| Summary: | Since the launch in 2002 of the Gravity Recovery and Climate Experiment (GRACE) satellites, several estimates of the mass balance of the Greenland Ice Sheet (GrIS) have been produced. To obtain ice mass changes estimates, data need to be corrected for the effect of deformation changes of the Earth's crust. This is usually done by independently modeling the Glaciological Isostatic Adjustment (GIA) trend and then by removing it from the data. Recently, Wu et al. (2010) proposed a new method to simultaneously estimate GIA and the present-day ice mass change, reporting an ice mass loss of around half of the previously published estimates and a general bedrock subsidence concentrated in the central parts of Greenland. This subsidence appears to be counterintuitive since the ice sheet is loosing mass at present. It was suggested by the authors that this could be a new evidence for additional net past ice accumulation. In this study, a 3-D ice-sheet model with a surface mass balance forcing based on a mass balance gradient approach has been used to: (a) analyze the bedrock response to changes in the ice load in order to evaluate whether bedrock subsidence and ice thinning can exist simultaneously; (b) study the magnitude and the pattern of the bedrock movement; and (c) evaluate if present-day bedrock subsidence could be the result of a net past mass accumulation. Under a sine forcing of the annual temperature, that mimics the temperature variations in the Holocene, mass changes yield a delay of the bedrock response of 200 years. Thinning of the ice as well as bedrock subsidence coexist during this period with an order of magnitude equal to the observations by Wu et al. (2010). Although, the resulting pattern of bedrock changes differs considerable: instead of the general bedrock subsidence reported before, we found areas of bedrock uplift as well as areas of bedrock subsidence. A simulation since the last glacial maximum (with the temperature represented as a linear increase from −10 K to present-day) yields a time lag ...
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