Extreme iceberg calving events are statistically unexceptional and they are not necessarily a consequence of climate change

By Emma J. MacKie, Joanna Millstein, and Katherine A. Serafin.

"Abstract Massive calving events result in significant instantaneous ice loss from Antarctica. The rarity and stochastic nature of these extreme events makes it difficult to understand their physical drivers, temporal trends, and future likelihood. To address this challenge, we turn to extreme value theory to investigate past trends in annual maxima iceberg area and assess the likelihood of high‐magnitude calving events. We use 47 years of iceberg size from satellite observations. Our analysis reveals no upward trend in the surface area of the largest annual iceberg over this time frame. This finding suggests that extreme calving events such as the recent 2017 Larsen C iceberg, A68, are statistically unexceptional and that extreme calving events are not necessarily a consequence of climate change. Nevertheless, it is statistically possible for Antarctica to experience a calving event up to several times greater than any in the observational record. 

"Plain Language Summary In Antarctica, massive icebergs are a consequence of calving, where blocks of ice detach from the continent's ice shelf. The calving of these massive icebergs is a rare occurrence with unpredictable variability, making it a difficult process to understand and statistically model. Here, we study calving using a statistical method called extreme value theory (EVT), which is specifically designed to model the nature of extreme events. We use EVT to statistically analyze the largest Antarctic calving events over the past 47 years; these calving events have been recorded in satellite observations. Our results show that the risk of experiencing a major calving event has not increased over the last 47 years, which suggests that climate change is not necessarily responsible for the calving of these large icebergs. However, it is statistically possible that Antarctica could generate bigger icebergs than any previously recorded. The methods used in this study could be combined with other data sets or physical information to enhance calving models that scientists use to make predictions about ice shelves."