Mapping ice loss in West Antarctica with ICESat-2

As an undergraduate research assistant in the Global Rivers Group, I've been spending a lot of time thinking about how water shapes our world. To explain why I chose to work with the Global Rivers Group, I need to go back to my last semester of undergraduate studies. During this time, I found myself drawn away from traditional topics like volcanology and petrography, and increasingly captivated by remote sensing and hydrology. This shift in focus culminated in a final undergraduate project in which I sought to tackle a problem with massive global implications: the stability of the West Antarctic Ice Sheet (WAIS).

The stability of the WAIS is one of the biggest question marks when projecting global sea level rise. I decided to focus my research on the Amundsen Sea embayment, specifically on the Pine Island and the Thwaites glaciers. These two massive ice streams fascinated me because they act as vital corks holding back the vast reservoir of ice in the West Antarctic interior. To measure the changing surface of this ice sheet, I utilized data from NASA’s ICESat-2 satellite. The satellite employs the ATLAS system, which is a photon-counting lidar system capable of precise elevation measurements even over the steep and rugged terrain of these glacial margins.

I conducted the spatial analysis for this project in QGIS. During processing, I encountered a significant technical challenge, which was the handling of the “NoData” values at the raster margins. My initial clipping operations created a bounding box of zero values that distorted the statistical analysis. To resolve this, I applied a transparency mask using the dataset’s Alpha band (Band 22). This mask ensured that I only included valid pixels representing actual ice surfaces in my final calculations.

To accurately quantify the impact on global sea levels, I converted the raw elevation change data into mass loss by calculating the volume change and multiplying it by the density of solid glacial ice. My resulting spatial analysis revealed that the distribution of thinning was highly heterogeneous. Over the Pine Island Glacier, I found that the thinning here manifests as a deep, narrow channel extending far inland from the grounding line. My zonal statistics calculations reveal that the glacier is currently losing approximately 53 Gt/yr. In contrast, over the Thwaites Glacier, I observed a broader, diffuse pattern of loss, spanning nearly the entire width of the glacier front. I calculated that Thwaites is currently losing approximately 49 Gt/yr.

Maps of ice loss over West Antarctica. (a) Rate of ice surface elevation change from ICESat-2, highlighting the contrast between severe dynamic thinning along the glacier trunks and relative stability in the interior. (b) Spatial distribution of mass loss in Gigatons per year (Gt/yr), revealing that the most significant mass deficits are heavily concentrated along the coastal grounding lines where the glaciers flow.

Crucially, discovering that the most intense mass loss aligns precisely with the grounding zones, proving that the ocean, rather than surface melt, drives the melting of the glaciers, completely solidified my career trajectory.  Navigating the complexities of these satellite data pipelines has given me a technical foundation in lidar remote sensing. The classes that I have taken at Virginia Tech, including Dr. Allen’s Remote Sensing of Hydrology class, and the work that I have conducted over the past year while working in the Global Rivers Group, have inspired me to pursue a Master’s program in Geospatial Data Science this fall at NC State University. The methodologies, data processing techniques and troubleshooting strategies developed during this research project will help me achieve my long-term goal of tackling advanced environmental challenges in the future.

Arya Rajmane is an undergraduate research assistant in the Global Rivers Group at Virginia Tech with a BS in Geological Sciences.