3D characterization of mélange dynamics inside large rifts in Filchner ice shelf in east Antarctica

There is little known about dynamics of mélange inside large rifts in Antarctic ice shelves and its role in rift propagation and the weakening of shelf stability. This lack of knowledge hinders our capability for long-term forecasting of the Antarctic ice sheet contribution to global sea level rise. We propose an innovative multi-temporal DEM adjustment model (MDAM) that builds a multi-satellite DEM time series from meter-level resolution small DEMs across large Antarctic ice shelves by removing biases, as large as ~6 m in elevation, caused by tides, ice flow dynamics, and observation errors. Using 30 REMA and ZY-3 sub-DEMs, we establish a cross-shelf DEM time series from 2014 to 2021 for the Filchner-Ronne Ice Shelf, the second largest in Antarctica. This unified and integrated DEM series, with an unprecedented submeter elevation accuracy, reveals quantitative 3D structural and mélange features of a ~50 km long rift, including rift lips, flank surface, pre-mélange cavities, and mélange elevations. We report that while the mélange elevation decreased by 2.1 m from 2014 to 2021, the mélange within the rift experienced a rapid expansion of (7.93±0.03) × 10⁹ km³, or 130%. This expansion is attributed to newly calved shelf ice from rift walls, associated rift widening, and other factors related to rift-mélange interactions. The developed MDAM system and the 3D mélange dynamics analysis methods can be applied for research on ice shelf instability and the future contribution of the Antarctic Ice Sheet to global sea level rise.