Otago scientists discover Antarctic fast ice secrets
University of Otago
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.
view moreCredit: Inga Smith, 2021
University of Otago – Ōtākou Whakaihu Waka scientists have successfully analysed more than 30 years of vital data on the thickness of landfast sea ice in Antarctica’s McMurdo Sound, which will prove useful to measure future impacts of climate change.
The study, published in the Journal of Geophysical Research: Oceans, set out to discover what key influences determine the thickness of landfast sea-ice, known as fast ice, using data from 1986 to 2022.
Fast ice is frozen ocean water that is attached to shorelines and persists for at least 15 days. It provides vital habitats for penguins and seals, as well as fish, krill and algae underneath the ice.
Scientists also traverse around McMurdo Sound on fast ice to perform experiments and measure the ocean underneath and the atmosphere above. The ice needs to be stable and thick enough to do this safely.
Instead of a long-term trend of increasing or declining thickness, the researchers found storm events, air temperature and winter wind speed cause fast ice thickness to vary year to year.
Lead researcher Dr Maren Richter, who completed the research as part of her PhD at Otago, says fast ice in McMurdo Sound has not (yet) seen strong effects of climate change.
“The ocean/ice/atmosphere system there seems to still be able to balance out effects of climate change.
“We see a slight increase in air temperatures over the last 10 years of our study period, but if we look at air temperature over a longer time period (from the mid-1980s to now) there is no clear trend,” she says.
The study data shows what variability is ‘normal’ for the fast ice in McMurdo Sound and this can then be used to detect when things start to change, for example if a year is unusual or if a series of years start to form a trend toward different fast ice conditions.
“The data analysed shows how important it is to monitor the Antarctic regularly and over many years. Only long time series of observations allow us to distinguish between natural variability and trends influenced by climate change.”
She hopes the new study will be useful for modellers to predict variations year to year, which would be useful for scientists planning research on the ice or to research station operators who want to know what ship to use to resupply the stations.
The study could also be used to verify and train models that look decades into the future and try to see what average fast ice conditions will be like in 100 years’ time with a lot more carbon dioxide in the atmosphere.
“Now might be the last time we can observe some systems before effects of climate change dominate over natural variability.”
Co-author and Dr Richter’s primary PhD supervisor, Associate Professor Inga Smith, of the Department of Physics, says although the total fast ice area is much smaller than the pack ice (broken up sea ice) in Antarctica, it has very important roles to play in Earth’s climate system and for the breeding success of penguins and seals.
“We know very little about how fast ice behaves over long periods of time which means we cannot currently predict future changes,” she says.
Dr Richter points out that 30 years of observations is still “quite short” when talking about trends in climate.
“There might have been changes in earlier years which we do not know about because we were not measuring fast ice thickness.
“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.”
*Dr Richter’s PhD research was supervised by Associate Professor Inga Smith, Dr Greg Leonard, of the School of Surveying, and Professor Pat Langhorne, of the Department of Physics.
She thanked the University of Otago, Antarctica New Zealand, NIWA, the Antarctic Science Platform, Te Pūnaha Matatini, and the Royal Society of New Zealand for funding that facilitated her research and fieldwork in McMurdo Sound.
Journal
Journal of Geophysical Research Oceans
Article Title
The Interannual Variability of Antarctic Fast-Ice Thickness in McMurdo Sound and Connections to Climate
Antarctic ice sheet faces “death by a thousand cuts”
University of Florida
A recent study conducted by University of Florida geologists and geographers has shed new light on the effects of climate change on Antarctic ice shelves. It found that while there has been broad ice shelf loss due to warming temperatures, the frequency and size of major iceberg calving events has not changed significantly.
This study was led by Assistant Professor of Geological Sciences Emma MacKie, Ph.D., and Assistant Professor of Geography Katy Serafin, Ph.D., along with a collaborator at the Colorado School of Mines.
“Our results suggest that the primary threat to our ice shelves is ‘death by a thousand cuts’ via small calving events, rather than catastrophic extremes,” said MacKie.
Calving, when chunks of ice break off from ice shelves to form icebergs, is common and increasingly influenced by climate change. For extremely large icebergs, this process is typically slow, often starting with small rifts that spread across the ice shelf before fully breaking off.
These rifts can be detected as they form and grow using satellite data, but their random nature and the risks associated with sending scientists to observe them in-person make it extremely difficult to predict when future rifts or calving events may occur. Major calving events are particularly challenging to study. While smaller calving events occur frequently, large events — where over 100 square kilometers of ice break away — are exceptionally rare.
This study is the first of its kind to focus on these large calving events. Even with 47 years’ worth of satellite data from 1976 to 2023, the team was still faced with a small sample size. This challenge was addressed with extreme value theory, a type of statistical analysis used when studying rare natural disasters like major earthquakes, extreme floods, or volcanic eruptions. As an expert on extreme flooding, Serafin was no stranger to this type of data analysis.
“Statistical models relating event size and frequency are tools that have been used for estimating rare flood events, like a 100-year flood, for decades,” said Serafin. “Now that satellite imagery can more consistently track large calving events, we thought we’d test whether we could apply the same tools for understanding how likely these massive calving events are.”
Using this method, the team analyzed extreme calving events found in the satellite record and developed a model to predict the likelihood of these events over time. While creating their models, researchers also developed scenarios to predict how large calving events could be. By their estimates, a once in a decade iceberg could be as large as 6,100 square kilometers, only slightly larger than an extreme calving event in 2017, when an iceberg roughly the size of Delaware broke off the Antarctic ice sheet. A once in a century eventcould produce an iceberg about 45,000 square kilometers, slightly larger than the entire country of Denmark.
“A once in a century iceberg would be several times larger than any in the observational record and would have a significant impact on ice-sheet stability and ocean processes,” said MacKie.
The team found no evidence that large icebergs have increased in size over the last half century, with the peak iceberg surface areas occurring between 1986 and 2000. This indicates that extreme calving events do not correlate with climate change, although overall ice shelf loss has increased due to climate change. While extreme calving events continue to be rare and may be part of a larger natural cycle, more numerous small calving events have dominated Antarctic ice shelf loss over the last half century.
This study was published November 29, 2024 by the American Geophysical Union.
Journal
Geophysical Research Letters
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
47 Years of Large Antarctic Calving Events: Insights From Extreme Value Theory
Mapping Antarctica’s hidden ice-free lands: a blueprint for conservation
UNSW researchers unveil a new map and classification system that will help protect the unique plants and animals of Earth’s most remote and fragile continent.
Antarctica, often regarded as the planet’s last true wilderness, harbours unique ecosystems that support extraordinary biodiversity and contribute to global diversity and environmental stability. These ecosystems, which occupy permanently ice-free land covering less than 0.5% of the continent, are now under growing threat from human activity and climate change.
Now, a team led by researchers at UNSW Sydney’s Centre for Ecosystem Science has developed a high-resolution map and hierarchical classification system of Antarctica’s ice-free lands, which can be seen in full in Scientific Data.
This new inventory categorizes Antarctica’s ecosystems into nine Major Environment Units, 33 Habitat Complexes, and 269 Bioregional Ecosystem Types, providing an unprecedented level of detail. Together they are a groundbreaking resource that will help protect the biodiversity of Antarctica’s ice-free lands.
Ice-free Antarctica
“Many people are surprised to learn that Antarctica has any permanently ice-free lands at all. And yet, these tiny habitat patches contain the vast majority of the continent’s biodiversity,” says lead author Dr Anikó B. Tóth.
The ice-free lands are home to uniquely adapted flora including ‘micro-forests’ of lichens, moss and two flowering plants, Antarctic hairgrass and pearlwort. They also sustain a variety of mites and springtails (very tiny arthropods related to spiders and insects, respectively), tardigrades, nematodes and many algaes and microbes. Seabirds, including land-breeding penguins, petrels, gulls, skuas and albatrosses have established breeding colonies in these areas too.
As the climate changes and ice melts, the patches will likely become milder and less isolated, opening them up to colonisation by hardy species from lower latitudes.
“It’s the opposite problem that many conventional ecosystems face today. Instead of fragmentation and loss of area, ice-free patches will become larger and more interconnected,” says Dr Tóth.
“This could completely change the dynamics and resident species of these ecosystems, whose distinctiveness is often founded on isolation.”
A game changer for conservation
Senior author, Professor David Keith, says this typology and map represent a transformative leap forward in our understanding of Antarctic ecosystems.
“By integrating biophysical and biological data, we’ve created a robust framework to guide conservation efforts under the Antarctic Treaty System.”
The classification aligns with the International Union for Conservation of Nature’s (IUCN) Global Ecosystem Typology, placing Antarctica in a global context and highlighting the continent’s critical role in sustaining planetary biodiversity. It will allow for systematic risk assessments, strategic placement of new protected areas, and effective monitoring of global conservation goals.
“The outcomes of the study bring new insights into the variety of Antarctica's terrestrial biodiversity, knowledge essential for its comprehensive conservation,” says Steven Chown, the director of the Australian Research Council’s special research initiative, Securing Antarctica’s Environmental Future and a coauthor on the study.
Why now?
The research comes at a pivotal time when advances in geospatial technology and ecological data have made it possible to capture the complexity of Antarctic ecosystems.
“With climate change accelerating and human activity increasing, this framework is essential to prepare us for the consequences of accelerating Antarctic greening,” says Dr Tóth.
The classification and maps are critical foundations to inform and support management and conservation of the Antarctic region through the Protocol on Environmental Protection to the Antarctic Treaty System. This is particularly important as the review of the Protocol approaches. Even though it might seem like a long way into the future (2048), work like this, and the actions that it underpins, are essential in demonstrating how effective the Protocol can be in protecting Antarctica.
“Beyond conservation, the study provides a foundation for future ecological research, enabling comparisons across regions and insights into ecosystem responses to environmental change,” says Dr Tóth.
“It also establishes a common language for researchers and policymakers worldwide, fostering collaboration on preserving Earth’s cryogenic environments.”
The research, published as open access in Scientific Data with the data download freely available from the Australia Antarctic Data Centre, reflects years of collaboration among experts in ecology, remote sensing, and Antarctic science. It sets the stage for developing a Red List of Antarctic Ecosystems to pinpoint the continent’s most threatened habitats and identify strategies to protect them.
Journal
Scientific Data
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
A dataset of Antarctic ecosystems in ice-free lands: classification, descriptions, and maps
Article Publication Date
22-Jan-2025
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