Observed and modelled surface meltwater-induced flexure and fracture on north George VI Ice Shelf, Antarctica

Hundreds of surface lakes are known to form each summer on north George VI Ice Shelf, Antarctic Peninsula. To investigate surface-meltwater induced ice-shelf flexure and fracture, we obtained Global Navigation Satellite System (GNSS) observations and ground-based timelapse photography over north George VI for three melt seasons from November 2019 to November 2022

In particular, we used these field observations to characterize the flexure and fracture behaviour of a pre-existing doline (i.e. drained lake basin) on north George VI during the record-high melt season of 2019/2020. The GNSS displacement timeseries shows a downward vertical displacement of the doline centre with respect to the doline rim of ~80 cm in response to loading from the development of a central meltwater lake. Viscous flexure modelling indicates that this vertical displacement likely generates flexure stresses of ~> 75 kPa. The GNSS data also show a 10s of days episode of rapid-onset, exponentially decaying horizontal displacement where the horizontal distance from the rim of the doline with respect to its center increases by ~70 cm. We interpret this event as the initiation and/or widening of a single fracture, possibly aided by the availability of surface meltwater (i.e. hydrofracture). Our observations document for the first time the initiation and/or widening of a “ring fracture” on an ice shelf, equivalent to those fractures proposed to be part of the chain reaction lake drainage process involved in the breakup of Larsen B Ice Shelf in 2002.