Scientists have uncovered evidence of a lush, temperate rainforest thriving near the South Pole approximately 90 million years ago, indicating that Earth’s climate during the Cretaceous period was significantly warmer than previously estimated.
An international research team, led by geoscientists from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Germany, in collaboration with experts from Imperial College London and other institutions, identified fossilized forest soil from the mid-Cretaceous period (115–80 million years ago) located just 900 km (560 miles) from the South Pole. Their analysis of well-preserved roots, pollen, and spores in the sediment core, published in Nature, reveals a surprisingly warm and humid environment capable of supporting dense vegetation, akin to modern temperate rainforests found in places like New Zealand.
A Window into a Warmer World
Professor Tina van de Flierdt, a co-author from Imperial College London’s Department of Earth Science & Engineering, remarked, “The exceptional preservation of this 90-million-year-old forest is remarkable, but what it tells us about the ancient climate is even more astonishing. Despite enduring four months of complete darkness during the polar night, swampy temperate rainforests flourished near the South Pole, pointing to a climate far warmer than we previously imagined.”
The mid-Cretaceous period, known as a time when dinosaurs roamed and tropical temperatures soared to 35°C (95°F), was the warmest in the past 140 million years. Sea levels were approximately 170 meters (560 feet) higher than today, and the new findings suggest that the Antarctic region, now covered in ice, was once free of large-scale ice caps. Instead, it supported a thriving ecosystem with annual mean air temperatures around 12°C (54°F)—comparable to modern-day Germany—and summer temperatures reaching about 19°C (66°F). Water temperatures in rivers and swamps hit up to 20°C (68°F), with rainfall patterns similar to those in present-day Wales.
Uncovering the Evidence
The evidence came from a sediment core drilled near the Pine Island and Thwaites glaciers in West Antarctica. A peculiarly colored section of the core, originally deposited on land, caught the researchers’ attention. Advanced CT scanning revealed a dense network of fossilized roots, so well-preserved that individual cell structures were visible. The sample also contained abundant pollen and spores, including the earliest evidence of flowering plants at such high Antarctic latitudes.
By studying the climatic conditions under which the modern relatives of these ancient plants thrive, along with temperature and precipitation indicators in the sample, the team reconstructed the prehistoric environment. Their findings suggest that Antarctica was blanketed in dense vegetation, with no significant ice sheets at the South Pole.
Challenging Climate Models
The discovery also points to much higher atmospheric carbon dioxide (CO2) levels during the mid-Cretaceous than previously thought. While earlier models estimated global CO2 concentrations at around 1,000 parts per million (ppm), the team’s climate simulations indicate levels between 1,120 and 1,680 ppm were necessary to sustain the warm temperatures observed in Antarctica. These elevated CO2 levels likely drove the extreme warmth, enabling temperate rainforests to flourish in a region that today is locked in ice.
Lead author Dr. Johann Klages from the Alfred Wegener Institute noted, “Our study overturns previous assumptions about the Cretaceous climate. The high CO2 levels we’ve calculated were critical to maintaining the warm, ice-free conditions that allowed such ecosystems to exist so close to the South Pole.”
Implications for Climate Science
This groundbreaking discovery not only reshapes our understanding of Antarctica’s ancient environment but also provides critical insights into how high CO2 levels can influence global climate. The absence of polar ice and the presence of lush forests highlight the dramatic impact of greenhouse gases on Earth’s past, offering a potential glimpse into the consequences of modern climate change if CO2 emissions continue unabated.
The findings, detailed in the study “Temperate rainforests near the South Pole during peak Cretaceous warmth” (published April 1, 2020, in Nature), underscore the importance of continued research into Earth’s climatic history to refine climate models and better predict future changes.
For further details, refer to the original study by Klages et al., published in Nature (DOI: [insert DOI if available]).
