Karina Nielsen (Technical University of Denmark, Denmark)

This research examines the effectiveness of the Surface Water and Ocean Topography (SWOT) mission in detecting and characterising ice jams in Arctic rivers, utilising both SWOT altimetry and optical satellite data. Arctic rivers, which remain ice-covered for much of the year, undergo a rapid and complex breakup each spring. This process can lead to the formation of ice jams—accumulations of ice that obstruct river flow—resulting in significant alterations to the river’s surface profile and slope. The primary objective of this study is to evaluate SWOT’s capability to observe such events and to contribute to improved monitoring and prediction of associated hydrological changes.

Ice jams typically form during spring breakup when dislodged ice accumulates and blocks the river channel, causing water to back up and potentially raising the upstream water surface elevation by several meters. This can trigger severe flooding and necessitate the evacuation of communities along the riverbanks. Due to the extreme environmental conditions and short-lived nature of ice jams, they have historically been poorly monitored. However, SWOT’s high spatial resolution, wide-swath coverage, and relatively frequent revisit intervals—down to every few days in polar regions—make it uniquely suited for capturing these ephemeral yet high-impact events. The level of detail achievable with SWOT far exceeds that of conventional satellite radar altimetry missions (Biancamaria et al., 2016).

During the calibration and validation (cal/val) phase of the SWOT mission, the satellite captured a ~15 km long ice jam on the Peace River that persisted for several days. Thanks to the daily revisit capability of the cal/val orbit, the ice jam was observed multiple times before its complete breakup. Combined with high-resolution optical imagery from Sentinel-2 (Drusch et al., 2012) and PlanetScope (Planet Labs PBC, 2025), the SWOT observations enabled a detailed analysis of the temporal evolution of both water surface elevation (WSE) and water surface slope (WSS) upstream of the jam. Comparisons with data from traditional altimetry missions, including Sentinel-3A/B (Seitz et al., 2010) and ICESat-2 (Neumann et al., 2019), reveal that these sensors lack the spatial and temporal resolution necessary to detect the full complexity of ice jam dynamics—highlighting the substantial leap forward that SWOT represents.

The transition from a fully ice-covered state to jammed flow and ultimately to an ice-free river contributes valuable insight into the hydrological and cryospheric processes operating in Arctic river systems. These findings underscore the transformative potential of SWOT data for advancing the understanding, monitoring, and prediction of extreme events in cold-region hydrology.


References:
M. Drusch and U. Del Bello and S. Carlier and O. Colin and V. Fernandez and F. Gascon and B. Hoersch and C. Isola and P. Laberinti and P. Martimort and A. Meygret and F. Spoto and O. Sy and F. Marchese and P. Bargellini, 2012, Sentinel-2: ESA's Optical High-Resolution Mission for GMES Operational Services, Remote Sensing of Environment, volume 120, pages 25-36, https://doi.org/10.1016/j.rse.2011.11.026

Planet Labs PBC, 2025, Planet Application Program Interface: In Space for Life on Earth, https://api.planet.com
Neumann, T. A. and Martino, A. J. and Markus, T. and Bae, S. and Bock, M. R. and Brenner, A. C. and Thomas, T. C., 2019, The ice, cloud, and land elevation satellite – 2 mission: A global geolocated photon product derived from the advanced topographic laser altimeter system, Remote Sensing of Environment, volume 233, 10.1016/j.rse.2019.111325

Seitz, B. and Mavrocordatos, C. and Rebhan, H. and Nieke, J. and Klein, U. and Borde, F. and Berruti, B., 2010, The sentinel-3 mission overview, booktitle 2010 IEEE International Geoscience and Remote Sensing Symposium, 10.1109/IGARSS.2010.5650772

S. Biancamaria and D.P. Lettenmaier and T.M. Pavelsky, 2016, The SWOT Mission and Its Capabilities for Land Hydrology, Surv Geophys, volume 37, 10.1007/s10712-015-9346-y