Smaller calving events, rather than massive icebergs, are primarily responsible for the loss of the Antarctic ice sheet.
A recent investigation by researchers from the University of Florida has provided new insights into how climate change impacts Antarctic ice shelves. Their findings indicate that, despite an overall reduction in ice shelves due to rising temperatures, the occurrence and scale of major iceberg calving events have remained largely unchanged.
This research was spearheaded by Emma MacKie, Ph.D., an Assistant Professor of Geological Sciences, alongside Katy Serafin, Ph.D., an Assistant Professor of Geography, and a colleague from the Colorado School of Mines.
According to MacKie, “Our findings imply that the main danger to our ice shelves comes from numerous small calving incidents rather than from rare, catastrophic events.”
Calving, the process where ice chunks break away from ice shelves and turn into icebergs, is common and has been increasingly affected by climate change. Large icebergs typically form through a slow process, often starting from small cracks that expand across the ice shelf before a full separation occurs.
These cracks can be monitored with satellite imagery as they develop, but predicting when new cracks or calving events might happen is difficult due to their unpredictable nature and the dangers involved in sending scientists to study them on-site. While small calving events are frequent, significant incidents — where more than 100 square kilometers of ice separate — are much rarer.
This research is pioneering in its examination of large calving events. Despite having 47 years’ worth of satellite data from 1976 to 2023, the team encountered a limited number of cases. They overcame this issue by employing extreme value theory, a statistical method designed for analyzing rare natural phenomena such as major earthquakes, severe floods, or volcanic eruptions. Serafin, with her background in extreme flooding, was well-acquainted with this analytical approach.
Serafin explained, “Statistical models that link the size and frequency of events have been used for years to predict rare flooding, like a 100-year flood. With advancements in satellite imaging that allow for better tracking of large calving events, we aimed to see if we could apply similar models to assess the probability of these significant calving incidents.”
By using this approach, the researchers examined the extreme calving events documented in satellite images and created a model to forecast the likelihood of these occurrences in the future. As they built their models, they also devised scenarios to estimate the potential sizes of future calving events. Their projections suggested that an iceberg occurring once every decade could measure up to 6,100 square kilometers, only slightly larger than a notable calving event in 2017, when an iceberg comparable in size to Delaware broke away from the Antarctic ice sheet. On the other hand, a once-in-a-century event could yield an iceberg approximately 45,000 square kilometers, a bit bigger than the entire country of Denmark.
MacKie noted, “A once-in-a-century iceberg would dwarf any we’ve recorded so far and could considerably affect the stability of ice sheets and oceanic processes.”
The research team discovered no indication that large icebergs have grown in size over the previous fifty years, with the largest observed iceberg sizes documented between 1986 and 2000. This shows that extreme calving events do not appear to be linked to climate change, even though the overall loss of ice shelves has escalated due to warming. While significant calving events remain infrequent and might form part of a larger natural cycle, the increase in smaller calving events has largely contributed to the decline of Antarctic ice shelves in the past fifty years.
