Quantifying the impact of bedrock topography uncertainty in Pine Island
Glacier projections for this century
Abstract
The predicted Antarctic contribution to global-mean sea-level rise is
one of the most uncertain among all major sources. Partly this is
because of instability mechanisms of the ice flow over deep basins.
Errors in bedrock topography can substantially impact the projected
resilience of glaciers against such instabilities. Here we analyze the
Pine Island Glacier topography to derive a statistical model
representation. Our model allows for inhomogeneous and spatially
dependent uncertainties and avoids unnecessary smoothing from spatial
averaging or interpolation. A set of topography realizations is
generated representing our best estimate of the topographic uncertainty
in ice sheet model simulations. The bedrock uncertainty alone creates a
5% to 25% uncertainty in the predicted sea level rise contribution at
year 2100, depending on friction law and climate forcing. Pine Island
Glacier simulations on this new set are consistent with simulations on
the BedMachine reference topography but diverge from Bedmap2
simulations.