Department Seminar: Bryony Freer

Title: Where Ice Meets Ocean: Observing Antarctic Grounding Zone Dynamics from Space

Abstract: The stability of the Antarctic Ice Sheet and its future contribution to sea-level rise are highly dependent on the behaviour of its surrounding floating ice shelves. A particularly critical region is the grounding zone (GZ), over which the ice transitions from grounded to floating, and where basal properties, ocean forcing, and ice dynamics interact. Accurate representation of GZ dynamics requires high-resolution measurements that resolve the 3D surface topography and capture the impact of atmospheric and oceanic influences that vary on hourly to decadal timescales. However, current observations have been under-resolved in both space and time.

In this talk, I will present two new satellite-based approaches that improve our understanding of Antarctic GZ dynamics. First, I introduce a method using ICESat-2 repeat-track laser altimetry to measure short-term, tide-forced grounding line (GL) migration. Applied to an Antarctic ice plain, this method reveals up to 15 km of tidal GL migration and four distinct migration modes. Second, I examine the spatial distribution and morphology of the surface bumps associated with the basal stress transition around the Ross Ice Shelf GZ. By combining digital elevation model and ICESat-2 observations of these surface features with viscous beam theory, I show that it is possible to improve estimates of GL location, basal properties, and ice thickness in Antarctic GZs.