Outbursts from an ice-marginal lake in Antarctica in 1969–1971 and 2017, revealed by aerial photographs and satellite data

Abstract

The liquid water around the Antarctic Ice Sheet plays a key role in modulating both the vulnerability of ice shelves to hydrofracturing and ice discharge from outlet glaciers. Therefore, it needs to be adequately constrained for precise future projections of ice-mass loss and global sea-level rise. Although glacial lake outburst floods (GLOFs) pose one of the greatest risks in glacierized mountainous regions, any long-term monitoring of Antarctic ice-marginal lakes and their associated potential for GLOFs has been neglected until recently owing to the limited number of such events reported in Antarctica. Here we present direct evidence of repeated GLOFs from Lake Kaminotani-Ike, an ice-sheet-dammed lake in East Antarctica, via an analysis of historical aerial photographs and recent satellite data. Two GLOFs occurred in 1969–1971 and 2017, with discharge volumes of (8.6 ± 1.5) × 107 and (7.1 ± 0.4) × 107 m3, respectively, making them two of the largest GLOFs in Antarctica. A southerly oceanward pathway beneath the ice sheet is the most likely drainage route of these GLOF events based on the available surface- and bed-elevation datasets. Furthermore, the 2017 event occurred during the austral winter, thereby implying the possibility of year-round active subglacial networks in Antarctica. Our results highlight that studies on Antarctic ice-marginal lakes provide an opportunity to better understand Antarctic hydrological processes and emphasize the need for both detailed monitoring of ice-marginal lakes and detailed surveying of the subglacial environments of the Antarctic Ice Sheet.