2025-04-01 東京海洋大学,国立極地研究所,海洋研究開発機構,北海道大学
＜関連情報＞
- https://www.nipr.ac.jp/info2025/20250401.html
- https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024GL112914
南半球環状モードに対する東南極海沿岸域における海洋の応答 Ocean Response Along the East Antarctic Coastal Margin to the Southern Annular Mode
K. Mizobata, D. Hirano, K. Kusahara, S. Aoki, J. Inoue, S. Takao, R. Makabe
Geophysical Research Letters Published: 15 March 2025
DOI:https://doi.org/10.1029/2024GL112914
Abstract
Ocean circulation around the Antarctic coastal margins plays a critical role in heat delivery to Antarctica, melting ice shelves. However, until recently, satellite-based sea-level observations have been limited by the presence of sea ice. With improved algorithms, it is now possible to monitor sea-level fluctuations over most of the Southern Ocean, including sea ice-covered areas. We identified several clockwise gyres along East Antarctic coastal margins in satellite-derived dynamic ocean topography (DOT). Singular value decomposition analyses revealed that the coastal DOT deepening and anomalous clockwise circulation consistently occur during the positive phase of the southern annular mode (SAM), which is associated with negative wind stress curl anomalies. Shifting of the SAM to a more positive phase since the 20th century and its expected continuation into the coming century could lead to enhanced clockwise gyres along East Antarctica, contributing to increased poleward ocean heat transport.
Key Points
- Variability of the ocean circulation along East Antarctica is investigated using satellite radar altimetry
- Clockwise ocean circulation varies in response to the negative wind stress curl, which depends on the Southern Annular Mode
- Expected trend toward the positive phase of SAM will leads to enhanced poleward ocean heat transport in the East Antarctic coastal area
Plain Language Summary
The Southern Ocean melts the Antarctic ice sheet. The poleward ocean heat, which controls ice-ocean interactions, is transported from offshore to coastal margins across the shelf break by ocean circulation. Satellite observations are powerful for monitoring global sea-level distribution which is closely related to ocean circulation; however, this approach is difficult to apply to polar regions with sea ice. This limitation has been addressed through the development of improved satellite algorithms, enabling monitoring in these regions. In this study, we utilized improved satellite sea-level data to investigate the relationship between sea-level variation and atmospheric circulation, with a focus on East Antarctic regions. Using analyses to find interlocking patterns in ocean and atmospheric variables, we found that several clockwise gyres form along the East Antarctic coastal margins along with deepening coastal sea levels during the positive phase of the Southern Annular Mode, the leading mode of the Southern Hemisphere atmospheric circulation. The negative wind stress curl tendency associated with the SAM positive phase is responsible for strengthening the regional ocean gyres. The continuous shift of the SAM to a positive phase, both in the past and near future, is expected to enhance these gyres and increase poleward ocean heat transport.
