Recent research has unveiled a critical piece of information regarding the potential stability of the West Antarctic Ice Sheet. The collapse of the ice sheet within the Ross Sea region can be prevented through adherence to a low-emissions pathway. The West Antarctic Ice Sheet holds over 5 meters of potential global sea-level rise, making it imperative to understand whether seemingly stable regions of the ice sheet might experience melting in the future.
The Siple Coast of West Antarctica is currently considered stable, with rivers of ice flowing over the continent and draining into the Ross Sea. The flow of ice in this region is impeded by the Ross Ice Shelf, a massive floating ice mass comparable in size to Spain. This ice shelf acts as a support for the glaciers of the ice sheet. Unlike other ice shelves in West Antarctica, the Ross Ice Shelf experiences minimal melting at its base due to the frigid ocean waters beneath it. However, historical data reveals that this area of the ice sheet has undergone significant changes in the past.
Data obtained from radiocarbon dating of sediments beneath the ice sheet indicates that about 7,000 years ago, the ice sheet retreated by hundreds of kilometers before readvancing to its current position within the last 2,000 years. A recent study conducted by GNS Science Te Pū Ao, Te Herenga Waka—Victoria University of Wellington, and an international team including NASA’s Jet Propulsion Laboratory has utilized computer model simulations to elucidate the processes behind this retreat and advance of the West Antarctic Ice Sheet.
The simulations performed in the study focused on how changes in the ocean and Earth’s crust influenced the behavior of the ice sheet. By understanding the events that transpired in the past, the researchers aimed to enhance predictions about future scenarios involving the ice sheet. Lead author Dan Lowry, a GNS Science ice sheet and climate modeler, emphasized the importance of unraveling the historical context to improve projections regarding the ice sheet’s response to changing environmental conditions.
One crucial aspect highlighted in the study is the impact of ocean dynamics on the stability of the West Antarctic Ice Sheet. When surface ocean water freezes to form sea ice, salt is released, leading to the creation of dense, cold, salty water that can penetrate deep into the ocean, including under the Ross Ice Shelf. This dense water acts as a barrier against warmer ocean water, preventing excessive melting of the ice shelf. However, evidence from Antarctic ice cores and geological records suggests that ocean mixing was weaker in the past, potentially resulting in higher melting rates.
Moreover, as the ice sheet undergoes changes in size, the Earth’s crust responds by slowly lifting up due to alterations in ice load. The rate of crustal uplift is influenced by the viscosity of the mantle beneath the Earth’s crust. The study indicates that the retreat and advance of the ice sheet can be attributed to variations in ocean temperature and the rate of crustal response, underscoring the interconnected nature of the ice sheet, ocean, and solid earth.
The findings of the research offer hope for the future stability of the West Antarctic Ice Sheet in the Siple Coast region. By implementing measures to reduce greenhouse gas emissions in alignment with the goals of the Paris Agreement, it is feasible to limit ocean warming to levels that would not trigger the collapse of the ice sheet. While other parts of West Antarctica are experiencing ongoing melting due to warm ocean cavities, the study suggests that preventing ice sheet retreat in the Siple Coast region is still achievable.
Global climate models under high-emissions scenarios point towards decreased sea ice formation and reduced deep ocean mixing, potentially leading to a scenario reminiscent of the extensive ice sheet retreat observed in the past. The research conducted by Lowry and his team incorporated a comprehensive range of processes, including the gravitational impact of the ice sheet as it melts, offering a more intricate analysis than previous models. By delving into these complexities, the study provides valuable insights into the factors influencing the stability of the West Antarctic Ice Sheet.