Inferring tide-induced ephemeral grounding and subsequent dynamical
response in an ice-shelf-stream system: Rutford Ice Stream, West
Antarctica
- Minyan Zhong,
- Mark Simons,
- Brent Minchew,
- Lijun Zhu
Abstract
Antarctic ice shelves play a key role in regulating the rate of flow in
tributary ice streams. Temporal variations in the associated ice-shelf
buttressing stress are observed to impact the flow in glaciers and ice
streams. Ephemeral grounding induced by tides is considered as an
important mechanism for modulating the buttressing stress. Here, we
develop an approach to inferring variations in 3-D surface displacements
at an ice-shelf-stream system that explicitly accounts for ephemeral
grounding. Using a temporally dense 9-month long SAR image acquisition
campaign collected over Rutford Ice Stream by the COSMO-SkyMed
4-satellite constellation, we infer the ephemeral grounding zones and
the spatial-temporal variation of the fortnightly flow variability.
Expanding on previous results, we find ephemeral grounding zones along
the western ice-shelf margin as well as a few prominent ephemeral
grounding points in the central trunk and in the vicinity of the
grounding zone. Our observations provide evidence for tide-modulated
buttressing stress and the temporally asymmetric response of ice-shelf
flow to tidal forcing. Our study suggests that RIS will accelerate if
the ice shelf thins sufficiently that the ephemeral grounding zones we
have identified remain permanently ungrounded over the tidal cycle.