| 08 May 2026
Greenland mass change using range acceleration from GRACE-FO
Abstract. Observations of ice mass change with GRACE and GRACE-FO are limited in both temporal and spatial resolution. For the Greenland ice sheet, standard processing can resolve monthly mass change at the scale of large drainage basins, not at the level of individual glaciers or smaller regions. For GRACE-FO, a method using the range acceleration measurements to calculate instantaneous line-of-sight gravity has been used to study hydrological extremes such as floods and storm surges. In this paper, we look at the Greenland ice sheet and use the line-of-sight gravity signal to estimate 5-day mass change for four summers. We also include altimetry data to try to improve the spatial resolution of the observed mass change. The amplitude of the estimated mass change is within the range of monthly mass change estimates. The choice of regularisation clearly affects the spatial distribution, which in turn affects estimates at basin scales or even at smaller scales. Additionally, the noise level increases relative to the monthly signal, and the regularisation based on altimetry data increases the correlation among mass points compared to Tikhonov regularisation. Estimating mass change based on line-of-sight gravity is possible, although the spatial distribution remains sensitive to the choice of regularisation. Nonetheless, the approach shows promise for resolving short‑term mass‑change events and motivates further refinement of line-of-sight gravity-based inversion techniques for future satellite gravimetry missions.
This is an interesting and well-presented manuscript, using line-of-sight gravity differences to attempt to estimate very high spatial resolution changes in mass over Greenland. The authors use an established technique but apply it to a cryospheric setting rather than hydrological as has been done previously.
major comments
1. Since the objectives of the paper are to assess whether and how well the LGD approach can estimate high spatial resolution mass change, it seems strange that the size of the mascons used to parameterise the mass changes is simply set to 45 km. Why was this value chosen? It seems likely that the setting of this value had significant impact on the results, yet no other values seem to have been used to make comparisons, nor has any justification been given for why 45 km was the chosen value. Also, the choice of regularisation will trade off with the size of the mascons used - the impact of the arbitrariy chooice of this parameter pervade through all the results, interpretations and conclusions of the paper. This deserves greater assessment, probably including showing results using different sizes of mascons to quantify the sensitivity of the approach to the mascon size.
2. It is not clear why Iceland and Ellesmere Island were included as point masses in the setup of the experiment. Mass changes there are never discussed, so why are they parameterised at all?
Minor comments
line 39: the LRI has not been running in diagnostic mode to reduce thruster activation and overall fuel usage. It has been running in diagnostic mode because no inter-satellite measurements are being made anymore due to reduced thruster activation.
line 42: change "to get" to something more formal
line 100: could a sigma of 10 nm/s^2 be throwing out actual signals? Some of the large mass loss signals are now causing range acceleration observations over 100 nm/s^2 (or is that only over Antarctica where the mass loss is larger?)
line 238: have you calculated altimetry height changes using linear trends? Won't the inclusion of linear changes affect the ability of the LGD approach to identify correctly any short-term mass changes? What is the impact of imposing linear height changes through the inclusion of the altimetry observations?
line 168: what is the origin of the -231.48 GT/yr trend that was restored?
Figure 5: please add the basin numbers (again) to the central figure. Also, why are all your time series chopped up into four individual boxes? Why can't they be shown as continuous time series?
line 204: the term "mascon" first appears here, without definition.