Reactivation of a Subglacial Channel Around the Grounding Zone of Roi Baudouin Ice Shelf, Antarctica

Subglacial water beneath the Antarctic Ice Sheet is often funneled via subglacial channels, which inject freshwater into ice‐shelf cavities where it interacts with ocean water. The temporal variability of this system has been poorly observed, but its importance for ice dynamics is well recognized. Airborne radar data show a subglacial channel evolving within a decade near of the grounding zone of the Roi Baudouin Ice Shelf (East Antarctica), while topographic signatures on the ice shelf indicate prior inactivity for 60 years. Combining our observations with subglacial hydrological modeling, we suggest that the interplay between episodic subglacial water pulses and ocean water intrusion drive the opening and closing of the channels. Our findings illuminate the short‐term transient nature of subglacial channel activity. This impacts ice‐shelf–ocean processes, which are important for constraining increasing ocean warming onto ice‐shelf basal mass balance, but pose significant challenges for subglacial hydrological modeling at the grounding zone. Plain Language Summary This study explores how water moves under the ice in Antarctica and how it interacts at the ice–ocean boundary. Using radar, we studied a part of the Roi Baudouin Ice Shelf in East Antarctica and found that water channels under the ice have changed significantly over the last decades. The radar images from 2011 to 2019 showed that these channels open and close within a decade, likely due to changes in water supply from the inland and intrusion of ocean water. This means that the water flow under the ice is not steady, influencing melting at the underside and affecting its movement. These discoveries show that the subglacial water system under Antarctic Ice Sheet is more complicated, making it harder to project future changes in sea‐level rise and the effects of climate change on the polar regions. Key Points Subglacial channels near the grounding zone are stable in space but toggle activity within decades Ice‐shelf channel morphology identifies one water outlet as active for hundreds of years before it shut down 60 years ago Radio‐echo sounding documents the reactivation of a subglacial channel within eight years near the grounding zone