2025-09-10 ワシントン大学(UW)
Under normal conditions, warm salty water melts the ice shelf from below. When winds from the north shift the sea ice, the ice shelf melts faster, increasing the amount of fresh water around the ice and drawing in more warm water from farther away. Gemma O’Connor
＜関連情報＞
- https://www.washington.edu/news/2025/09/10/key-to-antarctic-ice-loss-in-north-wind/
- https://www.nature.com/articles/s41561-025-01757-6
子午線風へのポリニャ反応が引き金となった西南極氷床損失の増大 Enhanced West Antarctic ice loss triggered by polynya response to meridional winds
Gemma K. O’Connor,Yoshihiro Nakayama,Eric J. Steig,Kyle C. Armour,LuAnne Thompson,Shuntaro Hyogo,Mira Berdahl & Taketo Shimada
Nature Geoscience Published:10 September 2025
DOI:https://doi.org/10.1038/s41561-025-01757-6
Abstract
West Antarctic outlet glaciers are in a stage of rapid ice loss, modulated by wind-driven exposure to warm ocean water. Rapid ice loss probably began in the mid-twentieth century and is often attributed to warmer ocean conditions near the ice shelves driven by strengthening westerly winds at the continental shelf break. This westerly wind trend is a feature of some historical climate simulations but is not supported by proxy (for example, ice-core, tree-ring) observations. Here we present an ensemble of regional ocean simulations and proxy-constrained climate reconstructions and show that shelf-break westerlies are a poor indicator of ocean conditions near the ice shelves. Instead, cumulative northerly wind anomalies close coastal polynyas (open-water regions), driving anomalous warming and freshening near the ice shelves, increasing ice-shelf melting. The increased meltwater leads to strengthening of the undercurrent that supplies warm water, further increasing melting. Our results highlight the importance of local northerly winds and associated sea ice changes for ice-shelf melting in West Antarctica. Proxy reconstructions show a significant historical northerly wind trend in this region, providing the atmospheric forcing that can explain the initiation of West Antarctic glacier retreat in the mid-twentieth century.
