Tuesday, December 4, 2012

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 (Ât(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 Ât(G) with the average surface air temperature in the Northern Hemisphere(SATNHt) remains positive through time, while the correlation of Ât(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 Ât(G) to SATNHt of 6.8% K-1 or 51 Gt K-1.

The reconstuction, Ât(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.

5 comments:

  1. yep,

    increase in snow accumulation is not an increase in the SMB. Overall ice loss is reported fro Greenland although there is more snow accumulation.

    This meeans melt is outpacing accumulation, isn't it?

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    Replies
    1. The same authors have submitted 2 additional articles addressing melt rates and mass balance, but they haven't been published yet & I don't know the results.

      Other papers do indicate overall ice loss in Greenland, but vary widely as to amount. Whether there is a link to AGW remains unproven.

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    2. So I'm wondering just how did those P38's get 250 ft down into the ice in Greenland?

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  2. This research says snow fall increases as global temperatures climb: "The correlation of Ât(G) with the average surface air temperature in the Northern Hemisphere(SATNHt) remains positive through time..."

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  3. thanks for sharing.

    ReplyDelete