Geoscientists have established a new climate record that sheds light on the early ice ages of Antarctica, indicating that the melting of the Antarctic ice sheet happened more quickly than was previously understood.
In a groundbreaking study, geoscientists from the University of Leicester and the University of Southampton have uncovered evidence of sudden melting events in the Antarctic ice sheet dating back over 20 million years.
Featured in the journal Nature Communications, this study highlights the sensitivity of our planet’s early ice ages to shifts in the Earth’s orbit around the Sun. It suggests that the Antarctic ice sheet may be less stable than previously assumed.
The research also offers an insight into how Antarctica might respond in a future where the Greenland Ice Sheet has melted as a result of ongoing emissions.
Historical records indicate fluctuations in the Antarctic ice sheet’s size have occurred over time, similar to a heartbeat. Current oceanic records from various locations show differing ‘rhythms’ in the evolution of early Antarctic ice ages. This discrepancy is puzzling, since the climate impact of the Antarctic ice sheet’s expansion and contraction should be consistent across the oceans, just like how your arm and leg shouldn’t have different pulse rates.
These rhythms are influenced by the Earth’s orbit shape around the Sun across long timescales of hundreds of thousands to millions of years. When the orbit is more eccentric, the distance from the Sun varies significantly during the year, leading to more heat exposure when closer and less when farther away. This added heat can result in rapid melting of the ice sheet, while a more circular orbit means greater stability and less melting.
This research, backed by UK Research and Innovation/Natural Environment Research Council and the German Science Foundation (DFG), focuses on the time frame between 28 and 20 million years ago when Earth was warmer than today, and only the Antarctic ice sheets were present. The study uses data gathered from geological cores collected by an Integrated Ocean Drilling Program (IODP) expedition, establishing a new benchmark climate record that helps scientists refine their climate models for reconstructing past climatic changes. This historical understanding is crucial for predicting the future implications of Antarctic ice sheet melting.
Dr. Tim van Peer, lead author and researcher from the University of Leicester, commented: “Our findings indicate that the Antarctic ice sheet is more vulnerable than was previously thought. We illustrate how sensitive the early Antarctic ice sheet was to Earth’s orbital and axial variations.”
“Historical climate shifts swiftly ended some early Antarctic ice ages, leading to significant melting. However, ‘swift’ should be considered in geological time scales, not as rapid as what we could expect with current climate change.”
“We must not assume that the present-day Antarctic ice sheet is stable. If greenhouse gas emissions continue as they are, we could see substantial melting of the Antarctic ice sheet. Addressing climate change by lowering emissions is essential to avoid reaching tipping points that threaten the stability of the Antarctic ice sheet.”
The study examined geological samples from cores acquired during an IODP expedition in 2012 in the northwest Atlantic Ocean. Fossilized microorganisms in these cores reflect ocean chemical conditions through the oxygen isotopes contained in their shells. By analyzing the oxygen isotope ratios, researchers can determine periods of ice sheet growth or shrinkage, creating a timeline based on the core samples’ depth.
Professor Paul Wilson, Principal Investigator at the University of Southampton, noted: “It’s intriguing to realize that by performing simple chemical analysis on tiny fossil shells from the deep ocean, we can monitor the Antarctic ice sheet’s status. The remarkable part is that we can trace this back through geological time for tens of millions of years. Earth science allows us to venture into the past and consistently uncover insights that can inform our future.”
The IODP is an international marine research initiative funded by 21 countries, dedicated to investigating Earth’s history and dynamics as recorded in seafloor sediments and rocks while examining sub-seafloor environments. Utilizing various platforms—a unique aspect of the IODP—scientists study the deep biosphere, oceanic changes, processes, effects and solid Earth cycles. This specific research incorporates samples collected during Expedition 342 and represents years of collaborative effort from a global team, primarily from the UK and Germany.
