Seasonal land-ice-flow variability and its drivers in the Antarctic Peninsula

Ice flow of the Antarctic Ice Sheet has experienced multi-annual acceleration in response to increased rates of ice thinning and retreat. Despite the well-documented seasonality of ice flow in Arctic and Alpine regions, little to no observations exist of seasonal ice-flow variability in Antarctica, due largely to a lack of systematic, high temporal-resolution satellite imagery. Accordingly, the mechanisms driving any such seasonality remain similarly undetermined. Such information is critical for understanding, modelling, and ultimately refining projections of the ongoing and future contribution of Antarctica to global sea-levels.

Here, we use high spatial- and temporal- (6/12-daily) resolution Copernicus Sentinel-1a/b synthetic aperture radar (SAR) observations spanning 2014 to 2020 to provide evidence for seasonal flow variability of land ice feeding George VI Ice Shelf (GVIIS), Antarctic Peninsula. Between 2014 and 2020, the flow of glaciers draining to GVIIS from Palmer Land and Alexander Island increased during the austral summertime (December – February) by ~15% relative to baseline rates of flow. This speedup is corroborated by independent observations of ice flow as imaged by the Landsat 8 Operational Land Imager.

To identify the likely drivers of this seasonality, we carry out statistical time-series analyses on an array of remotely sensed and reanalysis datasets of potential environmental forcing mechanisms. We find that both surface and oceanic forcing act as statistically significant precursors to summertime ice-flow acceleration. Ultimately, these findings imply that seasonality may be present elsewhere in Antarctica where comparable forcing mechanisms exist.