Research Australia (NIASRA), University of Wollongong, Wollongong, New South Wales, Australia

⁵ Institute of Marine and Atmospheric Research, Utrecht University, Utrecht, The Netherlands

⁶ Department of Geography, University of Utah, Salt Lake City, Utah, USA.

⁷ Centre for Ice and Climate, Niels Bohr Institute, Copenhagen, Denmark

⁸ Desert Research Institute, Reno, Nevada, USA

Abstract

Ice core data are combined with RACMO2 regional climate model (RCM) output (1958-2010) to develop a reconstruction of the Greenland ice sheet net snow accumulation rate (Â_t(G)) spanning years 1600-2009. Regression parameters from RCM output regressed on 86 ice cores are used with available cores in a given year resulting in the reconstructed values. Each core site’s residual variance is used to inversely weight the cores’ respective contributions. The interannual amplitude of the reconstructed accumulation rate is damped by the regressions and is thus calibrated to match that of the RCM data. Uncertainty and significance of changes is measured using statistical models.

We find a 12% or 86 Gt y^-1 increase in ice sheet accumulation rate from the end of the Little Ice Age in ~1840 to the last decade of the reconstruction. This 1840-1996 trend is 30% higher than that of 1600-2009, suggesting an accelerating accumulation rate. The correlation of Â_t(G) with the average surface air temperature in the Northern Hemisphere(SATNH_t) remains positive through time, while the correlation of Â_t(G) with local near-surface air temperatures or North Atlantic sea surface temperatures is inconsistent, suggesting a hemispheric-scale climate connection. We find an annual sensitivity of Â_t(G) to SATNH_t of 6.8% K^-1 or 51 Gt K^-1.

The reconstuction, Â_t(G), correlates consistently highly with the North Atlantic Oscillation index. Yet, at the 11-year time scale, the sign of this correlation flips four times in the 1870-2005 period.