Reactivation of lateral meltwater export from Bach Ice Shelf following a 9-year hiatus

Since the 1950’s ice-shelf surface meltwater has been implicated as a driver of partial and complete collapse events across several ice shelves on the Antarctic Peninsula. Many of these events occurred alongside marked increases in 2m air temperatures in the later half of the 20th century, which drove increased rates of surface melting. Whilst this warming was briefly punctuated by a partial cooling across the Antarctic Peninsula from 1999 to 2014, it has since resumed. Given projections of non-linear increases in surface melting under future climate scenarios, surface meltwater-driven instabilities become increasingly important. Whilst most studies to date have focussed on the potential for hydrofracture, it is important that we begin to consider the potential for ice-shelf run-off and lateral meltwater export as Antarctica progresses towards Greenlandification. 

Here we present remotely sensed evidence for the re-initiation of surface meltwater export from Bach Ice Shelf, following a 9-year hiatus.  We combine optical remote sensing (Landsat 7, 8, and 9) with 43 years of regional climate model outputs (RACMO2.3p2 and ERA5) to evidence this change and consider the climate conditions that may have driven it. Variables considered include modelled surface mass balance, melt, and 2 m air temperatures. Melt-to-SMB ratios were calculated from modelled surface mass balance and melt. 

In the austral summer of 2022/23, lateral meltwater export resumed on Bach Ice Shelf, ending the observed 9-year hiatus. This hiatus may have been driven by high surface mass balance and low snowmelt values, which resulted in low melt-to-SMB ratios. Such low melt-to-SMB ratios likely increased ice-shelf firn air content, which then took several years to overcome. The return of lateral meltwater export from Bach Ice Shelf in 2022/23 coincided with the highest modelled mean annual 2 m air temperatures. With continued atmospheric warming, we anticipate that Bach’s meltwater regime will continue to exhibit lateral meltwater export in the future, demonstrating the renewed importance of surface run-off for ice shelves on the Antarctic Peninsula.