A comprehensive comparison of seasonal to multidecadal drivers of outlet glacier mass loss in Greenland

Abstract:

The Greenland Ice Sheet (GrIS) is losing mass at accelerated rates in the 21^st century, due in part to faster flow at large outlet glaciers. These glaciers are sensitive to both inland ice-sheet processes and changes at the ice-ocean interface. More accurate projections of future outlet glacier change depend on constraining glacier sensitivities to these various processes over multiple temporal and spatial scales. Here, we sample rapid changes in thickness and velocity at all large outlet glaciers (n > 200) to compare the relative impact of two main perturbations: (1) changes at the front (i.e., episodes retreat or glacier advance) and (2) seasonal injection of surface meltwater to the subglacial drainage system. We discuss the potential for these processes to change net dynamic mass losses from the ice sheet and show how local geometric conditions at individual glaciers plays a large role in determining glacier sensitivity to these changing processes. Finally, we quantify net ice volume losses from both retreat and meltwater runoff during the 21^st century and discuss which processes will likely continue to drive mass loss in the future.