Abstract. In recent decades, the Greenland Ice Sheet has experienced an accelerated mass loss, contributing to approximately 25 % of contemporary sea level rise. This mass loss is caused by increased surface melt over a large area of the ice sheet and by the thinning, retreat and acceleration of numerous Greenland outlet glaciers. The latter is likely connected to enhanced submarine melting that, in turn, can be explained by ocean warming and enhanced subglacial discharge. The mechanisms involved in submarine melting are not yet fully understood and are only crudely incorporated in some models of the Greenland Ice Sheet. Here, we investigate the response of twelve representative Greenland outlet glaciers to atmospheric and oceanic warming using a coupled 1D line-plume glacier-flowline model. The model parameters have been tuned for individual outlet glaciers using present-day observational constraints. We then run the model from present to the year 2100, forcing the model with changes in surface mass balance and surface runoff from simulations with a regional climate model for the RCP 8.5 scenario, and applying a linear ocean temperature warming with different rates of changes representing uncertainties in the CMIP 5 model experiments for the same climate change scenario. We also used different initial temperature-salinity profiles obtained from direct measurements and from ocean reanalysis data. Using different combinations of submarine melting and calving parameters that reproduce the present-day state of the glaciers, we estimated uncertainties in the contribution to global sea level rise for individual glaciers. We also performed a factor analysis, which shows that the role of different forcing (change in surface mass balance, ocean temperature and subglacial discharge) are diverse for individual glaciers. We found that changes in, ocean temperature and subglacial discharge are of comparable importance for the cumulative contribution of all twelve glaciers to global sea level rise in the 21st century. The median range of the cumulative contribution to the global sea level rise for all twelve glaciers is about 14 mm from which roughly 85 % are associated with the response to increased submarine melting and the remaining part to surface mass loss. We also found a weak correlation (correlation coefficient 0.35) between present-day grounding line discharge and their future contribution to sea level rise in 2100. If the contribution of the twelve glaciers is scaled up to the total present-day discharge of Greenland, we estimate the contribution of all Greenland glaciers to 21st-century sea level rise to be approximately 50 mm. This result confirms earlier studies that the response of the outlet glaciers to global warming has to be taken into account to correctly assess the total contribution of Greenland to sea level change.
GRACE-derived ice-mass loss spread over Greenland
