Tidal influence on flow dynamics of Dotson Ice Shelf, West Antarctica

Abstract. On Dotson Ice Shelf, Antarctica, ice velocities derived from satellite image pairs and in-situ GPS measurements reveal an oscillating flow pattern that is correlated with tide height. The tidally-affected flow pattern is of limited extent, in an area near the Wunneberger Rock nunatak in the outflow of Kohler Glacier. Comparing variations in the region’s flow velocity derived from a series of 16-day repeat-pass Landsat 8 image pairs spanning 2014–2020, and a 64-hour GPS record in 2022 with the CATS2008 and TPXO9 tide-height models, indicates a significant correlation between tidal uplift and the direction of ice-flow. During high-tide periods the ice-shelf flows in a true north direction, while at low-tide periods flow direction shifts towards the northeast, marking an approximately 40˚ change in flow direction. GPS measurements describe a continuous corkscrew-like motion of the ice-shelf surface, confirming the link between tide height and ice-flow direction. We attribute the observed pattern to tidally controlled changes of buttressing along the ice-shelf margins and the fin-like shape of Wunneberger Rock. This leads to a dual pattern: (i) fast flow across the grounding line of the tributary Kohler Glacier during high tides aligning with Wunneberger Rock’s summit ridge; and (ii) slow flow during low tide height facing its flanks. We suggest that the link between tides and ice dynamics is related to the rapid ice-shelf thinning in the area. In light of the continued thinning of ice shelves surrounding Antarctica, we anticipate similar variations in flow direction and speed arising from changes in tidal influence on buttressing from pinning points and grounding zones.