11:15 〜 11:30
[MIS15-09] A primary driver of the recent summer Antarctic sea-ice minima: Ice-ocean albedo feedback
キーワード：海氷、南極海、アルベドフィードバック、海氷減少
The Antarctic sea-ice extent in summer has been decreasing significantly since 2016, reaching a record low in February 2023. This decline is occurring more rapidly than past Arctic sea-ice loss and could have profound impacts on the climate system. For instance, the loss of sea ice may disrupt the freshwater balance of the Southern Ocean, affecting its role in CO2 uptake and heat absorption from human activities. Additionally, sea-ice loss could also significantly impact Antarctic ice shelves and ecosystems. While the summer Antarctic sea-ice minima after 2016 have been analyzed for individual years and specific regions, the underlying mechanism driving this decline remains incompletely understood.
Our analysis, based on sea-ice concentration data from SMMR and SSMI-SSMIS satellite observations, along with ERA5 atmospheric data with heat flux calculations, suggests that the recent decline and the record minimum in 2023 are primarily driven by the ice-ocean albedo feedback mechanism across the entire Antarctic sea-ice zone. During the early ice-melt season, wind-forced divergent ice motion increases the open-water fraction of low-albedo. This, in turn, enhances anomalous solar heating of the upper ocean, accelerating sea-ice melt and further expanding the open water fraction, creating a positive feedback loop. Additionally, we propose a simplified coupled model that represents the feedback effect and successfully reproduces both the recent sea-ice decline and the record minimum. These findings demonstrate that wind-forced ice motion during the early melt season is a key driver of this feedback mechanism, which should be taken into account in future sea-ice predictions.
Our analysis, based on sea-ice concentration data from SMMR and SSMI-SSMIS satellite observations, along with ERA5 atmospheric data with heat flux calculations, suggests that the recent decline and the record minimum in 2023 are primarily driven by the ice-ocean albedo feedback mechanism across the entire Antarctic sea-ice zone. During the early ice-melt season, wind-forced divergent ice motion increases the open-water fraction of low-albedo. This, in turn, enhances anomalous solar heating of the upper ocean, accelerating sea-ice melt and further expanding the open water fraction, creating a positive feedback loop. Additionally, we propose a simplified coupled model that represents the feedback effect and successfully reproduces both the recent sea-ice decline and the record minimum. These findings demonstrate that wind-forced ice motion during the early melt season is a key driver of this feedback mechanism, which should be taken into account in future sea-ice predictions.