Antarctic ice sheet patterns point to rapid melting risks

Periods of sudden melting across the Antarctic ice sheet have been discovered in a new climate record dating back over 20 million years.

This research, led by geoscientists from the University of Leicester and the University of Southampton, sheds light on the sensitivity of Earth’s early ice ages to changes in the planet’s orbit.

The study highlights the implications for the Antarctic ice sheet’s stability in today’s warming world.

Antarctic ice sheet’s past

The Antarctic ice sheet has fluctuated in size throughout its history, akin to a heartbeat. However, records from different ocean locations have revealed variations in these “heartbeats” – an anomaly that has puzzled scientists.

This shouldn’t happen because Antarctic ice changes should leave the same mark across the ocean.

These variations are linked to the Earth’s eccentric orbit, which changes over hundreds of thousands to millions of years. During more eccentric orbits, Earth’s distance from the Sun fluctuates significantly, leading to periods of higher heat exposure when the planet is closer.

This increased heat disrupts the climate system, triggering rapid ice melting. Conversely, during more circular orbits, the ice sheet remains more stable and shows less melting.

Unstable Antarctic ice sheets

The researchers examined the period between 28 and 20 million years ago, a time when Earth was warmer.

The team utilized geological cores from an Integrated Ocean Drilling Program (IODP) expedition to reconstruct past climate changes.

These cores, recovered from the northwest Atlantic Ocean, contain oxygen isotope records that help scientists determine whether the ice sheet expanded or contracted at different times.

“From our research, we can see that the Antarctic ice sheet is more unstable than previously thought. We demonstrate how sensitive the geologically early Antarctic ice sheet was to changes in Earth’s orbit and axis,” explained Dr. Tim van Peer from the University of Leicester.

“We cannot assume that the modern-day Antarctic ice sheet is stable. If climate emissions continue unabated, we are on course to melt a large amount of the Antarctic ice sheet.”

“We need to mitigate climate change by reducing our emissions. This is the only way to not cross tipping points in the stability of the Antarctic ice sheet.”

Insights from microorganisms and fossils

The research team analyzed samples containing microorganisms from the geological cores. These microorganisms preserve ocean chemistry in their shells, which record the oxygen isotope ratio. By measuring these ratios, the scientists established a timeline of ice sheet growth and melting events.

“It may be a surprising thing to learn that we take the pulse of the Antarctic ice sheet by doing some simple chemistry on pinhead-sized fossil shells from the deep seafloor on the other side of the world,” noted Professor Paul Wilson from the University of Southampton.

“But the really beautiful thing is that we can do it back through the geological record over tens of millions of years. Earth science is about time travel into the past and we are always learning lessons to help us understand our future.”

Collaborative effort to understand Earth’s history

This research represents a multinational partnership, primarily involving scientists from the U.K. and Germany. It was supported by the U.K. Research and Innovation/Natural Environment Research Council and the German Science Foundation.

The IODP, a publicly funded international marine research program involving 21 countries, facilitated this work. IODP explores Earth’s history and dynamics by analyzing seafloor sediments and rocks. Samples for this study were collected during Expedition 342 and built upon years of collaborative effort.

The University of Leicester has a long-standing involvement in IODP, dating back to the 1980s. Recent expeditions include “Hawai’ian Drowned Reefs” and “Tracking Tsunamigenic Slip Across the Japan Trench (JTRACK).”

These expeditions continue to deepen our understanding of Earth’s climate history and inform predictions about the future.

Predicting the future of Antarctic ice sheets

The study’s findings provide a critical benchmark for improving climate models. By understanding past climate dynamics, scientists can better predict the future impacts of Antarctic ice sheet melting.

As the research highlights, reducing emissions remains the key to preventing irreversible changes to Earth’s climate system.

This glimpse into Earth’s ancient climate highlights the delicate balance of the Antarctic ice sheet and its profound implications for our planet’s future.

The study is published in the journal Nature Communications.

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