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Analysis of Subglacial Lake Activity in Recovery Ice Stream with ICESat-2 Laser Altimetry
1  College of Surveying and Geo-Informatics, Tongji University, Shanghai 200092, China
2  Center for Spatial Information Science and Sustainable Development Applications, Tongji University, Shanghai 200092, China
Academic Editor: Riccardo Buccolieri (registering DOI)

The Recovery Ice Stream is one of the longest ice streams in Antarctica, annually discharging a significant mass of ice into the Southern Ocean. Beneath the Recovery Ice Stream are numerous active subglacial lakes whose drainage and storage directly impact the flow velocity of the entire ice stream. This, in turn, has a considerable influence on ice dynamics, grounding line stability, and the mass balance of the East Antarctic Ice Sheet. Approximately twenty years ago, scientists discovered that the water transfer movements within subglacial lakes caused surface deformation on the ice sheet. The latest NASA Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2), utilizing laser altimetry technology, can capture more dense and precise spatial details, helping us better understand this hydrological process. Based on this, we use all the ICESat-2 data from September 2018 to July 2022 to reconstruct and analyze the activity of subglacial lakes under the Recovery Ice Stream. To investigate water transfer between the subglacial lakes and the latest subglacial lake outlines, we calculate the differential between measurement points and the reference Digital Elevation Model (DEM) to depict the surface elevation changes of each active subglacial lake in monthly time steps. The new lake outlines are defined as contour lines representing the average elevation changes of the static ice sheet. After obtaining the lake outlines, we further analyze the crossover tracks to generate higher temporal resolution elevation change time series for the regions of interest. We have observed differences in the location and volume of the subglacial lake signals compared to the previously published inventory. Firstly, we discover that Lake REC1, originally considered as one lake, is composed of two distinct lakes during the study period, displaying opposing elevation change trends in repeated orbits. While the left area of the REC1 lake experienced a rise of 1m, the right area showed a decrease of approximately 0.5m. Additionally, through calculations of temporal elevation changes, REC1, REC2, and REC3 exhibited characteristics of cascading responses from upstream to downstream. The upstream lake, REC6, initially drained and has been continuously refilling since late 2019, resulting in a surface elevation change of approximately 4m and consuming nearly 0.4 km3 of subglacial water. This substantial water supply has effectively lubricated the ice-bedrock interface, facilitating the fast flow of the Recovery ice stream. Finally, we estimated the hydraulic head of the lakes and predicted water flow paths that align with the sequence of lake activity depicted in the time series plot. In conclusion, the subglacial lakes within the Recovery ice stream constitute a well-connected hydrological system, and the hydrological dynamics in this region are closely associated with the unique subglacial topography of the Recovery area.

Keywords: Recovery ice stream; ICESat-2; Active subglacial lakes
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