Space for Shore: Sentinel-1 reveals Arctic glacier retreat

Calving, the process of which ice breaks off from a glacier terminus, is a major contributor to sea-level rise and poses increasing risks to coastal regions worldwide. Understanding these processes, particularly in the Arctic, is essential for predicting future impacts.

Through a recent phase of the ESA Coastal Erosion project Space for Shore, a collaboration between I-SEA (France) and NORCE (Norway), I have utilised over a thousand image acquisitions from the Sentinel-1 mission to monitor the evolution of Svalbard's coastal glaciers in detail.

By analysing Sentinel-1 data from 2015 to 2023, I have mapped glacier front lines and measured icebergs and growlers resulting from calving activity across Svalbard’s summer months, when calving intensities are at their highest.

Sentinel-1, part of the European Union’s Copernicus program, uses synthetic aperture radar (SAR) technology to capture high-resolution data under challenging Arctic conditions, ensuring consistent, year-round monitoring of these critical glaciers.

A key finding from the analysis is the yearly extent of glacier fronts. By examining images captured between July and September, summer glacier fronts can be defined as areas where glacier extent is maintained 95% of the time during these months.

Additionally, by detecting the radar reflection from floating icebergs and growlers, I have developed a proxy for summer calving intensity: summers with higher occurrence of icebergs and growlers—a term for smaller ice fragments that break off from glaciers—indicate more active calving and accelerated glacier retreat, which are critical indicators of a glacier’s health and stability.

In Kongsfjorden, a key study area, notable glaciers like Kronebreen and Kongsvegen show significant changes. In the animation above, the series of daily Sentinel-1 observations were used to classify the region into areas of glacier, iceberg and growler occurence in Kronebukta (Krone Bay) for the summers from 2015 to 2023. Instead of a snapshot of a glacier front position, the Sentinel-1 method provides a statistically defined composite of the summer glacier front positions and calving intensities, revealing the dynamic interactions between ice and ocean over time.

Manon Tranchand, lead researcher on the project, adds:

– This analysis gives us a clear picture of current changes in Arctic glaciers, and they’re crucial for predicting the future impacts of climate change on these sensitive region.

Without the consistent, high-resolution data from Sentinel-1, monitoring these dynamic ice-ocean interactions wouldn’t be possible. Ongoing warming is likely to accelerate ice loss, and our data show how that could contribute to global sea-level rise. Sentinel-1’s capabilities allow us to capture these shifts with unprecedented accuracy. The recent launch of Sentinel-1C marked a significant step forward in the monitoring of Arctic glaciers and global climate impacts.

As the next addition to the Sentinel-1 mission, Sentinel-1C will provide enhanced radar imaging capabilities and improved continuity for critical climate research. With its advanced technology, Sentinel-1C will strengthen our ability to capture detailed, year-round data on glacier front lines, calving rates and ice-ocean interactions, even in the challenging conditions of the Arctic.

This article was first published at ESA's webpage.