September 17th, 2024
A groundbreaking study by an international team of researchers has revealed significant long-term trends and previously unidentified cyclical patterns in the formation of Antarctic polynyas, crucial areas of open water amidst sea ice. The findings, published in the Proceedings of the National Academy of Sciences (PNAS), were conducted by Grant A. Duffy from the Department of Marine Science, University of Otago, Dunedin, New Zealand, alongside colleagues Fabien Montiel, Ariaan Purich, and Ceridwen I. Fraser.
Polynyas play a pivotal role in ocean-atmosphere interactions, acting as epicentres for sea-ice production, bottom-water formation, and primary productivity. Despite their importance, the dynamics of polynya formation have remained elusive, with existing climate models struggling to accurately simulate Antarctic polynya activity.
Using a 44-year time series of Antarctic sea ice data, the researchers have identified a pattern of linear increases in the area of Antarctic polynyas across most sectors, except the Amundsen and Bellingshausen seas. Notably, they discovered a cyclical pattern in the Ross Sea region, potentially linked to interactions between the Amundsen Sea Low and the Southern Annular Mode (SAM). These findings shed light on the complex drivers of polynya activity, enhancing our ability to predict environmental changes and their impact on Antarctic ecosystems.
Led by Dr. Grant Duffy from Otago’s Department of Marine Science, the team observed not only an unexpected increase in the area of these open waters but also discovered a cyclical growth and shrinkage pattern occurring roughly every 16 years. "These trends are fascinating – and we haven’t noticed them before," remarked Dr. Duffy, highlighting the novelty and significance of their findings, according to an Otago University media release.
Implications for Coastal Ecosystems:
Professor Ceridwen Fraser, the senior author of the study, noted the critical importance of these findings for understanding the future of coastal ecosystems in Antarctica. As the climate warms, the reduction in coastal ice could pave the way for non-native plants and animals to establish themselves, potentially altering the native Antarctic coastal ecosystems. "We know that many non-native plants and animals can reach Antarctica, for example by rafting on floating kelp," Professor Fraser noted, pointing out the ecological stakes at play.
A Changing Antarctic Coastline:
Dr. Duffy further elaborated on the implications of their research, indicating that the increasing areas of open water along Antarctic coasts, especially, are indicative of the broader impacts of climate warming. These evolving coastal environments will necessitate adaptations and changes within the ecosystems, potentially introducing new challenges for native species and conservation efforts.
Key Findings:
There has been a positive linear increase in the area of Antarctic polynyas over the past 44 years, with the expansion most pronounced in coastal polynyas.
A significant cyclical pattern was observed in the Ross Sea region, with a ~16-year cycle in coastal polynya area variability.
The cyclical pattern may arise from interactions between the Southern Annular Mode and the Amundsen Sea Low, suggesting complex climatic influences on polynya formation.
Implications for Antarctic Ecosystems:
Larger or longer-lasting polynyas could increase Antarctic coastal regions' vulnerability to ocean-driven erosion and invasions by non-native species, which are currently impeded by sea ice. As the Antarctic Peninsula experiences increasing coastal exposure and human activity, the findings highlight the urgent need for accurate sea-ice simulations to predict the potential impacts on nearshore ecosystems.
Towards Better Modelling and Prediction:
The study's insights into polynya dynamics and their driving factors are expected to improve regional climate models and projections of sea-ice decline. By enhancing our understanding of these dynamics, researchers aim to integrate the influence and response of Antarctic sea ice into global-scale models more effectively.
This research represents a significant advance in our understanding of Antarctic sea ice processes, marking a step towards more accurate predictions of environmental change in one of the planet's most remote and vulnerable regions.