Researchers at Ōtākou Whakaihu Waka have analyzed more than three decades of data on Antarctic fast ice, shedding light on the factors that influence its thickness. The findings, published in Journal of Geophysical Research: Oceans, provide a crucial baseline for monitoring future changes in McMurdo Sound and understanding the role of sea ice in the region’s ecosystem.
What is fast ice?
Fast ice, which forms when ocean water freezes and attaches to the shore, is essential for marine life. Penguins, seals, fish, and krill depend on it, while algae thrive beneath its surface. Scientists also rely on stable fast ice to conduct research, using it as a platform to study the ocean below and the atmosphere above.
Despite concerns about climate change, researchers found no clear long-term trend in the thickness of McMurdo Sound‘s fast ice over the 37-year study period. Instead, storm activity, air temperature, and winter wind speeds drive year-to-year variations.
Dr. Maren Richter, who led the research as part of her PhD at the University of Otago, noted that McMurdo Sound has not yet shown strong climate change effects. “The ocean/ice/atmosphere system there seems to still be able to balance out effects of climate change,” she explained. While air temperatures have increased slightly in the last decade of the study, a longer-term view — from the mid-1980s to the present — does not reveal a clear trend.
By documenting natural variations in fast ice thickness, the study provides a reference point for detecting future shifts. “The data analysed shows how important it is to monitor the Antarctic regularly and over many years,” Richter said. “Only long time series of observations allow us to distinguish between natural variability and trends influenced by climate change.”
Understanding these variations is particularly valuable for scientists planning research in the region, as well as for logistics teams operating Antarctic research stations. The data could help refine predictive models that estimate how fast ice conditions will evolve in the coming decades as carbon dioxide levels continue to rise. “Now might be the last time we can observe some systems before effects of climate change dominate over natural variability,” Richter added.
While the study found no significant trend in McMurdo Sound, fast ice conditions elsewhere in Antarctica are changing. “I also want to stress that although there was no trend in fast ice thickness in McMurdo Sound, other areas around Antarctica do show trends in fast ice thickness, extent, and persistence,” Richter said.
Her PhD supervisor and study co-author, Associate Professor Inga Smith from the University of Otago’s Department of Physics, emphasized the importance of fast ice beyond its relatively small coverage compared to Antarctica’s vast pack ice. “We know very little about how fast ice behaves over long periods of time, which means we cannot currently predict future changes,” she said.
Fast ice plays a significant role in Earth’s climate system and is vital for the breeding success of penguins and seals.
The research team found that fast ice thickness tends to increase in years with colder air temperatures, stronger southerly winds, and fewer storms. However, no single factor fully explains the variation. Instead, multiple atmospheric and oceanic forces interact to shape ice conditions each year. The study highlights the need for future research, particularly event-based analyses examining how extreme storms impact the stability and persistence of fast ice.
Richter pointed out that, despite the length of the dataset, 30 years is still a relatively short window for detecting long-term climate trends. “There might have been changes in earlier years which we do not know about because we were not measuring fast ice thickness,” she said. Continued monitoring will be essential to understanding how Antarctic fast ice responds to a warming climate.
By establishing a comprehensive record of McMurdo Sound’s fast ice conditions, the study provides a foundation for tracking future changes in one of the world’s most important polar environments.
Journal Reference:
Richter, M. E., Leonard, G. H., Smith, I. J., Langhorne, P. J., & Parry, M., ‘The interannual variability of Antarctic fast-ice thickness in McMurdo Sound and connections to climate’, Journal of Geophysical Research: Oceans 129, e2023JC020134 (2024). DOI: 10.1029/2023JC020134
Article Source:
Press Release/Material by University of Otago
Featured image: Maren Richter on the fast ice next to a measurement site from which a sea ice core was taken. Coring equipment and part of the automated measuring site is on the right. The Trans-Antarctic Mountains are visible in the background (2021). Credit: Inga Smith
