Coupled physical-biological processes in the Antarctic sea-ice zone during the melt season

Antarctic sea ice is a key component of Earth's climate system and plays a pivotal role in Southern Ocean ecosystem function and biogeochemical cycling. Satellite observations have shown a recent decline in Antarctic sea-ice extent, with 4 record summer minima recorded since 2022. This suggests that the ice cover may be entering a new state with strong, but poorly understood, follow-on effects for Southern Ocean ecosystem health and biogeochemical cycles. Contributing to international efforts, Australian scientists participated in a German-led multi-disciplinary research voyage (RV Polarstern voyage PS146) to study sea-ice zone processes during summer and autumn (December 2024 – March 2025). The team measured physical, biological and biogeochemical properties of sea-ice floes (and under-ice habitats) on small-to-regional scales using ice coring surveys, snow probes and under-ice water sampling. This new information of Antarctic sea ice and ecosystem processes will be utilised in the validation of satellite-derived products, and to inform parameterisation of sea-ice processes in climate and ecosystem models. This work is crucial to better understand drivers of recent sea-ice change and to constrain future predictions of Antarctic sea-ice extent and properties, and their impacts on Southern Ocean ecosystems and ecosystem services. Analyses of samples and data collected during the PS146 voyage are ongoing; preparations to participate in a second voyage (PS153, scheduled for February 2026 – April 2026) to the study area have started.

Satellite observations have shown a recent decline in Antarctic sea-ice extent, with 5 record summer minima recorded since 2018. This suggests that the ice cover may be entering a new state with strong, but poorly understood, flow-on effects for Southern Ocean ecosystems and biogeochemical cycles. Contributing to large European-led international efforts, Australian scientists plan to participate in multi-disciplinary voyages to study sea-ice zone processes during the summer melt-season. The team will measure physical and biological properties of sea-ice floes and under-ice habitats on small-to-regional scales using ice coring surveys, snow probes and novel under-ice water sampling methods. New information of Antarctic sea ice and ecosystem processes will be utilised in the validation of satellite-derived products, and to inform parameterisation of sea-ice processes in climate and ecosystem models. This work is crucial to understand drivers of recent sea-ice change and to constrain future predictions of Antarctic sea-ice extent and properties, and their impacts on Southern Ocean ecosystems and ecosystem services. Preparations for participation in collaborative European-led field work have been progressed over the last 12 months, with plans to participate in research voyages in the 2024/25 and 2025/26 seasons.

Antarctic sea ice is a key driver of Southern Ocean physical processes and a structuring component of Antarctic marine ecosystems. Satellite observations have shown extreme fluctuations in Antarctic sea-ice extent since 2016, with three record summer minima recorded in the last six year. Contributing to a large European-led international effort, Australian scientists plan to participate in a multi-disciplinary voyage to study sea-ice zone processes during the late summer melt-season. The team will measure the physical and biological properties of sea-ice floes and under-ice habitats on small-to-regional scales using ice coring surveys, snow probes and under-ice water sampling methods. Data collected will enhance our understanding of sea ice in Antarctic climate and ecosystem processes and will be utilised in the validation of satellite-derived products, and the parameterisation of sea-ice processes in climate and ecosystem models. This work is crucial to understand drivers of recent sea-ice fluctuations and to constrain future predictions of Antarctic sea-ice change, and its impact on Southern Ocean ecosystems. Preparation for collaborative European-led field work, currently planned for early 2025, is progressing well.