Between 1992 and 2017, the Antarctic Ice Sheet (AIS) lost ice equivalent to 7.6 ± 3.9 mm of sea level rise. AIS mass loss is mitigated by ice shelves that provide a buttress by regulating ice flow from tributary glaciers. However, ice‐shelf stability is threatened by meltwater ponding, which may initiate, or reactivate preexisting, fractures, currently poorly understood processes. Here, through ground penetrating radar (GPR) analysis over a buried lake in the grounding zone of an East Antarctic ice shelf, we present the first field observations of a lake drainage event in Antarctica via vertical fractures. Concurrent with the lake drainage event, we observe a decrease in surface elevation and an increase in Sentinel‐1 backscatter. Finally, we suggest that fractures that are initiated or reactivated by lake drainage events in a grounding zone will propagate with ice flow onto the ice shelf itself, where they may have implications for its stability.
Repeated Tidally Induced Hydrofracture of a Supraglacial Lake at the Amery Ice Shelf Grounding Zone
Surface melting and lakes are common to Antarctic ice shelves, and their existence and drainages have been invoked as a precursor for ice shelf collapse. Here, we present satellite observations over 2014–2020 of repeated, rapid drainages of a supraglacial lake at the grounding zone of Amery Ice Shelf, East Antarctica. Post‐drainage imagery in 2018 reveals lake bottom features characteristic of rapid, vertical lake drainage. Observed lake volumes indicate drainages are not associated with a threshold meltwater volume. Instead, drainages typically coincide with periods of high daily tidal amplitude, suggesting hydrofracture is assisted by tidally forced ice flexure inherent to the ice shelf grounding zone. Combined with observations of widespread grounding zone lake drainages on Amery, these findings indicate ice shelf meltwater accumulation may be inhibited by grounding zone drainage events, thus representing a potential stabilizing mechanism despite enhanced melting common to these regions.
more » « less- Award ID(s):
- 2021699
- NSF-PAR ID:
- 10381084
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 49
- Issue:
- 7
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract -
null (Ed.)Abstract Surface melting on Amery Ice Shelf (AIS), East Antarctica, produces an extensive supraglacial drainage system consisting of hundreds of lakes connected by surface channels. This drainage system forms most summers on the southern portion of AIS, transporting meltwater large distances northward, toward the ice front and terminating in lakes. Here we use satellite imagery, Landsat (1, 4 and 8), MODIS multispectral and Sentinel-1 synthetic aperture radar to examine the seasonal and interannual evolution of the drainage system over nearly five decades (1972–2019). We estimate seasonal meltwater input to one lake by integrating output from the regional climate model [Regional Atmospheric Climate Model (RACMO 2.3p2)] over its catchment defined using the Reference Elevation Model of Antarctica. We find only weak positive relationships between modeled seasonal meltwater input and lake area and between meltwater input and lake volume. Consecutive years of extensive melting lead to year-on-year expansion of the drainage system, potentially through a link between melt production, refreezing in firn and the maximum extent of the lakes at the downstream termini of drainage. These mechanisms are important when evaluating the potential of drainage systems to grow in response to increased melting, delivering meltwater to areas of ice shelves vulnerable to hydrofracture.more » « less
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