Cracking the Case of Antarctic Ice Shelf Rifting

Abstract

The stability of the ice shelves that float at the fringes of Antarctica may be the key to determining the future of the Antarctic Ice Sheet (AIS) and its contribution to sea level rise. Fracture exerts a fundamental control on the geometry of ice shelves and their ability to buttress the AIS. Yet our understanding of rifts, the largest fractures in Earth's ice, is limited by a lack of observations. We explore the diverse range of fracture processes at ice shelf rifts by using seismic recordings, environmental data, remotely-sensed measurements, and mechanical models to characterize the physics of the rifting process. We first examine icequakes generated by fracture at a rift in the Ross Ice Shelf and relate their timing to stresses imposed by changing air temperature and ocean tides. We then shift our focus to the rapidly-accelerating Pine Island Glacier. We characterize dynamic flexure generated by fracture in the shear margin and at a gradually-propagating rift, and we find that rift propagation is related to changes in ocean forcing and ice dynamics. Using seismic recordings and synthetic aperture radar, we observe the fastest recorded episode of rift propagation, and we use a coupled model of the fracture mechanics and hydrodynamics active during rifting to precisely explain the observed rate of propagation. Finally, we present the results of an ongoing project that uses distributed acoustic sensing to characterize the dynamics of a fast-flowing glacier in West Greenland. The work in this thesis provides a new level of detail in our observation of ice shelf rifts and represents a significant step towards better understanding their behavior and influence.