Maiolino, Marco (2025) Analisi di dati gravimetrici multipiattaforma per lo studio dello scioglimento delle calotte glaciali causato dal cambiamento climatico. [Tesi di dottorato]

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Abstract

In this thesis, I present two innovative approaches for analyzing ice sheet and ice shelf dynamics by modelling satellite and airborne gravity data, focusing on the Greenland Ice Sheet (GIS) the Antarctic Ice Sheet, as well as the Larsen Ice Shelf in Antarctica. These studies address critical gaps in understanding the processes driving ice mass loss and instability in Polar Regions, contributing to global sea level rise and ice shelf disintegration. For the Greenland and Antarctic Ice Sheets mass balance, I developed a novel approach to assess their mass variation using time-lapse gravity data from the Gravity Recovery and Climate Experiment (GRACE) NASA mission. By implementing an inversion algorithm in a spherical coordinate system, I modeled the gravity field through Equivalent Compact Sources. This method efficiently minimized leakage effects, isolating the gravity signal of the ice sheets from external contributions, and enabled us to estimate the melting rates across different basins defined by observed melt water outlets. My analysis revealed spatial patterns of melting, providing an accurate estimate of total mass loss between 2002 and 2017 for both regions. Specifically, the Greenland Ice Sheet lost -219 Gt/yr on average, contributing 0.66 mm/yr to global sea level rise, while the Antarctic Ice Sheet exhibited: -98 Gt/yr for the Amudsen Sea and -26 Gt/yr for the Antarctic Peninsula of ice melt, further emphasizing the significance of polar contributions to global sea level changes. In Antarctica, I also investigated the Larsen Ice Shelf, focusing on its vulnerability to basal melting driven by oceanic circulation of relatively warm waters underneath it. Ice shelf stability critically depends on accurate knowledge of the underlying bathymetry and cavity geometry, which remain poorly constrained. To address this, I applied the ITRESC method to 10 km resolution free-air gravity anomalies, integrating data from multiple surveys, including the IceBridge Mission. This approach allowed me to derive a new bathymetry and density contrast model for the Larsen Ice Shelf without relying on inversion processes or assumptions about seafloor lithology. The resulting model correlated with the thinning and detachment of iceberg A-68, highlighting the mélange zone's role within the suture region. Together, these studies demonstrate the utility of advanced gravity-based methods in characterizing ice sheet mass balance and under-ice shelf bathymetry. The methodologies developed offer valuable insights into the mechanisms driving ice loss and instability in polar regions, providing critical information for understanding and predicting their contributions to global sea level rise and climate change.

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