Remote Sensing of Surface Melt on Antarctica: Opportunities and Challenges

Abstract

Surface melt is an important driver of ice shelf disintegration and its consequent mass loss over the Antarctic Ice Sheet. Monitoring surface melt using satellite remote sensing can enhance our understanding of ice shelf stability. However, the sensors do not measure the actual physical process of surface 5 melt, but rather observe the presence of liquid water. Moreover, the sensor observations are influenced by the sensor characteristics and surface properties. Therefore, large inconsistencies can exist in the derived melt estimates from different sensors. In this study, we apply state-of-the-art melt detection algorithms to four 10 frequently used remote sensing sensors: two active microwave sensors, ASCAT (Advanced Scatterometer) and Sentinel-1, a passive microwave sensor SSMIS (Special Sensor Microwave Imager/Sounder), and an optical sensor MODIS (Moderate Resolution Imaging Spectroradiometer). We intercompare the 15 melt detection results over the entire Antarctic Ice Sheet and four selected study regions for the melt seasons 2015-2020. Our results show large spatiotemporal differences in detected melt between the sensors, with particular disagreement in blue ice areas, in aquifer regions, and during wintertime surface melt. 20We discuss that discrepancies between sensors are mainly due to (1) cloud obstruction and polar darkness, (2) frequencydependent penetration of satellite signals, (3) temporal resolution, and (4) spatial resolution, as well as (5) the applied melt detection methods. Nevertheless, we argue that different sensors can 25 complement each other, enabling improved detection of surface melt over the Antarctic Ice Sheet.

Where the White Continent Is Blue: Deep Learning Locates Bare Ice in Antarctica

“…In these regions, observations of surface melt-water production are hampered by limited satellite observations and discrepancies across different sensors are most pronounced over BIAs (Bell et al, 2018;De Roda Husman et al, 2023). Hence, the new BIA outlines can act as constraints for modeling and observing melt-water production that can lead to the development of (downstream) lakes, which in turn can eventually result in the collapse of ice shelves and hence an increase in mass loss of the ice sheet (Bell et al, 2018;De Roda Husman et al, 2023;Liston & Winther, 2005;Van den Broeke et al, 2023). Moreover, our BIA outlines can aid other geophysical mapping efforts, such as the Based on a set of processed Landsat scenes used for LIMA (Bindschadler et al, 2008) and the outlines of Hui et al (2014).…”

“…More specifically, in the grounding zone, BIAs enhance local‐scale melt, given the typically low albedo of BIAs in combination with katabatic winds that warm and mix the air when flowing downward over the sloping topography (Bell et al., 2018; Lenaerts et al., 2016). In these regions, observations of surface melt‐water production are hampered by limited satellite observations and discrepancies across different sensors are most pronounced over BIAs (Bell et al., 2018; De Roda Husman et al., 2023). Hence, the new BIA outlines can act as constraints for modeling and observing melt‐water production that can lead to the development of (downstream) lakes, which in turn can eventually result in the collapse of ice shelves and hence an increase in mass loss of the ice sheet (Bell et al., 2018; De Roda Husman et al., 2023; Liston & Winther, 2005; Van den Broeke et al., 2023).…”

“…BIAs also influence the future of the Antarctic ice sheet, as BIAs at low elevations enhance melt‐water production because of their low albedo compared to snow that covers most of the continent (e.g., Bell et al., 2018). Eventually, this enhanced melt can increase the mass loss of the Antarctic ice sheet and destabilize ice shelves which can lead to ice shelf collapse (Bell et al., 2018; De Roda Husman et al., 2023; Van den Broeke et al., 2023). Hence, while BIAs cover only a rather small surface of the ice sheet (ca.…”

Determining the Freshwater Fluxes from Antarctica with Earth Observation Data, Models, and In Situ Measurements: Uncertainties, Knowledge Gaps, and Prospects for New Advances

“…Meltwater volumes are difficult to assess from space but robust methodologies have produced datasets of ponded water (Tuckett et al, in review) and slush extent (Dell et al, 2022). Despite the significance of both for the melt-albedo feedback, neither are currently included explicitly in surface energy balance models, and EO estimates of meltwater production maybe inaccurate (Husman et al, 2023) though still of value to the modelling community for evaluation (Van Wessem et al, 2023).…”

“…The development of blended EO and model data products is already well advanced and a striking example is the use of "super-resolution" to fill in a surface melt product using input from a high resolution modelled area applied to a lower resolution model (Husman et al, 2023). In Hu et al (2023) a pure image super-resolution approach was contrasted with an advanced physics informed approach combining albedo and elevation blended with RCM output. Other presented applications have e.g.…”