Advancing Observation of Cryospheric Mass Changes from sub-monthly to decadal time scales with the NGM and MAGIC Gravity Missions

The mass balance estimates of the GRACE and GRACE-FO satellite missions have revolutionized our understanding of the cryosphere, yet the low spatial (~200 km) and temporal resolution (monthly) limit the detection of short-term events such as melt pulses and snowfall surges, or the onset and end of the ablation season. Furthermore, the relatively high noise at shorter time scales makes estimation of yearly mass balances challenging for the smaller glacier systems outside of the Greenland and Antarctic Ice Sheets. The MAss Change and Geosciences International Constellation (MAGIC) mission, consisting of the GRACE-C (NASA and DLR; scheduled for launch in 2028) and ESA’s Next-Generation Gravity Mission (NGGM; 2032) will drastically increase the temporal and spatial resolution of the gravimetric mass balance estimates.

Here, we combine daily surface mass balance (SMB) output from regional climate models with noise from end-to-end gravity simulations to assess NGGM and MAGIC’s capability to resolve sub-monthly mass changes over the Greenland and Antarctic ice sheets at basin scales, as well as seasonal mass balance and long-term trends of smaller glacier systems. We find that 5-daily MAGIC measurements enable the observation of extreme melt events comparable to the 2012 Greenland melt episode and capture storm-driven accumulation in Antarctica at sub-monthly time scales. For other glacier systems - such as Iceland, Patagonia, and High Mountain Asia - the mission allows the onset and termination of the ablation season to be identified within 2–3 days and constrains winter gain loss and summer mass loss to within a few gigatons, representing an order-of-magnitude improvement over GRACE(-FO). Uncertainties in long-term trends are reduced by a similar factor, such that the precision achieved by NGGM and MAGIC within a few years is comparable to that obtained by GRACE(-FO) only after 10–15 years of observations.

Overall, NGGM and MAGIC are expected to represent a step change in gravimetric cryosphere monitoring, enabling routine observation of short-term variability and supporting improved detection, attribution, and modelling of long-term mass-balance trends.