Displayed on Kai-Uwe Hinrichs‘ computer screen is a vibrant image illustrating the molecular distribution within a narrow section of sediment core, spanning only a few centimeters. These molecules act as mirrors, reflecting the ocean’s surface temperatures. Within the image, red signifies warmth, while green denotes cold, allowing for a quick visual grasp of temperature fluctuations spanning roughly a century.

Exploring Earth’s Warm Past: A Focus on Climate Dynamics and Future Projections

The period under investigation is the most recent epoch of Earth’s history that was warmer than today, around 125,000 years ago. Such periods form a central research focus of the University of Bremen’s

“The Ocean Floor” Cluster of Excellence. With the university’s MARUM – Center for Marine Environmental Sciences, the Alfred Wegener Institute, the Helmholtz Centre for Polar and Marine Research, the Max Planck Institute for Marine Microbiology, and the Leibniz Centre for Tropical Marine Research, this project includes four institutions of the U Bremen Research Alliance. “You have to go back a long time to find carbon dioxide concentrations comparable to those predicted for the coming century,” says Hinrichs. “These epochs from the past have a model character for the dynamics and interaction of future events.”

Hinrichs and his research group developed the imaging method, which shows high-resolution climate and environmental processes in the history of the earth. In some cases, the researchers can even extract information from the ocean floor samples month by month and read them like a climate diary.

Unraveling the Secrets of the Deep: Insights from Sediment and Microbial Life

“We now also decipher the fine print in the sediment, which we couldn’t do before because we lacked the necessary tools,” says Hinrichs.

The carriers of the information are the molecules that originate from dead seaweed from the past and are now made visible via the new imaging method.

“They tell a story,” Hinrichs explains.

Hinrichs and an international team have found microbial life even at a depth of 2.458 kilometers below the ocean crust, which is currently the record depth for the detection of microorganisms in the seafloor. Per milliliter of sediment, there are often well over one million cells that are still active even in 20 million-year-old sediments and, for example, convert the old organic material from algae and plants into methane.

“The deeper you go, the slower the processes become. It’s a completely different world. The synergies in Bremen, the opportunities for development, and the support from the university are outstanding,” Hinrichs emphasizes. “I’ve always enjoyed working here.”