Constraining Ice Shelf Basal Channel Melt Rates and Evolution

Abstract:

Meltwater channels that incise into the base of ice shelves remain among the most poorly understood features in the ice shelf/ocean system. Ice shelves are vulnerable to basal melting and it is largely unknown how melt rates within basal channels compare with ice shelf melt rates as a whole, or how the evolution of basal channels impacts ice shelf stability. Using a suite of remotely-sensed, high-resolution surface elevation, ice thickness, and velocity data from the early 2000s to the present, we observe changes in several Greenland and Antarctic basal channels through time and estimate basal melt rates assuming hydrostatic equilibrium. Analyses are performed in both Lagrangian (coordinate system moves with flow) and Eulerian (fixed coordinate system) frameworks in order to capture as much information as possible about channel behavior, which is dependent not only on ice flow, but also on the independent behavior of the underlying meltwater plume which cannot be studied with the data available. We find a variety of evolutionary behaviors of basal channels; some channels remain steady in time and space, with elevated melt rates only at the head, or landward end, some channels, particularly sinuous channels and those near shear margins, experience migration and elevated melt rates at more than one point along their length, and some channels are out of hydrostatic equilibrium where active melt is occurring. We attempt to categorize channels based not only on possible formation mechanism, but also on their evolutionary behavior, with the aim of identifying specific channels and specific behaviors that may negatively impact ice shelf stability. Our basal melt rate estimates and characterization of basal channel behavior are important for the accurate representation of ice shelves in ice sheet models predicting future sea level rise.