2025-07-09 ペンシルベニア州立大学 (PennState)
ペンシルベニア州立大学を中心とする研究チームは、南極の「終末の氷河」とも呼ばれるスウェイツ氷河の崩壊リスクを予測するための新手法を開発した。この氷河が完全に崩壊すれば、海面が最大約3.3メートル上昇する可能性がある。研究者らは、NASAの衛星ICESat-2のデータを用いて、氷棚内の亀裂を高解像度で3D解析し、どこで深刻な亀裂が生じているかを明らかにした。結果として、氷棚東部では亀裂の進行が著しく、西部は比較的安定していることが判明。研究は氷棚崩壊の早期警告システムの確立に貢献し、将来的には海面上昇の予測精度向上にも資すると期待される。今後、解析アルゴリズムやデータセットを他の研究者向けに公開予定。
氷棚崩壊の監視は気候変動による影響の把握にもつながり、政策立案や国際的な環境対策に資する重要な研究である。
＜関連情報＞
- https://www.psu.edu/news/earth-and-mineral-sciences/story/measuring-how-and-where-antarctic-ice-cracking-new-data-tool
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024JF008118
- https://tiisys.com/blog/2023/03/14/post-118483/
西南極、Thwaites棚氷の破壊特性と氷流における最近の変動性 Recent Variability in Fracture Characteristics and Ice Flow of Thwaites Ice Shelf, West Antarctica
Shujie Wang, Patrick M. Alexander, Richard B. Alley, Zhengrui Huang, Byron R. Parizek, Amanda G. Willet, Sridhar Anandakrishnan
Journal of Geophysical Research: Earth Surface Published: 24 May 2025
DOI:https://doi.org/10.1029/2024JF008118
Abstract
The rapidly changing Thwaites Ice Shelf is crucial for understanding ice-shelf dynamical processes and their implications for sea-level rise from Antarctica. Fractures, particularly their vertical structure, are key to ice-shelf structural integrity but remain poorly measured. To address this, we developed a fracture-characterization workflow using ICESat-2 ATL03 geolocated photon heights, producing the first time-series vertical measurements of fractures across Thwaites from 2018 to 2024. We introduced the fracture depth/freeboard ratio as a normalized metric to quantify vertical fracture extent, serving as an indicator of structural damage. This metric enabled us to track fracture evolution in both the eastern ice shelf and western glacier tongue. In the eastern section, fracturing intensified along the northwestern shear zone and near the grounding line, in a positive feedback loop between enhanced fracturing and accelerated flow. The western section maintained an active rift formation zone about 15 km downstream of the historical grounding line. Flow velocity changes in this section were primarily confined to the unconstrained downstream portion, exhibiting an overall deceleration trend, while the upstream area remained stable. This contrast highlights the role of lateral margin conditions in governing ice-shelf fracture and flow behavior. Changes in the eastern section showed some correspondence with warm winter air temperatures, reduced sea ice, and persistent warm ocean anomalies at shallower depths, suggesting that atmosphere-sea ice-ocean interactions influence ice-shelf structural integrity through basal processes. Future research should integrate satellite-derived fracture observations with numerical models of ice fracture and flow to better capture the dynamics of ice-shelf weakening and retreat.
Key Points
- A workflow is developed to extract fracture vertical measurements from ICESat-2 photon data applied to the Thwaites Ice Shelf (2018–2024)
- The fracture depth/freeboard ratio derived from ICESat-2 data provides a quantitative metric for characterizing vertical structural damage
- Increased fracturing and flow on the eastern section of Thwaites degrade ice-shelf structural integrity, contrasting with the western part
Plain Language Summary
Understanding the processes driving changes in Antarctic ice shelves is crucial for assessing how Antarctica will evolve and impact global sea levels. Modeling ice-shelf retreat is complex, especially due to limited data on ice fracturing. This challenge is pronounced at the Thwaites Ice Shelf in West Antarctica, which is known for its rapid changes, fractured surface, and fast ice flow. NASA’s ICESat-2 satellite allows us to examine ice-shelf fractures with unprecedented detail. We developed an advanced workflow to extract vertical fracture measurements from ICESat-2 data, providing the first record of how fractures evolved vertically over time in this region from 2018 to 2024. The eastern section experienced increased fracturing coupled with accelerated flow, creating a self-reinforcing feedback loop that further weakened the ice shelf. The western section behaved differently, remaining relatively stable overall, with flow changes primarily restricted to its downstream portions. Warmer winter air temperatures, reduced sea ice, and warmer ocean water at shallow depths may have contributed to fracture growth and accelerated ice flow in vulnerable parts of the ice shelf. Our study provides a new approach to measure ice-shelf fractures and highlights the importance of fracture-flow interactions for predicting the future behavior of Antarctic ice shelves.
