Day 4

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Paper title Arctic land ice committed mass loss of from Sentinel-3 optical retrievals and GRACE gravimetry
  1. Jason Box GEUS Speaker
  2. Adrien Wehrlé Earth Observation Input Output
  3. Baptiste Vandecrux GEUS
  4. Scott Williamson GEUS
  5. Bert Wouters Institute for Marine and Atmosphere Research and Delft University of Technology
Form of presentation Poster
  • A9. Polar Science and Cryosphere
    • A9.04 Mass Balance of the Cryosphere
Abstract text Arctic land ice is responding to anthropogenic climate heating through increased surface ablation and less well constrained dynamical flow processes. Nevertheless, the magnitude of committed loss and the lower bound of future Sea Level Rise (SLR) remains unresolved.
Here, we apply a well-founded theory to determine Arctic ice committed mass loss and SLR contribution. The approach translates observed ice mass balance fluctuations into area and volume changes that satisfy an equilibrium state. Ice flow dynamics are accounted implicitly via volume to area scaling. For our application, the key data requirements are met with 2017 to 2021 (5 year) inventories of regional Arctic: 1) mass balance from GRACE gravimetry; 2) the Accumulation Area Ratio (AAR) defined as the area with net mass gain divided by the total glacierized area, retrieved from Sentinel-3 optical imagery.
For seasonally ablating grounded ice masses, the maximum snowline altitude reached at the end of each melt season marks the transition between the lower bare ice and the upper snow accumulation areas. This equilibrium line conveniently integrates the competing effects of mass loss from meltwater runoff and gain from snow accumulation. Crucially, the regression property where mass balance is zero defines the time- and area-independent Equilibrium Accumulation Area Ratio (AAR0). The ratio AAR / AAR0 yields the fractional imbalance (α) that quantifies the area change required for the ice mass to equilibrate its shape to the climate that produced the observed AAR0. The resulting derivation for the adjustments in ice volume (ΔV) and committed eustatic SLR follow from glaciological area-volume scaling theory. The approach exploits how surface mass balance perturbations are at least an order of magnitude faster than the associated dynamic adjustment. Whilst the theoretical basis and derivation of ice area-volume scaling analysis applies equally to all terrestrial ice masses, independent of size, it has previously not been applied to determine all Arctic ice disequilibria.
The considered regions are Greenland; Arctic Canada North, Svalbard, Iceland and the Russian High Arctic Islands.