Netherlands Polar Data Center

Summary

In this project we address the centennial evolution of surface mass balance and in particular meltwater runoff from the Greenland ice sheet (GrIS). GrIS mass loss increased from ~150 Gt yr-1 in 2000-2005, to ~265 Gt yr-1 in 2005-2009 and ~380 Gt yr-1 in 2009-2012, contributing 20-30% to total global average sea level rise over the last decade. An increasingly large fraction of the mass loss (from ~55% in 2000-2005 to ~70% in 2009-2012) is caused by enhanced meltwater runoff. The rapidity of these recent developments is alarming, and we urgently need to address the following questions: how exceptional are recent GrIS surface melt events when viewed in a century-long perspective? What fraction can be ascribed to anthropogenic climate change, and what fraction to natural (decadal) variability? What is the role of transient firn processes and the albedo-melt feedback on meltwater runoff, and how does uncertainty in their representation affect the results? We address these issues by using the ECMWF 20th century global atmospheric re-analysis product, to be released in the summer of 2014, to force -in a fully transient fashion- the coupled regional climate/snow model RACMO2.3. This effort will provide a time series of GrIS surface mass balance, melt and runoff for the period 1900-2014, nearly doubling the length of the currently available time series and enabling us to provide physically-based answers to these pressing questions.

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