A new study that combines a model of glacial surface mass balance with a global climate model determines how much of the current and future increase in marginal melting and interior accumulation of the Greenland Ice Sheet is due to human activity rather than natural forces. The Greenland Ice Sheet, the largest continental glacier in the world, is shrinking at an increasing rate, but scientists are unsure how much of this shrinkage is due to natural versus human-driven climate change.
One primary way ice sheets evolve is via changes to the surface mass balance (SMB), the difference between interior snow accumulation and ice margin melting. To assess the human impact on Greenland SMB against the backdrop of natural SMB variability, glaciologists would need to measure SMB trends over timescales of decades to centuries. Available observations, however, span only a few decades for a limited set of locations, so glaciologists have turned to models to understand the human SMB signal.
Using output from a well-validated SMB simulation produced in 2013 by the global Community Earth System Model, Fyke et al. identified the emerging signal of human forcing from the year 1850 through the present day and up to 2100. The researchers are the first to produce a global climate model simulation with a realistic simulation of Greenland SMB and the first to address at what point human activity starts to clearly dominate natural SMB variability.
The researchers conclude that human-driven climate change is increasingly responsible for current trends in Greenland Ice Sheet melt and accumulation. Moreover, human activity will dominate further melt and accumulation patterns throughout the 21st century. Last, they conclude that one of the best ways to assess the impact of human forcing on the Greenland Ice Sheet may be to monitor snowfall over the summit region. (Geophysical Research Letters, doi:10.1002/2014GL060735, 2014)
—Jessica Orwig, Writer
Citation: Orwig, J. (2014), Human actions affect Greenland Ice Sheet surface mass balance, Eos Trans. AGU, 95(51), 492, doi:10.1002/2014EO510009.