The dynamic response of Pine Island Glacier to two decades of intermittent ice shelf regrounding

Over the last few decades, ice keels have intermittently bumped against the bedrock underneath Pine Island Ice Shelf. In general, it is thought that this process, termed regrounding, could enhance buttressing and potentially slow glacier flow or arrest retreat. Here, we test this hypothesis for Pine Island Glacier. Using offset tracking applied to satellite radar data, we reveal an extensive history of regrounding on the central shelf since 2009. Combining Earth observation and ice sheet modelling, we assess the direct effects this might have had on ice dynamics and indirect effects via its influencing on calving behaviour. Our results show that regrounding caused little additional drag on the base of the ice shelf. Furthermore, it plausibly contributed to the promotion of calving between 2015 and 2020 which is, in turn, held largely responsible for the increase in flow rate of the glacier over the last decade.