01 Jul 2024
 | 01 Jul 2024
Status: this preprint is open for discussion.

Grounded Ridge Detection and Characterization along the Alaskan Arctic Coastline using ICESat-2 Surface Height Retrievals

Kennedy A. Lange, Alice C. Bradley, Kyle Duncan, and Sinéad L. Farrell

Abstract. Grounded sea ice ridges are an important morphological feature that stabilize shorefast ice along Arctic coastlines. Investigating the development of shorefast ice around Utqiaġvik, AK, we employ high-resolution altimetry data from NASA’s ICESat-2 satellite to describe an approach to identify grounded ridges and to track the development of shorefast ice over the winter season. We apply the University of Maryland Ridge Detection Algorithm (Duncan and Farrell, 2022) using ICESat-2 ATL03 elevation data to identify and calculate ridge sail heights and estimate ridge depths using empirical relationships based on first-year ice ridge geometries surveyed in the Beaufort, Chukchi, and Bering Seas. The estimated ridge depths are then compared with 15 arc-second resolution bathymetric data from the General Bathymetric Chart of the Oceans (GEBCO) to detect likely grounded ridges. This approach for identifying and characterizing grounded ridges in shorefast ice is then applied across the entire Alaskan Arctic coastline in the 2021–2022 winter to characterize grounded ridge depth, height, width, number of ridges per track, and distance from shore. We find that distributions in ridge grounding depth skew towards shallower water and ridges are narrower and closer to shore on the Chukchi side of the Alaskan Arctic.  Mean grounding depths of 5.4 m in the Chukchi and 9.1m in the Beaufort are notably shallower than the traditional "stamuki" zone (≥10 m). With further application of the methods demonstrated here, we can begin to map patterns in shorefast ice stability, seasonality, and improve our understanding of near-shore ice dynamics across Arctic coastal regions in a changing climate.

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Kennedy A. Lange, Alice C. Bradley, Kyle Duncan, and Sinéad L. Farrell

Status: open (until 12 Aug 2024)

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Kennedy A. Lange, Alice C. Bradley, Kyle Duncan, and Sinéad L. Farrell

Data sets

ICESat-2 Sea Ice Surface Topography from the University of Maryland-Ridge Detection Algorithm: Coastal Alaska Kyle Duncan and Sinéad L. Farrell

Model code and software

Code set for June 2024 manuscript submission Kennedy A. Lange and Alice C. Bradley

Kennedy A. Lange, Alice C. Bradley, Kyle Duncan, and Sinéad L. Farrell


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Short summary
Grounded sea ice ridges stabilize nearshore sea ice by anchoring it in the seafloor. In this study, we develop a method to identify grounded ridges in satellite data, and measure the height, depth, distance from shore, and width of a thousand ridges across the Alaskan Arctic, finding regional differences in these metrics across the coastline. This method lays the groundwork for a better understanding of nearshore ice stability, holding importance for Arctic community food security and safety.