the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Jan 2026
Promotion of Dense Shelf Water formation in the Ross Sea under the future trend of the Amundsen Sea Low
Abstract. The Amundsen Sea Low (ASL) is a key low-pressure system influencing climate variability over West Antarctica. The Ross Sea is one of the major formation sites of Dense Shelf Water (DSW), precursor of the global ocean bottom water mass — Antarctic Bottom Water. This study uses CMIP6 multi-model ensemble means to project future changes in the ASL and the associated wind variations over the Ross and Amundsen Seas by the mid- and late-21st century. A high-resolution coupled ocean-sea ice-ice shelf model covering the Ross Sea and the Amundsen Sea is employed to assess how these ASL-driven future wind changes affect DSW formation in the Ross Sea. By applying ASL-induced wind perturbations to three key regions that modulate the Ross Sea DSW characteristics, the respective contributions of regional wind-driven ocean-ice coupling processes to the DSW formation are quantified. The results show that the future deepening and southward shift of the ASL will enhance sea ice production in the Ross Sea polynyas and reduce meltwater inflow from Amundsen Sea ice shelves, thereby promoting DSW formation. Relative to present conditions, ASL-related wind changes over the Ross Sea and adjacent Amundsen Sea are projected to increase DSW production by approximately 8 % by 2050 and 18 % by 2100. These findings suggest that future ASL changes could help counteract the diminishing trend of DSW in the Ross Sea and maintain the Southern Ocean meridional overturning circulation.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2026-13', Anonymous Referee #1, 14 Feb 2026
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RC2: 'Comment on egusphere-2026-13', Anonymous Referee #2, 21 Feb 2026
The authors present future projection simulations for the Amundsen–Ross Sea region to assess projected changes in ocean circulation and sea-ice conditions using CMIP6 multi-model mean forcing. While the overall concept of the study is valuable, I have several substantial concerns regarding the robustness of the conclusions. I recommend major revision or reject with encouragement to resubmit.
1. Insufficient model–data agreement in the Amundsen Sea
The most critical issue is that the simulation does not achieve sufficient agreement with observations in the Amundsen Sea to justify their conclusion (title). Model–data comparison presented in Xie et al., 2024 (Fig. 2) shows a major mismatch: the simulated CDW intrusion is colder than 0 °C, whereas observations indicate temperatures exceeding 1 °C. No model-data comparison is shown in this manuscript for the Amundsen Sea. This discrepancy is large enough to call into question the reliability of the model’s future projections. There is a substantial difference in their mean state. Without addressing this bias explicitly, it is difficult to place confidence in the projected future changes.2. Use of CMIP6 multi-model mean forcing and limitations of the ASL-related analyses
The authors rely on multi-model mean forcing and discuss impacts related to the Amundsen Sea Low (ASL), but the analyses do not sufficiently justify that the multi-model mean is appropriate for the conclusions drawn. Recent work by O'Connor et al., 2025 demonstrates that relatively small changes in northerly winds can strongly modify on-shelf conditions in the Amundsen Sea. A shift of less than ~100 km (may be much smaller distance) or even a small change in wind strength can significantly alter heat transport, especially given that wind stress scales with the square of wind speed. Because of such nonlinearities, conclusions regarding “enhanced dense shelf water formation in the Ross Sea under future ASL trends” cannot be supported without careful examination. I think the full ensemble for each perturbation rather than relying solely on multi-model means is required.3. Wind perturbation experiments and wind-stress curl
The manuscript uses sensitivity experiments in which wind perturbations are applied only to selected regions, but it is unclear to me how the authors address the resulting wind-stress curl patterns. Localized modifications to the wind field can generate unrealistic curl fields and associated circulation anomalies. The authors must demonstrate that the imposed perturbations do not introduce unphysical conditions, either by showing the resulting curl fields or by explaining how these artifacts are mitigated.Citation: https://doi.org/10.5194/egusphere-2026-13-RC2
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This study combines two scales of simulations as well as a coupled ice-ocean approach to explore future sea ice and AABW formation in the Ross Sea region of Antarctica. This is viewed through the lens of the impact of the Amundsen Sea Low atmospheric forcing. For good reasons, this is popular topic at the moment, and this study brings a useful multiscale perspective to the problem.
I have marked up a version of the manuscript.
It provides some useful perspectives and conclusions. I think there needs to be some modest restructuring to clarify the flow of information from the two modelling scales. I addition I think the model description could be reduced in favour of the referenced description papers. The topic is moving fast so there are a couple of new references. Finally, some clarity about how in and outflowing water masses might interact would be useful.