Quantifying Meltwater on the George VI Ice Shelf, Antarctica

Victoria McPeek¹, Luke Trusel², and Jessica Kromer²

¹Department of Meteorology, Millersville University,

²Department of Geography, Pennsylvania State University

The Antarctic ice sheet can potentially raise sea level by 58 meters. Ice shelves buttress the ice sheets and regulate ice flow from upstream areas, helping control sea level rise. Surface hydrology plays a crucial role in the stability of the ice shelves and the ice sheet. Surface meltwater can form on the ice shelves which can impact their health. When the meltwater accumulates, it can cause hydro-fractures in the ice shelf, leading to its retreat and total collapse. A collapse would lead to a more accelerated ice flow rate from the ice sheet into the ocean. The George VI ice shelf became the second-largest ice shelf on the Antarctic Peninsula after the collapse of the Larsen B ice shelf. This project aims to study the meltwater and lakes on the George VI ice shelf. Landsat 8/9 data from 2020 to present for 15 rows/paths for the George VI ice shelf were downloaded. We implemented the Moussavi et al (2020) method to classify water, rocks, and clouds in about 600 individual Landsat scenes. This classification technique uses spectral indices like the normalized water index (NDWI) and band reflectances with specifically adapted thresholds to accurately classify clouds, water, and rocks. Our code produces a color composite image, a classified image, and a Geotiff for all the masks. Manual inspection reveals that the classification approach accurately classifies water, rocks, and clouds, though some inaccuracies remain in separating water from shadows. Future work includes quantifying lake areas and depths. A time series from 2020 to present will be made to extend the existing 2013-2019 Moussavi et al (2020) time series. Next, maps will be made to show the evolution of meltwater overtime on the ice shelf. The results will be compared to two gridded estimates of meltwater production, ASCAT-ERA5 and RACMO2.3p2. As much of George VI's ice shelf is thought to be underlain by relatively impermeable ice, this comparison seeks to evaluate state-of-the-art estimates of meltwater production, thus enabling more informed future modeling of melt and ice shelf stability.