Evaluating the likelihood of flow reactivation at the sticky-spot of Whillans Ice Stream using ICESat-2 and swath radar topography

Abstract:

The slowdown of Whillans Ice Stream is likely driven by linked thermal and hydrologic processes occurring at the ice stream bed. Characterizing the stress evolution there requires capturing the subtle details of both the ice-sheet bed geometry and the surface elevation change, as low amplitude or spatially confined topographic features can exert substantial influence on the uniquely low-stress Whillans Ice Plain. In this study, we apply new coherent and burst noise removal algorithms together with direction of arrival analysis to reprocess radar data collected during the 2013/14 austral summer. These new techniques have been applied elsewhere in Antarctica to provide fine-resolution (50 m by 50 m) bed topography. In addition, we look at along-track height change products from ICESat-2, combined with the NASA Goddard Space Flight Center’s firn densification model, to evaluate local and short-time-scale changes in ice thickness occurring at the sticky spot of Whillans Ice Plain.

Together, these two data sets allow us to evaluate the likelihood of reorganization of the Whillans subglacial hydrologic system. As hypothesized by earlier work along the Siple Coast (Carter et al., 2012), we find that water currently routed westward along the southern margin of the Whillans Ice Plain is likely to divert into streaming flow if the modern thickening pattern persists. This could result in a negative feedback, where local dewatering of the till, thickening ice, and stagnation at the sticky spot results in a reorganization of water flow in the upstream catchment, ultimately diverting water to the region of greatest slow-down, resulting in reactivation of streaming flow.

Carter, S. P., & Fricker, H. A. (2012). The supply of subglacial meltwater to the grounding line of the siple coast, west antarctica. Annals of Glaciology, 53(60), 267–280. https://doi.org/10.3189/2012AoG60A119