By Abbas Nazil
A new scientific study has found that the Antarctic ice sheet became significantly more sensitive to climate change after a major shift in Earth’s ice age cycles around one million years ago, raising new concerns about how ice sheets may respond to modern global warming.
The research, published in Nature Geoscience, shows that changes in Earth’s climate system during the Mid-Pleistocene Transition altered the behaviour of large ice sheets, making Antarctica more responsive to atmospheric and ocean temperature changes than in earlier periods.
Antarctica, which contains the largest ice mass on Earth, plays a critical role in regulating global sea levels, and even small changes in its ice volume can have significant impacts on coastal regions worldwide.
Scientists say that around one million years ago, Earth’s climate cycles shifted, resulting in longer and more intense ice ages, but until now the exact response of Antarctic ice sheets to these changes had remained unclear.
To investigate, researchers from the Institute for Basic Science Center for Climate Physics at Pusan National University used advanced computer simulations that reconstructed global climate conditions over the past three million years.
These simulations were combined with an ice sheet model developed at Penn State University to study how temperature, precipitation, ice flow and ocean conditions influenced Antarctic ice dynamics over time.
The study found that after the Mid-Pleistocene Transition, the Antarctic ice sheet entered a new regime in which it became more unstable and more responsive to changes in climate forcing.
Researchers identified a critical atmospheric carbon dioxide threshold of around 240 parts per million, below which the Antarctic ice sheet began to show much larger variations in response to environmental changes.
The model results suggest that once this threshold is crossed, the ice sheet does not respond gradually but instead becomes significantly more sensitive to even small shifts in temperature and ocean conditions.
Scientists explained that colder ocean temperatures during glacial periods reduced melting beneath floating ice shelves, while lower global sea levels relieved pressure on the Antarctic bedrock, allowing ice to thicken along coastal regions.
These combined processes contributed to the formation of larger and more stable ice sheets during later ice age cycles.
Lead researcher Dr Kyung-Sook Yun said the findings demonstrate that the Antarctic ice sheet reacts more strongly to climate forcing after the transition, indicating that ice sheet behaviour can shift abruptly rather than gradually over time.
Co-author Professor Axel Timmermann added that the increased sensitivity of the Antarctic ice sheet raises important questions about how it may respond to current and future global warming trends.
The researchers emphasised that ice sheets do not respond in a simple linear way to climate change but can undergo sudden shifts that significantly alter their stability and contribution to sea level rise.
They noted that understanding these threshold behaviours is essential for improving predictions of future sea level rise under continued greenhouse gas emissions.
The study highlights that past climate transitions can provide valuable insight into how modern ice sheets might react to ongoing increases in global temperatures and atmospheric carbon dioxide levels.
Scientists warned that if similar thresholds are approached in the future, the Antarctic ice sheet could become more vulnerable to rapid changes, with serious implications for global coastal regions.
The findings underscore the importance of long-term climate modelling in understanding the complex interactions between atmospheric conditions, ocean systems and polar ice stability.
