A new study has revealed that ocean tides can directly influence when large Antarctic icebergs break off from the ice shelves surrounding the continent, a process known as calving. The research marks a major step toward accurately forecasting ice loss from the Antarctic Ice Sheet and improving projections of global sea level rise.
Published in Nature Communications, the study focuses on the Brunt Ice Shelf and a major crack known as Chasm-1 that calved a huge iceberg, known as iceberg A-81 in January 2023.
The Brunt Ice Shelf is the home of the British Antarctic Survey's Halley VI Research Station. Since 2021, three large icebergs have calved off this shelf, with the largest being the size of Greater London. Researchers have been studying the ice shelf in great detail to try to understand the processes that occur before a big calving happens.
By combining long-term GPS monitoring with radar data, the team tracked subtle movements and stresses within the ice shelf over time. Their results show that crack propagation – the process leading to iceberg calving – consistently occurs during spring tides, when tidal forces are at their strongest.
This pattern culminated in the dramatic calving of iceberg A-81, which occurred during a spring tide. A-81, spanning hundreds of square kilometres, detached suddenly from the Brunt Ice Shelf, underscoring the potential scale and abruptness of these events.
Dr Oliver Marsh, lead author of the study and a glaciologist at BAS, says:
"Icebergs like A-81 can be thousands of square kilometres in size and account for roughly half of all ice lost from Antarctica each year. Understanding what controls the timing of these events is crucial, because calving not only affects the shape and melt rate of ice shelves, but also their long-term stability."
"It's incredibly exciting to uncover a link between something as predictable as the tides and the dramatic, sudden process of iceberg calving. This kind of insight brings us closer to forecasting major ice loss events, and their impact on sea level, with far greater precision."
The findings suggest that external environmental forces, particularly tides and atmospheric winds, can play a key role in when cracks grow and icebergs are released. This could open the door to new, short-term prediction models for iceberg calving, which has previously been difficult to forecast with any accuracy.
Beyond ice loss, large icebergs also alter ocean circulation and local ecosystems as they drift, further emphasising the importance of predicting their formation.
Dr Marsh concludes: "This research helps us understand one of the mechanisms behind crack propagation in ice shelves. By recognising how tides and winds contribute to calving, we move closer to anticipating not just if, but when, major ice loss events will occur."
