82-3 Remote Sensing and Field Observations of Ice-Surface Texture and Sediment Abundance at Lakes Joyce and Fryxell, Antarctica: Implications for Depositional Models of Perennially Ice-Covered Lakes

Abstract:

Constraining variability in ice-surface texture and sediment properties in perennially ice-covered lakes (PICLs) is important for interpreting lake-bottom facies and predicting impacts on benthic microbial mats. Ice surface roughness controls sediment accumulation, while sediment properties (grain size, albedo, and abundance) and ice thickness influence melt-driven migration through the ice. These processes control sediment amount, distribution, and depositional style on the lake bottom, as well as light transmission and sediment delivery to benthic microbial mats. However, long-term, lake-wide observations jointly characterizing ice-surface roughness and sediment abundance are lacking, limiting evaluation of depositional models and predictions of PICL responses to environmental change. Here, we combine field observations and remote sensing to characterize the ice covers of Lakes Joyce and Fryxell, Antarctica. We use airborne LiDAR and field observations to establish lake-wide ice-surface morphology and Sentinel-1 C-band synthetic aperture radar data (10 m/pxl; HH and HV polarizations) to evaluate temporal changes in ice surface radar texture. Radar texture is calculated as the local standard deviation of HH and HV backscatter within 3x3-pixel neighborhoods for individual observations and monthly median composites. We apply spectral mixing analysis to Sentinel-2 imagery (10 m/pxl) to map sediment abundance and compare with Sentinel-1 radar texture, ice-cover thickness, and under-ice photosynthetically active radiation (PAR). Preliminary results suggest that radar texture exhibits seasonal cycles, with lake-wide values highest during austral summer and lowest during austral winter. At Lake Joyce, HV exhibits a greater seasonal range than HH, although neither polarization shows an obvious long-term trend. Lake Fryxell also exhibits greater seasonal variability in HV than HH, but both show a sustained baseline increase starting in 2022. This shift in Lake Fryxell coincides with documented ice-cover thinning, an increase in sediment abundance in 2022 followed by a decline in 2024, and increased under-ice PAR. We hypothesize that elevated summer radar texture in these PICLs reflects increased ice-surface roughness due to seasonal ablation and sediment-induced melting. For Lake Fryxell, we further hypothesize that the 2024 decline in ice-surface sediment and PAR increase reflects increased sedimentation to the lake bottom and predict this will reduce ice-surface roughness over time. Ongoing work will test these hypotheses by completing remote sensing analyses and comparing results with field observations of the ice cover and lake-bottom deposits to inform PICL depositional models.

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